U.S. patent application number 12/835047 was filed with the patent office on 2010-11-04 for rechargeable battery assembly and power system using same.
Invention is credited to Chun-Chieh Chang.
Application Number | 20100277124 12/835047 |
Document ID | / |
Family ID | 39871555 |
Filed Date | 2010-11-04 |
United States Patent
Application |
20100277124 |
Kind Code |
A1 |
Chang; Chun-Chieh |
November 4, 2010 |
RECHARGEABLE BATTERY ASSEMBLY AND POWER SYSTEM USING SAME
Abstract
A rechargeable battery, battery set or battery pack having a
circuit or a plurality of circuits for providing self-discharging
thereof electrically connected in parallel are used to form
rechargeable battery assemblies and electric power supply systems
for use in electric and hybrid vehicles and the like.
Inventors: |
Chang; Chun-Chieh; (Ithaca,
NY) |
Correspondence
Address: |
KRATZ, QUINTOS & HANSON, LLP
Greater Beneficial Union of Pittsburgh Building, 4232 Brownsville Road
Suite308
Pittsburgh
PA
15227
US
|
Family ID: |
39871555 |
Appl. No.: |
12/835047 |
Filed: |
July 13, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11805786 |
May 24, 2007 |
7782013 |
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12835047 |
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60923747 |
Apr 17, 2007 |
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60930646 |
May 18, 2007 |
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Current U.S.
Class: |
320/118 ;
320/136 |
Current CPC
Class: |
H01M 10/441 20130101;
H02J 7/0016 20130101; Y02E 60/10 20130101; Y02T 10/70 20130101 |
Class at
Publication: |
320/118 ;
320/136 |
International
Class: |
H02J 7/00 20060101
H02J007/00; H02J 7/04 20060101 H02J007/04 |
Claims
1. A rechargeable battery assembly, comprising a rechargeable
battery having a positive terminal and a negative terminal, and
means for self-discharging the rechargeable battery when a voltage
across said terminals is greater or equal to a preset value, said
means for self-discharging being electrically connected in parallel
with the battery terminals.
2. The rechargeable battery assembly of claim 1, wherein said means
for self-discharging comprises a resistance element and a switching
element connected in series, a voltage detecting element for
detecting the assembly voltage, and a switching element controller
for closing the switching element when the assembly voltage is
greater or equal to the preset value and opening the switching
element when the assembly voltage is less than the preset value by
a selected amount.
3. The rechargeable battery assembly of claim 2, wherein said
resistance element, said switching element and said switching
element controller are disposed on a printed circuit board.
4. The rechargeable battery assembly of claim 2, wherein said
switching element and said switching element controller are
disposed on a printed circuit board.
5. The rechargeable battery assembly of claim 2, wherein said
switching element is selected from a group consisting of a manual
switch, a solenoid controlled contactor, and a transistor.
6. The rechargeable battery assembly of claim 2, wherein said
resistance element is selected from a group consisting of a
resistor, a light bulb and an LED.
7. The rechargeable battery assembly of claim 2, wherein said
resistance element, said switching element and said switching
element controller are a transistor or a plurality of
transistors.
8. The rechargeable battery assembly of claim 2, wherein said
resistance element, said switching element and said switching
element controller are a combination of transistors and
resistors.
9. The rechargeable battery assembly of claim 2, wherein said
resistance element, said switching element and said switching
element controller are an LED or a plurality of LEDs.
10. The a rechargeable battery assembly of claim 2, wherein said
resistance element, said switching element and said switching
element controller are a combination of LEDs and resistors.
11. The rechargeable battery assembly of claim 2, wherein said
resistance element, said switching element and said switching
element controller are integrated on a semiconductor chip.
12. The rechargeable battery assembly of claim 2, wherein said
switching element and said switching element controller are
integrated on a semiconductor chip.
13. The rechargeable battery assembly of claim 2, wherein said
resistance element is controllable to vary its resistance value and
the resistance value is controlled by a resistance control element
in relation to voltage detected by said voltage detecting
element.
14. The rechargeable battery assembly of claim 1, wherein said
means for self-discharging is integrated on a semiconductor chip,
and said semiconductor chip is disposed on the rechargeable
battery.
15. The rechargeable battery assembly of claim 1, wherein said
means for self-discharging is integrated on a semiconductor chip,
each said rechargeable battery is enclosed in a case and said
semiconductor chip is disposed within the case.
16. A rechargeable battery pack, comprising a plurality of said
rechargeable battery assembly of claim 1, electrically connected in
series, parallel or a combination of series and parallel.
17. A rechargeable battery pack assembly, comprising the
rechargeable battery pack of claim 16, and means for
self-discharging the rechargeable battery pack when a voltage
across said battery pack is greater or equal to a preset value,
said means for self-discharging being electrically connected in
parallel with the battery pack.
18. An electric power supply system, comprising a plurality of said
rechargeable battery assembly of claim 1, electrically connected in
series, parallel or a combination of series and parallel system
circuit for charging the plurality of said rechargeable batteries,
a battery charger in the system circuit for charging the plurality
of rechargeable batteries, a system circuit breaking element in the
system circuit, and a system controller for detecting the voltage
across each said assembly in the system circuit in series form, for
opening the system circuit breaking element when a detected voltage
is greater or equal to a selected high voltage and for opening the
system circuit breaking element when a detected voltage is less
than or equal to a selected low voltage.
19. An electric power supply system, comprising a plurality of said
battery pack of claim 16 electrically connected in series, parallel
or a combination of series and parallel in a system circuit for
charging, a battery charger in the circuit, a system circuit
breaking element in the circuit, and a system controller for
detecting the voltage across each said assembly in the system
circuit in series form, for opening the system circuit breaking
element when a detected voltage is greater or equal to a selected
high voltage and for opening the system circuit breaking element
when a detected voltage is less than or equal to a selected low
voltage.
20. An electric power supply system, comprising a plurality of said
battery pack assembly of claim 17, electrically connected in
series, parallel or a combination of series and parallel in a
system circuit for charging, a battery charger in the circuit, a
system circuit breaking element in the circuit, and a system
controller for detecting the voltage across each said assembly in
the system circuit in series form, for opening the system circuit
breaking element when a detected voltage is greater or equal to a
selected high voltage and for opening the system circuit breaking
element when a detected voltage is less than or equal to a selected
low voltage.
21. The electric power supply system of claim 18, wherein the
system circuit breaking element is an electromagnetic switch
requiring no energy consumption when in the closed condition, and
said electromagnetic switch is opened by a signal from the system
controller.
22. The electric power supply system of claim 19, wherein the
system circuit breaking element is an electromagnetic switch
requiring no energy consumption when in the closed condition, and
said electromagnetic switch is opened by a signal from the system
controller.
23. The electric power supply system of claim 20, wherein the
system circuit breaking element is an electromagnetic switch
requiring no energy consumption when in the closed condition, and
said electromagnetic switch is opened by a signal from the system
controller.
24. A method for charging the rechargeable batteries of a plurality
of the assembly of claim 1, electrically connected in a series,
parallel or a combination of series and parallel circuit,
comprising providing a battery charger in the circuit for charging
the rechargeable batteries at a selected constant voltage, and
charging the rechargeable batteries for a time period greater than
a time required for a current in the circuit to be less than or
equal to a current passing through the resistance element of any
one of the plurality of the assembly.
25. A method for charging the rechargeable batteries of a plurality
of the assembly of claim 1, electrically connected in a series,
parallel or a combination of series and parallel circuit,
comprising providing a battery charger in the circuit for charging
the plurality of rechargeable batteries at a selected constant
current, and charging the rechargeable batteries for a time period
greater than a time required for a current in the circuit to be
less than or equal to a current passing through the resistance
element of any one of the plurality of the assembly.
26. A method for charging the rechargeable batteries of a plurality
of the assembly of claim 1, electrically connected in a series,
parallel or a combination of series and parallel circuit,
comprising providing a battery charger in the circuit for charging
the plurality of rechargeable batteries at a selected constant
current followed by a constant voltage, and charging the
rechargeable batteries for a time period greater than a time
required for a current in the circuit to be less than or equal to a
current passing through the resistance element of any one of the
plurality of the assembly.
27. A method for charging the rechargeable batteries of the power
supply system of claim 18, comprising providing a battery charger
in the circuit for charging the rechargeable batteries at a
selected constant voltage, and charging the rechargeable batteries
for a time period greater than a time required for a current in the
circuit to be less than or equal to a current passing through the
resistance element of any one of the plurality of the assembly.
28. A method for charging the rechargeable batteries of the power
supply system of claim 18, comprising providing a battery charger
in the circuit for charging the plurality of rechargeable batteries
at a selected constant current, and charging the rechargeable
batteries for a time period greater than a time required for a
current in the circuit to be less than or equal to a current
passing through the resistance element of any one of the plurality
of the assembly.
29. A method for charging the rechargeable batteries of the power
supply system of claim 18, comprising providing a battery charger
in the circuit for charging the plurality of rechargeable batteries
at a selected constant current followed by a constant voltage, and
charging the rechargeable batteries for a time period greater than
a time required for a current in the circuit to be less than or
equal to a current passing through the resistance element of any
one of the plurality of the assembly.
30. A method for charging the rechargeable batteries of the power
supply system of claim 19, comprising providing a battery charger
in the circuit for charging the rechargeable batteries at a
selected constant voltage, and charging the rechargeable batteries
for a time period greater than a time required for a current in the
circuit to be less than or equal to a current passing through the
resistance element of any one of the plurality of the assembly.
31. A method for charging the rechargeable batteries of the power
supply system of claim 19, comprising providing a battery charger
in the circuit for charging the plurality of rechargeable batteries
at a selected constant current, and charging the rechargeable
batteries for a time period greater than a time required for a
current in the circuit to be less than or equal to a current
passing through the resistance element of any one of the plurality
of the assembly.
32. A method for charging the rechargeable batteries of the power
supply system of claim 19, comprising providing a battery charger
in the circuit for charging the plurality of rechargeable batteries
at a selected constant current followed by a constant voltage, and
charging the rechargeable batteries for a time period greater than
a time required for a current in the circuit to be less than or
equal to a current passing through the resistance element of any
one of the plurality of the assembly.
33. A method for charging the rechargeable batteries of the power
supply system of claim 20, comprising providing a battery charger
in the circuit for charging the rechargeable batteries at a
selected constant voltage, and charging the rechargeable batteries
for a time period greater than a time required for a current in the
circuit to be less than or equal to a current passing through the
resistance element of any one of the plurality of the assembly.
34. A method for charging the rechargeable batteries of the power
supply system of claim 20, comprising providing a battery charger
in the circuit for charging the plurality of rechargeable batteries
at a selected constant current, and charging the rechargeable
batteries for a time period greater than a time required for a
current in the circuit to be less than or equal to a current
passing through the resistance element of any one of the plurality
of the assembly.
35. A method for charging the rechargeable batteries of the power
supply system of claim 20, comprising providing a battery charger
in the circuit for charging the plurality of rechargeable batteries
at a selected constant current followed by a constant voltage, and
charging the rechargeable batteries for a time period greater than
a time required for a current in the circuit to be less than or
equal to a current passing through the resistance element of any
one of the plurality of the assembly.
Description
[0001] This application is a Divisional application of pending U.S.
application Ser. No. 11/805,786 filed May 24, 2007, which claims
priority of U.S. Provisional Application Ser. No. 60/923,747 filed
Apr. 17, 2007 and Provisional Application Ser. No. 60/930,646 filed
May 18, 2007.
FIELD OF INVENTION
[0002] The present invention is concerned with rechargeable
batteries, and in particular with the recharging of rechargeable
batteries.
BACKGROUND OF THE INVENTION
[0003] 1. For batteries to be used for applications such as vehicle
starter, electric bikes, electric motorcycles, electric or hybrid
vehicles, etc, high voltage is essential owing to the increase of
efficiency and the decrease of cost. The increase of voltage
requires batteries to be connected in series. [0004] 2. Problems
associated with batteries in series are: [0005] a. when one battery
has a lower capacity, the capacity of the overall set of batteries
is dictated by the capacity of the battery of lower capacity;
[0006] b. if the battery possessing the lower capacity can not be
charged to full capacity during charging, the performance of the
entire battery set will be degraded owing to the lower capacity
battery. This is known in the art as cell imbalance; [0007] c. the
lower capacity of one specific battery can be caused by either high
self discharge or defects during battery production. [0008] 3.
Conventional ways to solve the cell imbalance problem are: [0009]
a. sorting the batteries in order to avoid inconsistency of the
batteries to be connected in series; [0010] b. charging the
batteries separately (e.g. U.S. Pat. No. 6,586,909), in order to
overcome the problems mentioned above, however, low voltage is
required for charging each battery to full (for example, the
lithium iron battery is charged to 3.65V) and this low voltage
charging is not energy efficient owing to conversions from normal
high voltage AC power source to low voltage DC power. Most prior
art systems and methods utilized in making the batteries balanced
during charging use complicated circuitry to detect and balance the
uncharged batteries (e.g. U.S. Pat. No. 7,068,011, U.S. Pat. No.
7,061,207, U.S. Pat. No. 6,882,129, U.S. Pat. No. 6,841,971, U.S.
Pat. No. 6,825,638, U.S. Pat. No. 6,801,014, U.S. Pat. No.
6,784,638, U.S. Pat. No. 6,777,908, U.S. Pat. No. 6,700,350, U.S.
Pat. No. 6,642,693, U.S. Pat. No. 6,586,909, U.S. Pat. No.
6,511,764, U.S. Pat. No. 6,271,645).
OBJECT OF THE INVENTION
[0011] It is an object of the present invention to provide a simple
device and method for charging a plurality of batteries
electrically connected in a series circuit.
SUMMARY OF THE INVENTION
[0012] The present invention is a rechargeable battery assembly,
having a rechargeable battery with a positive terminal and a
negative terminal, and means for self-discharging the rechargeable
battery when a voltage across the terminals is greater or equal to
a preset value. The means for self-discharging is electrically
connected in parallel with the battery terminals
DESCRIPTION OF THE DRAWINGS
[0013] The invention will become more readily apparent from the
following description thereof shown, by way of example only, in the
accompanying drawings, wherein:
[0014] FIGS. 1a-e are schematic illustrations of various
embodiments of battery assemblies of the invention;
[0015] FIG. 2a is a schematic illustration of a battery assembly of
the invention with an enlarged drawing of a self-discharging
circuit of the invention;
[0016] FIG. 2b is a schematic illustration the battery assembly of
the invention with an enlarged drawing of another embodiment of a
self-discharging circuit of the invention;
[0017] FIG. 3 is a schematic illustration of the battery assembly
of the invention having the self-discharging circuit disposed on a
case of the battery;
[0018] FIG. 4 is a schematic illustration of an electric power
supply system having battery assemblies of the invention;
[0019] FIGS. 5a-e are schematic illustrations of battery packs
having battery assemblies of the invention
[0020] FIGS. 6a-e are schematic illustrations of battery packs
having battery assemblies of the invention differing from those of
FIGS. 5a-e;
[0021] FIGS. 7a-e are schematic illustrations of battery packs
having battery assemblies of the invention differing from those of
FIGS. 5a-e and 6a-e;
[0022] FIGS. 8a-e are schematic illustrations of battery packs
having battery assemblies of the invention differing from those of
FIGS. 5a-e, 6a-e and 7a-e;
[0023] FIG. 9 is a schematic illustration of a battery pack
assembly having battery assemblies of the invention;
[0024] FIG. 10 is a schematic illustration of a battery system
having battery assemblies of the invention, as discussed in example
3; and
[0025] FIG. 11 is a schematic illustration of a battery system
having battery assemblies of the invention, as discussed in example
5.
DETAILED DESCRIPTION OF THE INVENTION
[0026] The present invention is especially important for resolving
the problems caused by batteries connected in series. A cell
imbalance problem during charging can be alleviated by creating a
device and methods that allows the leakage of current (energy) from
the batteries being overcharged. Instead of using very expensive
devices or ways to prevent overcharging, to achieve battery
equalization, as found in prior art devices and methods, the
present invention uses a method and device that reduces the current
being provided to a battery in the series circuit that is being
overcharged. Such method and device can be implemented for each
battery or battery set or battery pack being connected in series.
The terminology "battery set" used throughout the specification
means a plurality of batteries connected in parallel, or series, or
parallel-series, or series-parallel. The terminology "battery pack"
used throughout the specification means a plurality of battery sets
connected in parallel, or series, or parallel-series, or
series-parallel. The terminology "assembly" used throughout the
specification means a battery, a battery set, or a battery pack
accompanied with a means for self-discharge of the battery(s),
battery set or battery pack when the battery(s) is(are) being
overcharged
[0027] In the present invention a battery or batteries
self-discharge when overcharged. Since each battery, battery set,
or battery pack are provided with a "self-discharge" means, when
voltage reaches a preset parameter during charging, or even after
charging, a cell balance problem can be eliminated. This is the
core idea of the present invention.
[0028] FIG. 1(a) shows the structure of a "battery assembly". FIG.
1(b) shows the structure of a "parallel battery set assembly"; FIG.
1(c) shows the structure of a "series battery set assembly"; FIG.
1(d) shows the structure of a "parallel-series battery set
assembly"; and FIG. 1(e) shows the structure of a "series-parallel
battery set assembly". These assemblies are the basic units for use
in providing the battery pack. In these figures, as well as in the
remaining figures, an individual rechargeable battery is indicated
at 1, and a circuit for self-discharging the rechargeable
battery(s) is indicated at 3.
[0029] The present method of solving the cell imbalance problem is
shown in FIG. 2(a). As indicated in FIG. 2(a), each battery is
connected with a device 2 in parallel with the battery. Such device
is comprised of a switching element 6, a resistance element 7, a
voltage-detecting element 5a, and a switching element controller 5b
that opens or closes the switching element 6. The voltage-detecting
element detects the voltage of the battery and along with the
switching element controller controls the "opened" or "closed"
state of the switching element. The switching element, resistance
element, voltage-detecting element and switching element controller
can be disposed on a printed circuit board. However, since a
transistor can function as a combination of a voltage-detecting
element, controller, switching element, and a resistance element,
the device shown in FIG. 2(a) can be replaced by a transistor, or a
plurality of transistors connected in parallel (for adjusting the
resistance). Other possibilities are one transistor 8 connected
with a resistor 7 in series as shown in FIG. 2(b). In the case of
the transistor and resistor connected in series as indicated in
FIG. 2(b), the resistance of the resistor should be small in order
to minimize the voltage drop caused by the resistor thus affecting
the voltage detection of the transistor. The configuration of FIG.
2(b) can also be applicable to diodes such as LEDs, or a printed
circuit board consisting of the switching element and the
controller only.
[0030] When batteries are charged, if the voltage of one of the
batteries is above a preset upper limit, the switching element of
the device electrically connected in parallel to the battery
closes, therefore allowing current to flow through the resistor.
Thus, the charging current for the battery that passed the preset
upper limit voltage decreases, due to the presence of the device
connected in parallel to the battery. Such decrease is shown in
Example 1, below. Under such condition, other batteries are charged
in a normal current flow but the one that passed the upper voltage
limit has a decreased charging action. This is a basic mechanism of
the invention for the prevention of battery overcharging. It should
be mentioned that the resistance element can be any electronic
component that possesses a satisfactory resistance. For example, a
light bulb can be used as a source of resistance.
[0031] The elements of the device can be on a semiconductor chip 2,
which can be disposed anywhere close to the battery. FIG. 3 shows
one possibility of the semiconductor chip 2 being built-in on the
lid of a case of a battery. Also, for example, the chip can be
disposed between the cathode (the case) 11 and the anode (the
negative terminal) 12. Also, the chip can be placed inside the
battery case.
[0032] The resistor can be a variable one if further precise
control of the resistance is necessary. Details of the current
change for each battery during charging are further described
below:
Example 1
Theoretical Demonstration of how Cell Equalization can be
Achieved
Assumptions:
[0033] 1. Four battery assemblies are connected in series as
indicated in FIG. 2(a). [0034] 2. Batteries (1), (3), (4) have
internal resistance of 5 mOhm, battery (2) has an internal
resistance of 10 mOhm. [0035] 3. Batteries (1), (3), (4) have open
circuit voltage of 3.3V, battery (2) has an open circuit voltage of
3.6V. [0036] 4. For each battery assembly, a resistor of 1.0 Ohm is
connected parallel to the battery. [0037] 5. A power supply of 15V
is applied to the four battery assemblies connected in series.
Calculation Case 1 (when Paralleled Resistors are all open): During
charging of the four battery assemblies, the voltage of each
battery can be represented as:
[0037] V.sub.1=Vo.sub.1+I.sub.1R.sub.1, Battery (1):
V.sub.1 is the voltage of the battery (1) during charging, Vo.sub.1
is the open circuit voltage of battery (1), I.sub.1 is the current
passing through battery (1) and R.sub.1 is the internal resistance
of the battery (1).
V.sub.2=Vo.sub.2+I.sub.2R.sub.2, Battery (2):
V.sub.3=Vo.sub.3+I.sub.3R.sub.3, Battery (3):
V.sub.4=Vo.sub.4+I.sub.4R.sub.4, Battery (4):
Since no other resistors are connected,
I.sub.1=I.sub.2=I.sub.3=I.sub.4=I
15=(V.sub.1+V.sub.2+V.sub.3+V.sub.4)=(Vo.sub.1+Vo.sub.2+Vo.sub.3+Vo.sub.-
4)+I(R.sub.1+R.sub.2+R.sub.3+R.sub.4)
15-(Vo.sub.1+Vo.sub.2+Vo.sub.3+Vo.sub.4)=I(R.sub.1+R.sub.2+R.sub.3+R.sub-
.4)
15-3.3-3.6-3.3-3.3=I(0.005+0.01+0.005+0.005)
I=60 Amp--The current that passes through each battery Calculation
case 2, (when the Paralleled Resistor Circuit is Closed for Battery
(2)): Assume I' is the current passing through the resistor and R'
is the resistance of the resistor.
Then,
[0038] V.sub.2=I'R', I'=V.sub.2/R'
V.sub.2=Vo.sub.2+I.sub.2R.sub.2,
Considering the current balance:
(I'+I.sub.2)=I.sub.1=I.sub.3=I.sub.4=I
So,
V.sub.2=Vo.sub.2+(I-I')R.sub.2=Vo.sub.2+(I-V.sub.2/R')R.sub.2
Rearrange, then we get
V.sub.2=(Vo.sub.2+IR.sub.2)/(1+R.sub.2/R')
Thus,
15=(V.sub.1+V.sub.2+V.sub.3+V.sub.4)=(Vo.sub.1+Vo.sub.3+Vo.sub.4)+I(R.su-
b.1R.sub.3+R.sub.4)+(Vo.sub.2+IR.sub.2)/(1+R.sub.2/R')
So,
I=61.672 (A),
V.sub.2=(Vo.sub.2+IR.sub.2)/(1+R.sub.2/R')=4.175(V),
I'=V.sub.2/R'=4.175 (A),
I.sub.2=I-I'=57.497 (A)
[0039] If we substitute a resistor of 10 Ohm, then
I=60.168 (A),
V.sub.2=Vo.sub.2+(I-V.sub.2/R')R.sub.2=4.1975(V),
I'=V.sub.2/R'=0.4198 (A),
I.sub.2=I-I'=59.748 (A)
Conclusions from the Calculations: [0040] 1. With regards to
battery assembly of FIG. 2(a), when the switch of the resistor in
the parallel circuit is closed, current flows through the resistor,
and the charging current for battery (2) is decreased. [0041] 2.
While the switch of the paralleled resistor circuit is closed for
the battery assembly of FIG. 2(a), the charging current for other
batteries (1, 3, 4) is increased. [0042] 3. The resistance of the
resistor dictates the magnitude of the current decrease for battery
(2). The smaller the resistance, the bigger the magnitude of
current decrease. [0043] 4. Thus, the idea of incorporating a
resistor with each battery connected in series is effective in
balancing the capacity of all batteries by decreasing the charging
current of the battery that has a higher capacity, and by
increasing the charging current of the other batteries that have a
lower capacity. [0044] 5. It is clear that the resistor connected
in parallel with the battery should possess satisfactory cell
balancing function. Any electronic devices or components that
satisfy the function of voltage sensing and providing the source of
resistance are within the focus of the present invention.
Example 2
Theoretical Calculation Demonstrating a Method of Charging a
Battery Assembly
Assumptions:
[0044] [0045] 1. Four battery assemblies are connected in series as
indicated in FIG. 2(a). [0046] 2. Batteries (1), (3), (4) have
internal resistance of 5 mOhm, battery (2) has an internal
resistance of 10 mOhm. [0047] 3. Batteries (1), (3), (4) have open
circuit voltage of 3.3V, battery (2) has an open circuit voltage of
3.6V. [0048] 4. Batteries (1), (2), (3), and (4) are subjected to a
constant current charge. The current is 2 A. [0049] 5. For
demonstration purpose, the battery being investigated, battery (2),
a resistor of 1.0 Ohm is connected parallel to the battery and the
circuit switch is closed.
Calculations:
[0050] Considering the current balance:
(I'+I.sub.2)=I.sub.1I.sub.3=I.sub.4=I=2 (A)
V.sub.2=Vo.sub.2+(I-I')R.sub.2=Vo.sub.2+(I-V.sub.2/R')R.sub.2
Rearrange, then we get
V.sub.2=(Vo.sub.2+IR.sub.2)/(1+R.sub.2/R')
Substituting Vo.sub.2=3.6(V), I=2 (A), R.sub.2=0.01 Ohm, R'=1
Ohm
We get:
[0051] V.sub.2=3.5842 (V)
I'=V.sub.2/R'=3.5842 (A),
I.sub.2=I-I'=2-3.5842=-1.5842 (A)<0
Conclusions from the Calculations: [0052] 1. The battery that is
overcharged will undergo discharging when the circuit current (I)
is less than the current that passes the resistor (I'). That is,
(I-I'<0). [0053] 2. When batteries being overcharged undergo
discharge, cell balance can be achieved. [0054] 3. By combining the
calculation results shown in Example 1 and 2, it can also be
concluded that the cell balance charging method can be implemented
as either a constant voltage mode (but the charging time required
should be longer than the time required for the condition of
I<I'), or a constant current mode by passing a current (I) that
is less than the current that passes the resistor (I'). [0055] 4.
It can further be concluded that the charger can be designed to
have two modes for charging. One mode is the normal constant
current/constant voltage charge mode for a battery system's normal
use (end of charge executed by setting a certain charging time).
The other mode is the cell balance mode (constant current charging)
that can be used when a battery system possesses less capacity than
their normal use.
Example 3
A Battery Pack and a Battery System
[0056] As mentioned above, a battery pack can be comprised of
battery sets, or battery set assemblies as shown in FIG. 1(a)-(e).
In the present invention, a battery pack may also connect with a
parallel circuit containing a switching element, a
voltage-detecting element, a controller, and a resistance element
to form a "battery pack assembly". The possible structures of
battery packs constructed using battery set assemblies are shown in
FIGS. 5(a)-(e), FIGS. 6(a)-(e), FIGS. 7(a)-(e), and FIGS. 8(a)-(e).
These figures represent the five unit structures shown in FIGS.
1(a)-(e) being connected in various circuit arrangements. In series
(FIGS. 5(a)-(e)), in parallel (FIGS. 6(a)-6(e)), in parallel-series
(FIGS. 7(a)-7(e)), and in series-parallel (FIGS. 8(a)-8(e)). Each
of the cases shown in FIGS. 5, 6, 7, and 8 can again be combined
with a parallel circuit containing the switching element, the
controller, the voltage-detecting element and the resistance
element to form a "battery pack assembly". An example of a "battery
pack assembly" is shown in FIG. 9
[0057] Similar to the case as a battery pack that is comprised of
battery sets or battery set assemblies, a battery system is
comprised of battery packs or battery pack assemblies. Again, the
possible structures of a battery system constructed using battery
pack assemblies can be in series, parallel, parallel-series, and
series-parallel. An example of a "battery system" is shown in FIG.
10.
[0058] One practical case is described here, that is an example of
the battery system for an electric motorcycle. Referring to FIG.
10, a typical electric motorcycle uses a battery system having 53V,
and 40 Ah. The battery system is comprised of four battery packs
(13.3V) connected in series. Each of the battery packs consists of
four lithium iron battery sets (3.33V) connected in series. And,
each of the battery sets consists of four 10 Ah batteries connected
in parallel. In this case, the best structure of the battery system
is the utilization of battery pack assemblies and the battery set
assemblies, as building blocks for the battery system. In such
arrangement, overcharging of battery packs and overcharging of
battery sets can be prevented. If the battery system is constructed
using battery pack assemblies but the pack assemblies are
constructed by battery sets only, some possible overcharging in the
battery set may occur after long time cycling. If the battery
system is constructed using battery packs only and the battery
packs are constructed using battery sets rather than battery set
assemblies, cell imbalance accompanied with overcharging during
charging can occur.
Example 4
A Preferred Electric Power Supply System
[0059] An electric power supply system is the integration of
components including a charger 4, a battery system (packs or sets),
a control board 10, and a circuit breaker 9, as shown in FIG. 4.
Again, four battery assemblies of the invention are connected in
series as a simplest example for demonstration. Referring to FIG.
4, it can be seen that each battery is connected in parallel with a
circuit consisting of components as shown in FIG. 2(a) or FIG.
2(b). A control board is connected with electrical conductors to
each terminal of each of the batteries. Those electrical conductors
serve as a means for providing voltage detection. The other end of
the control board is connected to a circuit breaker. The charger is
connected directly to the two ends of the batteries electrically
connected in series. During a normal charging (constant
current/constant voltage), if any of the batteries exceeds a preset
overcharge voltage, the control board sends a signal to the circuit
breaker for charging termination. Similarly, during such
discharging, if any of the batteries is below the preset
termination voltage, the control board sends a signal to the
circuit breaker for discharging termination. These two actions
serve as battery protection to avoid overcharging and over
discharging. During normal charging, a preset time period is
allowed for the charging action (e.g. termination at 1.5 hours
after constant voltage charging). At that time, the batteries may
be more or less balanced. However, the batteries could be balanced
after several chargings, or by just starting a balance charging
(small current constant and current charge, current amplitude
I<I') mode, to allow constant current charging until all the
batteries are balanced.
[0060] In the present case, the control board can be a very simple
device for detecting the voltages of each battery connected in
series and sending signals to the circuit breaker for charging or
discharging action termination. The simplicity of the control board
is thus benefited by the characteristics of the batteries of the
invention since they possess current leakage during charging. In
the present invention, the shutting off of the charging is
preferably executed by a electromagnetic relay that turns off the
power input or output. This electromagnetic relay preferably
requires no power consumption during the idle state, and a pulse
signal generated by the control board determines the close and open
circuit status of the relay and therefore the on and off of the
battery charging.
Example 5
Methods to Achieve Cell Equalization as Described in Example 1
[0061] Referring to FIG. 11, in the present example, a total of
eight 10 Ah lithium iron batteries are used for demonstrating the
charging method and the cell balancing characteristic of the
batteries during charging. Two cells are first connected in
parallel to form a parallel battery set. Each set of the batteries
are then connected with a circuit (a printed circuit board, for
example) electrically connected in parallel with the battery set to
form a battery assembly. Four battery assemblies are then connected
in series. In the present case, the first set, second set, third
set, and the fourth set are named for the four battery set
assemblies connected in series for clarity. All four set assemblies
are first charged to 100% full. The first battery set assembly is
then subjected to discharge 10% capacity (2 Ah). After this
procedure, all four battery set assemblies are connected in series
and this setup is referred to as the battery pack. A preset
self-discharge activation voltage is set at 3.75V in the present
case. The self-discharge circuit that is parallel to each battery
set has a resistance of 2 Ohm. After the above mentioned
procedures, the battery pack is subjected to a constant current
charge of 1.7 A. The voltage changes versus time for each set of
the batteries are shown in Table I. From Table I it can be seen
that the 2.sup.nd, 3.sup.rd, and 4.sup.th battery set assembly had
a voltage increase beyond 3.75V in the initial state. 5 minutes
after, the 2.sup.nd, 3.sup.rd, and 4.sup.th battery set assembly
came back to be stabilized at 3.75V. At this time, the current
passing through the resistor is measured to be 1.8 A.
[0062] The 1.sup.st set of the battery set assembly increases its
voltage gradually to 3.75V after 80 minutes and this is the end of
the charge balance action. In the present experiment, I (power
supply current) is set to be less than I' (current passing
resistor). As a result, the voltages for the 2.sup.nd, 3.sup.rd,
and 4.sup.th sets of battery set assemblies were stabilized at
3.75V during charging. Full balances of the four sets of battery
set assemblies were achieved after a certain period of time. It was
observed that if current I is set to be slightly larger than
current I' (1.8 A in this case), and the voltages of the 2.sup.nd,
3.sup.rd, and 4.sup.th battery sets could be higher than 3.75V
during the constant current charge. However, if the constant
voltage charge is set at 15V as the second step charging, a voltage
decrease of 2.sup.nd, 3.sup.rd, and 4.sup.th battery sets can be
observed (when current I starts decreasing below current I') and
the four sets of battery set assemblies can be balanced eventually,
but requiring a longer time.
TABLE-US-00001 TABLE I Voltage versus time for each set of the
batteries. 40138 12V20Ah Lithium Iron Cell Balance Charging Test
Constant current charge (current = 1.7 A) Set Number 1 2 3 4
Initial Voltage (V) 3.344 3.354 3.348 3.35 Time (minutes) Voltage
for each set (V) 0 3.401 3.883 3.852 3.861 5 3.457 3.761 3.757
3.759 10 3.462 3.752 3.761 3.762 15 3.473 3.753 3.755 3.757 20
3.481 3.756 3.751 3.754 30 3.499 3.759 3.752 3.757 40 3.558 3.753
3.756 3.755 50 3.633 3.758 3.754 3.756 60 3.757 3.751 3.753 3.754
70 3.752 3.757 3.756 3.752 80 3.759 3.751 3.754 3.755
* * * * *