U.S. patent application number 11/851620 was filed with the patent office on 2008-01-03 for thermal management systems for battery packs.
Invention is credited to Daniele C. Brotto, David A. Carrier, Michael C. Doyle, Erik A. Ekstrom, Jeffrey J. Francis, Steven J. Phillips, Andrew E. JR. Seman, William D. Spencer, Danh T. Trinh, Daniel J. White, Christopher R. Yahnker.
Application Number | 20080003491 11/851620 |
Document ID | / |
Family ID | 34922235 |
Filed Date | 2008-01-03 |
United States Patent
Application |
20080003491 |
Kind Code |
A1 |
Yahnker; Christopher R. ; et
al. |
January 3, 2008 |
THERMAL MANAGEMENT SYSTEMS FOR BATTERY PACKS
Abstract
A cordless power tool has a housing which includes a mechanism
to couple with a removable battery pack. The battery pack includes
one or more battery cells as well as a system to dissipate heat
from the battery pack.
Inventors: |
Yahnker; Christopher R.;
(Raleigh, NC) ; Brotto; Daniele C.; (Baltimore,
MD) ; Ekstrom; Erik A.; (Woodstock, MD) ;
Seman; Andrew E. JR.; (White Marsh, MD) ; Carrier;
David A.; (Aberdeen, MD) ; Phillips; Steven J.;
(Ellicott City, MD) ; Doyle; Michael C.; (Baldwin,
MD) ; Trinh; Danh T.; (Parkville, MD) ;
Spencer; William D.; (Ellicott City, MD) ; Francis;
Jeffrey J.; (Nottingham, MD) ; White; Daniel J.;
(Baltimore, MD) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Family ID: |
34922235 |
Appl. No.: |
11/851620 |
Filed: |
September 7, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11075179 |
Mar 8, 2005 |
7270910 |
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11851620 |
Sep 7, 2007 |
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10959193 |
Oct 7, 2004 |
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11851620 |
Sep 7, 2007 |
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10954222 |
Oct 1, 2004 |
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11075179 |
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60551891 |
Mar 10, 2004 |
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60551803 |
Mar 11, 2004 |
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60510128 |
Oct 14, 2003 |
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60540323 |
Feb 2, 2004 |
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60510125 |
Oct 14, 2003 |
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60507955 |
Oct 3, 2003 |
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Current U.S.
Class: |
429/62 ; 429/120;
429/122; 429/90 |
Current CPC
Class: |
H01M 10/425 20130101;
H02J 7/027 20130101; H02J 7/0029 20130101; H01M 10/613 20150401;
H02J 7/007194 20200101; H01M 10/6235 20150401; H01M 10/643
20150401; H01M 10/6551 20150401; B25F 5/008 20130101; H01M 10/659
20150401; H02J 7/00036 20200101; H02J 7/00309 20200101; H02J
7/00047 20200101; H01M 10/4257 20130101; H01M 2200/00 20130101;
H01M 10/633 20150401; H01M 10/6561 20150401; H01M 10/6567 20150401;
H01M 50/24 20210101; H01M 10/486 20130101; H02J 7/0047 20130101;
Y02E 60/10 20130101; H01M 10/44 20130101; H01M 10/6554 20150401;
H01M 10/656 20150401; H01M 10/6552 20150401; H01M 50/581 20210101;
H01M 2200/10 20130101; H02J 7/0091 20130101; H01M 10/46 20130101;
H01M 50/213 20210101; H01M 10/6563 20150401; H02J 7/0031 20130101;
H01M 10/6572 20150401 |
Class at
Publication: |
429/062 ;
429/120; 429/122; 429/090 |
International
Class: |
H01M 10/50 20060101
H01M010/50; H01M 10/48 20060101 H01M010/48; H01M 6/00 20060101
H01M006/00 |
Claims
1. A battery pack comprising: a housing; at least one battery cell
within said housing; an electronic circuit connected to said at
least one battery cell and including an electronic control unit; a
temperature sensor for sensing a temperature within said housing
and in communication with said electronic circuit; wherein said
electronic control unit disables said electronic circuit when a
sensed temperature exceeds a predetermined temperature.
2. The battery pack according to claim 1, further comprising a
power supply within the said housing for providing electric power
to said electronic circuit.
3. The battery pack according to claim 1, further comprising a
driver circuit within said housing in communication with a pair of
semi-conductor devices of said electronic circuit.
4. A battery pack, comprising: a housing; a plurality of battery
cells disposed in said housing; and phase-change material disposed
in said housing in heat transfer relationship with said plurality
of battery cells.
5. The battery pack according to claim 4, wherein said phase-change
material individually surrounds each of said plurality of battery
cells.
6. The battery pack according to claim 4, wherein said phase-change
material is disposed in a gel-filled covering tube wrapped around
said plurality of battery cells.
7. The battery pack according to claim 6, wherein said plurality of
battery cells are individually wrapped by a plurality of gel-filled
coverings.
8. The battery pack according to claim 4, wherein said phase-change
material is disposed in a carrier that is disposed in heat transfer
relationship with said plurality of battery cells.
9. The battery pack according to claim 8, wherein said carrier is
formed from plastic.
10. The battery pack according to claim 8, wherein said carrier is
formed from a material selected from the group of aluminum, copper,
and carbon fiber.
11. The battery pack according to claim 8, wherein said
phase-change material is disposed between heat fins disposed on
said carrier.
12. The battery pack according to claim 4, wherein said housing is
made from metal.
13. A cordless power tool, comprising: a plastic tool housing; a
motor attached to said tool housing; a battery pack including a
metal pack housing connectable to said plastic tool housing and at
least one battery cell disposed in said pack housing.
14. The cordless power tool according to claim 13, further
comprising a drive mechanism attached to said motor.
15. The cordless power tool according to claim 13, wherein said
tool housing includes a handle portion.
16. The cordless power tool according to claim 13, wherein said
motor is disposed within said tool housing.
17. A battery pack, comprising: a housing; at least one battery
cell disposed in said housing; a circuit disposed in said housing;
a temperature sensor in said housing and in communication with said
circuit; and a temperature gauge mounted to said housing and in
communication with said circuit, said temperature gauge providing
an indication of a temperature level detected by said temperature
sensor.
18. The battery pack according to claim 17, wherein said circuit
directly connects said temperature sensor to said temperature
gauge.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 11/075,179, filed on Mar. 8, 2005, which claims the benefit of
U.S. Provisional Application No. 60/551,891, filed on Mar. 10,
2004, the disclosure of which is incorporated herein by reference.
In addition, U.S. application Ser. No. 11/075,179 is a
continuation-in-part of U.S. application Ser. No. 10/959,193, filed
on Oct. 7, 2004, which claims the benefit of U.S. Provisional
Application No. 60/551,803, filed on Mar. 11, 2004 and U.S.
Provisional Application No. 60/510,128, filed on Oct. 14, 2003, the
disclosures of which are incorporated herein by reference.
Furthermore, U.S. application Ser. No. 11/075,179 is a
continuation-in-part of U.S. application Ser. No. 10/954,222, filed
on Oct. 1, 2004, which claims the benefit of U.S. Provisional
Application No. 60/540,323, filed on Feb. 2, 2004, U.S. Provisional
Application No. 60/510,125, filed on Oct. 14, 2003 and U.S.
Provisional Application No. 60/507,955, filed on Oct. 3, 2003, the
disclosures of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to battery cooling systems
and, more specifically, to systems for cooling batteries for
cordless power tools.
BACKGROUND OF THE INVENTION
[0003] Cordless products which use rechargeable batteries are
prevalent throughout the workplace as well as in the home. From
housewares to power tools, rechargeable batteries are used in
numerous devices. Ordinarily, nickel-cadmium or nickelmetal-hydride
battery cells are used in these devices. Since the devices use a
plurality of battery cells, the battery cells are ordinarily
packaged as battery packs. These battery packs couple with the
cordless devices and secure to the device. The battery pack may be
removed from the cordless device and charged in a battery charger
or charged in the cordless device itself.
[0004] As the cordless power device is used, current flows through
the batteries to power the cordless device. As current is drawn off
the batteries, heat is generated within the battery pack. Also,
during charging of the battery pack, heat is likewise accumulated
during the charging process. The heat created during discharge of
the batteries as well as charging of the batteries which, in turn,
leads to increased temperatures, may have a severe effect on the
life expectancy and performance of the batteries. In order for
batteries to properly charge, the batteries must be below a desired
threshold temperature and the differential temperature between the
cells in the battery pack should be minimized. Likewise, if the
batteries become too hot during use, battery life will be cut
short. Also, if a battery is below a certain threshold temperature,
it will be too cold to charge and must be warmed before charging.
Thus, it is desirous to maintain batteries within a desired
temperature range for optimum performance as well as optimum
charging.
[0005] Further, battery packs typically contain some battery cells
close to the outer walls of the pack, while some battery cells are
surrounded by other battery cells. Those cells close to the outer
walls have better thermal conductivity to the outside ambient than
do the cells that are surrounded by other cells. When a battery
pack is discharging on the cordless device, the amount of heat
generated is approximately the same in each cell. However,
depending on the thermal path to ambient, different cells will
reach different temperatures. Further, for the same reasons,
different cells reach different temperatures during the charging
process. Accordingly, if one cell is at an increased temperature
with respect to the other cells, its charge or discharge efficiency
will be different, and, therefore, it may charge or discharge
faster than the other cells. This will lead to a decline in the
performance of the entire pack.
SUMMARY OF THE INVENTION
[0006] The present invention provides the art with a battery pack
which dissipates heat within the battery pack during charging of
the cells as well as during discharging of the cells while the
battery pack is in use.
[0007] In accordance with a first aspect of the present invention,
a heat exchange plate is provided in contact with the cells of the
battery pack and at least one fluid passage is provided in contact
with the at least one plate and in communication with a fluid
source. A pump is provided for carrying a cooling fluid through the
plate for withdrawing heat from the battery pack.
[0008] According to a second aspect of the present invention, a
heat pipe is provided in contact with a cooling plate which is in
heat exchange contact with the cells of the battery system. The
heat pipe withdraws heat from the battery pack by a wicking
process.
[0009] According to yet another aspect of the present invention, a
fluid is disposed in a battery pack housing and in surrounding
contact with the cells of the battery pack. The battery pack
housing includes at least one heat conductor metal plate in contact
with the fluid and exposed to an exterior of the housing. According
to a still further aspect of this invention, a stirring mechanism
is provided for stirring the fluid within the housing for enhancing
the cooling affect of the fluid around the cells. According to yet
another embodiment of the present invention, the fluid around the
cells is withdrawn and a cooled fluid can be inserted into the
housing for cooling the cells.
[0010] According to still another aspect of the present invention,
a CO.sub.2 cartridge is utilized in proximity to the cells of a
battery pack and is adapted to discharge when a temperature of the
cells exceeds a predetermined temperature so as to cool the cells.
The discharge of CO.sub.2 from the cartridge is controlled or can
be provided with a full release when it is determined that rapid
cooling is required.
[0011] According to still another aspect of the present invention,
a gel blanket or tubular sleeve containing a gel material with
microphase change crystals is provided against the battery cells.
The phase change materials maintain the battery pack at the melting
temperature of the phase change material. As a material changes
phase, the temperature remains constant until the change has
completely occurred. Thus, the temperature of the gel surrounding
the battery cells can be maintained at a constant temperature for a
prolonged period of time while the phase-change materials begin to
change phase. The phase change occurs at a relatively constant
temperature, maintaining the temperature of the cells below their
specified maximum operating temperature. According to still further
aspects of the present invention, the microphase change crystals
can also be disposed in a plastic material used for a cell carrier
of the battery cells or battery pack housing, or can be used with
other heat conductive materials, such as aluminum, copper, and
carbon fiber so that the phase change materials form part of a heat
sink for conducting heat away from the battery cells. The use of
phase change materials can also be utilized with a powder material,
wax material, or a slurry for suspending the phase change materials
in the housing around the battery cells.
[0012] According to another aspect of the present invention, a
power tool is provided including a plastic tool housing including a
handle portion. A motor and drive mechanism are disposed in the
tool housing. A battery pack is provided with a metal battery
housing releasably attached to the handle portion and having a
plurality of cells disposed in the metal battery housing. The metal
battery housing acts as a heat conductor for conducting heat away
from the battery cells.
[0013] According to another aspect of the present invention, a
battery system is provided, including a plurality of cells disposed
in a battery housing with the cells being movable within the
housing so that different ones of the plurality of cells can be
moved into and away from a cooling portion of the battery housing.
The cooling portion can include a cooling feature, such as a heat
sink, or otherwise actively cooled area.
[0014] According to yet another aspect of the present invention, a
power tool is provided with a tool housing including a handle
portion. A motor and drive mechanism are disposed in the tool
housing, and a first fan is disposed in the tool housing for
providing cooling of the motor. A battery housing is releasably
connected to the tool housing and includes a plurality of cells
disposed in the battery housing. A second fan is disposed in the
battery housing for cooling the plurality of cells within the
battery housing.
[0015] According to yet another aspect of the present invention, a
power tool is provided including a tool housing including a handle
portion. A motor and drive mechanism are disposed in the tool
housing, and a battery housing is releasably connected to the tool
housing. A plurality of cells are disposed in the battery housing,
and a cooling system is separately attachable to one of the tool
housing and the battery housing for cooling the plurality of cells
in the battery housing. The cooling system can include a heat sink,
a fan system for blowing air through the battery housing, a liquid
cooling system, or other active or passive cooling systems.
[0016] According to another aspect of the present invention, the
cooling system can also be separately attachable to a battery
charger unit and/or the battery housing for cooling the plurality
of cells in the battery housing during charging of the plurality of
cells.
[0017] According to yet another aspect of the present invention, a
cooling fluid source is connected to the battery pack housing for
providing cooling fluid to the battery pack housing. According to
one aspect, compressed air can be supplied as the cooling fluid for
cooling the plurality of cells within the battery pack housing.
[0018] According to yet another aspect of the present invention, a
battery system is provided including a housing having a plurality
of cells disposed in the housing. A rheological fluid is disposed
in the housing and an inductor coil is disposed in the housing for
generating a magnetic field within the housing for causing
circulation of the rheological fluid within the housing. The
rheological fluid is heat conducting and, therefore, provides
cooling of the battery cells as the rheological fluid flows past
the cells and conducts the heat away from the battery cells.
[0019] According to yet another aspect of the present invention, a
temperature sensor is disposed in the battery pack housing for
sensing a temperature of the cells within the battery housing. A
temperature gauge is disposed on the battery housing for indicating
to a user when a temperature in the housing exceeds a predetermined
temperature. According to yet another aspect of the present
invention, a disable circuit is provided for disconnecting
communication with one of a pair of output terminals when a
temperature in the housing exceeds a predetermined level.
[0020] 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
[0021] The present invention will become more fully understood from
the detailed description and the accompanying drawings,
wherein:
[0022] FIG. 1A is a cross-sectional view of a typical power tool
with which the thermal management systems, according to the
principles of the present invention, can be utilized;
[0023] FIG. 1B is a schematic system diagram of the functional
control of the battery pack and battery charger according to the
principles of the present invention; and
[0024] FIG. 1C is a schematic system diagram of the functional
control of the battery pack and tool according to the principles of
the present invention;
[0025] FIG. 2 is a cross-sectional view of a battery pack and
battery charger unit having a liquid cooling system according to
the principles of the present invention;
[0026] FIG. 3 is a schematic diagram of a refrigeration system for
cooling a battery pack according to the principles of the present
invention;
[0027] FIG. 4 is a schematic view of a battery pack filled with
cooling fluid according to the principles of the present
invention;
[0028] FIG. 5 is a schematic diagram of a system for cooling a
battery pack utilizing compressed air according to the principles
of the present invention;
[0029] FIG. 6 is a schematic diagram of a system for cooling a
battery pack utilizing a CO.sub.2 cartridge according to the
principles of the present invention;
[0030] FIG. 7 is a schematic diagram of a battery cooling system
for cooling cells of a battery pack utilizing a CO.sub.2 cartridge
within the battery pack;
[0031] FIG. 8 is a schematic diagram of a battery charger unit
including a CO.sub.2 cartridge for cooling the battery pack during
charging according to the principles of the present invention;
[0032] FIG. 9 is a schematic diagram of a control circuit for
controlling activation of a CO.sub.2 cartridge according to the
principles of the present invention
[0033] FIG. 10 is a schematic diagram illustrating a control
circuit for activating a CO.sub.2 cartridge within the battery pack
for cooling battery cells of the battery pack according to the
principles of the present invention;
[0034] FIG. 11 is a diagrammatic perspective view of a gel tube
containing microphase change crystals for cooling of battery cells
of a battery pack according to the principles of the present
invention;
[0035] FIG. 12 is a diagrammatic perspective view of a gel blanket
containing microphase change crystals for cooling cells of a
battery pack according to the principles of the present
invention;
[0036] FIG. 13 is a diagrammatic perspective view of a plastic
carrier containing microphase change crystals for cooling a
plurality of cells according to the principles of the present
invention;
[0037] FIG. 14 is a schematic illustration of the method of forming
the plastic carrier shown in FIG. 13;
[0038] FIG. 15 is a diagrammatic perspective view of a heat sink
made of conductive material including microphase change crystals
for providing a heat sink for cells of a battery pack, according to
the principles of the present invention;
[0039] FIG. 16 is a diagrammatic view of an exemplary battery pack
including a plurality of cells surrounded by a suspension medium
including microphase change crystals suspended in the suspension
medium according to the principles of the present invention;
[0040] FIG. 17 is a perspective view of a heat sink having fins for
cooling cells of a battery pack and including phase change material
between the fins for enhancing the cooling properties of the heat
sink according to the principles of the present invention;
[0041] FIG. 18 is a cross-sectional view of a power tool including
a plastic housing including a motor within the housing and an
integrally formed handle portion, with a battery pack having a
metal housing for conducting heat away from the plurality of cells
according to the principles of the present invention;
[0042] FIG. 19A is a side schematic diagram of a battery pack
having a plurality of cells movable within the battery pack for
moving the cells from a warm portion of the battery pack to a
cooling portion of the battery pack according to the principles of
the present invention;
[0043] FIG. 19B is a front schematic diagram of the battery pack
shown in FIG. 19A;
[0044] FIG. 20 is a schematic diagram of a power tool including a
fan provided in the battery pack for cooling a cell cluster within
the battery pack and a separate fan for cooling the motor of the
power tool;
[0045] FIG. 21 is a schematic illustration of a standard battery
pack and tool/charger system;
[0046] FIG. 22 is a schematic diagram of a tool and charger system
in combination with a battery pack and employing a modular cooling
system which is detachable to and from the tool/charger and/or
battery pack for providing selective cooling to the battery pack
when needed;
[0047] FIG. 23 is a schematic diagram of a battery system including
a plurality of cells disposed within a housing and including a
rheological fluid within the housing for conducting heat away from
the cell cluster;
[0048] FIG. 24 is a schematic diagram of a circuit for disabling a
battery pack when a temperature of the cells exceeds a
predetermined level;
[0049] FIG. 25 is a diagram of a circuit for activating temperature
gauges disposed on the battery pack for indicating to a user when
the pack reaches a predetermined temperature; and
[0050] FIG. 26 is a diagrammatic illustration of a battery pack for
a power tool including a temperature gauge disposed on the exterior
of the battery pack according to the principles of the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0051] 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.
[0052] With reference to FIG. 1, a cordless device, such as a power
tool, is illustrated and designated with reference numeral 1. The
cordless device 1 ordinarily includes a clam shell type housing 2.
The housing 2 includes a mechanism 3 to couple the housing 2 with a
battery pack 4. The cordless device 1 includes electrical elements
5 which couple with corresponding electrical elements 6 of the
battery pack 8. The device 1 includes a trigger 7 which is
activated for energizing a motor 8 provided within the housing 2,
as is well known in the art. Normally, a plurality of battery cells
9 are disposed within the battery pack 4.
[0053] With reference to FIG. 1B, the functional control features
of a battery pack 4 and battery charger 11, according to the
principles of the present invention, will be described. The power
connections for charging and discharging the battery pack 4 are
through terminals A and B. Inside the battery pack 4 there is a
pack ID (identification) component 12 which, when used with the
charger 11 or tool 1, can define the battery's chemistry, capacity,
and/or other battery characteristics to either the charger's
electronic control unit 13 or the tool electronic control unit 14
(see FIG. 1C). Battery pack 4 also has one or more temperature
sensor (such as a thermistor) 15 connected to both the charger unit
11 via connector 16 and the electronic control 17 inside the
battery pack 4. The electronic control 17 is responsible for the
protection of the cells 9 for any condition exposed on the
terminals A, B by the user (charger, tool, and/or user tampering).
The discharge or charge current can be clamped or discontinued by
the use of the semi-conductor devices Q1 and Q2. The electronic
circuit is powered by an internal power supply 18 as shown and the
semi-conductor devices Q1, Q2 are linked through a driver circuit
19.
[0054] When connected to a charger unit 11, the charger electronic
control 13 can be powered from the battery's power supply 18
through terminals A and C. This is only exemplary as other means
for powering the charger electronic control 13 can be employed.
Battery and charger information can be exchanged through serial
data on terminal D and E. The charger electronic control 13 then
will drive the power controller 20 to deliver the desired voltage
and current to the battery pack 4.
[0055] With reference to FIG. 1C, the battery pack 4 is shown
connected to a smart tool 1. The tool 1 also has an electronic
control 14 that can be powered from the battery power supply 18
through terminals A and C. The tool 1 contains a mechanical switch
S1 that pulls terminal B high when the semi-conductor Q1 is off. If
semi-conductor Q1 is left off while the battery pack 4 is dormant,
and suddenly the trigger 21 is pulled, terminal B could be used to
wake the battery pack 4 from a dormant mode of operation. The tool
electronic control 14 could be programmed to read the trigger 21
position and report that data back to the battery electronic
control 14 through serial line D and E. The battery electronic
control 14 will vary the PWM duty cycle through semi-conductor Q1
to obtain a desired motor speed in the tool 1. While semi-conductor
Q1 is off, the diode D1 in the tool 1 will re-circulate any
inductive motor current to prevent voltage spikes.
[0056] An alternative tool not having a smart controller (not
shown) may just have the trigger switch 21 configured as a
potentiometer and connected to terminals A, D or E, and C. The
battery electronic control 17 would then command the semi-conductor
Q1 to switch at the desired duty cycle to create the intended motor
speed. Even less intelligent tools could exist as on/off tools.
These require only the connection to terminals A and B for
operation.
[0057] The present application is directed to several methods of
managing the thermal environment around the battery cells of a
battery pack as used in a power tool and during charging of the
batteries when applied to a battery charger unit.
[0058] With reference to FIG. 2, a battery pack 30 is provided in
connection with a charger unit 32. The battery pack 30 includes a
housing 34 having a plurality of battery cells 9 mounted therein.
The battery cells 9 may be disposed between a pair of metal plates
38 which are sandwiched on opposite sides of the battery cells 9.
The plates 38 may be provided with liquid passages 40, including an
inlet passage 42 and an outlet passage 44, which extend through the
plates 38. The passages 40 are either metal (such as copper,
aluminum, etc.) tubing or heat pipes running through the plates 38.
As the cells 9 heat up, the plates 38 will act as heat sinks for
the heat that is generated. The copper tubes or heat pipes 40 are
used to carry the heat away from the plates so they never reach
temperature equilibrium with the cells. Since they never reach
equilibrium, they can continuously carry heat away.
[0059] For the system utilizing metal tubes, a fluid such as water
is pumped from a reservoir 46 provided in the charger unit 32 by a
pump 48. The heat exchanger 50 may be provided for extracting heat
from fluid returned to the storage vessel 46. The heat exchanger 50
can include fins for increasing the heat transfer, or
alternatively, an active cooling system such as a refrigeration
system or fan can be utilized for withdrawing heat from the fluid
in the storage vessel 46. The inlet and outlet 42, 44 of the fluid
passages 40 in the battery pack 30 can be connected to
corresponding tubing in the charger unit 32 in order to provide a
fluid connection with the fluid passage 52 coming from pump 48 and
the return passage 54. If the system of FIG. 2 is utilized
including heat pipes, the heat pipes would be terminated into a
heat sink mounted within the charger unit or the battery pack. When
the battery pack is placed in the charger, a fan would blow air
through the heat sink to carry the heat generated in the pack into
the air.
[0060] For the fluid cooling method using metal tubes, heat
transfer is dependent on the mass flow rate of the fluid. A higher
volume of fluid increases the amount of heat that can be carried
away. By tailoring the flow rate or tube size, the heat transfer
capability can be changed. The flow rate can also be changed based
on temperature inputs from the pack. Heat transfer is dependent on
the working fluid. The working fluid could be selected so that it
maximizes performance across all temperature ranges and
environmental conditions while maintaining low cost and high
reliability. The copper tube method could be reversed to heat the
pack if the pack is below the minimum charging temperature. Because
the movement and type of fluid can be completely controlled, this
method has a greater capacity to remove heat than the heat pipe
method. If the working fluid is cooled below ambient, for example,
by using a refrigeration device, there is a greater capacity for
removing heat from the pack.
[0061] The heat pipe method also has numerous advantages. The heat
pipe method is a completely enclosed system that does not require
fluid to move across the pack/charger boundary. If multiple
independent heat pipes are used in the system, the system would
continue to work if the pack/cooling system was damaged. The heat
pipe system is simpler in that heat pipes create fluid flow through
a wicking method. This eliminates the need for pumps or methods to
create fluid flow. Because air cooling from the charger is still
required to cool the heat sink where the heat pipes terminate, it
is possible to combine this system with a traditional fan cooled
system to enhance pack cooling further.
[0062] The above two systems could also be adapted to work while
the pack is in the tool.
[0063] With reference to FIG. 3, a battery pack 60 is provided
along with a refrigeration system for cooling the battery cells
within the pack 60. The refrigeration system may be provided within
a charger unit for cooling the pack during recharge of the battery
pack. In this system, the battery pack 60 acts as the evaporator in
a standard refrigeration cycle. The refrigerant is compressed by a
compressor 62. It is then passed to a condenser 64 where excess
heat is removed and the coolant is liquefied. From the condenser
64, the liquid coolant is passed to an expansion valve 66 where it
is throttled to a sub-cooled liquid. The liquid then passes into
interior passages in the battery pack 60 where it is evaporated to
a gas by absorbing heat from the pack 60. The vapor then passes
back to the compressor 62 to repeat the cycle.
[0064] The refrigeration system, as illustrated in FIG. 3, can be
employed in the charger unit 32, as illustrated in FIG. 2, wherein
the compressor, condenser, and evaporator 66 are each disposed
within the battery charger unit. The connection with the battery
pack can be obtained in the same manner as illustrated and
described with reference to FIG. 2.
[0065] With reference to FIG. 4, a battery pack 70 is provided
including a plurality of battery cells 72 disposed within a housing
74. The housing 74 is filled with a fluid which surrounds the
battery cells 72. The housing 74 is provided with a water-tight
seal and includes electrical contacts 78 that are insert molded
into the plastic enclosure 74. At least one heat conducting plate
80, such as an aluminum plate, may be insert molded into a sidewall
of the housing 74 in contact with the fluid 76 for conducting heat
from the fluid 76 to the exterior of the housing 74. A heat sink 82
may be provided in contact with the heat conducting plate 80 when
the battery pack 70 is inserted into the power tool or received in
a battery charger. The heat sink 82 helps to conduct heat away from
the heat conducting plate 80 and is provided with fins, or is
otherwise passively or actively cooled to provide additional
cooling to the heat conducting plate 80. The fluid 76 within the
housing 74 is optionally stirred by an ultrasonic device 84 or
other device which is turned on by a pack controller 414 to stir
the fluid in the enclosure. The stirring of the fluid increases
heat transfer form the cells 72 to the fluid 76 and from the fluid
76 to the heat conducting plate 80. The additional mass in the
system due to the fluid gives a larger thermal mass that also
improves the transient performance of the pack 70. Furthermore, hot
spots in the pack 70 are reduced or eliminated due to the improved
heat transfer within the system that is being stirred. The cooling
system requires little to no energy for the pack 70 to operate. If
the stirring device 84 is turned on, its current draw would be low
enough so as not to have a significant impact on the run time of
the pack 70. The system has the potential to absorb/dissipate a
tremendous amount of heat, thereby allowing for high charge and
discharge rates. The cooling method includes no moving parts and
is, therefore, durable and reliable.
[0066] With reference to FIG. 5, a battery pack 90 is shown
inserted in a battery charger 92. A compressor 94 is provided in
connection with the charger unit 92 to provide compressed air
through a high pressure air line 96 that introduces high pressure
air through a vent passage 98 in the housing 100 of the battery
pack 90. The housing 100 may be provided with additional vent
passages 102 which allow air to escape from within the battery pack
90 and, therefore, carry away heat from the battery cells 104. It
should be understood that the compressor 94 may be provided within
the charger or as a separate unit connected to the charger unit 92.
A valve 106 can be provided within the charger unit 92 in the high
pressure air line for controlling the flow of high pressure air for
cooling the pack 90. The charger controller 13 may be used to open
and close the valve 106 in response to a detected high temperature.
As air passes through the nozzle and expands back to ambient
pressure, its temperature will drop. By designing the system such
that the temperature can drop below the ambient, the air's ability
to carry away heat from the pack is improved.
[0067] Another advantage to this method is that as the air passes
through the nozzle, its velocity will increase. This, in turn,
means that air moving through the pack is moving at higher speed
than what would be possible with a fan. By raising the air
velocity, the heat transfer coefficient improves allowing for
better heat transfer from the pack to the air. Secondly, increasing
the air velocity increases the likelihood of turbulence which
further improves the air's ability to remove heat.
[0068] The compressor 94 which may preferably be of a
mini-compressor type could be cycled on and off as necessary to
supply air through the pack any time during the charging cycle.
This method of cooling may also be provided by providing a nipple
on the back of the charger 92 or battery pack 90 that would plug
into a portable compressor or shop air system 94. The compressed
air cooling system of the present invention improves cooling by
using air that has a temperature lower than ambient and utilizes a
high velocity air flow. The system is more robust than a standard
air cool system that utilizes a fan, and the system can be used to
provide cooling at any time during the charge cycle. This
compressed air system may be combined with a Hirsch Vortex device
to further enhance the cooling by further reducing the air
temperature as it passes into the battery pack 90.
[0069] With reference to FIG. 6, a battery pack 110 is provided in
connection with a battery charger unit 112. The battery pack 110
includes a cell cluster 114 and a thermistor 15 which senses the
temperature of the cell cluster 114. The thermistor 15 is
electrically connected to a control unit 13 provided within a
charger unit 112. The charger control unit 13 controls discharge of
CO.sub.2 from a CO.sub.2 cartridge 120 by opening and closing
pressure relief valve 122. The pressure relief valve 122 is in
communication with a passage 124 which communicates with a passage
126 provided within the housing 130 of the battery pack 110.
[0070] When the control unit 13 detects the temperature of the
battery pack exceeding a predetermined level (via the signal from
thermistor 15), the control unit 13 opens valve 122 to release
CO.sub.2 into the battery pack 110 for cooling the battery cell
cluster 114. The battery pack 110 may include vent passages 128
provided in the housing 130 for allowing escape of the air and
CO.sub.2 within the battery pack 110. If the pressure is released
from the CO.sub.2 cartridge 120, the temperature of the gas coming
from the cartridge is often less than 0 degrees Celsius. This
greatly reduces the ambient temperature in the pack thereby
improving the heat transfer from the cells to the ambient. This
method of cooling can be controlled by pulsing the pressure release
valve 122 on an as-needed basis to maintain the pack in the
operating temperature range. Since this method has a finite life
due to the limited capacity of the CO.sub.2 cartridge, the CO.sub.2
cartridge 120 is replaceable with off-the-shelf cartridges. A
pressure sensor 132 can be employed with the pressure relief valve
122 for providing pressure signals to the controller 13. When the
pressure sensed by the pressure sensor 132 drops below a
predetermined level, the control unit 13 can provide a signal to an
audible or visual signal device 133 to indicate to a user that the
CO.sub.2 cartridge needs to be replaced. In addition, the control
unit 13 can also deactivate the charger unit so that the charger
unit is not utilized until the CO.sub.2 cartridge is replaced and
the pressure sensed by pressure sensor 132 achieves a predetermined
level. The use of a CO.sub.2 cooling system provides active cooling
for a low cost with few moving parts. Due to the low number of
moving parts, the system is highly reliable. The system is user
serviceable to minimize down time, and can be constructed using
readily available parts and takes up relatively little space.
[0071] With reference to FIG. 7, a similar system is implemented by
providing a CO.sub.2 cartridge 134 within the battery pack 140
between the cells 136. A controller unit 17 is employed within the
pack 140 along with a thermistor 15 for detecting a temperature
within the battery pack 140. The control unit 17 controls discharge
of CO.sub.2 from the CO.sub.2 cartridge in the same manner as
controller 13, as discussed above. The system of FIG. 7 has two
advantages over utilizing the CO.sub.2 cartridge in the charger
unit. First, the surface at the CO.sub.2 cartridge will cool as gas
is released, and it can then absorb some of the heat from the
battery cells. Second, the system can be activated during discharge
as well as during charging of the battery pack 140.
[0072] In certain situations, such as overcharge or in extreme
environments, certain batteries can go into thermal runaway in
which the temperature rapidly increases. In the event that a
thermal runaway situation is detected, the high pressure CO.sub.2
cartridge can be fully discharged to rapidly cool the cells. As
illustrated in FIG. 8, the CO.sub.2 cartridge 150 is provided in a
charger unit 152 and has a nozzle portion 154 which discharges
directly through a passage 156 provided in the housing 158 of a
battery pack 160. Vent holes 162 are provided in the sides of the
pack housing 158 allowing CO.sub.2 to escape from the pack 160
while more CO.sub.2 is introduced. The use of CO.sub.2 cartridges
provides a low cost temperature control device. The CO.sub.2
cartridges can be easily replaced by a user. In the event that the
CO.sub.2 cartridge goes off, the pack input/output can be shut off
by the controller until the cartridge is replaced by the user. The
use of a CO.sub.2 cartridge for discharge during a runaway
situation prevents a hazardous situation from occurring. The
CO.sub.2 cartridge can be placed in the battery pack itself, as
illustrated in FIG. 7, or within the charger unit, as illustrated
in FIGS. 6 and 8. When the CO.sub.2 cartridge is placed within the
pack, the CO.sub.2 cartridge does not consume much more space than
one additional cell.
[0073] With reference to FIG. 9, a circuit diagram is provided in
which the battery cells 164 provided in the battery pack 160 are
connected to a charger unit 152. A thermistor 15 is provided for
sensing a temperature of the cells 164 and providing a signal to a
charger controller 13 provided within a charger unit 152. Upon
detection of the battery temperature exceeding a predetermined
level, the charger controller 13 sends a signal to activate a
solenoid actuation device 170 for discharging CO.sub.2 from the
CO.sub.2 cartridge 150. As illustrated in FIG. 8, the CO.sub.2
cartridge has a nozzle communicating with a passage in the battery
pack 160 so that the discharged CO.sub.2 engulfs the battery cells
164 within the pack 160 for rapid cooling thereof.
[0074] With reference to FIG. 10, an alternative embodiment of the
control circuit is illustrated in which the CO.sub.2 cartridge 134
is disposed within the battery pack 140 and a battery controller 17
receives a signal from a thermistor 15 which detects a temperature
of the battery cells 136. Upon detection of a temperature of the
battery cells exceeding a predetermined level, the battery
controller 17 provides a signal to a solenoid device 176 for
actuating the CO.sub.2 cartridge 134 to discharge within the
battery pack 140 for cooling the battery cells 136. With the setup
illustrated in FIG. 10, the CO.sub.2 cartridge and controller are
fully contained within the battery pack. Here, the temperature is
monitored by the controller 17 and if an over-temperature condition
is detected, the battery controller 17 activates the solenoid 176
to open the CO.sub.2 cartridge 134. With this setup, the CO.sub.2
could be released during discharge, for example, to prevent thermal
runaway if the pack was shorted. As the CO.sub.2 cartridge
container itself rapidly cools during discharge, it acts like a
heat sink in the pack to draw heat away from the battery cells
136.
[0075] With reference to FIG. 11, a cooling method is provided
which utilizes the latent heat of fusion of a phase-change material
to maintain the battery pack at the melting temperature of the
phase-change material. As the material changes phase (in this case
from a solid to a liquid), the temperature remains constant until
the phase change has completely occurred. As illustrated in FIG.
11, a battery cell 180 is provided with a gel tube 182 wrapped
around the cell 180. The gel tube 182 is a thin plastic sheet
having inner and outer layers that contain a gel solution. The gel
is comprised of a fluid medium such as water or other fluids with
micro phase-change crystals suspended in the solution. These micro
phase-change crystals are 25-50 microns in size and consist of a
wax-type material (i.e., paraffin) that is encapsulated in a
thermoplastic. As the battery cell 180 gives off heat, the heat is
transferred to the gel tube 182. Once the tube reaches the melt
temperature of the wax (i.e., 50 degrees Celsius), the phase-change
begins. As the wax melts, internal to the thermoplastic shells, it
will absorb the heat given off by the cell. Since the gel is able
to absorb the heat at the same rate the cell is dissipating the
heat, the system will remain at a constant temperature. As long as
the amount of micro-phase change crystals used is enough to ensure
that the phase change takes longer than the charge or discharge of
the battery pack, the system remains below the specified
temperature.
[0076] With reference to FIG. 12, the same affect can be
accomplished by wrapping a cell cluster 184 in a gel blanket 186.
Like the tube 182, the blanket 186 contains micro-phase change
crystals suspended in a fluid solution for absorbing heat from the
entire pack as it heats up. The gel tube or gel blanket cooling
system is a passive method of cooling with no moving parts and
nothing to wear out. The system is fully contained within the
battery pack and does not require any air flow through the pack or
heat sinking to the outside of the pack, although heat sinking and
air flow can also be utilized in combination with the gel tube or
blanket. This system is limited by time by delaying the temperature
rise, and is not limited by the amount of heat that can be
absorbed. The system can be cycled thousands of times. Once the
temperature drops below the melt temperature, the wax re-solidifies
allowing the process to repeat. Since the wax is encapsulated
within its own shell, there is no expansion of the material as it
melts. Since the crystals are suspended in a fluid solution, there
is an added benefit in that the thermal run time is extended by
having to heat the mass of the fluid solution to the phase
transition temperature before beginning the phase transition
process.
[0077] It is noted that some battery packs include paper or plastic
insulating tubes around the cell. The gel tube or gel blanket
replaces the paper tube and, therefore, does not take up a
significant amount of additional space.
[0078] With reference to FIG. 13, an alternative system utilizing
micro-phase change crystals is provided. The micro-phase change
crystals are mixed as a filler to the raw material that the battery
housing and cell carriers are made from. As illustrated in FIG. 13,
the cell carrier 190 is formed from a thermoplastic material that
includes micro-phase change crystals which are suspended in the
plastic of the carrier 190. As illustrated in FIG. 14, the
thermoplastic material used for making the plastic carrier and
battery housing is injected through a conventional screw-type
plastic injection molding device 194 into which micro-phase change
crystals 196 are introduced near the outlet end of the screw 194.
The thermoplastic material 192 mixed with micro-phase change
crystals 196 is introduced into a mold cavity 198 of a mold 200 for
forming the plastic carrier and/or housing of the battery pack.
[0079] As the battery cells 202 generate heat during charge or
discharge, the heat is transferred to the carrier 190 and housing
where it is absorbed by the wax in the crystals changing state.
Since the crystals have a high latent heat capacity, the system is
able to absorb the heat at the same rate the cell is dissipating
the heat, maintaining the system at a constant temperature. As long
as the amount of micro-phase change crystals used is enough to
ensure the phase change takes longer than the charge or discharge
of the battery pack, the system remains below the specified
operating temperature maximum.
[0080] The system of FIG. 13 provides a passive method of cooling
with no moving parts and nothing to wear out. The cooling system is
integrated into the plastic housing eliminating the need to provide
additional manufacturing processes to add gel or crystals to the
pack. The system is limited by the time required for the phase
change crystals to change phase and not by the amount of heat that
can be absorbed. The system can be cycled thousands of times. Once
a temperature drops below the melt temperature, the wax
re-solidifies allowing the process to be repeated. The system could
be further enhanced by using thermally conductive plastic to
transfer some of the heat to the ambient. The system would work
even if the crystals were damaged by the injection molding process
or due to pack damage, etc. since the wax is an integrated part of
the pack housing.
[0081] With reference to FIG. 15, a still further alternative
method of utilizing micro phase-change crystals for cooling the
battery cells 202 is provided in which micro phase-change crystals
are used to form a highly efficient heat sink 210. The heat sink
210 is formed from a heat conductive material such as aluminum,
copper, or carbon fiber with micro phase-change crystals dispersed
throughout the matrix. The heat sink 210 provides the benefits of
both the micro phase-change crystals and the high conductivity
metal. As an alternative design as illustrated in FIG. 17, the
micro phase-change crystals 212 can be inserted between the fins
214 of an aluminum, copper, or other heat conductive material heat
sink 216 which is disposed adjacent to battery cells 202. The use
of the micro phase-change crystals between the heat fins again
combines the benefits of the two cooling methods. The cooling
systems disclosed in FIGS. 15 and 17 provide a passive method of
cooling with no moving parts and nothing to wear out. The system is
contained within a battery pack, and does not require any air flow
through the pack. This system can be cycled thousands of times.
Once the temperature drops below the melt temperature, the
phase-change crystals re-solidify, allowing the process to
repeat.
[0082] With reference to FIG. 16, a battery pack 220 is provided
with a plurality of cells 222 disposed within a housing 224. The
housing 224 is filled with a wax, powder, or other solution 226
which includes micro-encapsulated phase-change material. When the
battery cells 222 reach a melting temperature of the
micro-encapsulating phase-change material, the micro-encapsulating
phase-change material begins to change phase. This phase change
occurs at a relatively constant temperature, maintaining the
temperature of the cells below their specified operating
temperature. The battery housing can be constructed of a metal
material, such as aluminum, which would act as a large heat sink
for the heat generated in the cells. The heat is conducted through
the wax, powder, or solution to the metal housing and is conducted
to the ambient. The system of FIG. 16 provides a passive method of
cooling with no moving parts and nothing to wear out. The system is
fully contained within the battery pack, and does not require any
air flow through the pack. This system is limited by time, not by
the amount of heat that can be absorbed. The system can be cycled
thousands of times and once the temperature drops below the melt
temperature, the phase-change material re-solidifies, allowing the
process to repeat. When the phase-change material is provided in a
slurry solution, the crystals are suspended in a fluid solution, so
there is an added benefit in that the thermal run time is extended
by having to heat the mass of the fluid solution to the transition
temperature before beginning the transition process of the phase
change.
[0083] With reference to FIG. 18, a power tool 230 is provided with
a plastic tool housing 232 including a handle portion 234. A motor
236 and drive mechanism 238 are disposed in the tool housing 232.
The drive mechanism 238 can include gear reduction mechanisms,
drive shafts, reciprocation devices, etc., as are well known in the
power tool art. A battery pack 240 is mounted to the tool housing
and includes a metal battery housing 242. The housing 242 includes
a plurality of cells 244 disposed therein. The use of a plastic
tool housing provides all the benefits of the use of plastics for
assembling the tool and molding the housing. The use of a metal
battery housing adds the additional heat conducting characteristics
of the battery housing to help in removing heat from the battery
cells 244.
[0084] With reference to FIGS. 19A and 19B, a battery pack 250 is
provided with a plurality of cells 252. The cells 252 are disposed
on a rotary wheel mechanism 254 which allows the battery cells to
be moved from hot portions of the battery pack to cooler portions
of the battery pack 250. For example, a cold source 256 such as a
heat sink, fan, Peltier device, or liquid cooling system can be
employed in one portion of the battery pack 250 so that the cooling
feature 256 provides adequate cooling of the cells disposed in the
vicinity of the cooling feature. However, additional cells which
are not disposed in proximity to the cooling feature may not be
properly cooled. Accordingly, the rotary wheel 254 can be rotated
to move hot cells from the hot area within the battery pack to a
cooler portion of the battery pack in order to remove heat from the
cells. It should be understood that the cooling position can
include a heat sink or other actively cooled area within the pack
250 where the heat from the hot cells can be extracted and
expelled, and the cells within the battery pack can be continually
moved or rotated or swapped so that the battery cells are
maintained within a predetermined temperature range. The swapping
or movement of the cells 252 can be performed manually by rotation
of a knob 258 mounted to the rotary wheel 254 upon indication to a
user that certain cells have achieved an undesirable temperature,
or can be performed automatically by a control system and drive
mechanism for driving the rotary wheel 254. Terminal brushes 259a,
259b provide an electrical contact between the rotary wheels 254a,
254b and terminals 257 to allow the rotary wheel 254 to be
rotated.
[0085] With reference to FIG. 20, a power tool 260 is provided,
including a tool housing 262 including a handle portion 264. A
motor 266 and drive mechanism (not illustrated) are disposed in the
tool housing 262, as is known in the art. A battery pack 270,
including a battery housing 272 is releasably connected to the tool
housing 262. The battery pack 270 includes a cell cluster 274
disposed within the housing 272 as well as a fan 276. Preferably,
the fan 276 is a DC motor fan that is controlled by a controller
provided within the battery pack which senses a temperature of the
cell cluster 274 and activates the fan 276 for cooling the cell
cluster once the cell cluster reaches a predetermined temperature.
The fan 276 draws air into the housing 272 of the battery pack 270.
The housing 272 can be configured with vents in order to control
the air flow through the battery pack 270 such that air can be
expelled into the tool housing 262 to be utilized for additional
cooling of the motor 266, or can alternatively be designed to expel
the air into the ambient directly from the battery pack housing
272. An additional DC motor driven fan 280 or a fan coupled to the
tool drive motor can optionally be provided within the tool housing
262 for providing direct cooling for the motor 266.
[0086] With reference to FIG. 21, a schematic illustration of a
battery pack 290 attached to either a tool or a battery charger 292
is shown. During this normal setup, the battery pack is directly
connected to the tool/charger.
[0087] With reference to FIG. 22A, a modular cooling system is
provided including an optional cooling system 294 that can be
mounted to the tool/charger 292 or to the pack 290, or both. As
illustrated in FIG. 22B, the cooling system 294 includes a fan unit
disposed within the cooling system pack for blowing air through the
battery pack 290 for cooling cells therein. The cooling system 294
is removable from the battery pack 290 so that in lighter duty
applications, the tool 292 and battery pack 290 can be utilized
without the cooling system 294. However, in heavy applications, the
cooling system 294 can be snapped onto the tool 292 or pack 290 for
providing desired cooling of the cells within the battery pack 290.
In addition, when the battery pack 290 is placed on a charger 292
(in FIG. 22C), the cooling system 294 can be employed for blowing
air through the pack in order to cool the cells within the pack
290. The modular arrangement of the cooling system 294 allows the
cooling system 294 to be sold as a separate item or as a kit with a
tool, charger, and pack system.
[0088] It should be noted that the modular cooling system 294 can
also take the form of a heat sink or other active cooling systems,
such as a fluid cooling system as disclosed above, which can be
removably mounted to the pack 290 or tool/charger 292.
[0089] With reference to FIG. 23, a battery pack 300 is provided
including a housing 302 in which a cell cluster 304 is disposed. A
rheological fluid 306 is provided in the housing 302 and surrounds
the cell cluster 304. The rheological fluid has good heat
conducting characteristics and, as is known in the art, when a
magnetic field is applied to the rheological fluid, the rheological
fluid changes from a generally liquid state to a solid state.
Accordingly, a conductor coil 308 is provided within the housing
302 to generate a pulsing magnetic field to cause the rheological
fluid 306 to alternate solid and liquid states that causes it to
circulate around the cell cluster 304. The circulating rheological
fluid 306 withdraws heat from the cell cluster and provides cooling
thereof.
[0090] With reference to FIG. 24, a battery pack control circuit is
provided within the battery pack 310 which includes a plurality of
cells 312. The circuit includes a thermistor 314 which detects the
temperature of the cells 312 and opens a switch, breaker, or
MOSFET, etc. 316, in order to disable the electrical connection
with the cells 312 in order to disable the battery pack 310 from
discharging or charging the cells. Thus, with the circuit provided
within the pack 310, the control circuit ensures that the batteries
312 cannot continue to be charged or discharged when a temperature
of the battery cells exceed a predetermined temperature.
[0091] With reference to FIGS. 25 and 26, a battery pack 320 is
schematically shown including a plurality of cells 322 employing a
circuit, including a thermistor 324 which senses a temperature of
the cells 322 and provides an appropriate signal to a temperature
gauge 326 which is mounted on the exterior surface of the housing
328 of the battery pack 320. The temperature gauge 326 (shown in
FIG. 26) shows the user when the pack is getting too hot for
continued use. The temperature gauge 326 provided on the battery
pack 320 can be used in combination with other cooling techniques
provided in the present disclosure for indicating to a user that
the cooling technique needs to employed. In particular, the
technique illustrated in FIG. 2 in which fluid cooling is provided
to the battery pack via a stored fluid chamber and pump system that
swaps the warm fluid within the pack with a cooler fluid can be
utilized. Furthermore, attaching the pack to the charger as
illustrated in FIG. 5 so that compressed air can be utilized for
cooling the pack for continued use by the operator. The gauge can
also be utilized in combination with the system disclosed in FIG.
19 as an indicator to the user that the batteries need to be
manually moved or swapped to a cooler position within the battery
pack. This system can also be utilized with the system disclosed in
FIGS. 22A and 22B to indicate to a user that a modular cooling
system needs to be added to the battery pack in order to actively
cool the cells within the pack.
[0092] The description of the invention is merely exemplary in
nature and, thus, variations that do not depart from the gist of
the invention are intended to be within the scope of the invention.
Such variations are not to be regarded as a departure from the
spirit and scope of the invention.
* * * * *