U.S. patent application number 12/828521 was filed with the patent office on 2011-01-06 for power source apparatus for vehicle.
This patent application is currently assigned to DENSO CORPORATION. Invention is credited to Atsushi IMAI, Teruhiko KAMEOKA, Shigenori SAITO, Takao SUENAGA, Hiroshi TAMURA.
Application Number | 20110001352 12/828521 |
Document ID | / |
Family ID | 42797188 |
Filed Date | 2011-01-06 |
United States Patent
Application |
20110001352 |
Kind Code |
A1 |
TAMURA; Hiroshi ; et
al. |
January 6, 2011 |
POWER SOURCE APPARATUS FOR VEHICLE
Abstract
A power source apparatus mounted to a vehicle is equipped with a
lead-acid battery and a lithium battery. An open circuit voltage
and an internal resistance of each of the batteries are determined
to satisfy the following conditions (a1), (a2), and (a3): (a1) In
the use range of SOC of the lead-acid battery and the use range of
SOC of the lithium battery, there is an equal voltage point Vds at
which the open circuit voltage V0 (Pb) of the lead-acid battery
becomes equal to the open circuit voltage V0 (Li) of the lithium
battery; (a2) The relationship of V0 (Li)>V0 (Pb) is satisfied
in the upper limit side of the use range of SOC of the battery; and
(a3) A terminal voltage Vc (Li) of the lithium battery is not more
than a set voltage Vreg of a regulator when a maximum current flows
in the lithium battery.
Inventors: |
TAMURA; Hiroshi; (Nagoya,
JP) ; KAMEOKA; Teruhiko; (Okazaki-shi, JP) ;
SUENAGA; Takao; (Oobu-shi, JP) ; IMAI; Atsushi;
(Gamagoori-shi, JP) ; SAITO; Shigenori;
(Nukata-gun, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 320850
ALEXANDRIA
VA
22320-4850
US
|
Assignee: |
DENSO CORPORATION
Kariya City
JP
|
Family ID: |
42797188 |
Appl. No.: |
12/828521 |
Filed: |
July 1, 2010 |
Current U.S.
Class: |
307/9.1 |
Current CPC
Class: |
B60L 58/15 20190201;
B60L 2210/30 20130101; Y02T 10/7066 20130101; B60L 58/22 20190201;
B60L 2240/12 20130101; Y02T 10/7072 20130101; Y02T 10/7216
20130101; B60L 58/20 20190201; Y02T 10/7061 20130101; Y02T 10/70
20130101; B60L 58/21 20190201; B60L 58/24 20190201; B60L 2240/545
20130101; H02J 7/0003 20130101; B60L 58/14 20190201; B60L 2240/549
20130101; B60L 1/00 20130101; Y02T 10/72 20130101; Y02T 10/7011
20130101; Y02T 10/7016 20130101; B60R 16/033 20130101; H02J 1/10
20130101; Y02T 10/7077 20130101; Y02T 10/7241 20130101; B60L 3/0046
20130101; Y02T 10/7044 20130101; B60L 7/12 20130101; B60L 58/13
20190201; B60L 50/16 20190201; B60L 2210/10 20130101; B60L 2240/547
20130101 |
Class at
Publication: |
307/9.1 |
International
Class: |
B60L 1/00 20060101
B60L001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 1, 2009 |
JP |
2009-156947 |
Sep 29, 2009 |
JP |
2009-223947 |
Claims
1. A power source apparatus which is mounted to a vehicle with an
alternator and a constant voltage control means capable of
adjusting a voltage of electric power generated by the alternator
to a set voltage, the power source apparatus comprising: a
lead-acid battery electrically connected to an alternator; and a
secondary battery, electrically connected in parallel to the
lead-acid battery, having an output power density and an energy
density which is higher than an output power density and an energy
density of the lead-acid battery, wherein an open circuit voltage
and an internal resistance of the lead-acid battery and an open
circuit voltage and an internal resistance of the secondary battery
are determined in order to satisfy the following conditions (a),
(b), and (c): (a) an equal voltage point, at which the open circuit
voltage of the lead-acid battery becomes equal to the open circuit
voltage of the secondary battery, is present in a use range of
state of charge (SOC) of the lead-acid battery and a use range of
SOC of the secondary battery; (b) the open circuit voltage of the
secondary battery is higher than the open circuit voltage of the
lead-acid battery at an upper limit side from the equal voltage
point in the use range of SOC of the secondary battery; and (c) a
terminal voltage of the secondary battery when a maximum charging
current flows in the secondary battery is not more than the set
voltage which is set by the constant voltage control means.
2. The power source apparatus according to claim 1, wherein the
open circuit voltage and the internal resistance of the lead-acid
battery and the open circuit voltage and the internal resistance of
the secondary battery are determined so that the open circuit
voltage of the secondary battery is lower than the open circuit
voltage of the lead-acid battery at the lower limit side from the
equal voltage point in the use range of SOC of the secondary
battery.
3. The power source apparatus according to claim 2, wherein the
open circuit voltage and the internal resistance of the lead-acid
battery and the open circuit voltage and the internal resistance of
the secondary battery are determined so that an upper part at the
upper limit side from the equal voltage point is wider than a lower
part at the lower limit side from the equal voltage point in the
use range of SOC of the secondary battery.
4. The power source apparatus according to claim 1, further
comprising voltage drop suppression means capable of suppressing
discharge from the secondary battery to a starter motor mounted to
the vehicle in order to suppress a voltage drop of the secondary
battery.
5. The power source apparatus according to claim 4, further
comprising protection control means capable of protecting the
secondary battery from overcharge by limiting a charging capacity
to the secondary battery and of protecting the secondary battery
from over discharge by limiting a discharging capacity from the
secondary battery so that the residual capacity of the secondary
battery is within the use range of the secondary battery, wherein
the protection control means limits the charging capacity to the
secondary battery or the discharging capacity from the secondary
battery by using the voltage drop suppression means.
6. The power source apparatus according to claim 1, further
comprising protection control means capable of protecting the
secondary battery from overcharge by controlling a charging
capacity into the secondary battery and protecting the secondary
battery from over discharge by controlling a discharging capacity
to the secondary battery so that the residual capacity of the
secondary battery is within the use range of the secondary battery,
wherein the protection control means outputs an instruction signal
which instructs the constant voltage control means to decrease the
set voltage in order to control the charging capacity to the
secondary battery.
7. The power source apparatus according to claim 4, wherein the
voltage drop suppression means is a switch means to open and close
an electric connection between the secondary battery and the
starter motor, and the switch means opens the electric connection
between the secondary battery and the starter motor when the
lead-acid battery supplies the electric capacity to the starter
motor.
8. The power source apparatus according to claim 7, wherein the
switch means is one of a manual switch, an electromagnetic relay,
and a semiconductor switch.
9. The power source apparatus according to claim 1, wherein the
secondary battery is a battery of non-aqueous electrolyte.
10. The power source apparatus according to claim 9, wherein the
secondary battery is comprised of a positive electrode made of
positive electrode active material, a negative electrode made of
negative electrode active material, and an electrolyte, the
negative electrode active material is one of carbon, graphite,
lithium-doped carbon or graphite, lithium titanium oxide,
silicon-containing alloy, and tin-containing alloy, and the
positive electrode active material is lithium metal composite oxide
or activated carbon.
11. The power source apparatus according to claim 10, wherein the
positive electrode active material is made of lithium iron
phosphate.
12. The power source apparatus according to claim 1, wherein the
secondary battery is comprised of a plurality of battery cells
electrically connected in series, and further comprising cell
equalizing means capable of detecting a voltage of each of the
battery cells and of equalizing a residual capacity of each of the
battery cells based on the detected voltage of each of the battery
cells.
13. The power source apparatus according to claim 1, wherein the
power source apparatus is mounted to a vehicle with an idling stop
function capable of automatically stopping and restarting the
operation of the internal combustion engine.
14. A power source apparatus which is mounted to a vehicle with an
alternator and a constant voltage control means capable of
adjusting a voltage of electric power generated by the alternator
to a set voltage, the power source apparatus comprising: a
lead-acid battery electrically connected to an alternator; a
secondary battery, electrically connected in parallel to the
lead-acid battery, is higher in output density or energy density
than the lead-acid battery; and rectifying means placed between the
lead-acid battery and the secondary battery so that a forward
current direction of the rectifying means becomes a direction from
the lead-acid battery to the secondary battery, and the rectifying
means having a barrier voltage to the current flowing in the
forward direction through the rectifying means, wherein an open
circuit voltage and an internal resistance of the lead-acid battery
and an open circuit voltage and an internal resistance of the
secondary battery are determined in order to satisfy the following
conditions (a'), (b'), and (c'): (a') an equal voltage point, at
which the open circuit voltage of the secondary battery is equal to
a subtracted voltage obtained by subtracting the barrier voltage of
the rectifying means from the open circuit voltage of the lead-acid
battery, is present in a use range of state of charge (SOC) of the
lead-acid battery and a use range of SOC of the secondary battery;
(b') the open circuit voltage of the secondary battery is higher
than the subtracted voltage of the lead-acid battery at an upper
limit side from the equal voltage point in the use range of SOC of
the secondary battery; and (c') a terminal voltage of the secondary
battery when a maximum charging current flows in the secondary
battery is not more than the set voltage which is set by the
constant voltage control means.
15. The power source apparatus according to claim 14, further
comprising: open and close means, connected in parallel to the
rectifying means, capable of electrically connecting the alternator
with the secondary battery and disconnecting the alternator from
the secondary battery; and open and close control means to instruct
the open and close means to close the electrical connection between
the alternator and the secondary battery when the secondary battery
is charged with electric power generated by the alternator, and to
instruct the open and close means to open the electrical connection
between the alternator and the secondary battery when the
rectifying means performs the rectifying operation.
16. The power source apparatus according to claim 15, wherein the
open and close means is composed of a semiconductor switch, and the
rectifying means is composed of a parasitic diode of the
semiconductor switch.
17. The power source apparatus according to claim 15, wherein the
open and close means is composed of an electromagnetic relay which
is connected in parallel to the rectifying means.
18. The power source apparatus according to claim 14, wherein the
open circuit voltage and the internal resistance of the lead-acid
battery and the open circuit voltage and the internal resistance of
the secondary battery are determined so that the open circuit
voltage of the secondary battery is lower than the subtracted
voltage of the lead-acid battery at the lower limit side from the
equal voltage point in the use range of SOC of the secondary
battery, where the subtracted voltage of the lead-acid battery is
obtained by subtracting the barrier voltage of the rectifying means
from the open circuit voltage of the lead-acid battery.
19. The power source apparatus according to claim 18, wherein the
open circuit voltage and the internal resistance of the lead-acid
battery and the open circuit voltage and the internal resistance of
the secondary battery are determined so that a range at the upper
limit side from the equal voltage point in the use range of SOC of
the secondary battery is wider than a lower part at the lower limit
side from the equal voltage point in the use range of SOC of the
secondary battery.
20. The power source apparatus according to claim 15, further
comprising protection control means capable of protecting the
secondary battery from overcharge by limiting a charging capacity
to the secondary battery and of protecting the secondary battery
from over discharge by limiting a discharging capacity from the
secondary battery so that the residual capacity of the secondary
battery is within the use range of the secondary battery, wherein
the protection control means limits the charging capacity to the
secondary battery or the discharging capacity from the secondary
battery by using the voltage drop suppression means.
21. The power source apparatus according to claim 15, further
comprising protection control means capable of protecting the
secondary battery from overcharge by controlling a charging
capacity to the secondary battery and protecting the secondary
battery from over discharge by controlling a discharging capacity
from the secondary battery so that the residual capacity of the
secondary battery is within the use range of the secondary battery,
wherein the protection control means outputs an instruction signal
which instructs the constant voltage control means to decrease the
set voltage in order to control the charging capacity to the
secondary battery.
22. The power source apparatus according to claim 14, wherein the
secondary battery is a battery of non-aqueous electrolyte.
23. The power source apparatus according to claim 22, wherein the
secondary battery is comprised of a positive electrode made of
positive electrode active material, a negative electrode made of
negative electrode active material, and an electrolyte, the
negative electrode active material is one of carbon, graphite,
lithium-doped carbon or graphite, lithium titanium oxide,
silicon-containing alloy, and tin-containing alloy, and the
positive electrode active material is lithium metal composite oxide
or activated carbon.
24. The power source apparatus according to claim 23, wherein the
negative electrode active material is made of lithium titanium
oxide.
25. The power source apparatus according to claim 14, wherein the
secondary battery is comprised of a plurality of battery cells
electrically connected in series, and further comprising cell
equalizing means capable of detecting a voltage of each of the
battery cells and of equalizing a residual capacity of each of the
battery cells based on the detected voltage of each of the battery
cells.
26. The power source apparatus according to claim 14, wherein the
power source apparatus is mounted to a vehicle with an idle stop
function capable of automatically stopping and restarting the
operation of the internal combustion engine.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is related to and claims priority from
Japanese Patent Applications No. 2009-156947 filed on Jul. 1, 2009
and No. 2009-223947 filed on Sep. 29, 2009, the contents of which
are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a power source apparatus to
be applied to vehicles.
[0004] 2. Description of the Related Art
[0005] A vehicle with an internal combustion engine generally has a
lead-acid battery in order to supply electric power to various
types of electrical loads such as a starter motor mounted on the
vehicle. The lead-acid battery is cheap in cost when compared with
high density energy batteries (high performance batteries) such as
nickel batteries and lithium batteries, but has a low durability
resistance to frequent charge and discharge. For example, because a
lead-acid battery mounted on a vehicle with idle reduction function
(which is a function to automatically stop idling to save and
reduce fuel consumption) discharges electric power frequently, this
causes a rapid deterioration of the lead-acid battery. In
particular, a lead-acid battery mounted on a vehicle with an
alternator capable of regenerating electric power when the vehicle
decelerates is charged with such regenerative electric power
frequently, this frequent charge would cause a rapid deterioration.
Using a high performance battery to avoid the above drawback of the
lead-acid battery would cause a large manufacturing cost.
[0006] Conventional techniques disclosed by the following technical
documents D1 to D5 have proposed an improved structure where high
performance batteries (as secondary battery) with high price and
lead-acid battery with low price are mounted in parallel to a
vehicle.
D1: Japanese patent laid open publication No. JP 2007-46508; D2:
Japanese patent laid open publication No. JP 2007-131134; D3:
Japanese patent laid open publication No. JP 2008-29058; D4:
Japanese patent laid open publication No. JP 2008-155814; and D5:
Japanese patent laid open publication No. JP 2009-126395.
[0007] That is, during idle reduction mode (which is capable to
stop the engine during idling in order to reduce fuel consumption),
electric power such as regenerative electric power is
preferentially supplied to the high performance battery, and
electric power of the high performance battery is preferentially
supplied to the electrical loads. On the other hand, from the above
viewpoint to reduce the electric power consumption while a vehicle
stops in a car park for a long period of time, it is controlled so
that the lead-acid battery supplies electric power to electrical
loads. As described above, a combination of two types of batteries
makes it possible to downsize the high performance battery, and to
suppress the increase of the manufacturing cost.
[0008] By the way, overcharge or over discharge of a battery would
cause a rapid deterioration. It is therefore preferable to use the
battery within an optimum SOC (state of charge, hereinafter, will
be referred to as the "the use range of SOC") which is not
overcharged or discharged, where the SOC indicates the charge state
of the battery, because an open circuit voltage of the battery
corresponds to SOC. In other words, the change of SOC of the
battery has a different open circuit voltage of the battery. In
general, the open circuit voltage (for example, 12.7 V to 12.8 V)
of a lead-acid battery is not equal, within the use range of SOC,
to an open circuit voltage of a high performance battery.
[0009] Because the lead-acid battery and the high performance
battery are connected in parallel in a power source apparatus, a
current flows from the battery with a high terminal voltage Vd to
the battery with a low terminal voltage when discharging, and this
would cause the batteries to be in an over discharged condition
which is out from the use range of SOC. In general, the terminal
voltage Vd of a battery can be expressed by the following formula
(1):
Vd=V0-Id.times.R (1),
where Id is a discharging current of the battery, R is an internal
resistance of the battery, and V0 is an open circuit voltage of the
battery.
[0010] The conventional techniques disclosed by the technical
documents D1 to D5 previously described have proposed a structure
to use a DC/DC converter which is placed between those batteries
such as a high performance battery and a lead-acid battery. This
structure can adjust the terminal voltage of the high performance
battery, which is higher in terminal voltage than that of the
lead-acid battery, by the DC/DC converter, and prevent a current
which flows from the high performance battery having a high
terminal voltage to the lead-acid battery of a low terminal voltage
in order to prevent the lead-acid battery from overcharge.
[0011] However, because such a DC/DC converter is a high price
device, it is difficult to decrease the total manufacturing cost of
a power source apparatus for vehicle which requires a DC/DC
converter in order to prevent a lead-acid battery from
overcharge.
SUMMARY OF THE INVENTION
[0012] It is an object of the present invention to provide a power
source apparatus which is mounted to vehicles equipped with a high
performance battery (or a high energy density battery which serves
as a secondary battery) and a lead-acid battery, which is capable
of suppressing deterioration of the lead-acid battery and reducing
its manufacturing cost without incorporating any DC/DC
converter.
[0013] In accordance with a first aspect of the present invention,
there is provided a power source apparatus which is applied to
various types of vehicles with an alternator and a constant voltage
control means. The constant voltage control means is capable of
adjusting a voltage of the electric power supplied from the
alternator to a set voltage. The power source apparatus is
comprised of a lead-acid battery and a secondary battery. The
lead-acid battery is electrically connected to an alternator. The
secondary battery is electrically connected in parallel to the
lead-acid battery. The secondary battery is higher in output power
density and energy density than the lead-acid battery.
[0014] In the power source apparatus according to the first aspect
of the present invention, an open circuit voltage and an internal
resistance of the lead-acid battery and an open circuit voltage and
an internal resistance of the secondary battery are determined in
order to satisfy the following conditions (a), (b), and (c): [0015]
(a) an equal voltage point at which the open circuit voltage of the
lead-acid battery becomes equal to the open circuit voltage of the
secondary battery is present in a use range of state of charge
(SOC) of the lead-acid battery and a use range of SOC of the
secondary battery; [0016] (b) the open circuit voltage of the
secondary battery is higher than the open circuit voltage of the
lead-acid battery at an upper limit side from the equal voltage
point in the use range of SOC of the secondary battery; and [0017]
(c) a terminal voltage of the secondary battery when a maximum
charging current flows in the secondary battery is less than the
set voltage which is set by the constant voltage control means.
[0018] In the power source apparatus according to the present
invention, the open circuit voltages and the internal resistance of
the lead-acid battery and the secondary battery (such as a lithium
battery) are determined in order to satisfy the above condition
(a). This allows that the terminal voltage Vd (Pd) within the use
range of SOC of the lead-acid battery is approximately equal to the
terminal voltage Vd (Li) within the use range of SOC of the lithium
battery, and this makes it possible to have a small difference
between or a same voltage potential between the lead-acid battery
and the secondary battery. Accordingly, this allows the secondary
battery to flow a very small current to the lead-acid battery
without using any DC/DC converter in the power source apparatus,
and it is thereby possible to prevent the lead-acid battery from
overcharge. It is therefore possible to produce the power source
apparatus with low manufacturing cost because of not using any
DC/DC converter.
[0019] In the power source apparatus according to the present
invention, the open circuit voltages and the internal resistance of
the lead-acid battery and the secondary battery are determined in
order to satisfy the above condition (b). This allows the lead-acid
battery to discharge because the secondary battery is higher in
open circuit voltage than the lead-acid battery when the secondary
battery is charged with an electric capacity which is higher than
that at the equal voltage point within the use range of SOC of the
secondary battery. This allows the secondary battery to
preferentially discharge rather than the lead-acid battery. Because
the lead-acid battery has a low durability to the frequent
discharge operation and the frequency of discharge from the
lead-acid battery is decreased, the structure of the power source
apparatus according to the present invention can prevent the
lead-acid battery from deterioration in charging capacity and
performance.
[0020] In the power source apparatus according to the first aspect
of the present invention, the open circuit voltages and the
internal resistance of the lead-acid battery and the secondary
battery are determined in order to satisfy the above condition (c).
This can increase the frequency of preferentially charging the
secondary battery rather than the lead-acid battery by the
following reasons.
[0021] That is, because the terminal voltage Vc (Pb) (expressed by
the following formula (F2)) of an available lead-acid battery when
the maximum charging current flows becomes larger than the set
voltage which is set by the constant voltage control means, it
would become difficult to charge the lead-acid battery when the
maximum charging current flows.
[0022] Even when the lead-acid battery has a less residual capacity
and the terminal voltage Vc (Pb) of the lead-acid battery is lower
than the set voltage, the terminal voltage Vc (Pb) of the lead-acid
battery is rapidly increased and it would becomes difficult to
charge the lead-acid battery because the lead-acid battery has a
large internal resistance value R (Pb) when the lead-acid battery
is charged. This would be difficult to charge the lead-acid
battery. The terminal voltage Vc of a battery during charge is
expressed by F2: Vc=V0+Ic.times.R . . . (F2), where Ic is a charge
current, R is an internal resistance of the battery, and V0 is an
open circuit voltage of the battery.
[0023] On the other hand, in the power source apparatus according
to the first aspect of the present invention, the terminal voltage
Vc (Li) of the secondary battery when the maximum charging current
flows in the secondary battery is set to a voltage which is lower
than the set voltage. In other words, because the terminal voltage
of the secondary battery is always below the set voltage even when
the terminal voltage Vc (Li) has the maximum voltage as the upper
limit in the use range of SOC of the secondary battery, it is
possible to always charge the secondary battery. Accordingly, this
makes it possible to increase the frequency of preferentially
charging the secondary battery rather than the lead-acid battery.
Because the frequency of discharge from the lead-acid battery can
be decreased and the lead-acid battery has a low durability to the
frequent discharge operation, it is possible to suppress the
deterioration of the lead-acid battery.
[0024] In accordance with a second aspect of the present invention,
there is provided a power source apparatus for vehicle, which is
applied to various types of vehicles with an alternator and a
constant voltage control means. The constant voltage control means
is capable of adjusting a voltage of electric power generated by
the alternator to a set voltage. The power source apparatus has a
lead-acid battery and a secondary battery, and a rectifying means.
The lead-acid battery is electrically connected to the alternator.
The secondary battery is electrically connected in parallel to the
lead-acid battery. The secondary battery is higher in output
density or energy density than the lead-acid battery. The
rectifying means is placed between the lead-acid battery and the
secondary battery so that a forward current direction of the
rectifying means has a direction from the lead-acid battery to the
secondary battery. The rectifying means has a barrier voltage
therein to the current which flows in the forward direction through
the rectifying means. In the power source apparatus, an open
circuit voltage and an internal resistance of the lead-acid battery
and an open circuit voltage and an internal resistance of the
secondary battery are determined in order to satisfy following
conditions (a'), (b'), and (c'): [0025] (a') an equal voltage point
is present in a use range of state of charge (SOC) of the lead-acid
battery and a use range of SOC of the secondary battery, where at
the equal voltage point, the open circuit voltage of the secondary
battery becomes equal to a subtracted voltage which is obtained by
subtracting the barrier voltage of the rectifying means from the
open circuit voltage of the lead-acid battery; [0026] (b') the open
circuit voltage of the secondary battery is higher than the
subtracted voltage of the lead-acid battery at an upper limit side
from the equal voltage point in the use range of SOC of the
secondary battery; and [0027] (c') a terminal voltage of the
secondary battery when a maximum charging current flows in the
secondary battery is not more than the set voltage, where the set
voltage is set by the constant voltage control means.
[0028] A description will now be given of the above effects (a'),
(b'), and (c'), and the technical feature for the power source
apparatus according to the second aspect of the present invention
equipped with the rectifying means.
[0029] In the power source apparatus according to second aspect of
the present invention, the open circuit voltages and the internal
resistance of the lead-acid battery and the secondary battery are
determined in order to satisfy the above condition (a').
[0030] This allows that the terminal voltage Vd (Pd) (in more
detail, the subtract voltage obtained by subtracting the barrier
voltage from the terminal voltage Vd (Pb) when discharging to the
electric load placed in position at the secondary battery side
observed from the rectifying means) within the use range of SOC of
the lead-acid battery becomes approximately equal to the terminal
voltage Vd (Li) within the use range of SOC of the lithium battery.
That is, this makes it possible to have a small difference in
voltage between the lead-acid battery and the secondary battery, or
a same voltage potential between the lead-acid battery and the
secondary battery. Accordingly, this allows the battery having a
high voltage to flow a very small current to another battery having
a low voltage without using any DC/DC converter in the power source
apparatus, and it is thereby possible to prevent each of those
batteries from overcharge and over discharge. It is therefore
possible to decrease the manufacturing cost of the power source
apparatus because of not using any DC/DC converter.
[0031] In the power source apparatus according to the second aspect
of the present invention, the open circuit voltages and the
internal resistance of the lead-acid battery and the secondary
battery are determined in order to satisfy the above condition
(b'). This allows for the secondary battery having a high open
circuit voltage to discharge because the open circuit voltage V0
(Li) of the secondary battery is higher than the subtracted voltage
which is obtained by subtracting the barrier voltage from the open
circuit voltage V0 (Pb) of the lead-acid battery when the secondary
battery is more charged rather than the charged capacity at the
equal voltage point within the use range of SOC of the secondary
battery. This makes it possible to increase the frequency of
preferentially discharge from the secondary battery rather than the
lead-acid battery. Because the frequency of discharging from the
lead-acid battery can be decreased, and the lead-acid battery has a
low durability to the frequent discharge operation, the feature of
the present invention can prevent the lead-acid battery from
deterioration.
[0032] In the power source apparatus according to the second aspect
of the present invention, the open circuit voltages and the
internal resistance of the lead-acid battery and the secondary
battery are determined in order to satisfy the above condition
(c'). This can increase the frequency of preferentially charging
the secondary battery rather than the lead-acid battery by the
following reasons.
[0033] That is, because the terminal voltage Vc (Pb) (expressed by
the following formula (F2)) of an available lead-acid battery is
larger than the set voltage which is set by the constant voltage
control means when the maximum charging current flows, it would
become impossible to charge the lead-acid battery when the maximum
charging current flows.
[0034] Even when the lead-acid battery has a less residual capacity
and the terminal voltage Vc (Pb) of the lead-acid battery is lower
than the set voltage, because the lead-acid battery has a large
internal resistance value R (Pb) when the lead-acid battery is
charged, the terminal voltage Vc (Pb) of the lead-acid battery is
rapidly increased rather than the set voltage. This would be
difficult to charge the lead-acid battery.
[0035] The terminal voltage Vc of a battery during charging is
expressed by the following formula (F2): Vc=V0+Ic.times.R . . .
(F2), where Ic is a charge current, R is an internal resistance of
the battery, and V0 is an open circuit voltage of the battery.
[0036] On the other hand, in the power source apparatus according
to the second aspect of the present invention, like the first
aspect of the present invention, previously described, the terminal
voltage Vc (Li) of the secondary battery, when the maximum charging
current flows in the secondary battery, is set to a voltage which
is lower than the set voltage. In other words, because the terminal
voltage of the secondary battery is always below the set voltage
even when the terminal voltage Vc (Li) has the maximum voltage in
the use range of SOC of the secondary battery, it is possible to
always charge the secondary battery. Accordingly, this makes it
possible to increase the frequency of preferentially charging the
secondary battery rather than the lead-acid battery. Because the
frequency of discharging from the lead-acid battery is decreased
and the lead-acid battery has a low durability to the frequent
discharge operation, the present invention can prevent the
lead-acid battery from deterioration.
[0037] The horizontal line in FIG. 12B designates the SOC of the
lithium battery 30 (secondary battery), the solid line A2 in FIG.
12B denotes a voltage characteristic line which shows a
relationship between the SOC and the open circuit voltage V0 (Li)
of the lithium battery 30. The solid line A1 in FIG. 12B denotes a
voltage characteristic line which shows a relationship between the
SOC and the open circuit voltage V0 (Pb) of the lead-acid battery
20. In FIG. 13B, the position at 0% in the horizontal line showing
the SOC of the lithium battery corresponds to the point at 88% of
SOC of the lead-acid battery.
[0038] The reference character Vds shown in FIG. 12B indicates the
equal voltage point at which the open circuit voltages of the
lithium battery (secondary battery) and the lead-acid battery are
equal together when the power source apparatus without any
rectifying means, which is different from the structure of the
power source apparatus of the present invention with the rectifying
means. Because the terminal voltage Vd (Pb) of the lead-acid
battery is higher than the open circuit voltage Vd (Li) of the
secondary battery at the lower limit side from the equal voltage
point in the use range W2 (Li) of SOC of the lithium battery
(secondary battery), the lead-acid battery discharges its electric
power, and the secondary battery does not discharge. Accordingly,
it is sufficient to shift the equal voltage point Vds toward the
lower limit side in the use range W2 (Li) of SOC of the lithium
battery (secondary battery) in order to increase the frequency of
preferentially discharging from the secondary battery rather than
from the lead-acid battery.
[0039] In the above viewpoint, the power source apparatus according
to the second aspect of the present invention is equipped with the
rectifying means (which is composed of a diode, for example) in
order to shift the equal voltage point toward the lower limit side
(Vds--->Vds') by the barrier voltage Vbar, where at the equal
voltage point, the open circuit voltage of the secondary battery
becomes equal to the open circuit voltage of the lead-acid
battery.
[0040] In other words, the voltage characteristic line A1 of the
lead-acid battery is apparently shifted toward the lower limit side
as expressed by the long and dash line shown in FIG. 12B. This can
expand the upper area by the area W2d' toward the upper limit side
from the equal voltage point Vds in the use range W2 (Li) of SOC of
the lithium battery (secondary battery). This can increase the
opportunity for the lithium battery to preferentially discharge
rather than from the lead-acid battery.
[0041] The starter motor requires a larger electric power than
other electric loads mounted to vehicles when the starter motor
starts to operate. Supplying such a large electric power from the
secondary battery to the starter motor prevents the secondary
battery from being downsized because the secondary battery is in
general a higher price device than the lead-acid battery.
Accordingly, it is preferable for the lead-acid battery instead of
the lithium battery (secondary battery) to supply such a large
electric power to the starter motor of a large power
consumption.
[0042] In the above viewpoint, the power source apparatus according
to the second aspect of the present invention has the rectifying
means (such as a diode, for example) which is placed so that the
forward current direction in the rectifying direction becomes the
direction from the lead-acid battery to the secondary battery.
Accordingly, when the power source apparatus has the structure in
which the electric load (such as a starter motor) is electrically
connected with a node in the lead-acid battery side which is
opposite from the secondary battery side observed from the
rectifying means, it is possible for the rectifying means to
prevent the current supplied from the secondary battery to the
electric load such as a starter motor which requires a large
electric power.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] A preferred, non-limiting embodiment of the present
invention will be described by way of example with reference to the
accompanying drawings, in which:
[0044] FIG. 1A and FIG. 1B are block diagrams showing a schematic
electric circuit of a power source apparatus for vehicles according
to a first embodiment of the present invention;
[0045] FIG. 2A is a view showing a use range of SOC of a lead-acid
battery mounted to a vehicle with the power source apparatus
according to the first embodiment of the present invention;
[0046] FIG. 2B is a view showing a use range of SOC of a lithium
battery (secondary battery) mounted to the vehicle with the power
source apparatus according to the first embodiment of the present
invention;
[0047] FIG. 3 is a view showing a difference in I-V characteristics
between the lead-acid battery and the lithium battery in the power
source apparatus according to the first embodiment of the present
invention;
[0048] FIG. 4A shows a current change of the lead-acid battery and
the lithium battery in the elapse of time;
[0049] FIG. 4B shows a terminal voltage change of the lead-acid
battery and the lithium battery in the elapse of time;
[0050] FIG. 5 is a block diagram showing a schematic electric
circuit of a power source apparatus for vehicle according to a
second embodiment of the present invention;
[0051] FIG. 6 is a block diagram showing a schematic electric
circuit of a power source apparatus for vehicle according to a
third embodiment of the present invention;
[0052] FIG. 7 is a block diagram showing a schematic electric
circuit of a power source apparatus for vehicles according to a
fourth embodiment of the present invention;
[0053] FIG. 8 is a block diagram showing a schematic electric
circuit of a power source apparatus for vehicle according to a
fifth embodiment of the present invention;
[0054] FIG. 9 is a block diagram mainly showing a detailed
structure of the battery state detection means in the power source
apparatus according to a sixth embodiment of the present
invention;
[0055] FIG. 10 is a block diagram mainly showing a detailed
structure of the battery state detection means in the power source
apparatus according to a seventh embodiment of the present
invention;
[0056] FIG. 11A, FIG. 11B, and FIG. 11C are block diagrams showing
a schematic electric circuit of a power source apparatus for
vehicles according to an eighth embodiment of the present
invention;
[0057] FIG. 12A is a view showing a use range of SOC of a lead-acid
battery mounted to a vehicle with the power source apparatus
according to the eighth embodiment of the present invention;
[0058] FIG. 12B is a view showing a use range of SOC of a lithium
battery mounted to the vehicle with the power source apparatus
according to the eighth embodiment of the present invention;
[0059] FIG. 13 is a view showing a difference in I-V
characteristics between the lead-acid battery and the lithium
battery in the power source apparatus according to the first
embodiment of the present invention;
[0060] FIG. 14A and FIG. 14B show a change of a current and a
terminal voltage of the lead-acid battery and the lithium
battery;
[0061] FIG. 15 is a block diagram showing a schematic electric
circuit of a power source apparatus for vehicle according to a
ninth embodiment of the present invention;
[0062] FIG. 16 is a block diagram showing a schematic electric
circuit of a power source apparatus for vehicle according to a
tenth embodiment of the present invention;
[0063] FIG. 17 is a block diagram showing a schematic electric
circuit of a power source apparatus for vehicle according to an
eleventh embodiment of the present invention;
[0064] FIG. 18 is a block diagram showing a schematic electric
circuit of a power source apparatus for vehicle according to a
twelfth embodiment of the present invention;
[0065] FIG. 19 is a block diagram showing a schematic electric
circuit of a power source apparatus for vehicle according to a
thirteenth embodiment of the present invention;
[0066] FIG. 20 is a block diagram showing a schematic electric
circuit of a power source apparatus for vehicle according to a
fourteenth embodiment of the present invention; and
[0067] FIG. 21 is a block diagram showing a schematic electric
circuit of a power source apparatus for vehicle according to a
fifteenth embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0068] Hereinafter, various embodiments of the present invention
will be described with reference to the accompanying drawings. In
the following description of the various embodiments, like
reference characters or numerals designate like or equivalent
component parts throughout the several diagrams.
First Embodiment
[0069] A description will now be given of the power source
apparatus for vehicle according to the first embodiment of the
present invention with reference to FIG. 1A, FIG. 1B, FIG. 2A, FIG.
2B, FIG. 3, FIG. 4A, and FIG. 4B.
[0070] The power source apparatus according to the first embodiment
can be applied to vehicles with an internal combustion engine. For
example, the power source apparatus according to the first
embodiment can be applied to various types of vehicles equipped
with an idle reduction apparatus. The idle reduction apparatus
automatically stops the operation of the internal combustion engine
when a predetermined engine stop condition is satisfied, and then
automatically restarts the internal combustion engine when a
predetermined engine restart condition is satisfied. The idling
reduction apparatus will be referred to as the "idle stop apparatus
or idle stop function" through the following explanation.
[0071] The vehicle equipped with the power source apparatus
according to the first embodiment has a starter motor to rotate a
crank shaft of the internal combustion engine when the internal
combustion engine starts to operate. However, the vehicle in the
first embodiment does not mount any driving motor capable of
assisting the vehicle to drive
[0072] FIG. 1A and FIG. 1B are block diagrams showing a schematic
electric circuit of the power source apparatus according to the
first embodiment. As shown in FIGS. 1A and 1B, an alternator 10
(electric generator), a regulator 11 (constant voltage control
means), a lead-acid battery 20, a lithium battery 30 (secondary
battery), and electrical loads 40 such as a starter motor. The
lead-acid battery 20, the lithium battery 30, and the electrical
loads 40 are electrically connected in parallel to the alternator
10.
[0073] The alternator 10 generates electric power when receiving a
rotary energy transmitted through the crank shaft of the internal
combustion engine. Specifically, the rotor of the alternator 10
engages with the crank shaft. Rotation of the rotor of the
alternator 10 when receiving the rotary energy of the crank shaft
generates an exciting current in a rotor coil 10a of the alternator
10. The exciting current then flows in the rotor coil 10a. An
alternating current is induced in a stator coil of the alternator
10 according to the magnitude of the exciting current. A rectifier
(not shown) rectifies the induced alternating current to a direct
current. The regulator 11 adjusts the magnitude of the rectified
current which is flowing through the rotor coil 10a so as to
control a voltage of the alternator 10 generated by the induced
current to be constant (a constant voltage Vreg). This makes it
possible to suppress fluctuation of the output voltage of the
alternator 10. In the first embodiment, the constant voltage Vreg
is 14.5 V.
[0074] The electric power generated in the alternator 10 is
supplied to the electrical loads 40, and also supplied to the
lead-acid battery 20 and the lithium battery 30. During the
operation not to generate any electric power by the alternator 10
when the internal combustion engine stops, the lead-acid battery 20
and the lithium battery 30 supply the electric power to the
electrical loads 40. The power source apparatus according to the
first embodiment is equipped with a protection control means (not
shown). This protection control means controls a discharge capacity
and a charge capacity so as to keep the electric energy of the
battery within the use range of SOC (state of charge) of each
battery such as the lead-acid battery 20 and the lithium battery
30. The SOC is a residual capacity or energy in the battery. By the
way, the SOC is a ratio of a charged energy to a full charged
energy of the battery, the above discharged capacity is the
electric energy supplied from the lead-acid battery 20 and the
lithium battery 30 to the electrical loads 40, and the above
charged capacity is the electric energy supplied from the
alternator 10 to the lead-acid battery 20 and the lithium battery
30.
[0075] In the first embodiment, the alternator 10 generates the
electric power by the regenerative energy of the vehicle which is
generated when the vehicle speed is decreased. The regenerative
electric power is charged to the lead-acid battery 20 and the
lithium battery 30 (mainly charged to the lithium battery 30). Such
regenerative electric power is obtained only when the vehicle speed
is increased, for example, when the vehicle runs downhill, and a
fuel injection to the internal combustion engine is stopped.
[0076] The lead-acid battery 20 is a known usual battery.
Specifically, the lead-acid battery 20 is composed of a plurality
of cells connected in series and an electrolytic solution. Each of
the cells in the lead-acid battery 20 has a positive electrode, and
a negative electrode. Lead dioxide (PbO.sub.2) is used as the
positive electrode active material, lead (Pb) is used as the
negative electrode active material, and sulfuric acid
(H.sub.2SO.sub.4) is used as the electrolytic solution. In general,
the lead-acid battery 20 is larger in charge capacity than the
lithium battery 30.
[0077] On the other hand, the lithium battery 30 uses oxide which
contains lithium (for example, lithium metal composite oxide) as
the positive electrode active material and/or adsorbent material
(for example, activated carbon) as the positive electrode.
Specifically, LiCoO.sub.2, LiMn.sub.2O.sub.4, LiNiO.sub.2,
LiFePO.sub.4, etc. are used as the positive electrode active
material. In addition, the lithium battery 30 uses carbon,
graphite, lithium-doped carbon or graphite, lithium titanium oxide
(Li.sub.2TiO.sub.2) or alloy which contains Si or Sn as the
negative electrode active material. The lithium battery 30 contains
an organic electrolyte as electrolytic solution. Like the structure
of the lead-acid battery 20, the lithium battery 30 is composed of
a plurality of cells having the above electrodes connected in
series.
[0078] In FIG. 1A, and FIG. 1B, reference numbers 21 and 31
designate a battery cell assembly of the lead-acid battery 20 and a
battery cell assembly of the lithium battery 30, respectively, and
reference numbers 22 and 32 denote an internal resistance of the
lead-acid battery 20 and the lithium battery 30, respectively.
[0079] In the following explanation, an open circuit voltage V0 of
the battery is a voltage generated by the battery cell assemblies
21 and 31. The terminal voltages Vd and Vc of the battery are
voltages expressed by the following equation:
Vd=V0-Id.times.R (F1); and
Vc=V0+Ic.times.R (F2),
where Id is a discharge current, Ic is a charge current, R is an
internal resistance of the battery, and V0 is an open circuit
voltage of the battery.
[0080] An exciting current of the alternator 10 is flowing to the
battery having a low terminal voltage Vc when each of the lead-acid
battery 20 and the lithium battery 30 is charged by the current
generated by the alternator 10 because the lead-acid battery 20 and
the lithium battery 30 are connected in series. On the other hand,
the battery having a high terminal voltage Vd charges a current to
the electrical loads 40 when the electric power is supplied to the
electrical loads 40.
[0081] During the regenerative mode of the vehicle, it is
controlled for the terminal voltage Vd (Li) of the lithium battery
30 to become many times lower than the terminal voltage Vd (Pb) of
the lead-acid battery 20 in order to preferentially charge the
lithium battery 30 rather than the lead-acid battery 20. In
addition, during the discharging mode, it is also controlled for
the terminal voltage Vd (Li) of the lithium battery 30 to become
many times higher than the terminal of the lead-acid battery 20 in
order to preferentially discharge the electric energy from the
lithium battery 30 rather than the lead-acid battery 20.
[0082] The above control can be achieved by adjusting the open
circuit voltage V0 and the internal resistance R of each of the
lead-acid battery 20 and the lithium battery 30. That is, the open
circuit voltage V0 of the battery can be adjusted by selecting an
optimum positive electrode active material, an optimum negative
electrode active material, and an optimum electrolytic solution of
the lithium battery 30.
[0083] A description will now be given of the method of setting the
condition to satisfy the relationship of Vc (Li: Lithium
battery)<Vc (Pb: lead-acid battery) during a regenerative
generation and the condition to satisfy the relationship of Vd
(Li)>Vd (Pb) during discharge, in the power source apparatus
according to the first embodiment with reference to FIG. 2A, FIG.
2B, and FIG. 3.
[0084] FIG. 2A is a view showing the use range of SOC of the
lead-acid battery 20 mounted to the vehicle with the power source
apparatus according to the first embodiment. FIG. 2B is a view
showing the use range of SOC of the lithium battery 30 in the power
source apparatus according to the first embodiment.
[0085] In FIG. 2A, the horizontal line designates the SOC of the
lead-acid battery 20, the solid line A1 denotes a voltage
characteristic line which shows a relationship between the SOC and
the open circuit voltage V0 (Pb) of the lead-acid battery 20. As
shown in FIG. 2A, the more the SOC increases by increasing the
charged energy, the more the open circuit voltage V0 (Pb)
increases.
[0086] In FIG. 2B, the horizontal line designates the SOC of the
lithium battery 30, the solid line A2 denotes a voltage
characteristic line which shows a relationship between the SOC and
the open circuit voltage V0 (Li) of the lithium battery 30. The
more the SOC increases by increasing the charged energy, the more
the open circuit voltage V0 (Li) increases. In particular, although
the SOC increases according to the increase of the charged energy,
the slope which shows the voltage characteristic line of the
lead-acid battery 20 becomes low during a range between inflection
points P1 and P2 shown in FIG. 2A.
[0087] The overcharge state and the over discharge state of each of
the lead-acid battery 20 and the lithium battery 30 would cause a
rapid deterioration. Accordingly, it is necessary for the
protection control means, previously described, to control the
charging capacity to the lithium battery 30 and the lead-acid
battery 20, and the discharging capacity from the lead-acid battery
20 and the lithium battery 30. That is, it is necessary to use each
of the lead-acid battery 20 and the lithium battery 30 within the
use range of SOC.
[0088] The use range W1 (Pb) of SOC of the lead-acid battery 20 is
within the range of 88% to 100% of SOC. On the other hand, the use
range W2 (Li) of SOC of the lithium battery 30 is within the range
of 10% to 90% of SOC. The upper limit of the use range W2 (Li) of
SOC of the lithium battery 30 is smaller than 100%, and the lower
limit of the use range W2 (Li) of SOC of the lithium battery 30 is
larger than zero %.
[0089] Accordingly, the range of 0% to 88% of SOC of the lead-acid
battery 20 causes the rapid deterioration. FIG. 2B also shows an
expansion of the area indicated by the dotted line shown in FIG. 2A
which indicates the use range W1 (Pb) of SOC of the lead-acid
battery 20. The position of 0% of SOC of the lithium battery 30
indicated by the horizontal line in FIG. 2B corresponds to the
position of 88% of the use range W1 (Pb) of SOC of the lead-acid
battery 20.
[0090] The lithium battery 30 is set in order to obtain the voltage
characteristic A2 of the lithium battery 30 which satisfies the
following conditions (a), (b), (c), (d), and (e). Specifically, it
is possible to obtain the voltage characteristic A2 which satisfies
the conditions (a), (b), (c), (d), and (e) by selecting an optimum
combination of the positive electrode active material, the negative
electrode active material, and the solid electrolyte of the lithium
battery 30.
<Condition (a)>
[0091] There is an equal voltage point Vds at which the open
circuit voltage V0 (Pb) of the lead-acid battery 20 is equal to the
open circuit voltage V0 (Li) of the lithium battery 30 in the use
range W1 (Pb) of SOC of the lead-acid battery 20 and the use range
W2 (Li) of SOC of the lithium battery 30. This equal voltage point
Vds is present in the range of the inflection points P1 and P2,
where a slope of voltage characteristic line A2 of the lithium
battery 30 in this range is small.
<Condition (b)>
[0092] The open circuit voltage V0 (Li) of the lithium battery 30
is higher than the open circuit voltage V0 (Pb) of the lead-acid
battery 20 at the upper limit side of the equal voltage point Vds
in the use range W2 (Li) of SOC of the lithium battery 30. In more
detail, the equal voltage point Vds is present at the lower limit
side rather than the upper limit side (90%) of the use range W2
(Li) of SOC of the lithium battery 30 in order to set the equal
voltage point Vds within the range of P1 and P2. The slope of the
voltage characteristic line A2 of the lithium battery 30 is larger
than the slope of the voltage characteristic line A1 of the
lead-acid battery 20 at the upper limit side of the equal voltage
point Vds in the use range W2 (Li) of SOC of the lithium battery
30.
<Condition (c)>
[0093] The terminal voltage Vc (Li) of the lithium battery 30 when
the maximum charging current flows in the lithium battery 30 is
smaller than the constant voltage Vreg which is controlled by the
regulator 11. In other words, the terminal voltage Vc (Li) of the
lithium battery 30 is smaller than the constant voltage Vreg, which
is the terminal voltage Vc (Li) (see the solid line A3 shown in
FIG. 2B) when the lithium battery 30 is charged at the upper limit
value (90%) of the use range W2 (Li) of SOC of the lithium battery
30.
[0094] Reference character .DELTA.V shown in FIG. 2B indicates a
voltage drop part by the internal resistance 32 at the upper limit
value (90%), which corresponds to the term (Ic.times.R) in the
equation (F2), previously described.
<Condition (d)>
[0095] The open circuit voltage V0 (Li) of the lithium battery 30
is lower than the open circuit voltage V0 (Pb) of the lead-acid
battery 20 in the lower limit side from the equal voltage point Vds
in the use range W2 (Li) of SOC of the lithium battery 30. In more
detail, the equal voltage point Vds is set to a value at the upper
limit side from the lower limit side (10%) of the use range W2 (Li)
of SOC of the lithium battery 30 in order to set the equal voltage
point Vds in the range of P1 to P2.
[0096] In the range in the lower limit side observed from the equal
voltage point Vds in the use range W2 (Li) of SOC of the lithium
battery 30, the slope of the voltage characteristic line A2 of the
lithium battery 30 is larger than the slope of the voltage
characteristic line A1 of the lead-acid battery 20.
<Condition (e)>
[0097] The range in the upper limit side observed from the equal
voltage point Vds is wider than the range in the lower limit side
observed from the equal voltage point Vds in the use range W2 (Li)
of SOC of the lithium battery 30. In more detail, the equal voltage
point Vds is set to a value in the lower limit side observed from
the intermediate point between the range of P1 and p2 in order to
set the equal voltage point Vds in the range of P1 to P2. This
satisfies the relationship of Vd (Li)>Vd (Pb) in a large part in
the use range W2 (Li) of SOC of the lithium battery 30.
[0098] FIG. 3 is a view showing a difference in I-V characteristics
between the lead-acid battery 20 and the lithium battery 30 in the
power source apparatus according to the first embodiment. In FIG.
3, the solid line B1 indicates the I-V characteristic of the
lead-acid battery 20, the solid line B2 designates the I-V
characteristic of the lithium battery 30, the solid line B3 denotes
the constant voltage Vreg, the horizontal line indicates the
current value Ic and the current value Id, the vertical line
indicates the terminal voltage Vc and the terminal voltage Vd. In
FIG. 3, the current Ic during charging is expressed by a positive
value, and the current Id during discharging is expressed by a
negative value.
[0099] In the I-V characteristic B1 and the I-V characteristic B2,
the more the charging current Ic increase, the more the terminal
voltage Vc increases (Ic.times.R is increased). The more the
charging current Ic decreases, the more the terminal voltage Vc
decreases (Ic.times.R is decreased). That is, the change of the
charging current Ic is in proportion to the change of the charging
current Ic. The slope of each of the I-V characteristic B1 and the
I-V characteristic B2 indicates the internal resistance R. In
particular, the lithium battery 30 has the same internal resistance
value R (Pb) during both charging and discharging. On the other
hand, an internal resistance value R (Pb) in charging of the
lead-acid battery 20 is larger than that in discharging of the
lead-acid battery 20.
[0100] In the first embodiment, it is set to satisfy the
relationship of R (Li)<R (Pb) in charging, and to satisfy the
relationship of R (Li).ltoreq.R (Pb) in discharging. It is also set
to satisfy the relationship of Vd (Li)>Vd (Pb) in discharging,
to satisfy the relationship of Vc (Li).gtoreq.Vc (Pb) in a range
close to Ic=zero, and to satisfy the relationship of Vc (Li)<Vc
(Pb) in other part. The above setting control can be achieved by
the condition where the internal resistance value R (Li) of the
lithium battery 30 is smaller than the internal resistance value R
(Pb) of the lead-acid battery 20 in charging.
[0101] The power source apparatus having the above structure
according to the first embodiment of the present invention has the
following features (A1) to (A6).
(A1) Making the voltage characteristic A2 to satisfy the condition
(a) (the equal voltage point Vds is present in the range between
the inflection points P1 and P2) generates the state without any
large voltage difference between the lithium battery 30 and the
lead-acid battery 20 because the terminal voltage Vd (Li) in the
use range of SOC of the lithium battery 30 is approximately equal
to the terminal voltage Vd (Pb) in the use range W1 of SOC of the
lead-acid battery 20 during discharge, as shown in FIG. 2A.
[0102] Therefore even if does not use any DC/DC converter (which is
used in the conventional power source apparatus), it is possible to
prevent a current which flows from the lithium battery 30 to the
lead-acid battery 20, in other words, it is possible to flow a
current of an extremely small quantity from the lithium battery 30
to the lead-acid battery 20. The structure of the power source
apparatus according to the first embodiment can thereby suppress
the lead-acid battery 20 from being in overcharge state without any
DC/DC converter. This makes it possible to adequately reduce the
manufacturing cost of the power source apparatus because of not
using any DC/DC converter.
(A2) Making the voltage characteristic A2 to satisfy the condition
(b) (the relationship of Vd (Li)>Vd (Pb) at the upper limit side
observed from the equal voltage point Vds) to the voltage
characteristic A1 allows the lithium battery 30 to discharge a
current, for example, to the electric load 43 which requires a
constant voltage, because the open circuit voltage of the lithium
battery 30 is higher than that of the lead-acid battery 20, in the
state where the lithium battery 30 is higher charged than the equal
voltage point Vds in the use range W2 (Li) of SOC of the lithium
battery 30.
[0103] Because this condition increases the frequency of
discharging a current from the lithium battery 30 when compared
with from the lead-acid battery 20 and decreases the frequency of
discharging a current from the lead-acid battery 20 with a low
durability to frequent discharging, this makes it possible to
suppress the deterioration of the lead-acid battery 20.
(A3) Making the voltage characteristic A2 to satisfy the condition
(c) (Vc (Li)<Vreg when the maximum charging current flows) to
the voltage characteristic A1 can increase the frequency of
charging the lithium battery 30 rather than the lead-acid battery
20 by the following reasons.
[0104] In the case of charging the lead-acid battery 20 with the
regenerative energy without using the lithium battery 30, because
the internal resistance 22 of the lead-acid battery 20 is larger
than that of the lithium battery 30, as shown in FIG. 3, the
terminal voltage Vc (Pb) of the lead-acid battery 20 reaches the
constant voltage Vreg at the point when the charging current
reaches the current value Ia. On the other hand, the structure of
the power source apparatus equipped with the lithium battery 30
satisfies the relationship of Vc (Li)<Vreg even when the
charging current has the maximum value, it is possible to further
charge the lithium battery 30.
[0105] In the example shown in FIG. 3, the terminal voltage Vc (Li)
of the lithium battery 30 reaches the constant voltage Vreg when
the charging current reaches the current value Ib which is larger
than the maximum charging current Imax.
[0106] This will be explained in detail with reference to FIG. 4A
and FIG. 4B. FIG. 4A shows a current change of the lead-acid
battery 20 and the lithium battery 30 in the elapse of time. FIG.
4B shows a terminal voltage change of the lead-acid battery 20 and
the lithium battery 30 in the elapse of time. In FIG. 4A and FIG.
4B, the solid lines C1 and D1 indicate the change of the charging
current and the terminal voltage Vc (Pb) when the lead-acid battery
20 is charged with the regenerative electric power at the maximum
charging current Imax without using the lithium battery 30. The
solid lines C2 and D2 in FIG. 4A and FIG. 4B show the change of the
charging current and the change of the terminal voltage Vc (Li),
respectively, when the lithium battery 30 is charged with the
regenerative electric power at the maximum charging current Imax in
the power source apparatus according to the first embodiment.
[0107] As previously explained with reference to FIG. 3, because
the relationship of Imax>Ia is satisfied when the lead-acid
battery 20 is charged with the regenerative electric power, the
charging current rapidly drops at the timing t1 and converges
toward zero, as shown in FIG. 4A. This state would be difficult to
charge the lead-acid battery 20. In this case, the area designated
by slanting lines in FIG. 4A corresponds to the charged capacity of
the lead-acid battery 20.
[0108] On the other hand, because the relationship of
Imax.ltoreq.Ib is satisfied when the lithium battery 30 is charged
with the regenerative electric power, the charging current
maintains the value Imax until the timing t2 where the SOC of the
lithium battery 30 reaches the upper limit value (90%). This allows
the lithium battery 30 to be usually charged and to increase its
changeable capacity.
[0109] As described above, according to the first embodiment of the
present invention, it is possible to increase the frequency to
charge the lithium battery 30 rather than the frequency to charge
the lead-acid battery 20. This can decrease the accumulated charged
capacity of the lead-acid battery 20 which has a low durability,
and suppress the deterioration of the lead-acid battery 20.
(A4) Making the voltage characteristic A2 to satisfy the condition
(d) (Vd (Li)<Vd (Pb) at the lower limit side observed from the
equal voltage point Vds) to the voltage characteristic A1 allows
the lead-acid battery 20, instead of the lithium battery 30, to
discharge the electric power to the electrical loads 40 when the
lithium battery 30 preferentially discharge the electric power to
the electric load 40 and the SOC of the lithium battery 30 is lower
than the equal voltage point Vds.
[0110] Further, the current flows from the lead-acid battery 20 to
the lithium battery 30, this increases the SOC of the lithium
battery 30 toward the equal voltage point Vds. As a result, it is
possible to suppress the lithium battery 30 from over
discharge.
(A5) Making the voltage characteristic A2 to satisfy the condition
(e) to the voltage characteristic A1 allows the range to satisfy
the relationship of Vd (Li)>Vd (Pb) based on the condition (b),
where the condition (e) satisfies that the range in the upper limit
side observed from the equal voltage point Vds is wider in area
than the range in the lower limit side observed from the equal
voltage point Vds. This makes it possible to increase the frequency
of preferentially discharging from the lithium battery 30 rather
than from the lead-acid battery 20. This makes it possible to
increase the deterioration resistance of the lead-acid battery 20.
(A6) Adding the lithium battery 30 which satisfies the conditions
(a) to (e) into a power source apparatus which is comprised of the
alternator 10, the regulator 11, and the lead-acid battery 20 makes
it possible to obtain the features of the present invention,
previously described without using any DC/DC converter. It is
possible to realize the power source apparatus according to the
first embodiment of the present invention in a conventional power
source apparatus with a less change in hardware design.
Second Embodiment
[0111] A description will be given of the power source apparatus
according to the second embodiment of the present invention with
reference to FIG. 5. FIG. 5 is a block diagram showing a schematic
electric circuit of the power source apparatus according to the
second embodiment.
[0112] In the structure of the power source apparatus according to
the second embodiment shown in FIG. 5, the lithium battery 30
supplies the electric power to electrical loads 43 which require an
approximate constant voltage or a voltage which is changed within
at least a predetermined voltage range. For example, there are a
navigation system and an audio system as the electrical loads 43
mounted to vehicles. When the power source apparatus supplies
electric power, a voltage of which is fluctuated, not constant, or
changed out from a predetermined allowable range, and when the
voltage of the electric power temporarily drops below a minimum
operation voltage, the navigation system and/or audio system as the
electric load 43 are reset in operation. This would cause various
problems. In order to avoid this, it is necessary for the power
source apparatus to supply the voltage of the electric power which
is an approximate constant voltage which is larger than the minimum
operation voltage.
[0113] On the other hand, the lead-acid battery 20 supplies the
electric power to the starter motor 41 and usual electrical loads
42 such as a defroster heater for a rear window, and a ventilation
fan for an air conditioner system. The starter motor 41 requires a
large electric power when compared with the electrical loads 42 and
43. When the lead-acid battery 20 supplies such a large electric
power to the starter motor 41, the terminal voltage Vd (Pb) of the
lead-acid battery 20 rapidly drops.
[0114] However, the structure of the power source apparatus
according to the second embodiment has the electromagnetic relay 50
to open and close the electric connection between the lithium
battery 30 and the starter motor 41 in order to avoid the rapid
drop of the terminal voltage Vd (Li) of the lithium battery 30.
Specifically, while the lead-acid battery 20 supplies the electric
power to the starter motor 41, the electromagnetic relay 50 is
opened in order to avoid the voltage drop of the lithium battery
30. This makes it possible for the lithium battery 30 to supply a
stable electric power, a voltage of which is slightly changed
within a predetermined voltage range, to the electrical loads
43.
[0115] When the lead-acid battery 20 does not store an adequate
capacity to start the starter motor 41, it is possible to turn on
the electromagnetic relay 50 to supply the electric power to the
starter motor 41. That is, when the lead-acid battery 20 has a low
SOC, it is controlled so that the lithium battery 30 rather than
the lead-acid battery 20 preferentially supplies the electric power
to the starter motor 41.
[0116] As described above, the power source apparatus according to
the second embodiment of the present invention has the following
effect (7) in addition to the effects (1) to (6), previously
described in the first embodiment. (7) The lithium battery 30
supplies the electric power to the electrical loads 43 which
require an approximate constant voltage or a stable voltage which
is changed within the predetermined voltage range, and the
lead-acid battery 20 supplies the electric power to the starter
motor 41. While the lead-acid battery 20 supplied the electric
power to the starter motor 41, the electromagnetic relay 50
operates to open. This makes it possible to supply to the
electrical loads 43 the electric power whose voltage has a small
fluctuation in voltage.
Third Embodiment
[0117] A description will be given of the power source apparatus
according to the third embodiment of the present invention with
reference to FIG. 6. FIG. 6 is a block diagram showing a schematic
electric circuit of the power source apparatus according to the
third embodiment of the present invention.
[0118] The power source apparatus according to the third embodiment
has a protection control means 60 which controls the charging
capacity to and discharging capacity from the lithium battery 30 in
order to avoid the overcharging to the lithium battery 30 and the
over discharging from the lithium battery 30.
[0119] The protection control means 60 always receives detection
signals regarding the terminal voltages Vc and Vd or the open
circuit voltage V0 (Li) of the lithium battery 30, and a detection
signal transferred from a current detection means 61 which detects
a current flowing in the lithium battery 30.
[0120] The protection control means 60 instructs the
electromagnetic relay 50 to open (voltage drop suppression
operation) when the terminal voltage Vd of the lithium battery 30
during discharging becomes below the lower limit voltage. This
control protects the lithium battery 30 from over discharge. It is
possible to set the lower limit voltage based on a voltage which
corresponds to the lower limit SOC value (10%) shown in FIG.
2B.
[0121] When the terminal voltage Vc of the lithium battery 30
during charge exceeds the upper limit voltage, the protection
control means 60 instructs the electromagnetic relay 50 to open
(voltage rise suppression operation). This control protects the
lithium battery 30 from over charging. It is possible to set the
upper limit voltage based on a voltage which corresponds to the
upper limit SOC value (90%) shown in FIG. 2B.
[0122] The protection control means 60 further outputs an
instruction signal to the regulator 11 to change the constant
voltage Vreg of the regulator 11 according to the voltage of the
lithium battery 30. This makes it possible to prevent or protect
the lithium battery 30 from overcharge and over discharge.
[0123] That is, the protection control means 60 instructs the
regulator 11 to increase the constant voltage Vreg when the voltage
of the lithium battery 30 becomes lower than the lower limit value.
This increases the charging capacity to the lithium battery 30 and
protects the lithium battery 30 from over discharge.
[0124] On the other hand, the protection control means 60 instructs
the regulator 11 to decrease the constant voltage Vreg when the
voltage of the lithium battery 30 exceeds the upper limit value.
This suppresses the charging capacity to the lithium battery 30,
and protects the lithium battery 30 from overcharge.
[0125] As describe above, the power source apparatus according to
the third embodiment of the present invention reliably avoids the
lithium battery 30 from over discharge because the protection
control means 60 instructs the electromagnetic relay 50 to open
when the terminal voltage of the lithium battery 30 becomes lower
than the use range W2 (Li) of the lithium battery 30 in addition
during the supply of the electric power to the starter motor
41.
[0126] Further, the power source apparatus according to the third
embodiment of the present invention can reliably avoid the lithium
battery 30 from overcharge because the protection control means 60
instructs the electromagnetic relay 50 to open.
[0127] Because the power source apparatus according to the third
embodiment of the present invention performs the over discharge and
overcharge protection operation by changing the constant voltage
Vreg by the protection control means 60. This can precisely control
the voltage of the lithium battery 30, and this makes thereby it
possible to perform the over discharge protection and the
overcharge protection for the lithium battery 30 with high
accuracy.
Fourth Embodiment
[0128] A description will be given of the power source apparatus
according to the fourth embodiment of the present invention with
reference to FIG. 7. FIG. 7 is a block diagram showing a schematic
electric circuit of a power source apparatus according to the
fourth embodiment.
[0129] In the third embodiment previously described, the power
source apparatus has the protection control means 60 to protect the
lithium battery 30 from overcharge and over discharge.
[0130] On the other hand, the protection control means 60 in the
power source apparatus of the fourth embodiment further performs
the overcharge operation and the over discharge operation for the
lead-acid battery 20 in addition to the function of the third
embodiment.
[0131] That is, the protection control means 60 instructs the
regulator 11 to increase the constant voltage Vreg when the voltage
of the lead-acid battery 20 becomes under the lower limit voltage.
This performs the over discharge operation of the lead-acid battery
20. On the other hand, the protection control means 60 instructs
the regulator 11 to decrease the constant voltage Vreg when the
voltage of the lead-acid battery 20 exceeds the upper limit
voltage. This performs the overcharge operation of the lead-acid
battery 20.
[0132] As describe above, the power source apparatus according to
the fourth embodiment of the present invention correctly changes
the constant Vreg according to the voltage of the lead-acid battery
20, in addition to changing the constant voltage Vreg according to
the voltage of the lithium battery 30. This can precisely control
the voltage of the lead-acid battery 20 in addition to the voltage
of the lithium battery 30, and makes thereby it possible to perform
the over discharge protection and the overcharge protection for the
lead-acid battery 20 as well as the lithium battery 30 with high
accuracy.
Fifth Embodiment
[0133] A description will be given of the power source apparatus
according to the fifth embodiment of the present invention with
reference to FIG. 8. FIG. 8 is a block diagram showing a schematic
electric circuit of the power source apparatus according to the
fifth embodiment.
[0134] The power source apparatus according to the fifth embodiment
has a plurality of the lithium batteries 30. In the structure of
the power source apparatus according to the fifth embodiment, the
electric power is supplied from the different lithium batteries 30
to various types of the electric loads 43, 44, and 45, where the
electrical loads 43 requires an approximate constant voltage or a
stable voltage which is changed within the predetermined voltage
range, the electric loads 44 requires a large electric power, and
the electric load 45 requires a voltage in order to reliably
operate when an emergency occurs.
[0135] Specifically, there is an electric motor mounted to a power
steering apparatus as one example of the electric load 44 which
requires a large electric power. The electric load 44 can operate
by some fluctuating voltage, which is different from the electrical
loads 43 which require an approximate constant voltage, previously
described.
[0136] There is a communication apparatus as one example of the
electric load 45 which requires a certain operation when an
emergency occurs. This communication apparatus transmits
abnormality information to a repair operator in a car dealership to
diagnose and repair the vehicle, for example, when the internal
combustion engine mounted to the vehicle has a failure and does not
start. Therefore it is not necessary for such a type of the
electric load 44 to use a large electric power and a constant
voltage.
[0137] The power source apparatus according to the fifth embodiment
shown in FIG. 8 has a plurality of the electromagnetic relays 50,
battery state detection means 70, and the current detection means
61, like the power source apparatus shown in FIG. 6. That is, the
electromagnetic relay 50, the battery state detection means 70, and
the current detection means 61 are placed every lithium battery
30.
[0138] The battery state detection means 70 always detects the
terminal voltages Vc, Vd or the open circuit voltage V0 (Li) of the
lithium battery 30, and a current flowing through the lithium
battery 30. The battery state detection means 70 then transfers the
detection signals to the protection control means 60. The
protection control means 60 receives the detection signals
transferred from the battery state detection means 70, and performs
the overcharge control and the over discharge control by using the
electromagnetic relay 50, and also performs the overcharge and over
discharge protection control by adjusting the constant voltage
Vreg, like the protection control means 60 shown in FIG. 6.
[0139] As describe above, the power source apparatus according to
the fifth embodiment of the present invention has a plurality of
the lithium batteries 30. The lithium batteries 30 correspond to
the electrical loads, respectively. This structure makes it
possible to suppress the deterioration of each of the lithium
batteries 30. In particular, because the electric load 45 for
emergency has the dedicated lithium battery 30, it is possible to
suppress the deterioration of the lithium battery 30 and to avoid
the risk of not supplying the electric power to the electric load
45.
Sixth Embodiment
[0140] A description will be given of the power source apparatus
according to the sixth embodiment of the present invention with
reference to FIG. 9. FIG. 9 is a block diagram mainly showing a
detailed structure of the battery state detection means 70 in the
power source apparatus shown in FIG. 8.
[0141] The battery state detection means 70 is comprised of a cell
voltage switch means 71, a battery state detection control means
72, a temperature detection means 73, and a cell equalizing means
74. The cell voltage switch means 71, the battery state detection
control means 72, the temperature detection means 73, and the cell
equalizing means 74 serve as equalizing means.
[0142] The cell voltage switch means 71 detects the voltage of each
of a plurality of the battery cells 33 which form the lithium
battery 30. The cell voltage switch means 71 has a function to
select one of the battery cells 33 in order to detect its voltage.
The cell voltage switch means 71 detects the voltage of the
selected battery cell and then transfers the detected voltage value
to the battery state detection control means 72. The battery state
detection control means 72 also receives a detected current value
of the current which flows in the lithium battery 30. The battery
state detection control means 72 further receives a temperature
value of the lithium battery 30 detected by the temperature
detection means 73.
[0143] The battery state detection control means 72 calculates the
terminal voltages Vc, Vd or the open circuit voltage V0 (Li) of the
lithium battery 30 based on the voltage of each of the battery
cells 33. The battery state detection control means 72 transfers
the calculated voltage, the current value of the lithium battery
30, and the temperature value of the lithium battery 30 to the
protection control means 60 through the communication interface 75.
The protection control means 60 receives the information such as
the above voltage value, the current value, and the temperature
value transferred from the battery state detection control means
72, and performs the protection control based on the received
information.
[0144] The battery state detection control means 72 calculates a
discharge capacity from the battery cell 33 having a high SOC, and
a charge capacity to the battery cell 33 having a low SOC based on
the received voltage value of the battery cell 33. The battery
state detection control means 72 outputs an equalizing instruction
signal corresponding to the calculation result to the cell
equalizing means 74. When receiving the equalizing instruction
signal, the cell equalizing means 74 instructs each of the battery
cells 33 to discharge or charge based on the received equalizing
instruction signal in order to equalize the SOC (state of charge as
a residual capacity) in each of the battery cells 33.
[0145] As describe above, the power source apparatus according to
the sixth embodiment of the present invention can equalize the SOC
in each of the battery cells 33. This makes it possible to avoid
the presence of the overcharged battery cells 33 and the battery
cells having an adequate SOC during charging. Like this, it is also
possible to avoid the presence of the over discharged battery cells
33 and the battery cells having an adequate SOC during discharging.
The power source apparatus according to the sixth embodiment can
suppress the advance of deterioration of the lithium battery
30.
Seventh Embodiment
[0146] A description will be given of the power source apparatus
according to the seventh embodiment of the present invention with
reference to FIG. 10.
[0147] In the power source apparatus according to the sixth
embodiment previously described shown in FIG. 9, the cell voltage
switch means 71 and the battery state detection control means 72
are formed with different circuit parts. The power source apparatus
according to the seventh embodiment has a single IC 710 (integrated
circuit as cell equalizing abnormal detection means) which is
composed of the cell voltage switch means 71 and the cell
equalizing means 74.
[0148] FIG. 10 is a block diagram mainly showing a detailed
structure of the battery state detection means 70 comprised of the
single IC chip 710 in the power source apparatus according to the
seventh embodiment.
[0149] The cell equalizing abnormal detection means 710 detects the
voltage of each of the battery cells 33, and calculates the
charging capacity to or discharging capacity from each of the
battery cells 33 based on the detected voltage. The cell equalizing
abnormal detection means 710 equalizes the residual capacity of
each of the battery cells 33 by charging and discharging each of
the battery cells 33 based on the calculation result.
[0150] The cell equalizing abnormal detection means 710 further
detects whether or not the detected voltage of each of the battery
cells 33 is within a predetermined normal range in order to detect
the abnormality of each of the cell batteries 33. When receiving an
abnormal diagnosis instruction signal transferred from the battery
state detection control means 72, the cell equalizing abnormal
detection means 710 starts to perform the abnormal detection
operation previously described, and transfers the detection result
to the battery state detection control means 72.
[0151] A voltage down means 76 decreases the voltage of the lithium
battery 30 to a voltage of not more than 5 V, with which a
microcomputer can operate. Such a voltage signal decreased by the
voltage down means 76 is transferred to the battery state detection
control means 72, and then further transferred to the protection
control means 60 through the communication interface 75.
[0152] As described above, the power source apparatus according to
the seventh embodiment of the present invention has the effect to
perform the abnormal detection operation for each of the battery
cells 33 in addition to have the same effects of the power source
apparatus according to the sixth embodiment.
(Other Modifications)
[0153] The present invention is not limited by the first to seventh
embodiments previously described. It is possible to have the
following structures or to selectively combine the structures of
the first to seventh embodiments.
[0154] For example, it is possible to use a semiconductor switch
such as MOSFET and IGBT or a manual switch instead of the
electromagnetic relay 50. Such a semiconductor switch has a
superior response function and superior durability when compared
with the electromagnetic relay 50, but is generally a high
price.
[0155] It is also possible to use a combination of a diode and a
resistance instead of using the electromagnetic relay 50 which has
a switching mechanism to connect the lithium battery 30 with the
starter motor 41, and to disconnect the electrical connection
between the lithium battery 30 and the starter motor 41. The
combination of the diode and the resistance can suppress the
current which flows to the starter motor 41 from the lithium
battery 30 in order to suppress the voltage drop of the lithium
battery 30.
[0156] Although each of the first to seventh embodiments uses the
lithium battery 30 having the voltage characteristic A2 composed of
non-aqueous electrolyte, it is possible to use a nickel battery
composed of nickel compound, instead of using the lithium battery
30, unless it satisfies at least the conditions (a) to (c),
previously described.
[0157] In each of the first to seventh embodiments, the equal
voltage point Vds is present at the upper limit side observed from
the lower limit value (10%) in the use range W2 (Li) of SOC of the
lithium battery 30. However, the concept of the present invention
is not limited by this. For example, it is possible to set the
equal voltage point Vds to the lower limit value.
[0158] In each of the first to seventh embodiments, the vehicles
with the power source apparatus have the regenerative function.
However, the concept of the present invention is not limited by
this. For example, it is possible to apply the power source
apparatus to vehicles without the regenerative function. By the
way, because the vehicle having the regenerative function has a
high frequency to charge the regenerative energy to the battery, it
is possible to show the feature of the present invention to
suppress the deterioration of the lead-acid battery 20 by reducing
the accumulated charged capacity in the lead-acid battery 20 with a
low durability.
Eighth Embodiment
[0159] A description will now be given of the power source
apparatus according to the eighth embodiment of the present
invention with reference to FIG. 11A, FIG. 11B, FIG. 11C, FIG. 12A,
FIG. 12B, FIG. 13; and FIG. 14A, and FIG. 14B.
[0160] The power source apparatus according to the eighth
embodiment can be applied to various types of vehicles with an
internal combustion engine. For example, the power source apparatus
according to the eighth embodiment can be applied to a vehicle
equipped with an idle reduction apparatus. The idle reduction
apparatus automatically stops the operation of the internal
combustion engine when a predetermined engine stop condition is
satisfied, and also automatically restarts the internal combustion
engine when a predetermined engine restart condition is satisfied,
as previously described. The idling reduction apparatus will be
referred to as the "idle stop apparatus or idle stop function"
through the following explanation.
[0161] In the eighth embodiment, the vehicle equipped with the
power source apparatus has a starter motor to rotate a crank shaft
of the internal combustion engine when the internal combustion
engine starts to operate. However, the vehicle does not mount any
driving motor capable of assisting the vehicle to drive.
[0162] FIG. 11A, FIG. 11B, and FIG. 1C are block diagrams showing a
schematic electric circuit of the power source apparatus for
vehicle according to the eighth embodiment. As shown in FIG. 11A,
FIG. 11B, and FIG. 11C, the alternator 10 (electric generator), the
regulator 11 (constant voltage control means), the lead-acid
battery 20, the lithium battery 30 (secondary battery), and various
types of electrical loads 41, 42, and 43, and a MOS FET 50' (open
and close means, rectifying means). The lead-acid battery 20, the
lithium battery 30, and the electrical loads 41, 42, and 43 are
electrically connected in parallel to the alternator 10.
[0163] The MOS FET 50' is placed between the lithium battery 30 and
a connection node which connects the alternator 10 with the
lead-acid battery 20. The MOS FET 50' serves as the open and close
means to close (ON) and open (OFF) the electric connection between
the lithium battery 30 and the connection node which connects the
alternator 10 with the lead-acid battery 20.
[0164] The MOS FET 50' also serves as the rectifier means in views
of its structure. That is, the internal circuit of the MOS FET 50'
is equivalent to a circuit in which a semiconductor switch part 52
(open and close control means) and a parasitic diode 51 connected
in parallel. The open and close control means 601 generates and
transfers an control signal to the gate of the semiconductor switch
part 52. That is, the open and close control means 601 controls to
switch ON operation (close) and OFF operation (open) of the MOS FET
50'.
[0165] The electric load 43 in the electric loads 41 to 43 requires
a constant voltage or a stable voltage which is changed within a
predetermined voltage range. The electric load 43 is connected to
the lithium battery 30 side observed from the MOS FET 50'. This
structure allows the lithium battery 30 to supply electric power to
the electric load 43 (see the solid arrow mark at right side in
FIG. 11B and FIG. 11C).
[0166] For example, there are a navigation system and an audio
system as the electrical load 43, for example, mounted to vehicles.
When the power source apparatus supplies electric power, a voltage
of which is fluctuated, not constant, or changed out from a
predetermined voltage range, and when the voltage of the electric
power temporarily drops below a minimum operation voltage, the
navigation system and/or audio system as the electric load 43 are
reset in operation. This would cause various problems. In order to
avoid these problems, it is necessary for the power source
apparatus to supply the electric power, a voltage of which must be
an approximate constant voltage which is larger than the minimum
operation voltage.
[0167] On the other hand, the electric load 41 is a starter motor
to start the operation of the internal combustion engine. The
electric load 42 is a usual electrical load such as a defroster
heater for a rear window and a ventilation fan for an air
conditioner system. The starter motor 41 and the electric load 42
are connected to the lead-acid battery 20 side observed from the
MOS FET 50'. That is, the lead-acid battery 20 supplies electric
power to the starter motor 41 and the usual electric load 42 (see
the solid arrow line at left side in FIG. 11B and the outline arrow
mark at left side in FIG. 11C).
[0168] The starter motor 41 requires a large electric power when
compared with other electrical loads 42 and 43. When the lead-acid
battery 20 supplies such a large electric power to the starter
motor 41, the terminal voltage Vd (Pb) of the lead-acid battery 20
rapidly drops.
[0169] However, the structure of the power source apparatus
according to the eighth embodiment has the MOS FET 50' to open and
close the electric connection between the lithium battery 30 and
the starter motor 41 in order to avoid the rapid drop of the
terminal voltage Vd (Li) of the lithium battery 30. Specifically,
while the lead-acid battery 20 supplies the electric power to the
starter motor 41, the MOS FET 50' is switched in order to prevent
the voltage drop of the lithium battery 30. This makes it possible
for the lithium battery 30 to supply electric power, a voltage of
which is slightly changed within a predetermined voltage range, to
the electrical loads 43.
[0170] When the lead-acid battery 20 does not store an adequate
capacity to start the starter motor 41, it is possible to turn on
the MOS FET 50' to supply the electric power to the starter motor
41. That is, when the lead-acid battery 20 has a low SOC, it is
controlled so that the lithium battery 30 rather than the lead-acid
battery 20 preferentially supplies the electric power to the
starter motor 41. In the example shown in FIG. 11A, FIG. 11B, and
FIG. 11C, the usual electric load 42 is electrically connected to
the lead-acid battery 20 side observed in position from the MOS FET
50'. However, it is also possible to electrically connect the usual
electric load 42 with the lithium battery 30 in order for the
lithium battery 30 to supply a part of the electric power which is
required by the electric load 42.
[0171] The open and close control means 601 instructs the MOS FET
50' to open (to be turned off) during the ordinary mode, but,
instructs it to close (to be turned on) in order to charge the
lithium battery 30 with a large current, and to discharge the
electric capacity of the lithium battery 30 to the lead-acid
battery 20 (see FIG. 11A). For example, the open and close control
means 601 instructs the MOS FET 50' to be turned on in order to
efficiently charge the lithium battery 30 with a large current of
regenerative electric power generated when the vehicle speed is
decreased, or in order to charge the lead-acid battery 20 from the
lithium battery 30 when the lead-acid battery 20 is in the
overcharged state based on information such as the SOC of the
lead-acid battery 20 and the vehicle speed.
[0172] During the turned-off state of the MOS FET 50', the
parasitic diode 51 rectifies the charging current which flows to
the lithium battery 30 or discharging current which flows from the
lithium battery 30. That is, during the off state of the MOS FET
50', the current can flow from the alternator 10 or the lead-acid
battery 20 to the lithium battery 30, but cannot flow from the
lithium battery 30 to the alternator 10 or the lead-acid battery 20
(see FIG. 11C).
[0173] Because the parasitic diode 51 has a barrier voltage Vbar
(which is a voltage required to cause an electric conduction at a
connection part between two different materials such as p-n
junction), a voltage drop is generated in the electric power
flowing through the parasitic diode 51 by the barrier voltage Vbar.
Therefore, a current flows to the lithium battery 30 through the
parasitic diode 51. The lithium battery 30 is thereby charged when
the terminal voltage Vd (Li) when the lithium battery 30 is not
more than a difference voltage obtained by subtracting the barrier
voltage Vbar from the voltage of the electric power generated by
the alternator 10 or the terminal voltage Vd (Pb) of the lead-acid
battery 20 when the MOS FET 50' is turned off.
[0174] Under the turned off state of the MOS FET 50' when the
lithium battery 30 is charged with the regenerative electric power
which is regenerated by the alternator during the deceleration of
the vehicle, a large current flows to the lithium battery 30
(secondary battery) through the parasitic diode 51. This causes a
large energy loss when the generated current flows through the
parasitic diode 51.
[0175] In order to avoid such the large energy loss in the
parasitic diode 51, the power source apparatus according to the
eighth embodiment instructs the MOS FET 50' to be turned on when
the lithium battery 30 is charged with the regenerative energy
generated by the alternator when the vehicle speed is decreased
(see FIG. 11C). This control operation of the power source
apparatus allows the current of the regenerative electric power to
flow into the lithium battery 30 by bypassing it through the
parasitic diode 51. This eliminates the energy loss generated in
the parasitic diode 51. That is, it is possible to avoid the energy
loss generated by the alternator 10.
[0176] The power source apparatus according to the eighth
embodiment instructs the MOS FET 50' to be turned on in order to
charge the lead-acid battery 20 with the electric power (electric
capacity) from the lithium battery 30, for example, when the
lead-acid battery 20 has not an adequate capacity to supply the
electric power to the usual electric load 42 and the starter motor
41 (see dotted arrow lines shown in FIG. 11B).
[0177] The control to turn on the MOS FET 50' when the terminal
voltage Vd (Pb) of the lead-acid battery 20 is lower than the
terminal voltage Vd (Li) of the lithium battery 30 makes it
possible to supply the electric power from the lithium battery 30
to the lead-acid battery 20, and to the usual electric load 42 and
the starter motor 41.
[0178] The alternator 10 generates electric power when receiving a
rotary energy transmitted through the crank shaft of the internal
combustion engine. Specifically, the rotor of the alternator 10
engages with the crank shaft. Rotation of the rotor of the
alternator 10 when receiving the rotary energy of the crank shaft
generates an exciting current in a rotor coil 10a of the alternator
10. The exciting current then flows in the rotor coil 10a. An
alternating current is thereby induced in a stator coil of the
alternator 10 according to the magnitude of the exciting current. A
rectifier (not shown) rectifies the induced alternating current to
a direct current. The regulator 11 adjusts the magnitude of the
rectified current which is flowing through the rotor coil 10a so as
to control a voltage of the alternator 10 generated by the induced
current to be constant (a constant voltage Vreg). This makes it
possible to suppress fluctuation of the output voltage of the
alternator 10. In the eighth embodiment, the constant voltage Vreg
is 14.5 V.
[0179] The electric power generated in the alternator 10 is
supplied to the electrical loads 41, 42, and 43, and also supplied
to the lead-acid battery 20 and the lithium battery 30. During the
operation not to generate any electric power in the alternator 10
when the internal combustion engine stops, the lead-acid battery 20
and the lithium battery 30 supply the electric power to the
electrical loads 41, 42, and 43. The power source apparatus
according to the eighth embodiment is equipped with a protection
control means (not shown). This protection control means controls a
discharged capacity and a charged capacity so as to keep the
electric energy of the battery within the use range of SOC (state
of charge) of the battery such as the lead-acid battery 20 and the
lithium battery 30, where the SOC is a ratio of a charged energy to
a full charged energy of the battery, the above discharged capacity
is the electric capacity supplied from the lead-acid battery 20 and
the lithium battery 30 to the electrical loads 41, 42, and 43, and
the above charged capacity is the electric energy supplied from the
alternator 10 to the lead-acid battery 20 and the lithium battery
30.
[0180] In the eighth embodiment, the alternator 10 generates the
electric power by the regenerative energy of the vehicle which is
generated when the vehicle speed is reduced. The regenerative
electric power is charged to the lead-acid battery 20 and the
lithium battery 30 (mainly to the lithium battery 30). Such a
regenerative electric power is obtained only when the vehicle speed
is reduced in the deceleration state and a fuel injection to the
internal combustion engine is stopped.
[0181] The lead-acid battery 20 is a known usual battery.
Specifically, the lead-acid battery 20 is composed of a plurality
of cells connected in series and an electrolytic solution. Each of
the cells in the lead-acid battery 20 has a positive electrode, and
a negative electrode. Lead dioxide (PbO.sub.2) is used as the
positive electrode active material, lead (Pb) is used as the
negative electrode active material, and sulfuric acid
(H.sub.2SO.sub.4) is used as the electrolytic solution. In general,
the lead-acid battery 20 is larger in charging capacity than the
lithium battery 30.
[0182] On the other hand, the lithium battery 30 uses oxide
containing lithium (for example, lithium metal composite oxide) as
the positive electrode active material and/or adsorption material
(for example, activated carbon) as the positive electrode.
Specifically, LiCoO.sub.2, LiMn.sub.2O.sub.4, LiNiO.sub.2,
LiFePO.sub.4, etc. are used as the positive electrode active
material. Further, the lithium battery 30 uses carbon, graphite,
lithium-doped carbon or graphite, lithium titanium oxide (for
example, Li.sub.2TiO.sub.2), or alloy which contains Si or Sri as
the negative electrode active material. The lithium battery 30
contains an organic electrolyte as electrolytic solution. Like the
structure of the lead-acid battery 20, the lithium battery 30 is
composed of a plurality of cells having the above electrodes
connected in series. In particular, the eighth embodiment uses
lithium titanium oxide as the negative electrode active material in
the lithium battery 30.
[0183] In FIG. 11A, FIG. 11B, and FIG. 11C, reference numbers 21
and 31 designate a battery cell assembly of the lead-acid battery
20 and a battery cell assembly of the lithium battery 30,
respectively, and reference numbers 22 and 32 indicate an internal
resistance of the lead-acid battery 20 and the lithium battery 30,
respectively.
[0184] In the following explanation, an open circuit voltage V0 of
the battery is a voltage generated by the battery cell assemblies
21 and 31. The terminal voltages Vd and Vc of the battery are
voltages expressed by the following equation:
Vd=V0-Id.times.R (F1); and
Vc=V0+Ic.times.R (F2),
where Id is a discharging current, Ic is a charging current, R is
an internal resistance of the battery, and V0 is an open circuit
voltage of the battery.
[0185] As shown in the equations (F1) and (F2), the more the
internal resistance R increases, the more the terminal voltage Vd
of the battery decreases when the battery discharges its capacity.
Further, the more the internal resistance R increases, the more the
terminal voltage Vc of the battery increases when the battery is
charged.
[0186] Because the lead-acid battery 20 and the lithium battery 30
are connected in parallel, as shown in FIG. 11A, the induced
current generated in the alternator 10 flows into the battery with
a low terminal voltage during charging. On the other hand, the
electric energy of the battery with a high terminal voltage is
supplied to the electric load 40 during discharge.
[0187] During the regenerative mode of the vehicle, it is
controlled for the terminal voltage Vd (Li) of the lithium battery
30 to be many times lower than the terminal voltage Vd (Pb) of the
lead-acid battery 20 in order to preferentially charge the lithium
battery 30 rather than the lead-acid battery 20. In addition,
during the discharging mode, it is controlled for the terminal
voltage Vd (Li) of the lithium battery 30 to be many times higher
than the terminal voltage of the lead-acid battery 20 in order to
preferentially discharge the electric energy from the lithium
battery 30 rather than the lead-acid battery 20, where the terminal
voltage Vd (Pb) of the lead-acid battery 20 is the voltage obtained
by subtracting the barrier voltage Vbar of the parasitic diode from
the terminal voltage Vd (Pb).
[0188] The above control can be achieved by adjusting the open
circuit voltage V0 and the internal resistance R of each of the
lead-acid battery 20 and the lithium battery 30. That is, the open
circuit voltage V0 of the battery can be adjusted by selecting an
optimum positive electrode active material, an optimum negative
electrode active material, and an optimum electrolytic solution of
the lithium battery 30.
[0189] A description will now be given of the method of setting the
condition to satisfy the relationship of Vc (Li: Lithium
battery)<Vc (Pb: lead-acid battery) during a regenerative energy
charging and the condition to satisfy the relationship of Vd
(Li)>Vd (Pb) during discharge, in the power source apparatus
according to the eighth embodiment with reference to FIG. 12A, FIG.
12B, and FIG. 13.
[0190] FIG. 12A is a view showing a use range of SOC of the
lead-acid battery 20 in the power source apparatus according to the
eighth embodiment. FIG. 12B is a view showing a use range of SOC of
the lithium battery 30 in the power source apparatus according to
the eighth embodiment.
[0191] In FIG. 12A, the horizontal line designates the SOC of the
lead-acid battery 20, the solid line A1 denotes a voltage
characteristic line which shows a relationship between the SOC and
the open circuit voltage V0 (Pb) of the lead-acid battery 20. As
shown in FIG. 12A, the more the SOC increases by increasing the
charged energy, the more the open circuit voltage V0 (Pb)
increases.
[0192] In FIG. 12B, the horizontal line designates the SOC of the
lithium battery 30, the solid line A2 denotes a voltage
characteristic line which shows a relationship between the SOC and
the open circuit voltage V0 (Li) of the lithium battery 30. The
more the SOC increases by increasing the charged energy, the more
the open circuit voltage V0 (Li) increases. In particular, although
the SOC increases according to the increase of the charged energy,
the slope which shows the voltage characteristic line of the
lead-acid battery 20 becomes low during a range between inflection
points P1 and P2 shown in FIG. 12A.
[0193] The overcharged state and the over discharged state of each
of the lead-acid battery 20 and the lithium battery 30 would cause
a rapid deterioration thereof. Accordingly, it is necessary for the
protection control means, previously described, to control the
charging capacity to the lithium battery 30 and the lead-acid
battery 20, and the discharging capacity from the lead-acid battery
20 and the lithium battery 30, that is, to use each of the
lead-acid battery 20 and the lithium battery 30 within the use
range of SOC.
[0194] The use range W1 (Pb) of SOC of the lead-acid battery 20 is
within a range of 88% to 100%. On the other hand, the use range W2
(Li) of SOC of the lithium battery 30 is within a range of 10% to
90%. The upper limit of the use range W2 (Li) of SOC of the lithium
battery 30 is smaller than 100%, and the lower limit of the use
range W2 (Li) of SOC of the lithium battery 30 is larger than zero
%.
[0195] Accordingly, the range of 0% to 88% of SOC of the lead-acid
battery 20 causes the rapid deterioration. FIG. 12B also shows an
expansion of the area indicated by the dotted line shown in FIG.
12A which indicates the use range W1 (Pb) of SOC of the lead-acid
battery 20. The position at 0% of SOC of the lithium battery 30
indicated by the horizontal line in FIG. 12B corresponds to the
position of 88% of the use range W1 (Pb) of SOC of the lead-acid
battery 20.
[0196] The lithium battery 30 is set in order to obtain the voltage
characteristic A2 of the lithium battery 30 which satisfies the
following conditions (a'), (b'), (c'), (d'), and (e').
Specifically, it is possible to obtain the voltage characteristic
A2 which satisfies the conditions (a'), (b'), (c'), (d'), and (e')
by selecting an optimum combination of the positive electrode
active material, the negative electrode active material, and the
solid electrolyte of the lithium battery 30.
<Condition (a')>
[0197] There is the equal voltage point Vds at which the open
circuit voltage V0 (Pb) of the lead-acid battery 20 is equal to the
open circuit voltage V0 (Li) of the lithium battery 30 in the use
range W1 (Pb) of SOC of the lead-acid battery 20 and the use range
W2 (Li) of SOC of the lithium battery 30. The equal voltage point
Vds is present in the range between the inflection points P1 and
P2, where a slope of voltage characteristic line A2 of the lithium
battery 30 in this range is small. In particular, the equal voltage
point at which the lithium battery 30 is equal in open circuit
voltage to the lead-acid battery 20 is shifted toward the lower
limit side of SOC of the lithium battery 30 by the barrier voltage
Vbar (see Vds' shown in FIG. 12B). In other words, the voltage
characteristic line A1 of the lead-acid battery 20 is shifted
toward the low voltage side as indicated by the alternate long and
dash line shown in FIG. 12B.
<Condition (b')>
[0198] The open circuit voltage V0 (Li) of the lithium battery 30
is higher than the voltage, which is obtained by subtracting the
barrier voltage Vbar of the parasitic diode 51 from the open
circuit voltage V0 (Pb), at the upper limit side of the equal
voltage point Vds' in the use range W2 (Li) of SOC of the lithium
battery 30. In more detail, the equal voltage point Vds' is present
at the lower limit side rather than the upper limit side (90%) of
the use range W2 (Li) of SOC of the lithium battery 30 in order to
set the equal voltage point Vds' within the range of P1 and P2. The
slope of the voltage characteristic line A2 of the lithium battery
30 is larger than the slope of the voltage characteristic line A1
of the lead-acid battery 20 at the upper limit side of the equal
voltage point Vds' in the use range W2 (Li) of SOC of the lithium
battery 30.
<Condition (c')>
[0199] The terminal voltage Vc (Li) of the lithium battery 30 when
the maximum charging current flows in the lithium battery 30 is
smaller than the constant voltage Vreg which is controlled by the
regulator 11. In other words, the terminal voltage Vc (Li) of the
lithium battery 30, as the terminal voltage Vc (Li) (see the solid
line A3 shown in FIG. 12B) when the lithium battery 30 is charged,
at the upper limit value (90%) of the use range W2 (Li) of SOC of
the lithium battery 30, is smaller than the constant voltage Vreg.
Reference character .DELTA.V shown in FIG. 12B indicates a voltage
drop part by the internal resistance 32 at the upper limit value
(90%), which corresponds to the term (Ic.times.R) in the equation
(F2), previously described.
<Condition (d')>
[0200] The open circuit voltage V0 (Li) of the lithium battery 30
is lower than the open circuit voltage V0 (Pb) of the lead-acid
battery 20 in the lower limit side from the equal voltage point
Vds' in the use range W2 (Li) of SOC of the lithium battery 30. In
more detail, the equal voltage point Vds' is set to a value at the
upper limit side from the lower limit side (10%) of the use range
W2 (Li) of SOC of the lithium battery 30 in order to set the equal
voltage point Vds' in the range of P1 to P2.
[0201] In the range in the lower limit side observed from the equal
voltage point Vds' in the use range W2 (Li) of SOC of the lithium
battery 30, the slope of the voltage characteristic line A2 of the
lithium battery 30 is larger than the slope of the voltage
characteristic line A1 of the lead-acid battery 20.
<Condition (e')>
[0202] The range in the upper limit side observed from the equal
voltage point Vds' is wider than the range in the lower limit side
observed from the equal voltage point Vds' in the use range W2 (Li)
of SOC of the lithium battery 30. In more detail, the equal voltage
point Vds' is set to a value at the lower limit side from the
intermediate point between the range of P1 and p2 in order to set
the equal voltage point Vds' in the range of P1 to P2. This
satisfies the relationship of Vd (Li)>Vd (Pb)-Vbar in a large
part in the use range W2 (Li) of SOC of the lithium battery 30.
[0203] FIG. 13 is a view showing a difference in I-V
characteristics between the lead-acid battery 20 and the lithium
battery 30 in the power source apparatus according to the first
embodiment. In FIG. 13, the solid line B1 indicates the I-V
characteristic of the lead-acid battery 20, the solid line B2
designates the I-V characteristic of the lithium battery 30, the
solid line B3 denotes the constant voltage Vreg, the horizontal
line indicates the current value Ic and the current value Id, the
vertical line indicates the terminal voltage Vc and the terminal
voltage Vd. In FIG. 13, the current Ic during charge is expressed
by a positive value, and the current Id during discharging is
expressed by a negative value.
[0204] In the I-V characteristics B1 and B2, the more the charging
current Ic increases, the more the terminal voltage Vc increases
(Ic.times.R is increased). The more the charging current Id
decreases, the more the terminal voltage Vd decreases (Ic.times.R
is decreased). That is, the change of the charging current Ic is in
proportion to the change of the charging current Ic. The slope of
each of the I-V characteristics B1 and B2 indicates the internal
resistance R. In particular, the lithium battery 30 has the same
internal resistance value R (Pb) during both charge and discharge.
On the other hand, an internal resistance value R (Pb) in charging
of the lead-acid battery 20 is larger than that in discharging of
the lead-acid battery 20.
[0205] In the eighth embodiment, it is set to satisfy the
relationship of R (Li)<R (Pb) in charging, and to satisfy the
relationship of R (Li).ltoreq.R (Pb) in discharging. It is also set
to satisfy the relationship of Vd (Li)>Vd (Pb)-Vbar in
discharging when the MOS FET 50' is turned off (on the other hand,
to satisfy the relationship of Vd (Li)>Vd (Pb) when the MOS FET
50' is turned on), further to satisfy the relationship of Vc
(Li).gtoreq.Vc (Pb) in a range which is close to Ic=zero during
charging when the MOS FET 50' is turned on, and to satisfy the
relationship of Vc (Li)<Vc (Pb) in other part (Vc
(Li)+Vbar<Vc (Pb)) when the MOS FET 50' is turned off). The
above setting control can be achieved by the condition where the
internal resistance value R (Li) of the lithium battery 30 is
smaller than the internal resistance value R (Pb) of the lead-acid
battery 20 in charging.
[0206] The power source apparatus having the above structure
according to the eighth embodiment of the present invention has the
following features (B1) to (B12).
(B1) Making the voltage characteristic A2 to satisfy the condition
(a') (the equal voltage point Vds is present in the range between
the inflection points P1 and P2, and the equal voltage point Vds'
is present when the MOS FET 50' is turned on) generates the state
without any large voltage difference between the lithium battery 30
and the lead-acid battery 20 because the terminal voltage Vd (Li)
in the use range of SOC of the lithium battery 30 is approximately
equal to the terminal voltage Vd (Pb) in the use range W1 of SOC of
the lead-acid battery 20 during discharging, as shown in FIG.
12A.
[0207] Therefore even if does not use any DC/DC converter (which is
used in the conventional power source apparatus) and the MOS FET
50' is turned on, it is possible to suppress a current from the
lithium battery 30 to the lead-acid battery 20, in other words, it
is possible to flow a current corresponding to an extremely small
capacity from the battery having a high voltage to the battery
having a low voltage in the lithium battery 30 and the lead-acid
battery 20. The structure of the power source apparatus according
to the eighth embodiment can thereby suppress the lithium battery
30 and the lead-acid battery 20 from being in overcharge and over
discharge without using any DC/DC converter. This makes it possible
to adequately reduce the manufacturing cost of the power source
apparatus because of using no DC/DC converter.
(B2) Making the voltage characteristic A2 to satisfy the condition
(b') (the relationship of Vd (Li)>Vd (Pb)-Vbar at the upper
limit side from the equal voltage point Vds') to the voltage
characteristic A1 allows the lithium battery 30 to discharge a
current to the electric load 43 which requires a constant voltage,
because the open circuit voltage of the lithium battery 30 is
higher than that of the lead-acid battery 20, in the state where
the lithium battery 30 is charged higher rather than the capacity
at the equal voltage point Vds' in the use range W2 (Li) of SOC of
the lithium battery 30.
[0208] Because this condition increases the frequency of
discharging a current from the lithium battery 30 when compared
with from the lead-acid battery 20 and decreases the frequency of
discharging a current from the lead-acid battery 20 with a low
durability to a frequent discharging, this makes it possible to
suppress deterioration of the lead-acid battery 20.
[0209] In the structure where the electric load 42 is placed in
position at the lithium battery 30 side observed from the MOS FET
50', and the lithium battery 30 supplies the electric energy
(capacity) to the electric load 42, it is possible to
preferentially discharge the electric energy from the lithium
battery 30 rather than the lead-acid battery 20 when the voltage
characteristic A2 is made in order to satisfy the above condition
(b').
(B3) Making the voltage characteristic A2 to satisfy the condition
(c') (Vc (Li)<Vreg when the maximum charging current flows) to
the voltage characteristic A1 can increase the frequency of
charging the lithium battery 30 rather than the lead-acid battery
20 by the following reasons.
[0210] In the case of charging the lead-acid battery 20 with the
regenerative energy without using the lithium battery 30, because
the internal resistance 22 of the lead-acid battery 20 is larger
than that of the lithium battery 30, as shown in FIG. 13, the
terminal voltage Vc (Pb) of the lead-acid battery 20 reaches the
constant voltage Vreg at the point when the charging current
reaches the current value Ia.
[0211] On the other hand, the structure of the power source
apparatus equipped with the lithium battery 30 satisfies the
relationship of Vc (Li)<Vreg even when the charging current
becomes the maximum value, it is possible to further charge the
lithium battery 30.
[0212] In the example shown in FIG. 13, the terminal voltage Vc
(Li) of the lithium battery 30 reaches the constant voltage Vreg
when the charging current reaches the current value Ib which is
larger than the maximum charging current Imax.
[0213] This will be explained in detail with reference to FIG. 14A
and FIG. 14B. FIG. 14A shows a current change of the lead-acid
battery 20 and the lithium battery 30 in the elapse of time. FIG.
14B shows a terminal voltage change of the lead-acid battery 20 and
the lithium battery 30 in the elapse of time. In FIG. 14A and FIG.
14B, the solid lines C1 and D1 indicate the change of the charging
current and the terminal voltage Vc (Pb) when the lead-acid battery
20 is charged with the regenerative electric power at the maximum
charging current Imax without using the lithium battery 30. The
solid lines C2 and D2 in FIG. 14A and FIG. 14B show the change of
the charging current and the change of the terminal voltage Vc
(Li), respectively, when the lithium battery 30 is charged with the
regenerative electric power at the maximum charging current Imax in
the power source apparatus according to the eighth embodiment.
[0214] As previously explained with reference to FIG. 13, because
the relationship of Imax>Ia is satisfied when the lead-acid
battery 20 is charged with the regenerative electric power, the
charging current rapidly drops at the timing t1 and converges to
zero, as shown in FIG. 14A. This state would be difficult to charge
the lead-acid battery 20. In this case, the area designated by
slanting lines in FIG. 14A corresponds to the charged capacity of
the lead-acid battery 20.
[0215] On the other hand, because the relationship of
Imax.ltoreq.Ib is satisfied when the lithium battery 30 is charged
with the regenerative electric power, the charging current
maintains the value Imax until the timing t2 where SOC of the
lithium battery 30 reaches the upper limit value (90%). This allows
the lithium battery 30 to be always charged and to increase the
quantity of chargeable capacity.
[0216] As described above, according to the eighth embodiment of
the present invention, it is possible to increase the frequency to
charge the lithium battery 30 rather than the frequency to charge
the lead-acid battery 20. This can decrease the accumulated charged
capacity of the lead-acid battery 20 which has a low durability,
and suppress the deterioration of the lead-acid battery 20.
(B4) Making the voltage characteristic A2 to satisfy the condition
(d') (Vd (Li)<Vd (Pb) at the lower limit side from the equal
voltage point Vds') to the voltage characteristic A1 allows the
lead-acid battery 20, instead of the lithium battery 30, to
discharge the electric power to the electrical loads 40 when the
lithium battery 30 preferentially discharges the electric power
(capacity) to the electric load 40 and the SOC of the lithium
battery 30 is lower than the equal voltage point Vds'.
[0217] Further, the current flows from the lead-acid battery 20 to
the lithium battery 30, this increases the SOC of the lithium
battery 30 toward the equal voltage point Vds'. As a result, it is
possible to suppress the lithium battery 30 from over
discharge.
(B5) Making the voltage characteristic A2 to satisfy the condition
(e') to the voltage characteristic A1 allows the range to satisfy
the relationship of Vd (Li)>Vd (Pb)-Vbar based on the condition
(b'), where the condition (e') satisfies that the range at the
upper limit side from the equal voltage point Vds' is wider in area
than the range at the lower limit side from the equal voltage point
Vds'. This makes it possible to increase the frequency to
preferentially discharge from the lithium battery 30 rather than
from the lead-acid battery 20. This makes it possible to increase
the effect of the deterioration resistance of the lead-acid battery
20. (B6) The power source apparatus according to the eighth
embodiment has is the MOS FET 50', previously explained. The
presence of the MOS FET 50' shifts the equal voltage point
(Vds--->Vds') toward the lower limit side by the barrier voltage
Vbar of the parasitic diode 51, where the open circuit voltage of
the lithium battery 30 is equal to the open circuit voltage of the
lead-acid battery 20 at the equal voltage point. In other words,
the voltage characteristic line A1 of the lead-acid battery 20 is
apparently shifted toward the lower limit voltage as designated by
the long and dash line shown in FIG. 12B. This makes it possible to
expand the area (discharging area W2d), as designated by W2d', in
the upper limit side observed from the equal voltage point Vds' in
the use range W2 (Li) of SOC of the lithium battery 30, and further
to increase the frequency of discharging the energy from the
lithium battery 30, rather than from the lead-acid battery 20, to
the electric load 43 which requires a constant voltage. (B7) In
general, the starter motor 41 requires a large electric power when
it starts to operate, when compared with other electric loads 42
and 43. Supplying a large electric power from the lithium battery
30 to the electric load such as the starter motor 41 prevents the
size reduction of the lithium battery 30 which is a high price
rather than that of the lead-acid battery 20.
[0218] In the eighth embodiment, the lead-acid battery 20 supplies
a large electric power to the starter motor 41 which consumes a
large energy when it starts to operate in order to reduce the size
and capacity of the lithium battery 30. Still further, because the
forward direction of the parasitic diode 51 in the MOS FET 50' is
set to the current direction from the lead-acid battery 20 to the
lithium battery 30, this structure can prevent the current from
flowing to the starter motor 41 from the lithium battery 30.
Moreover, because the MOS FET 50' is turned off during the
operation of the starter motor 41, it is possible to reliably
prevent the current from flowing to the starter motor 41 from the
lithium battery 30.
(B8) When the lithium battery 30 is charged with the electric power
generated by the alternator 10, it is necessary to turn on the MOS
FET 50'. The charging current, that is, a generated current in the
alternator 10 flows into the lithium battery 30 by bypassing the
parasitic diode 51. Bypassing the parasitic diode 51 can avoid the
energy loss to be caused by the parasitic voltage Vbar of the
parasitic diode 51, it is possible to decrease the energy loss
generated by the alternator 10. In particular, because the MOS FET
50' is turned on when the lithium battery 30 is charged with the
regenerative energy generated in the alternator 10, it is possible
to decrease the energy loss which is caused when a large
regenerative current flows through the parasitic diode 51. This is
one of superior features of the present invention. (B9) When the
conditions (a'), (b'), and (c'), previously described, are
satisfied under the use of lithium phosphate (which serves as
positive electrode material) and graphite (which serves as negative
electrode material) as a combination of the positive electrode
material and the negative electrode material of the lithium battery
30, it is necessary to increase the electrode area of the lithium
battery 30 because the lithium phosphate has a large internal
resistance rather than other materials.
[0219] In order to avoid this drawback, the power source apparatus
according to the present invention uses lithium cobalt oxide,
lithium manganese oxide or lithium nickelate compound as the
positive electrode material, and lithium titanium oxide as the
negative electrode material. This makes it possible to reduce the
size and cost of the lithium battery 30 while satisfying the
conditions (a'), (b'), and (c').
[0220] The use of lithium titanium oxide as the negative electrode
material, when compared with using graphite, would cause a drawback
to shift the equal voltage point Vds toward the upper limit side,
where the open circuit voltage of the lithium battery 30 is equal
to the open circuit voltage of the lead-acid battery 20 at the
equal voltage point Vds. However, the structure of the power source
apparatus according to the eighth embodiment can solve it because
it has the MOS FET 50' which is capable of shifting the equal
voltage point Vds toward the lower limit side (Vds--->Vds').
Accordingly, the power source apparatus according to the present
invention can solve the above drawbacks and also decrease the
electrode area of the lithium battery 30.
(B10) The lithium battery 30 supplies the electric capacity
(energy) to the electrical loads 43 which require an approximate
constant voltage or a stable voltage which is changed within the
predetermined voltage range, and the lead-acid battery 20 supplies
the electric power to the starter motor 41. While the lead-acid
battery 20 supplied the electric power to the starter motor 41, the
MOS FET 50' is turned off. This makes it possible to supply to the
electrical loads 43 the electric power whose voltage has a small
fluctuation in voltage. (B11) Adding the lithium battery 30 which
satisfies the conditions (a') to (e') into an power source
apparatus which is comprised of the alternator 10, the regulator
11, and the lead-acid battery 20 makes it possible to obtain the
features of the present invention, previously described, without
using any DC/DC converter. It is possible to realize the power
source apparatus according to the eighth embodiment of the present
invention by using a conventional power source apparatus with a
less change in hardware design. (B12) The power source apparatus
according to the eighth embodiment uses the MOS FET 50' which
serves the open and close means and the rectifying means. Because
the parasitic diode 51 (which is always formed in the MOS FET 50')
serves as the rectifying means, it is not necessary to add any
additional diode as the dedicated rectifying means.
Ninth Embodiment
[0221] A description will be given of the power source apparatus
according to the ninth embodiment of the present invention with
reference to FIG. 15. FIG. 15 is a block diagram showing a
schematic electric circuit of the power source apparatus according
to the ninth embodiment.
[0222] The power source apparatus according to the ninth embodiment
has a protection control means 600 which controls the charging
capacity to and discharging capacity from the lithium battery 30 in
order to avoid overcharge to the lithium battery 30 and over
discharge from the lithium battery 30.
[0223] The protection control means 600 controls the input signal
which is transferred to the gate of the semiconductor switch part
52 in order to switch on-state and off-state of the MOS FET 50',
like the open and close control means 601 disclosed in the eighth
embodiment, previously described,
[0224] The protection control means 600 always receives detection
signals regarding the terminal voltages Vc and Vd or the open
circuit voltage V0 (Li) of the lithium battery 30, and a detection
signal regarding the current transferred from a current detection
means 61 which detects a current which flows in the lithium battery
30.
[0225] The protection control means 600 instructs the MOS FET 50'
to open when the terminal voltage Vd of the lithium battery 30
during discharging becomes below the lower limit voltage. This
control protects the lithium battery 30 from over discharge. It is
possible to set the lower limit voltage based on a voltage which
corresponds to the lower limit SOC value (10%) shown in FIG.
12B.
[0226] When the terminal voltage Vc of the lithium battery 30
during charge exceeds the upper limit voltage, the protection
control means 600 instructs the MOS FET 50' to turn off (voltage
rise suppression operation). This control protects the lithium
battery 30 from overcharge. It is possible to set the upper limit
voltage based on a voltage which corresponds to the upper limit SOC
value (90%) shown in FIG. 12B.
[0227] The protection control means 600 further outputs an
instruction signal to the regulator 11 to change the constant
voltage Vreg of the regulator 11 according to the voltage of the
lithium battery 30. This makes it possible to protect the lithium
battery 30 from overcharge and over discharge.
[0228] That is, the protection control means 600 instructs the
regulator 11 to increase the constant voltage Vreg when the voltage
of the lithium battery 30 becomes lower than the lower limit value.
This increases the charge capacity to the lithium battery 30 and
protects the lithium battery 30 from over discharge.
[0229] On the other hand, the protection control means 600
instructs the regulator 11 to decrease the constant voltage Vreg
when the voltage of the lithium battery 30 exceeds the upper limit
value. This suppresses the charge capacity to the lithium battery
30, and protects the lithium battery 30 from overcharge.
[0230] As describe above, the power source apparatus according to
the ninth embodiment of the present invention reliably prevent the
lithium battery 30 from over discharge because the protection
control means 600 instructs the MOS FET 50' to turn on when the
terminal voltage of the lithium battery 30 becomes lower than the
use range W2 (Li) of the lithium battery 30 in addition during the
supply of the electric power to the starter motor 41.
[0231] Further, the power source apparatus according to the ninth
embodiment of the present invention reliably avoids the lithium
battery 30 from overcharge because the protection control means 600
instructs the MOS FET 50' to turn off.
[0232] Because the power source apparatus according to the ninth
embodiment of the present invention performs the over discharge and
overcharge protection operation by changing the constant voltage
Vreg by the protection control means 600. This can precisely
control the voltage of the lithium battery 30, and this makes
thereby it possible to perform the over discharge protection and
the overcharge protection for the lithium battery 30 with high
accuracy.
Tenth Embodiment
[0233] A description will be given of the power source apparatus
according to the tenth embodiment of the present invention with
reference to FIG. 16. FIG. 16 is a block diagram showing a
schematic electric circuit of the power source apparatus according
to the tenth embodiment.
[0234] In the ninth embodiment, the power source apparatus has the
protection control means 600 to protect the lithium battery 30 from
overcharge and over discharge, previously described. In the tenth
embodiment, the protection control means 600 further performs the
overcharge and over discharge operation for the lead-acid battery
20 in addition to the function of the ninth embodiment.
[0235] That is, the protection control means 600 instructs the
regulator 11 to increase the constant voltage Vreg when the voltage
of the lead-acid battery 20 becomes under the lower limit voltage.
This performs the over discharge operation of the lead-acid battery
20. On the other hand, the protection control means 600 instructs
the regulator 11 to decrease the constant voltage Vreg when the
voltage of the lead-acid battery 20 exceeds the upper limit
voltage. This performs the overcharge operation of the lead-acid
battery 20.
[0236] As describe above, the power source apparatus according to
the tenth embodiment of the present invention correctly changes the
constant Vreg according to the voltage of the lead-acid battery 20,
in addition to changing the constant voltage Vreg according to the
voltage of the lithium battery 30. This can precisely control the
voltage of the lead-acid battery 20 in addition to the voltage of
the lithium battery 30, and makes thereby it possible to perform
the over discharge protection and the overcharge protection for the
lead-acid battery 20 as well as the lithium battery 30 with high
accuracy.
Eleventh Embodiment
[0237] A description will be given of the power source apparatus
according to the eleventh embodiment of the present invention with
reference to FIG. 17. FIG. 17 is a block diagram showing a
schematic electric circuit of the power source apparatus according
to the eleventh embodiment.
[0238] The power source apparatus according to the eleventh
embodiment has a plurality of the lithium batteries 30. In the
structure of the power source apparatus according to the eleventh
embodiment, the electric power is supplied from the different
lithium batteries 30 to various types of the electric loads 43, 44,
and 45, where the electrical loads 43 require an approximate
constant voltage or a stable voltage which varies within the
predetermined voltage range, the electric loads 44 require a large
electric power, and the electric load 45 requires a voltage in
order to reliably operate when an emergency occurs.
[0239] Specifically, there is an electric motor mounted to a power
steering apparatus as one example of the electric load 44 which
requires a large quantity of the electric power. The electric load
44 can operate with some fluctuating voltage, which is different
from the electrical loads 43 which require an approximate constant
voltage, previously described.
[0240] There is a communication apparatus as one example of the
electric load 45 which requires a certain operation when an
emergency occurs. This communication apparatus transmits abnormal
information to a repair operator in a car dealership to repair the
vehicle, for example, when the internal combustion engine mounted
to the vehicle causes a failure and does not start to operate.
Therefore it is not necessary for such a type of the electric load
44 to use a large electric power and a constant voltage.
[0241] The power source apparatus according to the eleventh
embodiment shown in FIG. 17 has a plurality of the MOS FETs 50',
the battery state detection means 70, and the current detection
means 61, like the power source apparatus shown in FIG. 15. That
is, the MOS FETs 50', the battery state detection means 70, and the
current detection means 61 are placed every lithium battery 30.
[0242] The battery state detection means 70 always detects the
terminal voltages Vc, Vd or the open circuit voltage V0 (Li) of
each of the lithium batteries 30, and a current flowing through
each of the lithium batteries 30. The battery state detection means
70 then transfers the detection signals to the protection control
means 600. The protection control means 600 receives the detection
signals transferred from the battery state detection means 70, and
performs the overcharge control and the over discharge control by
using the MOS FETs 50', and also performs the overcharge and over
discharge protection control by adjusting the constant voltage
Vreg, like the protection control means 600 shown in FIG. 15.
[0243] The electric load 43, the electric load 44, and the electric
load 45 are electrically connected to the MOS FETs 50' at the
lithium batteries 30 side, not at the lead-acid battery 20 side,
observed from the MOS FETs 50' side. This structure makes it
possible to supply necessary electric power from the lithium
batteries 30 to the corresponding electric loads 43, 44, and 45,
respectively.
[0244] As describe above, the power source apparatus according to
the eleventh embodiment of the present invention has a plurality of
the lithium batteries 30. The lithium batteries 30 correspond to
the electrical loads, respectively. This structure makes it
possible to suppress the deterioration of each of the lithium
batteries 30. In particular, because the electric load 45 for
emergency has the dedicated lithium battery 30, it is possible to
suppress the deterioration of the lithium battery 30 and to avoid
the risk of not supplying the electric power to the electric load
45.
Twelfth Embodiment
[0245] A description will be given of the power source apparatus
according to the twelfth embodiment of the present invention with
reference to FIG. 18.
[0246] FIG. 18 is a block diagram mainly showing a detailed
structure of the battery state detection means 70 in the power
source apparatus shown in FIG. 17.
[0247] The battery state detection means 70 is comprised of a cell
voltage switch means 71, a battery state detection control means
72, a temperature detection means 73, and a cell equalizing means
74. The cell voltage switch means 71, the battery state detection
control means 72, the temperature detection means 73, and the cell
equalizing means 74 serve as equalizing means.
[0248] The cell voltage switch means 71 detects the voltage of each
of a plurality of the battery cells 33 (the twelfth embodiment
shows the fifth battery cells 33) which form the lithium battery
30. The cell voltage switch means 71 has a function to select one
of the battery cells 33 in order to detect its voltage. The cell
voltage switch means 71 detects the voltage of the selected battery
cell and then transfers the detected voltage value to the battery
state detection control means 72. The battery state detection
control means 72 also receives a detected current value of the
current which flows in the lithium battery 30. The battery state
detection control means 72 further receives a temperature value of
the lithium battery 30 detected by the temperature detection means
73.
[0249] The battery state detection control means 72 calculates the
terminal voltages Vc, Vd or the open circuit voltage V0 (Li) of the
lithium battery 30 based on the voltage of each of the battery
cells 33. The battery state detection control means 72 transfers
the calculated voltage, the current value of the lithium battery
30, and the temperature value of the lithium battery 30 to the
protection control means 600 through the communication interface
75. The protection control means 600 receives the information such
as the above voltage value, the current value, and the temperature
value transferred from the battery state detection control means
72, and performs the protection control based on the received
information.
[0250] The battery state detection control means 72 calculates a
discharge capacity from the battery cell 33 having a high SOC, and
a charge capacity for the battery cell 33 having a low SOC based on
the received voltage value of the battery cell 33. The battery
state detection control means 72 outputs an equalizing instruction
signal corresponding to the calculation result to the cell
equalizing means 74. When receiving the equalizing instruction
signal, the cell equalizing means 74 instructs each of the battery
cells 33 to discharge or charge based on the received equalizing
instruction signal in order to equalize the SOC (state of charge as
a residual electric energy) in each of the battery cells 33.
[0251] As describe above, the power source apparatus according to
the twelfth embodiment of the present invention can equalize the
SOC in each of the battery cells 33. This makes it possible to
avoid the presence of the overcharged battery cells 33 and the
battery cells having an adequate SOC during charging. Like this, it
is also possible to avoid the presence of the over discharged
battery cells 33 and the battery cells having an adequate SOC
during discharging. The power source apparatus according to the
eleventh embodiment can suppress the advance of deterioration of
the lithium battery 30.
Thirteenth Embodiment
[0252] A description will be given of the power source apparatus
according to the thirteenth embodiment of the present invention
with reference to FIG. 19.
[0253] In the power source apparatus according to the twelfth
embodiment shown in FIG. 18, the cell voltage switch means 71 and
the battery state detection control means 72 are formed with
different circuit parts. The power source apparatus according to
the thirteenth embodiment has a single IC 710 (integrated circuit
as cell equalizing abnormal detection means) which is composed of
the cell voltage switch means 71 and the cell equalizing means
74.
[0254] FIG. 19 is a block diagram mainly showing a detailed
structure of the battery state detection means 70 comprised of the
single IC chip 710 in the power source apparatus according to the
thirteenth embodiment.
[0255] The cell equalizing abnormal detection means 710 detects the
voltage of each of the battery cells 33, and calculates the
charging capacity to or discharging capacity from each of the
battery cells 33 based on the detected voltage. The cell equalizing
abnormal detection means 710 equalizes the residual energy (or
residual capacity) of each of the battery cells 33 by charging and
discharging each of the battery cells 33 based on the calculation
result.
[0256] The cell equalizing abnormal detection means 710 further
detects whether or not the detected voltage of each of the battery
cells 33 is within a predetermined normal range in order to detect
the abnormality of each of the cell batteries 33. When receiving an
abnormal diagnosis instruction signal transferred from the battery
state detection control means 72, the cell equalizing abnormal
detection means 710 starts to perform the abnormal detection
operation previously described, and transfers the detection result
to the battery state detection control means 72.
[0257] A voltage down means 76 decreases the voltage of the lithium
battery 30 to a voltage of not more than 5 V, with which a
microcomputer is operable. Such a voltage signal decreased by the
voltage down means 76 is transferred to the battery state detection
control means 72, and then further transferred to the protection
control means 600 through the communication interface 75.
[0258] As described above, the power source apparatus according to
the thirteenth embodiment of the present invention has the effect
to perform the abnormal detection operation for each of the battery
cells 33 in addition to have the same effects of the power source
apparatus according to the twelfth embodiment.
Fourteenth Embodiment
[0259] A description will be given of the power source apparatus
according to the fourteenth embodiment of the present invention
with reference to FIG. 20.
[0260] FIG. 20 is a block diagram showing a schematic electric
circuit of the power source apparatus according to the fourteenth
embodiment.
[0261] As shown in FIG. 20, the power source apparatus according to
the fourteenth embodiment uses an electromagnetic relay 52R and a
diode 51a connected in parallel, instead of the MOS FET 50'. In
this structure, the electromagnetic relay 52R serves as the open
and close means, and the diode 51a serves as the rectifying means.
Like the parasitic diode 51 has a barrier voltage Vbar, the diode
51a also has a barrier voltage Vbar.
[0262] The open and close control means 601 allows a current to
flow in an electromagnetic coil 52b and prevents the current from
flowing in the electromagnetic coil 52b of the electromagnetic
relay 52R in order to control the operation of the switch part 52a
of the electromagnetic relay 52R.
[0263] In the fourteenth embodiment, when the open and close
control means 601 allows the current to flow in the electromagnetic
coil 52b, the switch part 52a of the electromagnetic relay 52R is
turned on. This allows the lithium battery 30 to supply electric
energy to the alternator 10 and the lead-acid battery 20.
[0264] On the other hand, when the open and close control means 601
prevents the current from flowing in the electromagnetic coil 52b,
the switch part 52a of the electromagnetic relay 52R is turned off.
This prevents the electric energy from being supplied from the
lithium battery 30 to the alternator 10 and the lead-acid battery
20.
[0265] As described above, the structure of the power source
apparatus according to the fourteenth embodiment has the same
effects of that of the eighth embodiment.
[0266] There are the following differences between the eighth
embodiment using the MOS FET 50' and the fourteenth embodiment
using the electromagnetic relay 52R and the diode 51a:
[0267] That is, because the MOS FET 50' has the function of the
open and close means and the function of the rectifying means, it
is possible to decrease the size and the total number of the
components which form the power source apparatus when the power
source apparatus uses the MOS FET 50' when compared with the total
number of the components in the power source apparatus which uses
the electromagnetic relay 52R and the diode 51a, instead of the MOS
FET 50'.
[0268] Further, it is possible for the semiconductor switch 52 to
have a superior response to the operation instruction (regarding
the gate voltage and the exciting current) from the open and close
control means 601 when compared with the response in the power
source apparatus using the electromagnetic relay 52R and the diode
51a.
[0269] Further, because the control terminal (gate terminal) of the
MOS FET 50' is completely and electrically insulated from other
control terminals (the source and drain terminals) of the MOS FET
50' when the power source apparatus uses the MOS FET 50', it is
necessary to have a high operation voltage, to be supplied to the
control terminal (gate terminal), which is obtained by adding the
voltage at the other terminals (source and drain terminals) and the
control voltage. It requires a circuit to generate such a high
operation voltage.
[0270] On the other hand, because the switch part 52a in the
electromagnetic relay 52R is completely and electrically insulated
from the electromagnetic coil 52b when the power source apparatus
uses the electromagnetic relay 52R, instead of the MOS FET 50',
this does not require any circuit to generate a high operation
voltage. Because using the electromagnetic relay 52R does not
require a high operation voltage, it is possible to avoid any high
voltage generating circuit to generate the high operation voltage,
and it is possible for the open and close control means 601 to
perform a simple on-off control.
Fifteenth Embodiment
[0271] A description will be given of the power source apparatus
according to the fifteenth embodiment of the present invention with
reference to FIG. 21.
[0272] FIG. 21 is a block diagram showing a schematic electric
circuit of an power source apparatus for vehicles according to the
fifteenth embodiment.
[0273] The power source apparatus according to the fifteenth
embodiment has the diode 51a (which serves as the rectifying
means), but does not have the electromagnetic relay 52R (which
serves as the open and close means). The diode 51a and the
electromagnetic relay 52R are used in the power source apparatus
according to the fourteenth embodiment.
[0274] The power source apparatus according to the fifteenth
embodiment has the feature to shift the equal voltage point toward
the lower limit side (Vds--->Vds') by the barrier voltage Vbar
of the diode 51a, where the open circuit voltage of the lithium
battery 30 is equal to the open circuit voltage of the lead-acid
battery 20 at the agree point.
[0275] Further, because the direction of the diode 51a is placed in
the forward direction, through which a current flows from the
lead-acid battery 20 to the lithium battery 30, this structure
makes it possible to prevent the current from flowing to the
starter motor 41 from the lithium battery 30.
[0276] Because the current of the regenerative power flows into the
lithium battery 30 through the diode 51a when the lithium battery
30 is charged with the regenerative power, the structure of the
power source apparatus according to the fifteenth embodiment
somewhat causes an energy loss.
(Other Modifications)
[0277] The present invention is not limited by the eighth to
fifteenth embodiments previously described. It is possible to have
the following structures or to selectively combine the structures
of the eighth to fifteenth embodiments.
[0278] Although the eighth to thirteenth embodiments use the MOS
FET 50' which serves as the open and close means to open and close
the electric connection from the lithium battery 30 to the starter
motor 41, it is possible to use a semiconductor switch (field
effect transistor) such as IGBT, instead of the MOS FET 50', for
example. Such a semiconductor switch has a superior response
function and superior durability when compared with the MOS FETs
50'. In particular, because the current in the IGBT flows in the
direction which is opposite to the forward direction of the
parasitic diode, this requires an additional bypass means in order
to decrease an energy loss caused by the barrier voltage of the
parasitic diode. On the other hand, using the MOS FET 50' has a
feature which does not require any additional bypass means.
[0279] Although each of the eighth to fifteenth embodiments uses
the lithium battery 30 having the voltage characteristic A2
composed of non-aqueous electrolyte, it is possible to use a nickel
battery composed of nickel compound, instead of using the lithium
battery 30, unless it satisfies at least the conditions (a') to
(c'), previously described.
[0280] In each of the eighth to fifteenth embodiments, the equal
voltage point Vds' is present at the upper limit side from the
lower limit value (10%) in the use range W2 (Li) of SOC of the
lithium battery 30. However, the concept of the present invention
is not limited by this. For example, it is possible to set the
equal voltage point Vds' to the lower limit value.
[0281] In each of the eighth to fifteenth embodiments, the vehicles
with the power source apparatus have the regenerative function.
However, the concept of the present invention is not limited by
this. For example, it is possible to apply the power source
apparatus to vehicles without the regenerative function. By the
way, because the vehicle having the regenerative function has a
high frequency to charge the regenerative energy to the battery, it
is possible to show the feature of the present invention to
suppress the deterioration of the lead-acid battery 20 by reducing
the accumulated charged-capacity in the lead-acid battery 20 with a
low durability.
OTHER FEATURE OF THE PRESENT INVENTION
[0282] In the power source apparatus as another aspect of the
present invention, the open circuit voltage and the internal
resistance of the lead-acid battery and the open circuit voltage
and the internal resistance of the secondary battery are determined
so that the open circuit voltage of the secondary battery is lower
than the open circuit voltage of the lead-acid battery in the lower
limit side from the equal voltage point in the use range of SOC of
the secondary battery.
[0283] In the state where the secondary battery is charged rather
than the charged capacity which is more than the capacity at the
equal voltage point within the use range of SOC of the secondary
battery, the secondary battery is preferentially charged rather
than the lead-acid battery. When the residual capacity of the
secondary battery drops after continuous discharge, there is a
probability of causing overcharge of the secondary battery. In
order to avoid the over discharge of the secondary battery, because
the open circuit voltage of the secondary battery is lower than the
open circuit voltage of the lead-acid battery in the lower limit
side observed from the equal voltage point, the lead-acid battery
starts to discharge the electric capacity when the residual
capacity of the secondary battery becomes lower than that indicated
by the equal voltage point, and the current flows from the
lead-acid battery to the secondary battery to charge the secondary
battery. This increases the residual capacity of the secondary
battery to that designated by the equal voltage point, and it is
thereby possible to prevent the secondary battery from
overcharge.
[0284] In the power source apparatus as another aspect of the
present invention, the open circuit voltage and the internal
resistance of the lead-acid battery and the open circuit voltage
and the internal resistance of the secondary battery are determined
so that an upper limit side observed from the equal voltage point
is wider than the lower limit side observed from the equal voltage
point in the use range of SOC of the secondary battery.
[0285] The upper range from the equal voltage point is a range
where the open circuit voltage of the secondary battery becomes
higher than the open circuit voltage of the lead-acid battery
(condition (b'). The more the range at the upper limit side is
wide, the more the frequency to preferentially discharge the
electric capacity from the secondary battery is increased rather
than that from the lead-acid battery. This makes it possible to
more suppress the deterioration of the lead-acid battery.
[0286] The power source apparatus as another aspect of the present
invention further has a voltage drop suppression means which is
capable of suppress discharging from the secondary battery to a
starter motor mounted to the vehicle in order to suppress a voltage
drop of the secondary battery.
[0287] In general, a starter motor requires a large electric power
when the internal combustion engine starts to operate. The voltage
of the battery rapidly drops when it supplies electric power to the
starter motor. When the voltage of the battery becomes lower than
the minimum operable voltage of the electric loads such as a
navigation apparatus and an audio stereo system (which require a
stable constant voltage), this can cause the electric loads such as
a navigation system and an audio stereo apparatus to reset their
operation.
[0288] In order to avoid this, the power source apparatus according
to the present invention has the voltage drop suppression means
which suppresses the discharge of the secondary battery to the
starter motor and suppress the voltage drop of the secondary
battery. This can avoid that the voltage of the electric power to
be supplied to the starter motor becomes lower than the minimum
operable voltage of the electric loads which require a stable
constant voltage.
[0289] The power source apparatus as another aspect of the present
invention further has a protection control means which is capable
of protecting the secondary battery from overcharge by limiting a
charging capacity into the secondary battery. The protection
control means further protects the secondary battery from over
discharge by limiting a discharging capacity from the secondary
battery so that the residual capacity of the secondary battery is
within the use range of the secondary battery. In the power source
apparatus according to the present invention, the protection
control means limits the charging capacity to the secondary battery
or the discharging capacity from the secondary battery by using the
voltage drop suppression means.
[0290] This makes it possible to prevent overcharge to the
secondary battery and over discharge from the secondary battery
during the time period other than the time to drive the starter
motor by the voltage drop suppression means capable of suppressing
the discharge from the secondary battery to the starter motor. For
example, it is possible for the voltage drop suppression means to
prevent the charging capacity to the secondary battery, and to
avoid the overcharge of the secondary battery when the open circuit
voltage of the secondary battery exceeds a threshold value.
[0291] In addition, it is possible for the voltage drop suppression
means to decrease the discharging capacity from the secondary
battery when the open circuit voltage of the secondary battery
becomes below the threshold value.
[0292] The power source apparatus according to another aspect of
the present invention further has a protection control means which
is capable of protecting the secondary battery from overcharge by
controlling a charge capacity into the secondary battery and so
that the residual capacity of the secondary battery is within the
use range of the secondary battery. In the power source apparatus,
the protection control means outputs an instruction signal which
instructs the constant voltage control means to decrease the set
voltage in order to control the charge capacity to the secondary
battery.
[0293] This makes it possible for the constant voltage control
means to prevent the secondary battery from overcharge and over
discharge. For example, it is possible to decrease the charging
capacity to the secondary battery by supplying the instruction
signal to the constant voltage control means in order to decrease
the set voltage when the open circuit voltage of the secondary
battery exceeds the threshold value.
[0294] In addition, it is possible to decrease the discharged
capacity from the secondary battery by supplying the instruction
signal to the constant voltage control means in order to increase
the set voltage when the open circuit voltage of the secondary
battery becomes below the threshold value.
[0295] In the power source apparatus as another aspect of the
present invention, the voltage drop suppression means is a switch
means to open and close an electric connection between the
secondary battery and the starter motor, and the switch means opens
the electric connection between the secondary battery and the
starter motor when the lead-acid battery supplies the electric
capacity to the starter motor.
[0296] Because this completely prevents the secondary battery from
discharging to the starter motor, it is possible to avoid the
voltage drop of the secondary battery when the starter motor starts
to operation.
[0297] In the power source apparatus as another aspect of the
present invention, the switch means is one of a manual switch, an
electromagnetic relay, and a semiconductor switch.
[0298] In the power source apparatus as another aspect of the
present invention, the secondary battery is a battery of
non-aqueous electrolyte. This makes it possible to easily set the
open circuit voltage and the internal resistance of the secondary
battery with high energy density in order to satisfy the conditions
(a), (b), and (c), previously described, when compared with the
case of using a nickel battery.
[0299] In the power source apparatus as another aspect of the
present invention, the secondary battery is comprised of a positive
electrode made of positive electrode active material, a negative
electrode made of negative electrode active material, and an
electrolyte, and the negative electrode active material is made of
one of carbon, graphite, lithium-doped carbon or graphite, lithium
titanium oxide, silicon-containing alloy, and tin-containing alloy,
and the positive electrode active material is lithium metal
composite oxide and/or adsorbent material (for example, activated
carbon) as the positive electrode.
[0300] Thus, in order to satisfy the conditions (a), (b), and (c),
previously described, it is possible to easily set the open circuit
voltage and the internal resistance of the secondary battery with
high energy density by optimally selecting the positive electrode
active material and the negative electrode active material capable
of occluding and discharging lithium ions
[0301] In the power source apparatus as another aspect of the
present invention, the positive electrode active material is made
of lithium iron phosphate. Thus, in order to satisfy the conditions
(a), (b), and (c), previously described, it is possible to easily
set the open circuit voltage and the internal resistance of the
secondary battery having a high energy density by selecting and
using lithium iron phosphate as the positive electrode active
material in the secondary battery.
[0302] In the power source apparatus as another aspect of the
present invention, the secondary battery is comprised of a
plurality of battery cells electrically connected in series, and
further comprising cell equalizing means capable of detecting a
voltage of each of the battery cells and of equalizing a residual
capacity of each of the battery cells based on the detected voltage
of each of the battery cells.
[0303] When the secondary battery is charged and each of the
battery cells has a different residual capacity, it would cause for
the terminal voltage of the secondary battery to rapidly reach the
set voltage. When reaching the set voltage, the battery cell having
a high residual capacity exceeds the upper limit of the use range,
and on the other hand, the battery cell having a less residual
capacity does not reach the upper limit of the use range. This
state promotes deterioration of the secondary battery.
[0304] Like the charging operation, when the secondary battery
discharges and each of the battery cells has a different residual
capacity, the battery cell having a less residual capacity becomes
over discharge, and the battery cell having a high residual
capacity falls to the state of not reaching the lower limit of the
use range. Accordingly, this state also promotes deterioration of
the secondary battery.
[0305] In the power source apparatus according to the present
invention, the cell equalizing means monitors the voltage of each
of the battery cells and equalizes the residual capacity of each of
the battery cells. Accordingly, this can avoid the state in which
the over charged battery cell and the battery cell having an extra
ability to charge the capacity are simultaneously present when the
secondary battery is charged. Similarly, this can also avoid the
state in which the over discharged battery cell and the battery
cell having an extra ability to charge the capacity are
simultaneously present when the secondary battery is discharged.
This makes it possible to more suppress the deterioration of the
secondary battery.
[0306] The power source apparatus as another aspect of the present
invention, further has an open and close means and an open and
close control means. The open and close control means is connected
in parallel to the rectifying means, and is capable of electrically
connecting the alternator with the secondary battery and
disconnecting the alternator from the secondary battery. The open
and close control means instructs the open and close means to close
the electrical connection between the alternator and the secondary
battery when the secondary battery is charged with electric power
generated by the alternator. In addition, the open and close
control means instructs the open and close means to open the
electrical connection between the alternator and the secondary
battery when the rectifying means performs the rectifying
operation.
[0307] When the power source apparatus does not have the open and
close means, a thermal energy of energy loss (which corresponds to
the power of "a barrier voltage.times.a current of generated
power") occurs when the current of the generated power flows
through the rectifying means when the current of the electric power
generated in the alternator flows into the secondary battery to
charge the secondary battery. In particular, when the alternator
generates the electric power by the regenerative energy, a large
current flows into the secondary battery, and the energy loss is
thereby extremely increased.
[0308] In order to solve the above problem, because the open and
close means starts to operate when the alternator supplies the
electric energy to the secondary battery in order to charge the
secondary battery, the current of the generated electric power
flows into the secondary battery by bypassing the rectifying means.
This can eliminate the energy loss caused by the barrier voltage in
the rectifying means, it is possible to decrease the energy loss of
the electric power generated by the alternator.
[0309] In a case other than the case to charge the secondary
battery, because the open and close means is turned off, it is
possible for the power source apparatus according to the present
invention to have the following effects (x1) and (x2): (x1) the
effect to expand the discharge area W2d' by shifting the equal
voltage point Vds' toward the lower limit side which is achieved by
the rectifying means; and (x2) the effect to prevent the current
which flows from the secondary battery to the electric load which
requires a large electric power such as a starter motor.
[0310] In the power source apparatus as another aspect of the
present invention, the open and close means is composed of a
semiconductor switch, and the rectifying means is composed of a
parasitic diode of the semiconductor switch (see FIG. 11A, FIG.
11B, and FIG. 11C).
[0311] Further, In the power source apparatus as another aspect of
the present invention, the open and close means is composed of an
electromagnetic relay which is connected in parallel with the
rectifying means (see FIG. 20).
[0312] That is, because the open and close means and the rectifying
means are realized by using the single semiconductor electric part
(semiconductor switch shown in FIG. 11A, FIG. 11B, and FIG. 11C),
it is possible to decrease the total number of components and to
reduce the entire size of the power source apparatus when compared
with the case where the open and close means and the rectifying
means are formed with different components.
[0313] Still further, it is possible to increase the response
characteristic to the instruction to be transferred to the open and
close means when compared with the case where the open and close
means is composed of an electromagnetic relay.
[0314] However, when the open and close means is composed of such a
semiconductor switch, because the control terminal of the
semiconductor switch (for example, a gate terminal of a MOS FET) is
completely and electrically insulated from other control terminals
of the semiconductor switch (source and drain terminals of the MOS
FET), it is necessary to have a high operation voltage, to be
supplied to the control terminal (gate terminal), which is obtained
by adding the voltage at the other terminals (source and drain
terminals) and the control voltage. It requires a circuit to
generate such a high operation voltage.
[0315] On the other hand, because the switch part of an
electromagnetic relay is completely and electrically insulated from
the electromagnetic coil when the power source apparatus uses the
electromagnetic relay, instead of the semiconductor switch (such as
a MOS FET), this does not require any circuit to generate a high
operation voltage. Because using the electromagnetic relay does not
require a high operation voltage, it is possible to avoid any high
voltage generating circuit to generate the high operation voltage,
and it is possible for the open and close control means to perform
a simple on-off control.
[0316] It is preferable to use a MOS FET as the semiconductor based
on the following reasons. That is, a MOS FET essentially has a
parasitic diode therein. This parasitic diode serves as a
rectifying means (see the parasitic diode 51 shown in FIG. 11A,
FIG. 11B, and FIG. 11C, for example.) In other words, the internal
circuit of the MOS FET is equivalent to the circuit composed of the
open and close means (semiconductor switch part 52) and the
rectifying means which are connected in parallel. Accordingly,
incorporating the MOS FET with the power source apparatus makes it
possible for the parasitic diode, which is always formed in the MOS
FET, to serve as the rectifying means without any additional diode
(as the rectifying means).
[0317] In the power source apparatus as another aspect of the
present invention, the open circuit voltage and the internal
resistance of the lead-acid battery and the open circuit voltage
and the internal resistance of the secondary battery are determined
so that the open circuit voltage of the secondary battery is lower
than the subtracted voltage of the lead-acid battery at the lower
limit side from the equal voltage point in the use range of SOC of
the secondary battery, where the subtracted voltage of the
lead-acid battery is obtained by subtracting the barrier voltage of
the rectifying means from the open circuit voltage of the lead-acid
battery.
[0318] As previously described, the secondary battery more
discharges electric power rather than that from the lead-acid
battery when the secondary battery is charged rather than the
charged capacity at the equal voltage point in the use range of SOC
of the secondary battery. When continuing the discharge, the
secondary battery would enter the over discharge state.
[0319] According to the present invention, because the open circuit
voltage of the secondary battery becomes lower than the subtracted
voltage in the lower limit side from the equal voltage point, the
lead-acid battery starts to discharge, and the current flows from
the lead-acid battery to the secondary battery when the SOC of the
secondary battery becomes lower than the voltage indicated by the
equal voltage point, where the subtracted voltage is obtained by
subtracting the barrier voltage from the open circuit voltage V0
(Pb) of the lead-acid battery. This can prevent the secondary
battery from over discharge.
[0320] In the power source apparatus as another aspect of the
present invention, the open circuit voltage and the internal
resistance of the lead-acid battery and the open circuit voltage
and the internal resistance of the secondary battery are determined
so that a range at the upper limit side from the equal voltage
point in the use range of SOC of the secondary battery is wider
than a lower part at the lower limit side from the equal voltage
point in the use range of SOC of the secondary battery.
[0321] The upper range from the equal voltage point is a range
(which satisfies the condition (b), previously described) where the
open circuit voltage of the secondary battery is higher than the
subtracted voltage which is obtained by subtracting the barrier
voltage from the open circuit voltage V0 (Pb) of the lead-acid
battery. Therefore the more the upper range from the equal voltage
point is expanded, the more the frequency to preferentially
discharge from the secondary battery is increased. This makes it
possible to increase the effect to suppress the deterioration of
the lead-acid battery.
[0322] The power source apparatus as another aspect of the present
invention further has the protection control means which is capable
of protecting the secondary battery from overcharge by limiting a
charging capacity to the secondary battery, and of protecting the
secondary battery from over discharge by limiting a discharging
capacity from the secondary battery so that the residual capacity
of the secondary battery is within the use range of the secondary
battery. In the power source apparatus, the protection control
means limits the charging capacity to the secondary battery or the
discharging capacity from the secondary battery by using the
voltage drop suppression means.
[0323] For example, when the terminal voltage of the secondary
battery becomes more than a threshold value during charging with
the regenerative energy, turning off the open and close means can
decreases the charging capacity to the secondary battery. This can
prevent the secondary battery from overcharge. Further, when the
open circuit voltage of the secondary battery becomes more than the
threshold value by the overcharge when the charging is completed,
because the open circuit voltage of the lead-acid battery is lower
than the open circuit voltage of the secondary battery, turning on
the open and close means can discharge from the secondary battery.
Accordingly, it is possible to decrease the charging capacity to
the secondary battery which is in the overcharge state, and this
can prevent the secondary battery from overcharge.
[0324] When the open circuit voltage of the secondary battery
becomes lower than the threshold value, the open circuit voltage is
always lower than the subtracted voltage which is obtained by
subtracting the barrier voltage from the open circuit voltage of
the lead-acid battery. Performing the open and close means in
addition to the charging to the secondary battery from the
lead-acid battery through the rectifying means can increase the
charging capacity from the lead-acid battery to the secondary
battery and thereby prevent the secondary battery from over
discharge.
[0325] The power source apparatus as another aspect of the present
invention further has a protection control means which is capable
of protecting the secondary battery from overcharge by controlling
a charging capacity to the secondary battery and protecting the
secondary battery from over discharge by controlling a discharging
capacity from the secondary battery so that the residual capacity
of the secondary battery is within the use range of the secondary
battery. In the power source apparatus, the protection control
means outputs an instruction signal which instructs the constant
voltage control means to decrease the set voltage in order to
control the charging capacity to the secondary battery.
[0326] It is possible to prevent the secondary battery from
overcharge and over discharge by using the constant voltage control
means. For example, when the open circuit voltage of the secondary
battery becomes more than the threshold value, outputting the
instruction signal to the constant voltage control means to
decrease the set voltage can decrease the threshold value, and
further suppress the secondary battery from overcharge.
[0327] In addition, when the open circuit voltage of the secondary
battery becomes less than the threshold value, outputting the
instruction signal to the constant voltage control means to
increase the set voltage can increase the threshold value, and
further suppress the secondary battery from over discharge.
[0328] In the power source apparatus as another aspect of the
present invention, the secondary battery is a battery of
non-aqueous electrolyte. This makes it possible for the secondary
battery to have a high output power density and a high energy
density, and to easily set the open circuit voltage and the
internal resistance of the secondary battery in order to satisfy
the conditions (a'), (b'), and (c'), when compared with the case
using a nickel battery as the secondary battery.
[0329] In the power source apparatus as another aspect of the
present invention, the secondary battery is comprised of a positive
electrode made of positive electrode active material, a negative
electrode made of negative electrode active material, and an
electrolyte, the negative electrode active material is one of
carbon, graphite, lithium-doped carbon or graphite, lithium
titanium oxide, silicon-containing alloy, and tin-containing alloy,
and the positive electrode active material is lithium metal
composite oxide or activated carbon. Thus, selecting an optimum
positive electrode active material and an optimum negative
electrode active material to absorb and discharge lithium ions in
the secondary battery can easily set the open circuit voltage and
the internal resistance of the secondary battery in order to
satisfy the conditions (a'), (b'), and (c'), previously
described.
[0330] In the power source apparatus as another aspect of the
present invention, the negative electrode active material is made
of lithium titanium oxide. Selecting lithium titanium oxide as the
negative electrode active material in the secondary battery can
easily set the open circuit voltage and the internal resistance in
order to satisfy the conditions (a'), (b'), and (c'), previously
described.
[0331] Because the internal resistance of the positive electrode
active material the following combination is larger than that of
another active material, it must be required to somewhat increase
the electrode area of the positive electrode in order to satisfy
the conditions (a'), (b'), and (c'), previously described, where
the combination is composed of lithium iron phosphate
(LiFePO.sub.4) as the positive electrode active material and
graphite as the negative electrode active material.
[0332] We provide one improved combination of lithium titanium
oxide as the negative electrode active material and an usually used
positive electrode active material such as (lithium, lithium
manganese oxide, and lithium nickelate compound. This combination,
that is, using lithium titanium oxide as the negative electrode
active material, makes it possible to reduce the electrode area,
the size of the secondary battery, and the manufacturing cost while
satisfying the conditions (a'), (b'), and (c'), previously
described.
[0333] In the above viewpoint, the secondary battery in the power
source apparatus according to the present invention uses lithium
titanium oxide as the negative electrode active material. As
described above, this makes it possible to downsize the secondary
battery and to reduce the manufacturing cost of the power source
apparatus because the electrode area of the secondary battery can
be decreased.
[0334] Although the use of lithium titanium oxide as the negative
electrode material in the secondary battery (lithium battery), when
compared with using graphite, would cause a drawback to shift the
equal voltage point Vds toward the upper limit side, where the open
circuit voltage of the secondary battery is equal to the open
circuit voltage of the lead-acid battery at the equal voltage point
Vds. However, the structure of the power source apparatus according
to the second aspect of the present invention can eliminate such a
drawback because it has the MOS FET 50 capable of shifting the
equal voltage point Vds toward the lower limit side
(Vds--->Vds'). Accordingly, the poser source apparatus according
to the second aspect of the present invention can solve the above
drawback and also decrease the electrode area of the secondary
battery (lithium battery).
[0335] In the power source apparatus as another aspect of the
present invention, the secondary battery is comprised of a
plurality of battery cells. Those battery cells are electrically
connected in series. The power source apparatus as another aspect
of the present invention further has a cell equalizing means
capable of detecting a voltage of each of the battery cells and of
equalizing a residual capacity of each of the battery cells based
on the detected voltage of each of the battery cells.
[0336] When each of the battery cells has a different charged
capacity, the terminal voltage of the secondary battery rapidly
reaches the set voltage on a charging step. When the terminal
voltage of the secondary battery reaches the set voltage, the
battery cell having a high charged capacity before the charging
step exceeds the capacity at the upper limit of the use range of
SOC of the secondary battery, and on the other hand, a battery cell
having a low charged capacity before the charging step does not
reach (becomes less than) the upper limit when terminal voltage of
the secondary battery reaches the set voltage. This promotes the
deterioration of the secondary battery.
[0337] From the above viewpoint, the power source apparatus
according to the second aspect of the present invention has the
cell equalizing means which is capable of detecting a voltage of
each of the battery cells and of equalizing a residual capacity of
each of the battery cells based on the detected voltage of each of
the battery cells. It is thereby possible to suppress avoid a
mixing state of the battery cells of different charged capacities,
overcharged and less charged battery cells, when the secondary
battery is charged. Similarly, it is thereby possible to suppress a
mixing state of the battery cells of different charged capacities
when the secondary battery is discharged.
[0338] In the structure of the power source apparatus according to
the present invention, the secondary battery supplies the electric
power to the electric loads which require a stable constant voltage
or a stable voltage which is fluctuated within the predetermined
voltage range. The rectifying means or the open and close means
prevent the electric connection between the secondary battery with
the starter motor which required a large electric power when it
starts to operate in order to avoid the rapid voltage drop in the
secondary battery.
[0339] In general, the starter motor requires a large electric
power rather than other electric loads mounted to vehicles. When
the battery supplies such a large electric power to the starter
motor when the starter motor starts to operate, the terminal
voltage of the battery rapidly drops. When the battery supplies the
decreased voltage of the electric power voltage, after supplying a
large electric power to the starter motor, to usual electrical
loads such as a defroster heater for a rear window, it would reset
the operation of the usual electric loads such as the navigation
system and/or the audio system. This would cause various problems
in operation. In order to avoid this, the power source apparatus
according to the present invention can avoid the secondary battery
discharging to the starter motor in order to avoid any rapid
voltage drop in the secondary battery and to supply a stable
voltage to the usual electric loads such as the navigation system
and the audio system.
[0340] While specific embodiments of the present invention have
been described in detail, it will be appreciated by those skilled
in the art that various modifications and alternatives to those
details could be developed in light of the overall teachings of the
disclosure. Accordingly, the particular arrangements disclosed are
meant to be illustrative only and not limited to the scope of the
present invention which is to be given the full breadth of the
following claims and all equivalents thereof.
* * * * *