U.S. patent application number 09/769226 was filed with the patent office on 2001-11-15 for intelligent switch for battery.
Invention is credited to Choi, Kong Fan, NG, Wai Man.
Application Number | 20010040441 09/769226 |
Document ID | / |
Family ID | 24263354 |
Filed Date | 2001-11-15 |
United States Patent
Application |
20010040441 |
Kind Code |
A1 |
NG, Wai Man ; et
al. |
November 15, 2001 |
Intelligent switch for battery
Abstract
An intelligent switch for preventing over discharge of a vehicle
battery includes a switch connected to toggle between a first state
for preventing current flow from the battery and a second state for
allowing current flow from the battery. A voltage monitor provides
a voltage signal indicative of the voltage level of the battery. A
vibration sensor provides a vibration signal indicative of vehicle
vibration. A controller is connected to receive the voltage signal
and the vibration signal and generate a control signal for toggling
the switch to the first state when no vibration of the vehicle is
detected and the voltage level of the battery falls below a
predetermined voltage threshold. The controller generates another
control signal when vibration is detected to toggle the switch to
the second state. Multiple voltage thresholds and associated timers
are used to maintain an adequate battery charge level under
variable load conditions.
Inventors: |
NG, Wai Man; (Kowloon Bay,
CN) ; Choi, Kong Fan; (Kowloon Bay, CN) |
Correspondence
Address: |
ALIX YALE & RISTAS LLP
750 MAIN STREET
SUITE 600
HARTFORD
CT
06103
|
Family ID: |
24263354 |
Appl. No.: |
09/769226 |
Filed: |
January 24, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09769226 |
Jan 24, 2001 |
|
|
|
09566549 |
May 8, 2000 |
|
|
|
Current U.S.
Class: |
320/104 |
Current CPC
Class: |
H02J 7/0032 20130101;
H02J 2310/46 20200101; B60R 16/03 20130101 |
Class at
Publication: |
320/104 |
International
Class: |
H02J 007/14 |
Claims
What is claimed is:
1. An intelligent switch for preventing undesirable discharge of a
battery of a vehicle, comprising: a switch connected in circuit
with the battery and being configured to toggle between a first
state for preventing current flow from the battery and a second
state for allowing current flow from the battery; a voltage monitor
connected to the battery and being configured to provide a voltage
signal indicative of the voltage level of the battery; a vibration
sensor configured to detect vibration of the vehicle and provide a
vibration signal indicative thereof; and a controller connected to
receive the voltage signal and the vibration signal and being
configured to generate a control signal for toggling the switch to
the first state when no vibration of the vehicle is detected and
the voltage level of the battery falls below a predetermined
voltage threshold and to the second state when vibration is
detected regardless of the voltage level of the battery.
2. The intelligent switch of claim 1, wherein the voltage monitor
is configured to output the voltage signal when the voltage from
the battery falls below the predetermined voltage threshold, the
voltage signal being detected by the controller.
3. The intelligent switch of claim 1, wherein the controller
comprises a central processing unit.
4. The intelligent switch of claim 1, wherein the controller
comprises a microprocessor.
5. The intelligent switch of claim 1, further comprising a timer
circuit for providing a predetermined delay between when the
voltage level falls below the predetermined threshold value and the
output of the control signal from the controller so that should
vibrations be detected the control signal will not be output from
the controller.
6. The intelligent switch of claim 5, wherein the predetermined
delay is about thirty seconds.
7. The intelligent switch of claim 1, wherein the switch comprises
a latching relay.
8. The intelligent switch of claim 7, wherein the control signal
comprises a control pulse.
9. The intelligent switch of claim 1, wherein the vibration sensor
outputs a vibration signal upon vibration of the vehicle.
10. The intelligent switch of claim 9, wherein vibration sensor
comprises a piezoelectric disc or a magnetic sensor.
11. The intelligent switch of claim 7 further comprising a power
management unit for supplying power to the voltage monitor,
vibration sensor, controller and latching relay.
12. The intelligent switch of claim 1, wherein the predetermined
voltage threshold is approximately 12.1 volts.
13. The intelligent switch of claim 1 wherein the battery comprises
a positive terminal and the intelligent switch is incorporated
within the battery in circuit with the positive terminal.
14. An intelligent switch for preventing undesirable discharge of a
battery for a vehicle, comprising: a switch connected in circuit
with the battery and being configured to toggle between a first
state for preventing current flow from the battery and a second
state for allowing current flow from the battery; a voltage monitor
connected to the battery and being configured to provide a low
voltage signal when the voltage from the battery falls below a
predetermined voltage threshold level; a vibration sensor
configured to detect vibration of the vehicle and provide a
vibration signal indicative thereof; and a controller connected to
receive the low voltage signal and the vibration signal and being
configured to generate a control signal for toggling the switch to
the first state when no vibration of the vehicle is detected and to
the second state when vibration is detected.
15. A method of preventing undesirable discharge of a battery for a
vehicle, comprising the steps of: monitoring a voltage level of the
battery and providing a voltage signal indicative of the voltage
level; detecting vibration of the vehicle and providing a vibration
signal indicative thereof; receiving the voltage signal and the
vibration signal; generating a control signal based on the voltage
signal when the voltage level from the battery falls below a
predetermined threshold voltage level and based on the vibration
signal when no vibration of the vehicle is detected, the control
signal toggling a switch to a first state for preventing current
flow from the battery; and generating another control signal for
toggling the switch to a second state for allowing current flow
from the battery when vibration is again detected.
16. The method of claim 15 further comprising the step of delaying
the generation of the control signal after the voltage level falls
below the predetermined voltage threshold value.
17. The method of claim 16, wherein the delay is about thirty
seconds.
18. The method of claim 15, wherein the switch comprises a latching
relay.
19. The method of claim 18, wherein the control signal comprises a
control pulse.
20. The method of claim 15, wherein the predetermined voltage
threshold value is about 12.1 volts.
21. An intelligent switch for preventing undesirable discharge of a
rechargeable vehicle battery, comprising: a switch connected in
circuit with the battery and being configured to toggle between a
first state for preventing current flow from the battery and a
second state for allowing current flow from the battery; a voltage
monitor connected to the battery and being configured to provide a
voltage signal indicative of the voltage level of the battery; a
vibration sensor configured to detect vibration of the vehicle and
provide a vibration signal indicative thereof; a controller
connected to receive the voltage signal and the vibration signal
and being configured to generate a control signal for toggling the
switch to the first state when no vibration of the vehicle is
detected subsequent to the voltage level of the battery falling
below a predetermined voltage threshold and to the second state
when vibration is detected; and at least one timer configured to
start counting a predetermined period of time in response to the
voltage level of the battery falling below the predetermined
voltage threshold, at the end of which predetermined period of time
the controller is to generate said control signal for toggling the
switch to the first state.
22. The intelligent switch of claim 21, wherein the controller
comprises a microprocessor.
23. The intelligent switch of claim 21, wherein the battery
comprises a positive terminal and the intelligent switch is
incorporated within the battery in circuit with the positive
terminal.
24. The intelligent switch of claim 21, wherein the switch
comprises a latching relay.
25. The intelligent switch of claim 21, wherein the vibration
sensor comprises a piezoelectric disc or a magnetic sensor.
26. The intelligent switch of claim 24, further comprising a power
management unit for supplying power to the voltage monitor,
vibration sensor, controller, at least one timer and latching
relay.
27. The intelligent switch of claim 21, wherein the battery is a
battery for starting an engine of the vehicle.
28. The intelligent switch of claim 21, wherein the battery
comprises a first part primarily for starting the engine of the
vehicle and a second part primarily for supplying power to an
electrical load of the vehicle, to which first and second battery
parts the voltage monitor is connected, and the intelligent switch
includes first and second said switches connected in circuit with
the first and second battery parts respectively.
29. The intelligent switch of claim 28, wherein the controller is
configured to generate a first control signal for toggling the
first switch to the first state when no vibration of the vehicle is
detected subsequent to the voltage level of the first battery part
falling below a first predetermined voltage threshold and
subsequently to generate a second control signal for toggling the
second switch to the first state when no vibration of the vehicle
is detected and the voltage level of the second battery part falls
below a second predetermined voltage threshold, said second
predetermined voltage threshold being lower than said first
predetermined voltage threshold.
30. The intelligent switch of claim 29, wherein the first and
second predetermined voltage thresholds are about 12.8 volts and
10.8 volts, respectively.
31. The intelligent switch of claim 21, wherein the controller is
configured with at least two said predetermined voltage thresholds,
and the intelligent switch includes one said timer associated with
each said predetermined voltage threshold, a first of said timers
being for counting a relatively longer predetermined period of time
corresponding to the predetermined voltage threshold that is
relatively higher, and a second of said timers being for counting a
relatively shorter predetermined period of time corresponding to
the predetermined voltage threshold that is relatively lower.
32. The intelligent switch of claim 31, wherein the controller is
configured to generate said control signal when any one of the
predetermined periods of time is counted to an end.
33. The intelligent switch of claim 21, wherein the controller is
configured with five said predetermined voltage thresholds, and the
intelligent switch includes one said timer associated with each
predetermined voltage threshold for counting predetermined periods
of time associated with each predetermined voltage threshold, the
predetermined period of time associated with a higher voltage
threshold being longer than the predetermined period of time
associated with a relatively lower voltage threshold.
34. The intelligent switch of claim 33, wherein each timer is
configured to stop counting when the voltage level of the battery
rises back above the predetermined voltage threshold associated
with the timer and to resume counting if the voltage level of the
battery falls below the predetermined voltage threshold associated
with the timer, said timer resuming said counting where said
counting stopped and counting for a period of time corresponding to
a remainder of said predetermined period of time associated with
said timer.
35. The intelligent switch of claim 21, wherein each said at least
one timer comprises a count down timer.
36. The intelligent switch of claim 34, wherein the controller is
configured to generate said control signal when any one of the
predetermined periods of time is counted to an end.
37. A method of preventing undesirable discharge of a battery for a
vehicle, comprising the steps of: monitoring a voltage level of the
battery and providing a voltage signal indicative of the voltage
level; detecting vibration of the vehicle and providing a vibration
signal indicative thereof; receiving the voltage signal and the
vibration signal; generating a control signal based on the voltage
signal when the voltage level from the battery falls below a
predetermined threshold voltage level in the absence of vehicle
vibration, the control signal toggling a switch to a first state
for preventing current flow from the battery; and generating
another control signal for toggling the switch to a second state
for allowing current flow from the battery when vibration is again
detected.
38. The method of claim 37, further comprising the step of delaying
the generation of the control signal after the voltage level falls
below the predetermined voltage threshold value.
39. The method of claim 38, wherein said step of delaying comprises
the steps of starting to count a first predetermined period of time
when the voltage level from the battery falls below a first
predetermined threshold voltage level, and the step of starting to
count a second, relatively shorter predetermined period of time
when the voltage level from the battery falls below a second,
relatively lower predetermined threshold voltage level, prior to
the generation of the control signal.
40. The method of claim 39, wherein the control signal is generated
when any one of the predetermined periods is counted to an end.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This is a continuation-in-part of U.S. application Ser. No.
09/566,549 filed May 8, 2000.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to switches and,
more particularly, to battery disconnect switches for preventing
undesirable discharge of a battery.
[0004] 2. Description of the Related Art
[0005] A rechargeable battery for use in providing initial energy
for starting a motor of a vehicle, such as an automobile, a truck,
a bus, a boat and most lawnmowers, is well known. As also well
known, once the engine of the vehicle begins to run, an electrical
generator provides power to recharge the battery and to energize an
electrical load of the vehicle. The electrical load typically
includes electrical appliances such as various lights, including
safety and illumination lights, power accessories such as power
door locks and power windows, and a radio. When the engine of the
vehicle is not running, the electrical generator produces no power
and the battery becomes the sole source. As most operators have
experienced, a substantial risk of over discharging the battery
arises when the engine is off and the load has not been
disconnected from the battery such as in the case of an automobile
where the headlights are left on after the engine has been shut
off. In such a case, the battery may be discharged to a level where
insufficient power exists to restart the engine of the
vehicle--possibly causing the operator to be stranded. In addition,
over discharging a battery will shorten the battery life because
sulphuration may occur. Sulphuration involves an abnormal sulfate
formed on the surface of the battery plates which hinders the
battery plate from receiving and accepting a charge because of an
increased resistance thereof.
[0006] Currently, disconnect switches are available for monitoring
the state of the battery and disconnecting the battery from the
electric load of the vehicle when the battery is discharging at a
high rate or low rate after the engine has been shut off. However,
these devices suffer from the draw back that once the battery has
been disconnected from the electric load of the vehicle, they must
be manually reset by the operator in order to start the engine.
SUMMARY OF THE INVENTION
[0007] Briefly stated, the invention in a preferred form is an
intelligent switch for preventing undesirable discharge of a
battery of a vehicle. The intelligent switch includes a switch
connected in circuit with the battery that is configured to toggle
between a first state for preventing current flow from the battery
and a second state for allowing current flow from the battery. A
voltage monitor is connected to the battery and is configured to
provide a voltage signal indicative of the voltage level of the
battery. A vibration sensor is configured to detect vibration of
the vehicle and provide a vibration signal indicative thereof. A
controller is connected to receive the voltage signal and the
vibration signal and generate a control signal for toggling the
switch to the first state when no vibration of the vehicle is
detected and the voltage level of the battery falls below a
predetermined voltage threshold and to the second state when
vibration is detected regardless of the voltage level of the
battery.
[0008] In a particular aspect of the invention, the voltage monitor
is configured to output the voltage signal when the voltage from
the battery falls below the predetermined voltage threshold, the
voltage signal being detected by the controller.
[0009] In other aspects of the invention, the controller comprises
a central processing unit, in particular, a microprocessor and a
timer circuit for providing a predetermined delay between when the
voltage level falls below the predetermined threshold value and the
output of the control signal from the controller so that should
vibrations be detected the control signal will not be output from
the controller.
[0010] The battery may include a first part primarily for starting
the engine of the vehicle and a second part primarily for supplying
power to electrical load of the vehicle and connectable in parallel
with the first part, to which battery parts the voltage monitor is
connected. An intelligent switch configured for use in conjunction
with such a battery includes first and second said switches
connected in circuit with the first and second battery parts
respectively. The controller is configured to generate a first
control signal for toggling the first switch to the first state
when no vibration of the vehicle is detected and the voltage level
of the battery parts connected in parallel falls below a first
predetermined voltage threshold. The controller generates a second
control signal for toggling the second switch to the first state
when no vibration of the vehicle is detected and the voltage level
of the second battery part falls below a second, relatively lower
predetermined voltage threshold.
[0011] To protect the battery against over discharge in different
current drain situations, the controller is configured with at
least two predetermined voltage thresholds. The intelligent switch
includes at least two said timers associated with said
predetermined voltage thresholds. A first of said timers counting a
relatively longer predetermined period of time corresponding to the
predetermined voltage threshold that is relatively higher, and a
second timer being for counting a relatively shorter predetermined
period of time corresponding to the predetermined voltage threshold
that is relatively lower, etc.
[0012] A controller equipped with multiple voltage thresholds and
multiple timers has the capability to more accurately measure the
discharge condition of the battery. According to one aspect of the
invention, the controller is configured with five said
predetermined voltage thresholds. The intelligent switch includes a
timer associated with each predetermined voltage threshold for
counting respective predetermined periods of time the lengths of
which increase or decrease with the levels of the corresponding
voltage thresholds.
[0013] Advantageously, the timer is configured to stop counting
when the voltage level of the battery rises back above the
predetermined voltage threshold and to continue to count when the
voltage level of the battery falls below the predetermined voltage
threshold again for the uncounted part of the predetermined period
of time. The controller is configured to generate said control
signal for toggling the switch to the first state at the time when
any one of the predetermined periods is counted to an end.
[0014] In another aspect of the invention, a method of preventing
undesirable discharge of a battery for a vehicle, comprises the
steps of: monitoring a voltage level of the battery and providing a
voltage signal indicative of the voltage level; detecting vibration
of the vehicle and providing a vibration signal indicative thereof;
receiving the voltage signal and the vibration signal; generating a
control signal based on the voltage signal when the voltage level
from the battery falls below a predetermined threshold voltage
level and based on the vibration signal when no vibration of the
vehicle is detected, the control signal toggling a switch to a
first state for preventing current flow from the battery; and
generating another control signal for toggling the switch to a
second state for allowing current flow from the battery when
vibration is again detected.
[0015] The method further comprises the step of starting to count a
first, relatively longer predetermined period of time when the
voltage level from the battery falls below a first, relatively
higher predetermined threshold voltage level, and the step of
starting to count a second, relatively shorter predetermined period
of time when the voltage level from the battery falls below a
second, relatively lower predetermined threshold voltage level,
prior to the generation of the control signal. The control signal
is generated when any one of the predetermined periods is counted
to an end.
[0016] An object of the present invention is to provide a new and
improved intelligent switch that prevents over discharge of a
battery.
[0017] Another object of the invention is to provide a new and
improved intelligent switch that automatically resets itself after
disconnection of the battery so that an operator may restart the
vehicle.
[0018] A further object of the invention is to provide a new and
improved intelligent switch for a battery that protects the battery
from over discharge under variable load conditions.
[0019] A yet further object of the invention is to provide a new
and improved intelligent switch for incorporation within the
battery.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a schematic diagram of an electrical system for a
vehicle incorporating an intelligent switch for a battery in
accordance with an embodiment of the present invention;
[0021] FIG. 2 is a functional block diagram, partly in schematic,
of the intelligent switch for battery of FIG. 1;
[0022] FIG. 3 is a schematic diagram of one embodiment of the
intelligent switch of FIG. 1;
[0023] FIG. 4 is a schematic diagram of an alternative embodiment
of the intelligent switch of FIG. 1;
[0024] FIG. 5 is a table illustrating the relationship between
loading conditions, voltage reference levels and timer length for
an embodiment of an intelligent switch in accordance with the
present invention;
[0025] FIG. 6 is a functional block diagram, partly in schematic,
of an alternative embodiment of an intelligent switch in accordance
with the present invention; and
[0026] FIG. 7 is a schematic diagram of the intelligent switch of
FIG. 6.
DETAILED DESCRIPTION OF THE INVENTION
[0027] Referring to FIG. 1, an intelligent switch 10 is illustrated
as being incorporated within a battery 12 via an internal switch
box 13 and in circuit with a positive terminal 13A and a negative
terminal 13B. It will be appreciated, however, that the intelligent
switch 10 may instead be located externally of the battery 12 such
as in an external switch box (not shown) and connected via wire
(also not shown) to the battery 12. The intelligent switch 10 is
shown for use in conjunction with a vehicle electrical system 14
such as a 12 volt system, although it will be appreciated that the
intelligent switch may be employed with other suitable electrical
systems employing a battery. The vehicle electrical system 14 may
be used in conjunction with automobiles, trucks, buses, marine
craft, lawn mowers, etc.
[0028] The electrical system 14 comprises an electrical generator
16 which turns mechanical energy from the vehicle motor (not shown)
into electrical energy useful for energizing a load 18 of the
electrical system 14. The load 18 may comprise an ignition system
20, headlights 22 and accessories 24. The ignition system 20, as is
well known, may include a main coil and spark plugs (both not
shown). The accessories 24 may include additional electronic
devices such as a radio or a GPS navigational system. A starter 26
is further provided for cranking the vehicle motor (not shown) in a
well known matter. A ground 28 completes the circuit between
battery 12 and the electrical generator 16, load 18 and starter
26.
[0029] Referring now to FIG. 2, an intelligent switch in accordance
with the present invention is illustrated generally at 10. The
intelligent switch 10 is connected in circuit with the positive
terminal 13A of the battery 12 via a switch 30 and also comprises a
vibration detection unit 32, a controller 34, and a battery voltage
monitor 36. A power management unit 38 may be provided for
supplying the appropriate voltage and current to the switch 30,
vibration detection unit 32, controller 34 and battery voltage
monitor 36. The power management unit 38 may comprise a regulator
as is well known and is connected to receive power from the battery
12 and input 40. An output 42 of the power management unit 38
provides power to the vibration detection unit 32, controller 34
and battery voltage monitor 36 shown by lines 44, 46 and 48,
respectively. An additional lead 49 may be provided so that the
power management unit 38 may function via an additional power
source such as the vehicle generator 16 (FIG. 1) in the event
battery 12 is discharged to a low voltage level and the switch 30
is in the open state.
[0030] The battery voltage monitor 36 includes an input 50 from the
battery 12 and, in a preferred embodiment, functions to output a
voltage signal on line 52 when the low voltage level of the battery
12 falls below a predetermined threshold of about 12.10 volts. The
battery voltage monitor may be any suitable device for performing
the foregoing function, although, it is preferably a voltage
reference device sold by the S.C.S Thomson Corporation. The battery
voltage monitor 36 may comprise a solid state circuit including,
e.g., a comparator and an analog to digital (A/D) converter.
[0031] The switch 30 is shown in an open state and preferably
comprises a MOSFET latching relay which functions to toggle between
the open state and a closed state based upon a control signal input
via line 54. When an electric circuit pulse is received, the switch
30 will toggle from one state to the other state and will remain
until another electric current pulse is received. The latching
relay is preferably an electro-mechanical device sold by the Glory
Win International Group Ltd.
[0032] The vibration detection unit 32 functions to sense
vibrations to, in turn, also identify when the vehicle is ready to
be operated or is in operation. In particular, the vibration
detection unit 32 senses any vibrations such as a door of the
vehicle opening, an operator entering the vehicle and/or engine of
the vehicle running and provides a vibration signal output via line
56. Preferably the presence of the vibration signal indicates that
vibrations are sensed. The vibration detection unit 32 may comprise
any suitable device for sensing vibration such as a piezoelectric
disc or a magnetic sensor arranged to transform a mechanical force
into electrical energy. Examples of a magnetic sensor useful in the
practice of this invention include a magnetic field intensity
sensor for sensing, e.g., a variation in the intensity of a
magnetic field caused by physical vibration or movement of a magnet
or a device for measuring variations in mutual inductance between
magnetically coupled coils which may vibrate or move
individually.
[0033] The controller 34 preferably comprises a central processing
unit such as a microprocessor which is programmed to receive input
from both the battery voltage monitor 36 and vibration detection
unit 56 and output a control signal to drive, e.g., a MOSFET to
deliver an electrical control pulse to the switch 30 via line 54.
It will be appreciated that additional circuitry may be employed to
shape or otherwise provide an appropriate control signal to the
switch 30. Preferably, the controller 34 comprises a microprocessor
manufactured by the S.C.S Thomson Corporation. However, it will be
understood that the controller 34 may instead comprise a solid
state electronic circuit comprising, e.g., one or more comparators
and/or one or more electronic gates rather than a processor.
[0034] A timer 58 may optionally be employed to provide a delay
time, as discussed below, of approximately thirty (30) seconds. The
timer 58 communicates with the controller 34 via communication line
60. It will be appreciated, however, that the controller 34 may
include a built-in timer. In addition, where the controller
comprises a microprocessor the timer function may be provided via
firmware or the like.
[0035] In operation, the controller 34 receives input from the
battery voltage monitor 36 via line 52 and vibration detection unit
32 via line 56. When the vehicle has been shut down, vibration
detection unit 32 will cease to provide a vibration signal to the
controller 34. Should the voltage fall below a threshold voltage
level of about 12.1 volts, the battery voltage monitor 52 will
provide a low voltage signal to the controller 34. The controller,
after a delay from timer 58 of about thirty (30) seconds will send
a control pulse to the switch 30. The switch 30 will thus change
from the closed state to the open state preventing flow of current
from battery 12 to the load 18 (FIG. 1) of the vehicle. At this
time, the controller 34 continuously monitors the vibration
detection unit 32. Upon receiving a vibration signal from the
vibration detection unit, the controller 34 will send another
control pulse switching the switch 30 to the closed state and
allowing transfer of energy from the battery 12 to the load 18
illustrated in FIG. 1.
[0036] The intelligent switch 10 is used to protect the battery 12
from damage by over discharge and to ensure that the battery 12
will always reserve sufficient power to start the vehicle, by
disconnecting the battery 12 according to certain cut off criteria.
The state of charge of the battery 12 is used as such cut off
criteria, and one of the methods to determine the state of charge
is to measure the output voltage of the battery 12. However, the
output voltage is not directly proportional to the state of charge
of the battery 12. Under different loading conditions, the terminal
voltage is different for the same state of charge of the battery
12.
[0037] For example, with a small load such as a radio inside the
car compartment (current drain at 0.2 A) draining 50% of the
battery capacity, the terminal voltage may be lowered to 12.4V. In
contrast, with a large load such as the headlights (current drain
at 30 A) draining 50% of the battery capacity, the terminal voltage
may be lowered to 11.8V.
[0038] With the use of a single voltage threshold or reference
level to cut off the battery 12, for example 12.1V as described
above, the remaining battery capacity will vary according to
different loading conditions. If the voltage reference level is set
to a relatively high level such as 12.4V, with a 0.2 A loading, the
remaining battery capacity after cut off will be about 50% as
intended. However, with a 30 A loading, the remaining battery
capacity after cut off will be about 80%, which represents a
pre-mature cut off of power to the user. In contrast, if the
voltage reference level is set to a relatively low level such as
11.8V, with a 30 A loading, the remaining battery capacity after
cut off will be about 50% as intended, but with a 0.2 A loading,
the battery will be severely over discharged at the same terminal
voltage.
[0039] Accordingly, for the purpose of reserving the battery
capacity at about 50% for various loading conditions after cut off,
the use of a single voltage reference level is not practical. More
than one or several voltage reference levels should preferably be
used to cater for different load currents. In order to improve the
performance of the described embodiment, five voltage reference
levels are preset in the controller 34 and, in addition, five count
down timers for counting different lengths of time are incorporated
in the controller 34 corresponding to the voltage reference levels.
The lengths of the timers are longer for higher voltage reference
levels. An example of the settings of the voltage reference levels
and associated timer lengths with respect to different loading
currents for a typical model of the battery 12 is shown in FIG. 5,
in that the timer lengths increase or decrease in the same order as
the corresponding voltage thresholds. It should be noted that the
settings will vary for batteries of different capacities and/or
different electrical loads.
[0040] In operation, when the battery voltage falls below a voltage
reference level, the corresponding timer will start to count down.
When any one of the five timers counts to zero, the switch 30 cuts
off the battery 12. The timers will continue to count even when the
battery voltage falls below the next lower voltage reference
level.
[0041] In the situation that the battery 12 is being discharged at
a 0.2 A load current, the battery voltage will drop slowly. Upon
the battery voltage falling below the first voltage reference level
of 12.4375V, the first timer will start to count down for 22 hours.
If the discharge current (rate of discharge) remains the same, the
battery 12 is cut off by the switch 30 at the end of the 22-hour
period. At this time, about 50% of the maximum capacity remains in
the battery 12. It should be noted that the battery voltage will
not reach the next lower or second voltage reference level by the
end of the 22 hours.
[0042] In a different situation that the battery 12 is being
discharged at a 1.0 A load current for example, the battery voltage
will drop faster than under a 0.2 A loading condition. When the
battery voltage falls below the first voltage reference level, the
22-hour timer will start to count down. Since the rate of voltage
drop is faster, the battery voltage will fall below the second
voltage reference level of 12.3125V before the first timer expires.
Upon the battery voltage falling below the second voltage reference
level, the second timer will start to count down for 5.5 hours. It
should be noted that the first timer will continue to count even
after the second timer has started to count. While the discharge
current remains the same, the battery 12 will be cut off at the end
of the 5.5-hour period. At this time, about 50% of the maximum
capacity remains in the battery 12.
[0043] When the discharge current of the battery 12 is 3.3 A, the
third timer will start to count down for 24 minutes upon the
battery voltage falling below the third voltage reference level of
12.1875V. When the timer has expired, the battery 12 will be cut
off to reserve about 50% of the maximum capacity. With the
discharge current being 10 A, the fourth timer will start when the
battery voltage falls below the fourth voltage reference level of
12.125V and count down for 5 minutes, at the end of which the
battery 12 will be cut off. The fifth timer will start when the
battery voltage falls below 12V, while the battery 12 is
discharging at a current larger than 25 A, and count down for 10
seconds before the battery 12 is cut off.
[0044] The intelligent switch is also responsive to changing load
conditions that switch between small and large load currents, such
as user's switching on of a radio (current drain at 0.2 A) and
automatic switching on and off of a cooling fan (current drain at
10 A). The first timer will start when battery voltage falls below
the first voltage reference level (12.4375V). When the cooling fan
is switched on, the battery voltage will fall rapidly to below the
second level (12.3125V), then the third level (12.1875V) and
eventually the fourth level (12.125V), with the second, third and
fourth timers starting to count down at respective different
moments.
[0045] If the cooling fan is switched off after a certain time
period of say 3 minutes from the moment when the fourth timer
started, the battery voltage will stop falling and rise up slowly
to pass the fourth, third and second voltage reference levels
sequentially. The timers will stop counting when the battery
voltage rises back over the corresponding levels, but the counted
value of each timer will not be cleared. The counted value is
useful to indicate or record how much power has been drained out
from the battery 12.
[0046] If the cooling fan is subsequently switched on again after
say 10 minutes and when the battery voltage falls to below each
next lower voltage reference level again, the corresponding timer
will start to count from the value that it has previously counted
and stopped at. When the battery voltage eventually falls below the
fourth voltage reference level, the fourth timer will start to
count down for only for the uncounted part that is 2 minutes
because it has already counted 3 minutes on the previous occasion.
At the expiry of the 2-minute period, the battery 12 will be cut
off and there will be about 50% of the maximum capacity reserved in
the battery 12.
[0047] All the timers will be reset automatically after the battery
12 has been charged up, as a result of the restarting of the
vehicle engine, to above a predetermined high voltage level and for
a predetermined period of time, such as above 13V for 1 minute.
[0048] Reference is finally made to FIGS. 6 and 7. The use of the
subject intelligent switch in conjunction with the aforesaid
electrical system 14 can be extended to a 12-cell lead acid battery
that consists of two parts connected in parallel. A first part of
the battery acts as a cranking battery 12A and a second part acting
as an auxiliary battery 12B. The cranking battery 12A is designed
primarily for supplying a very large current to start the vehicle,
and the auxiliary battery 12B primarily to withstand deep cycles of
power consumption by accessories during periods when the vehicle
charging system is not operating.
[0049] An alternative embodiment of the intelligent switch 10A is
illustrated in FIGS. 6 and 7. The intelligent switch 10A has a
configuration very similar to that of the first switch 10, with
equivalent parts designated by the same reference numerals.
Intelligent switch 10A incorporates a pair of starting and
auxiliary latching relay switches 30A and 30B for cutting off the
respective loads from the cranking and auxiliary batteries 12A and
12B respectively. Although the switches 30A and 30B are shown to be
triggerable via the same line 54, they are responsive to
distinctive control signals as provided by the controller 34 for
independent switching. Alternatively, a separate line 54 may be
used for the controller 34 to toggle each corresponding switch 30A
or 30B.
[0050] Due to the presence of two batteries 12A and 12B and the use
of separate switches 30A and 30B to control them, two lines 40A and
40B (equivalent to the aforesaid line 40) are included for
supplying battery power to the power management unit 38. For the
same reasons, two lines 50A and 50B (equivalent to the aforesaid
line 50) are included for the battery voltage monitor 36 to monitor
the output voltage of the batteries 12A and 12B.
[0051] The intelligent switch 10A is used to protect both of the
cranking and auxiliary batteries 12A and 12B, which are connected
in parallel for use, from damage due to over discharge. The
intelligent switch also ensures that sufficient power is reserved
in the cranking battery 12A to start the vehicle. In order to
ensure that the cranking battery 12A always has sufficient power,
the starting switch 30A should be opened whenever the vehicle is
stopped with its engine shut down.
[0052] The battery voltage monitor 36 continuously monitors the
voltage of the auxiliary and cranking batteries 12A and 12B. When
the terminal voltage of the inter-connected batteries 12A and 12B
is higher than 13.0V, the vehicle is running and the generator 16
of the vehicle is generating power, both of the starting and
auxiliary switches 30A and 30B should be closed to enable charging
of the batteries 12A and 12B. If the terminal voltage of the
batteries 12A and 12B falls below 12.8V and the generator 16 is not
generating any power, the starting switch 30A is toggled open after
a time delay of say 30 seconds to disconnect the cranking battery
12A from the electrical load 18 of the vehicle. The cranking
battery 12A will be re-connected automatically upon detection of
vibration for restarting the vehicle.
[0053] Since the intelligent switch 10A always ensures that the
cranking battery 12A has sufficient power reserved for starting the
vehicle, the cranking battery 12A is always maintained at a high
state of charge and therefore protected from damage by reason of
over discharge.
[0054] The auxiliary battery 12B serves to supply power to operate
the electrical load 18. The intelligent switch 10A also protects
the auxiliary battery 12B from damage due to over discharge. When
the vehicle is stopped with its engine off and the cranking battery
12A disconnected, the battery voltage monitor 36 will continue to
monitor the status of the auxiliary battery 12B. When the
headlights or radio are switched on, the remaining battery capacity
will fall to a predetermined value of say 10.8V, whereupon the
battery voltage monitor 36 detects it and then signals the
controller 34 to open the auxiliary switch 30B to disconnect the
auxiliary battery 12B after a time delay of say 30 seconds. Before
the time delay expires, if the battery voltage rises back to a
level higher than the predetermined value, the controller 34 will
not disconnect the auxiliary battery 12B.
[0055] As the cranking battery 12A is dedicated to reserve
sufficient power to start the vehicle, there is no need for the
auxiliary battery 12B to retain too much power. Only a small
percentage, say 5% to 10%, of the maximum capacity will need to be
reserved in order to safeguard the auxiliary battery 12B against
damage by over discharge, whereby the capacity of the auxiliary
battery 12B can be fully utilized by the vehicle user.
[0056] While both the starting and the auxiliary switches 30A and
30B are open, when vibration is detected the controller 34 will
initially close the starting switch 30A to connect the cranking
battery 12A for starting the vehicle. After the vehicle has been
started, the cranking battery 12A will be charged by the generator
16 of vehicle. When the voltage of cranking battery 12A rises to a
predetermined level (say 13V), the auxiliary switch 30B will then
be closed to enable the auxiliary battery 12B to be charged
simultaneously with the cranking battery 12A.
[0057] While the present invention has been described in connection
with what is presently considered to be the most practical and
preferred embodiments, it is to be understood that the present
invention is not limited to the disclosed embodiments. Rather, it
is intended to cover all the various modifications and equivalent
arrangements included within the spirit and scope of the appended
claims.
* * * * *