U.S. patent application number 11/134999 was filed with the patent office on 2006-11-23 for electronic battery module (ebm) with bidirectional dc-dc converter.
Invention is credited to Paul Gamboa, John J. C. Kopera.
Application Number | 20060261783 11/134999 |
Document ID | / |
Family ID | 36636879 |
Filed Date | 2006-11-23 |
United States Patent
Application |
20060261783 |
Kind Code |
A1 |
Gamboa; Paul ; et
al. |
November 23, 2006 |
Electronic battery module (EBM) with bidirectional DC-DC
converter
Abstract
A telecommunication switching station includes telecommunication
equipment, a DC power supply having an output connected to the
telecommunication equipment, and a plurality of rechargeable DC
power supplies connected in parallel with the output of the DC
power supply. Each DC power supply includes a pair of power supply
terminals, a rechargeable battery, and a bidirectional DC-DC
converter module connected between the rechargeable battery and the
pair of power supply terminals. The DC power supply provides power
to the telecommunication equipment and recharges the plurality of
rechargeable DC power supplies. The plurality of rechargeable DC
power supplies serve as a back-up for the DC power supply.
Inventors: |
Gamboa; Paul; (Chicago,
IL) ; Kopera; John J. C.; (Ortonville, MI) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Family ID: |
36636879 |
Appl. No.: |
11/134999 |
Filed: |
May 23, 2005 |
Current U.S.
Class: |
320/138 |
Current CPC
Class: |
H02J 1/10 20130101; H02J
7/0072 20130101; H02J 2207/20 20200101; H02J 7/007194 20200101;
H01M 10/425 20130101; Y02E 60/10 20130101; H01M 10/486
20130101 |
Class at
Publication: |
320/138 |
International
Class: |
H02J 7/00 20060101
H02J007/00 |
Claims
1. A telecommunication switching station, comprising:
telecommunication equipment; a DC power supply having an output
connected to said telecommunication equipment; and a plurality of
rechargeable DC power supplies connected in parallel with said
output of said DC power supply, each including: a pair of power
supply terminals; a rechargeable battery; and a bidirectional DC-DC
converter module connected between said rechargeable battery and
said pair of power supply terminals, wherein said DC power supply
provides power to said telecommunication equipment and recharges
said plurality of rechargeable DC power supplies and said plurality
of rechargeable DC power supplies serve as a back-up for said DC
power supply.
2. The telecommunication switching station of claim 1 wherein each
of said rechargeable DC power supplies further includes: a control
module that communicates an enable signal to a respective one of
said bidirectional DC-DC converter modules, wherein said respective
bidirectional DC-DC converter module selectively creates an open
circuit condition between said pair of power supply terminals in
accordance with said enable signal.
3. The telecommunication switching station of claim 2 wherein each
of said rechargeable DC power supplies further includes: a data
communication port in communication with a respective one of said
control modules.
4. The telecommunication switching station of claim 2 wherein each
of said rechargeable DC power supplies further includes: a battery
temperature sensor positioned in proximity of a respective one of
said rechargeable batteries and providing a battery temperature
signal to a respective one of said control modules.
5. The telecommunication switching station of claim 4 wherein each
said battery temperature sensor is positioned inside of said
respective one of said rechargeable batteries.
6. The telecommunication switching station of claim 2 wherein each
of said rechargeable DC power supplies further includes: a current
sensor providing a signal to a respective one of said control
modules and being connected between a respective one of said
rechargeable batteries and a respective one of said bidirectional
DC-DC converter modules.
7. The telecommunication switching station of claim 6 wherein said
signal is indicative of a magnitude and direction of current flow
through said respective one of said rechargeable batteries.
8. The telecommunication switching station of claim 1 wherein each
of said rechargeable DC power supplies further includes: a switch
having a control input and being connected between a respective one
of said rechargeable batteries and a respective one of said
bidirectional DC-DC converter modules and wherein said switch opens
and closes in response to said control input.
9. The telecommunication switching station of claim 1 wherein each
of said control modules further communicates a desired output
voltage signal to said respective one of said bidirectional DC-DC
converter modules and wherein said respective one of said
bidirectional DC-DC converter modules regulates a load voltage
across a respective one of said pair of power supply terminals in
accordance with said desired output voltage signal.
10. A rechargeable DC power supply, comprising: a housing including
an interior, an exterior, and an integral heat sink including a
heat absorbing surface formed in said interior and a heat
dissipating surface formed in said exterior; a rechargeable battery
having battery terminals positioned in said interior; power supply
terminals positioned at said exterior of said housing; and a first
printed circuit board (PCB) assembly including a bidirectional
DC-DC converter module connected between said battery terminals and
said power supply terminals, said first PCB assembly being in
coplanar contact with said heat absorbing surface.
11. The rechargeable DC power supply of claim 10 further
comprising: a battery tray connected to said housing and containing
said rechargeable battery.
12. The rechargeable DC power supply of claim 10, wherein said
rechargeable battery comprises a plurality of rechargeable cells
having cell terminals, further comprising: a second PCB assembly
positioned on said cell terminals and having PCB traces connecting
said cell terminals to form said battery terminals.
13. The rechargeable DC power supply of claim 10 wherein said
housing nests on said rechargeable battery.
14. The rechargeable DC power supply of claim 12 further
comprising: a battery temperature sensor positioned in proximity of
said rechargeable battery and connected said second PCB
assembly.
15. The rechargeable DC power supply of claim 14 wherein said
battery temperature sensor is located inside of said battery.
16. The rechargeable DC power supply of claim 10 further
comprising: a control module positioned in said interior of said
housing and having a data communication port; and a connector in
communication with said data communication port and accessible from
said exterior of said housing.
17. A rechargeable DC power supply system for providing power to a
DC load, comprising: a plurality of rechargeable DC power supplies,
each including: a rechargeable battery; a pair of power supply
terminals; a bidirectional DC-DC converter module connected between
said rechargeable battery and said power supply terminals; and a
controller module receiving at least one signal indicative of a
condition of said rechargeable battery and communicating an enable
signal to said corresponding bidirectional DC-DC converter module
in accordance with said condition; and parallel connections between
said power supply terminals of said plurality of rechargeable DC
power supplies and said load, wherein one of said enable signals
causes a respective one of said corresponding rechargeable DC power
supplies to electrically connect and disconnect from said load.
18. The rechargeable DC power supply system of claim 17 wherein
each of said rechargeable DC power supplies further includes a data
communication port that communicates data indicative of said
condition.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to rechargeable DC
power supplies having an integral DC-DC converter.
BACKGROUND OF THE INVENTION
[0002] Rechargeable DC power supplies are useful in many types of
applications. For example, cellular towers and other stationary
applications use rechargeable DC power supplies as an
uninterruptible power source. The rechargeable DC power supplies
provide backup power during a main grid outage.
[0003] Referring now to FIG. 1, an example application of
rechargeable DC power supplies is shown. A direct current (DC)
power supply 2 receives power from a main grid 4. The DC power
supply 2 generally provides power to a load 6 and to a plurality of
rechargeable DC power supplies 8-1, 8-2, . . . , 8-N, referred to
collectively as rechargeable DC power supplies 8. Each rechargeable
DC power supply 8 includes a corresponding battery 10 and charging
control circuit 12.
[0004] The battery 10 provides a voltage that is less than a load
voltage needed by the load 6. If the DC power supply 2 becomes
inoperative, the series-connected rechargeable DC power supplies 8
provide the load voltage. However, because the rechargeable DC
power supplies are connected in series, the load 6 may not receive
sufficient voltage if one of more of the rechargeable DC power
supplies 8 is in a discharged or open circuit condition.
SUMMARY OF THE INVENTION
[0005] A telecommunication switching station includes
telecommunication equipment, a DC power supply having an output
connected to the telecommunication equipment, and a plurality of
rechargeable DC power supplies connected in parallel with the
output of the DC power supply. Each DC power supply includes a pair
of power supply terminals, a rechargeable battery, and a
bidirectional DC-DC converter module connected between the
rechargeable battery and the pair of power supply terminals. The DC
power supply provides power to the telecommunication equipment and
recharges the plurality of rechargeable DC power supplies. The
plurality of rechargeable DC power supplies serve as a back-up for
the DC power supply.
[0006] In other features, each of said rechargeable DC power
supplies further includes a control module that communicates an
enable signal to a respective one of said bidirectional DC-DC
converter modules. The respective bidirectional DC-DC converter
module selectively creates an open circuit condition between said
pair of power supply terminals in accordance with said enable
signal.
[0007] In other features, each of said rechargeable DC power
supplies further includes a data communication port in
communication with a respective one of said control modules. Each
of said rechargeable DC power supplies can further includes a
battery temperature sensor positioned in proximity of a respective
one of said rechargeable batteries and providing a battery
temperature signal to a respective one of said control modules.
Each battery temperature sensor is positioned inside of said
respective one of said rechargeable batteries.
[0008] In other features, each rechargeable DC power supplies
further includes a current sensor providing a signal to a
respective one of said control modules and being connected between
a respective one of said rechargeable batteries and a respective
one of said bidirectional DC-DC converter modules. The signal can
be indicative of a magnitude and direction of current flow through
said respective one of said rechargeable batteries.
[0009] In other features, each of the rechargeable DC power
supplies further includes a switch having a control input and being
connected between a respective one of said rechargeable batteries
and a respective one of said bidirectional DC-DC converter modules
and wherein said switch opens and closes in response to said
control input.
[0010] In other features, each of said control modules can
communicate a desired output voltage signal to said respective one
of said bidirectional DC-DC converter modules. The respective one
of said bidirectional DC-DC converter modules regulates a load
voltage across a respective one of said pair of power supply
terminals in accordance with said desired output voltage
signal.
[0011] A rechargeable DC power supply includes a housing including
an interior, an exterior, and an integral heat sink including a
heat absorbing surface formed in said interior and a heat
dissipating surface formed in said exterior. The rechargeable DC
power supply includes a rechargeable battery having battery
terminals positioned in said interior, power supply terminals
positioned at said exterior of said housing, anda first printed
circuit board (PCB) assembly including a bidirectional DC-DC
converter module connected between said battery terminals and said
power supply terminals. The first PCB assembly is in coplanar
contact with said heat absorbing surface.
[0012] In other features, a battery tray is connected to said
housing and contains said rechargeable battery. The rechargeable
battery can include a plurality of rechargeable cells having cell
terminals. A second PCB assembly can be positioned on said cell
terminals and include PCB traces connecting said cell terminals to
form said battery terminals. The housing can nest on said
rechargeable battery.
[0013] In other features, the rechargeable DC power supply can
include a battery temperature sensor positioned in proximity of
said rechargeable battery and connected to said second PCB
assembly. The battery temperature sensor can be located inside of
said battery.
[0014] In other features, a control module is positioned in the
interior of said housing and has a data communication port. A
connector in communication with said data communication port can be
accessible from said exterior of said housing.
[0015] A rechargeable DC power supply system for providing power to
a DC load, includes a plurality of rechargeable DC power supplies.
Each rechargeable DC power supply includes a rechargeable battery,
a pair of power supply terminals, a bidirectional DC-DC converter
module connected between said rechargeable battery and said power
supply terminals, and a controller module receiving at least one
signal indicative of a condition of said rechargeable battery and
communicating an enable signal to said corresponding bidirectional
DC-DC converter module in accordance with said condition. Said
power supply terminals of said plurality of rechargeable DC power
supplies and said load are connected by parallel connections. One
of said enable signals causes a respective one of said
corresponding rechargeable DC power supplies to electrically
connect and disconnect from said load. Each of said rechargeable DC
power supplies can include a data communication port that
communicates data indicative of said condition.
[0016] Further areas of applicability of the present invention will
become apparent from the detailed description provided hereinafter.
It should be understood that the detailed description and specific
examples, while indicating the preferred embodiment of the
invention, are intended for purposes of illustration only and are
not intended to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The present invention will become more fully understood from
the detailed description and the accompanying drawings,
wherein:
[0018] FIG. 1 is a functional block diagram of a load connected to
a DC power supply and series-connected rechargeable DC power
supplies according to the prior art;
[0019] FIG. 2 is a functional block diagram of a load connected to
a DC power supply and parallel-connected rechargeable DC power
supplies;
[0020] FIG. 3 is a functional block diagram of a rechargeable DC
power supply including a bidirectional DC-DC converter;
[0021] FIG. 4 is an exploded view of a rechargeable DC power
supply;
[0022] FIG. 5 is a perspective view of the rechargeable DC power
supply of FIG. 4; and
[0023] FIG. 6 is a method of operating a rechargeable DC power
supply.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] The following description of the preferred embodiment(s) is
merely exemplary in nature and is in no way intended to limit the
invention, its application, or uses. For purposes of clarity, the
same reference numbers will be used in the drawings to identify
similar elements. As used herein, the term module and/or device
refers to an application specific integrated circuit (ASIC), an
electronic circuit, a processor (shared, dedicated, or group), and
memory that execute one or more software or firmware programs, a
combinational logic circuit, and/or other suitable components that
provide the described functionality. For purposes of clarity, the
same reference numerals will be used to identify similar
elements.
[0025] Referring now to FIG. 2, a plurality of rechargeable DC
power supplies 14-1, 14-2, . . . , 14-N, referred to collectively
as rechargeable DC power supplies 14, are shown. The rechargeable
DC power supplies 14 include corresponding positive 16 and negative
18 power supply terminals that are connected in parallel. Each
rechargeable DC power supply 14 has a corresponding rechargeable
battery 20 and a bidirectional DC-DC converter module 22 connected
between the battery 20 and the positive 16 and negative 18 power
supply terminals. A battery voltage of each battery 20 can be less
than a DC load voltage needed by a load 24. Examples of loads
include, by way of non-limiting example, telecommunication
equipment including multiplexers and/or switching circuitry,
cellular communications transmitters and/or receivers, and electric
and hybrid electric vehicles. The bidirectional DC-DC converter
modules 22 convert the battery voltage to the load voltage and vice
versa. In some embodiments, the battery voltage is about 12V and
the load voltage is between about 24V and 48V. The load 24 connects
to the positive 16 and negative 18 power supply terminals.
[0026] A main grid 26 provides power to a DC power supply 28. The
DC power supply 28 has positive and negative outputs connected to
the load 24 and to the positive 16 and negative 18 power supply
terminals. The main grid 26 can be an AC line voltage, such as
provided by a public electric utility, or a DC line voltage such as
may be provided by an alternative energy source such as solar cells
and/or generators.
[0027] When the main grid 26 is powered, the DC power supply 28
provides power to operate the load 24 and to recharge the batteries
20. The bidirectional DC-DC converter modules 22 reduce the load
voltage to the battery voltage and regulate a charging current
provided to the batteries 20.
[0028] When the main grid 26 loses power, the rechargeable DC power
supplies 14 provide power to operate the load 24. The bidirectional
DC-DC converter modules 22 increase the battery voltage to the load
voltage.
[0029] Turning now to FIG. 3, a functional block diagram of the
rechargeable DC power supply 14 is shown. The rechargeable battery
20 has at least one rechargeable cell 30, such as, by way of
non-limiting example, nickel-metal hydride, nickel-cadmium,
lithium-ion, and/or lead-acid cells. The rechargeable cells 30 can
connect in series, parallel, or series-parallel. A battery
temperature sensor 32 can be positioned in proximity of the battery
20. In some embodiments, the temperature sensor 32 is positioned
between two of the cells 30 and near a center of mass of the
battery 20. By way of non-limiting example, the battery temperature
sensor 32 can be a thermistor having a negative temperature
coefficient.
[0030] A current sensor 34 can connect between a positive battery
terminal 36 and a positive module terminal 38 of the bidirectional
DC-DC converter module 22. The current sensor 34 provides a current
signal 40 indicative of a magnitude of battery current flowing
through the battery 20. In some embodiments, the current signal 40
also provides an indication of a direction of the battery current.
First mating connectors 42-1 and 42-2, referred to collectively as
the first connector 42, can be used between the positive battery
terminal 36 and the current sensor 34. The first connector 42
facilitates installation and removal of the battery 20.
[0031] A switch 44 selectively connects a negative battery terminal
46 to a negative module terminal 48 of the bidirectional DC-DC
converter module 22. The switch 44 has a switch control input 50
that controls whether the switch 44 is open or closed. In some
embodiments, the switch 44 can be a transistor, electromechanical
relay, or solid-state relay. Second mating connectors 52-1 and
52-2, referred to collectively as the second connector 52, can be
used between the negative battery terminal 46 and the switch 44 to
facilitate installation and removal of the battery 20. The DC-DC
converter module 22 can include the current sensor 34 and/or the
switch 44.
[0032] A control module 54 receives various signals indicative of
voltages and current in the rechargeable DC power supply 14. A
battery temperature input 56 connects to the battery temperature
sensor 32. A battery voltage input 58 connects to the positive
battery terminal 36 and the negative battery terminal 46. A
terminal voltage input 60 connects to the positive power supply
terminal 16 and the negative power supply terminal 18. A supply
voltage input 62 connects to the positive module terminal 38 and
the negative module terminal 48. A current sense input 64 connects
to the current signal 40. The control module 54 senses the load
voltage through the terminal voltage inputs 60.
[0033] The control module 54 also provides a number of output
signals. An over-voltage protection (OVP) output 66 connects to the
switch control input 50. A current limit signal 68, a desired
output voltage signal 70, and an enable signal 72 connect to the
bidirectional DC-DC converter module 22. The bidirectional DC-DC
converter module 22 uses the current limit signal 68 to limit the
battery current. The bidirectional DC-DC converter module 22 uses
the desired output voltage signal 70 to establish the load voltage
at the positive 16 and negative 18 power supply terminals. For
example, the desired output voltage signal 70 can indicate that the
load voltage should be set to a value between about 24V and 48V.
The bidirectional DC-DC converter module 22 uses the enable signal
72 to turn the positive 16 and negative 18 power supply terminals
on and off. The positive 16 and negative 18 power supply terminals
are turned on during normal operation. However, if the rechargeable
DC power supply 14 is supposed to be providing power to the load 24
and some condition prevents it from doing so, such as the battery
26 is discharged, then the controller 54 can use the enable signal
72 to turn off the positive 16 and negative 18 power supply
terminals. This electrically disconnects the rechargeable DC power
supply 14 from the load 24 and also prevents it from undesirably
discharging the other rechargeable DC power supplies 14.
[0034] A CPU 74 uses the inputs and outputs of the control module
54. The CPU 74 executes a computer program stored in a read-only
memory (ROM) 76. The ROM 76 can include other types of non-volatile
computer memory, such as, by way of non-limiting example, flash,
EPROM, and/or EEPROM. The CPU 74 stores variables, such as the load
voltage, battery voltage, and battery current, in a random access
memory (RAM) 78. The control module 54 can also have a
bidirectional data communication port 80 in communication with the
CPU 74. A user can access the data communication port 80 and
interact with the CPU 74 to read the variables from the RAM 78
and/or change the computer program stored in the ROM 76. By way of
non-limiting example, the data communication port 80 can be serial,
parallel, RS-232, controller area network (CAN), and/or
Ethernet.
[0035] Turning now to FIG. 4, an exploded view is shown of one of
various embodiments of the rechargeable DC power supply 14. The
bidirectional DC-DC converter module 22 can be assembled on a first
printed circuit board (PCB) 82. The first PCB 82 has at least one
planar area on an upper surface 84 that comes into coplanar contact
with a planar heat absorbing surface 86 located on an interior of a
housing 88. The region of coplanar contact between the planar area
of the first PCB 82 and the heat-absorbing surface 86 can contain a
material that enhances thermal conductivity, such as a thermal
compound or a thermal pad. One or more screws 90 can engage the
housing 88 and bias the planar area of the first PCB 82 towards the
heat-absorbing surface 86. Springs and/or clamps can also be used
to supplement, or as substitute for, the function of the screws 90.
The heat-absorbing surface 86 can include one or more recesses 92
that accommodate components positioned on the upper surface 84. An
exterior of the housing 88 can include a heat-dissipating portion
94, such as fins, pins, fluid channels, or other structure to
dissipate heat from the housing 88.
[0036] Openings 96 formed in a terminal plate 98 receive the
positive and negative power supply terminals 16, 18. The terminal
plate 98 should be formed of an insulating material to prevent the
positive and negative power supply terminals 16, 18 from shorting
together. Alternatively, the terminal plate 98 can be formed from a
conductive material and insulators can be positioned in the
openings 96 between the positive and negative power supply
terminals 16, 18 and the terminal plate 98. The housing 88 has an
opening 100 that receives the terminal plate 98 and allows the
positive and negative power supply terminals 16, 18 to connect to
the first PCB 82.
[0037] The control module 54 can be assembled on a second PCB 102.
The second PCB 102 has a plurality of terminals 104, such as
plated-through holes, adapted to connect to positive and negative
terminals located on a top 106 of each cell 30. Circuit traces on
the second PCB 102 connect the terminals 104. The circuit traces
make the connections between the cells 30 and provide the positive
and negative battery terminals 36, 46. An arrangement of the
circuit traces depends on whether the battery 20 includes cells 30
connected in a series, parallel, or series-parallel manner.
Fasteners, such as screws 108, secure the connection between the
terminals 104 and the terminals of each cell 30. Alternatively, the
terminals 104 can be adapted to connect directly to the positive
and negative battery terminals 36, 46 when the connections between
the cells 30 are integral with the battery 20.
[0038] A connector 110 can be located on the second PCB 102 to make
the connection between the battery temperature sensor 32 and the
control module 54. One or more straps 112 can urge the cells 30
together. The straps 112 can help reduce bending moments or other
stresses in the second PCB 102.
[0039] A positive battery cable 114, a negative battery cable 116,
and a ribbon cable 118 provide connections between the first PCB 82
and the second PCB 102. The positive battery cable 114 has one end
connected to the positive battery terminal 36 formed on the second
PCB 102. The other end of the positive battery cable 114 is fitted
with the first mating connector 42-1. The first mating connector
42-1 connects to the second mating connector 42-2, which mounts on
the first PCB 82. The negative battery cable 116 has one end
connected to the negative battery terminal 46 formed on the second
PCB 102. The other end of the negative battery cable 116 is fitted
with the first mating connector 52-1. The first mating connector
52-1 connects to the second mating connector 52-2, which mounts on
the first PCB 82. One end of the ribbon cable 118 connects to the
first PCB 82 and the other end connects to the second PCB 102. The
ends of the ribbon cable 118 can be fitted with connectors 120, 122
that plug into mating connectors on the first and second PCBs 82,
102. The ribbon cable 118 carries the control module 54 signals
between the first and second PCBs 82, 102. In some embodiments, all
hardware except the positive and negative power supply terminals
16, 18 and the battery temperature sensor 32, can be on a single
PCB. The single PCB would then provide the functionality of the
first and second PCBs 82, 102.
[0040] The second PCB 102 includes a communication connector 124
connected to the communication port 80. The communication connector
124 aligns with an opening 126 in the housing 88.
[0041] The housing 88 is adapted to nest on top of the battery 20.
In one adaptation, the housing 88 can have a peripheral ledge 128
formed around its interior. The peripheral ledge 128 rests upon a
mating ledge 130 formed in a top periphery of the battery 20. When
the housing 88 nests on top of the battery 20, the interior of the
housing 88 encloses the first PCB 82, the second PCB 102, and the
positive and negative battery terminals 36, 46.
[0042] A battery tray 132 contains the battery 20 and has
upstanding portions 134 that secure to the housing 88. The battery
tray 132 can include integral mounting tabs 136. The mounting tabs
136 facilitate fastening the rechargeable DC power supply 14 to a
supporting surface. FIG. 5 shows one of various embodiments of an
assembled rechargeable DC power supply 14.
[0043] Referring now to FIG. 6, a method 150 is shown that can be
used to charge the battery 20. The method 150 can be included in
the computer software stored in the ROM 76 and executed by the CPU
74. Control begins in start block 152 and proceeds to decision
block 154. In decision block 154, control determines whether the
battery temperature is greater than a first predetermined
temperature. By way of non-limiting example, the first
predetermined temperature can be about 52 deg. C. Control proceeds
to block 156 when the determination of decision block 154 yields an
affirmative result. In block 156, control determines a charging
current that is approximately equal to one-third of an amp*hour
(Ah) rating of the battery 20. For example, if the battery has a
rating of 85 Ah, then control will determine the charging current
to be about 28 amperes.
[0044] Control proceeds from block 156 to block 158 and determines
whether the battery temperature is greater that a second
predetermined temperature. In some embodiments, the second
predetermined temperature is, by way of non-limiting example, 60
deg. C. Control discontinues charging and proceeds to exit block
160 when the determination of decision block 158 yields an
affirmative result. Alternatively, control proceeds to decision
block 162 when the determination of decision block 158 yields a
negative result. In decision block 162, control determines whether
a battery temperature rate of change is greater than a
predetermined rate of change. In some embodiments, by way of
non-limiting example, the predetermined rate of change is about 12
deg. C./hr. Control returns to block 156 when the determination of
decision block 162 yields a negative result. Alternatively, control
proceeds to decision block 164 when the determination of decision
block 162 yields an affirmative result.
[0045] In decision block 164, control determines whether the
battery temperature is greater than a third predetermined
temperature. In some embodiments, by way of non-limiting example,
the third predetermined temperature is about 35 deg. C. When the
determination of decision block 164 yields a negative result,
control proceeds to block 166 and determines a state of charge
(SOC) of the battery 20. In block 166, the SOC is determined by the
equation SOC=100%-eff(Tend-25 deg. C.)
[0046] where eff is a predetermined charge acceptance efficiency of
the battery 16 and Tend is the current battery temperature in deg.
C. From block 166, control proceeds to exit block 160.
[0047] Alternatively, if the determination of decision block 164
yields an affirmative result, then control moves to block 168 and
charges the battery at a predetermined current. In some
embodiments, by way of non-limiting example, the predetermined
current is approximately 5 amperes. Control then proceeds to
decision block 170 and determines whether the battery temperature
is above a fourth predetermined temperature. In some embodiments,
by way of non-limiting example, the fourth predetermined
temperature is approximately 45 deg. C. Control discontinues
charging and proceeds to exit block 160 when the determination of
decision block 170 yields an affirmative result. Alternatively, if
the determination of decision block 170 yields a negative result,
then control proceeds to decision block 172.
[0048] In decision block 172 control determines whether the battery
20 is sufficiently charged to provide at least 100% of its Ah
rating. If the determination of decision block 172 returns an
affirmative result, then control proceeds to block 174.
Alternatively, if the determination in decision block 172 returns a
negative result, then control proceeds to decision block 176. In
decision block 176, control determines whether the battery
temperature rate of change is greater than a second predetermined
rate of change. In some embodiments, by way of non-limiting
example, the second predetermined rate of change is about 12 deg.
C./hr. Control returns to block 168 when the determination of
decision block 176 yields a negative result. Alternatively, control
proceeds to block 174 when the determination of decision block 176
yields an affirmative result. In block 174, control sets the SOC
equal to 100%, discontinues charging, and then proceeds to exit
block 160.
[0049] The applicant has found the various predetermined values
disclosed herein to be suitable for use with a particular type of
NiMH battery 16 having an 85 Ah rating. It is appreciated by those
skilled in the art that the predetermined values will vary with the
type and Ah rating of the battery 20.
[0050] Those skilled in the art can now appreciate from the
foregoing description that the broad teachings of the present
invention can be implemented in a variety of forms. Therefore,
while this invention has been described in connection with
particular examples thereof, the true scope of the invention should
not be so limited since other modifications will become apparent to
the skilled practitioner upon a study of the drawings, the
specification and the following claims.
* * * * *