U.S. patent application number 17/062935 was filed with the patent office on 2021-01-21 for battery pack including plural electrochemical cells encapsulated by encapsulant and method of manufacture.
The applicant listed for this patent is Cummins Battery Systems North America LLC. Invention is credited to Paul A. Daniel, Lawrence O. Hilligoss, Adrian G. Lamy.
Application Number | 20210020881 17/062935 |
Document ID | / |
Family ID | 1000005131915 |
Filed Date | 2021-01-21 |
View All Diagrams
United States Patent
Application |
20210020881 |
Kind Code |
A1 |
Hilligoss; Lawrence O. ; et
al. |
January 21, 2021 |
BATTERY PACK INCLUDING PLURAL ELECTROCHEMICAL CELLS ENCAPSULATED BY
ENCAPSULANT AND METHOD OF MANUFACTURE
Abstract
Embodiments of encapsulated battery packs, control circuitry,
and their methods of manufacture are described. In one such
embodiment, a battery pack includes a plurality of electrochemical
pouch cells and an elastomeric encapsulant that forms at least one
external surface of the battery pack. In another embodiment, a
battery pack includes a plurality of electrochemical pouch cells
with a portion of an encapsulant disposed between the
electrochemical pouch cells and the outer housing. In yet another
embodiment, a method of controlling an operation of a system
includes using a current threshold of one or more electrochemical
cells determined at least in part on at least one of a temperature
and a state of charge of the one or more electrochemical cells.
Inventors: |
Hilligoss; Lawrence O.;
(Ashland, OR) ; Daniel; Paul A.; (Ashland, OR)
; Lamy; Adrian G.; (Hillsborough, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cummins Battery Systems North America LLC |
Columbus |
IN |
US |
|
|
Family ID: |
1000005131915 |
Appl. No.: |
17/062935 |
Filed: |
October 5, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15525346 |
May 9, 2017 |
10797285 |
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PCT/US2017/023776 |
Mar 23, 2017 |
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17062935 |
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62317604 |
Apr 3, 2016 |
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62412425 |
Oct 25, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 50/209 20210101;
H01M 10/486 20130101; H01M 10/615 20150401; H01M 10/48 20130101;
H01M 50/24 20210101; H01M 10/482 20130101; H01M 50/502 20210101;
H01M 10/441 20130101; H01M 2220/20 20130101; H01M 10/443 20130101;
H01M 10/425 20130101; H01M 50/20 20210101; H01M 10/6555
20150401 |
International
Class: |
H01M 2/10 20060101
H01M002/10; H01M 10/48 20060101 H01M010/48; H01M 10/44 20060101
H01M010/44; H01M 10/42 20060101 H01M010/42 |
Claims
1. A battery pack, comprising: a plurality of electrochemical
cells; a battery monitoring unit (BMU) in electrical communication
with the electrochemical cells; and a flash memory external to the
BMU, the flash memory being configured to load updates into the
flash memory with interrupting re-flashing of the BMU, thereby
improving security of bootloading.
2. The battery pack of claim 1, wherein the BMU is configured to
re-flash using the updates loaded into the flash memory.
3. The battery pack of claim 1, wherein the flash memory is a 128k
byte memory device.
4. The battery pack of claim 1, wherein the updates are firmware
updates.
5. A battery system, comprising: a battery system controller; at
least one battery pack including: one or more electrochemical
cells; one or more voltage sensors associated with the one or more
electrochemical cells; and at least one battery monitoring unit
(BMU) including: a secondary overvoltage protection circuit; and an
interlock MOSFET in electrical communication with the secondary
overvoltage protection circuit, wherein the secondary overvoltage
protection circuit is configured to respond to the one or more
voltage sensors sensing an overvoltage condition in the one or more
electrochemical cells by causing the interlock MOSFET to change
state.
6. The battery system of claim 5, wherein the battery system
controller is configured to determine a current threshold of the
one or more electrochemical cells based at least in part on at
least one of a temperature and a state of charge of the one or more
electrochemical cells, and wherein the at least one controller
controls an operation of the system using the current
threshold.
7. The battery system of claim 6, wherein the battery system
controller determines at least two of a discharging current
threshold, a regenerative charging current threshold, and a
continuous charging current threshold.
8. The battery system of claim 5, wherein the battery system
controller is in electrical communication with the interlock
MOSFET, the battery system controller being configured to detect
the change in state of the interlock MOSFET and respond by
inhibiting further charging of the at least one battery pack.
9. The battery system of claim 8, wherein the battery system
controller is configured to respond to the detected change of state
of the interlock MOSFET by discharging the battery pack.
10. The battery system of claim 5, wherein the interlock MOSFET is
part of a system interlock daisy-chain.
11. The battery system of claim 5, wherein the one or more sensors
sense an overvoltage condition in the one or more electrochemical
cells when a voltage of a cell exceeds a predetermined threshold
voltage.
12. A battery system, comprising: a plurality of electrochemical
cells; a battery monitoring unit (BMU) in electrical communication
with the electrochemical cells, the BMU including a plurality of
input ports in electrical communication with a first set of
electrochemical cells of the plurality of electrochemical cells to
monitor voltages of the first set of electrochemical cells and at
least one auxiliary input channel in electrical communication with
at least one electrochemical cell of a second set of
electrochemical cells of the plurality of electrochemical cells to
monitor a voltage of the at least one electrochemical cell of the
second set; and at least one secondary circuit in electrical
communication with the at least one auxiliary input channel and the
at least one electrochemical cell of the second set.
13. The battery system of claim 12; wherein the at least one
secondary circuit includes an N-Channel MOSFET to inhibit current
leakage during a sleep mode of the BMU.
14. The battery system of claim 12, wherein the at least one
secondary circuit includes a voltage divider circuit to reduce a
sensed voltage of the at least one electrochemical cell of the
second set for input to the at least one auxiliary input
channel.
15. The battery system of claim 12, wherein the second set of
electrochemical cells includes a plurality of electrochemical
cells.
16. A battery system, comprising: a plurality of electrochemical
cells; a battery monitoring unit (BMU) in electrical communication
with the electrochemical cells; and a standby power supply
switch-over circuit in electrical communication with the battery
monitoring unit, the switch-over circuit including a normally
closed relay configured to respond to standby signal from the BMU
by sourcing a voltage to bias a standby circuit of the BMU and to
respond to an active signal from the BMU by opening to remove the
voltage from the standby circuit.
17. The battery system of claim 16, wherein the switch-over circuit
further includes an opto diode in electrical communication with the
BMU, and wherein a current flow through the opto diode in response
to the active signal causes the normally closed relay to open.
18. The battery system of claim 16, wherein the standby signal is a
first voltage and the active signal is a second voltage that is
greater than the first voltage.
19. The battery system of claim 16, wherein the standby signal
indicates that the BMU is operating in a sleep mode and the active
signal indicates that the BMU is operating in an active mode.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 15/525,346, filed May 9, 2017, which is a national stage filing
under U.S.C. .sctn. 371 of PCT International Application
PCT/US2017/023776, filed Mar. 23, 2017, which claims the benefit of
priority under 35 U.S.C. .sctn. 119(e) of U.S. provisional
application Ser. No. 62/317,604, filed Apr. 3, 2016, and U.S.
provisional application Ser. No. 62/412,425, filed Oct. 25, 2016,
the disclosures of each of which are incorporated by reference
herein in their entirety.
FIELD
[0002] Disclosed embodiments relate generally to battery packs and
methods of manufacture of battery packs.
BACKGROUND
[0003] In general, battery packs or modules are comprised of
multiple individual batteries, also referred to as cells, contained
within a housing. For example, battery packs are typically
constructed using parallel and/or series combinations of individual
battery cells to form a Cell Module Assembly (CMA). A battery pack
may also include various types of electrical connections between
the CMA and an electrical system or other associated battery packs.
For example, in many applications, a Battery Monitoring Unit (BMU)
may be used to manage State of Charge (SOC) and State of Health
(SOH) during the charge and discharge of a CMA, as well as monitor
and manage the CMA's individual parallel cell voltages, series
current, and temperature. In most architectures, the BMU may
serially communicate these managed CMA conditions to, and receive
control from, a system's Battery Management Controller (BMC) using
any appropriate method for placing these components in electrical
communication with one another including, for example, a local
and/or area network communication link.
SUMMARY
[0004] In one embodiment, a battery pack includes a plurality of
electrochemical pouch cells and an elastomeric encapsulant
encapsulating at least a portion of the electrochemical pouch
cells. The elastomeric encapsulant forms at least one external
surface of the battery pack.
[0005] In another embodiment, a battery pack includes a plurality
of electrochemical pouch cells and a first encapsulant
encapsulating at least a portion of the electrochemical pouch
cells. The battery pack also includes a housing at least partially
embedded in the first encapsulant. The housing includes an interior
space isolated from the first encapsulant.
[0006] In yet another embodiment, a battery pack includes a
plurality of electrochemical cells and an encapsulant flow path
extending from a first portion of the battery pack to a second
portion of the battery pack.
[0007] In another embodiment, a method of encapsulating a battery
pack includes: flowing encapsulant from a first portion of the
battery pack to a second portion of the battery pack; and flowing
the encapsulant from the second portion of the battery pack towards
the first portion of the battery pack, wherein the encapsulant
encapsulates a plurality of electrochemical cells as the
encapsulant flows towards the first portion of the battery
pack.
[0008] In still another embodiment, a battery pack includes a
plurality of electrochemical pouch cells and an outer housing
surrounding at least a portion of the plurality of electrochemical
pouch cells. An elastomeric encapsulant encapsulates at least a
portion of the electrochemical pouch cells, and at least a portion
of the encapsulant is disposed between the electrochemical pouch
cells and the outer housing.
[0009] In yet another embodiment, a battery pack includes a
plurality of electrochemical pouch cells arranged in a plurality of
cell blocks. The cell blocks are stacked in one or more complete
rows and one or more incomplete rows. An intermediate plate is
disposed between the one or more complete rows and the one or more
incomplete rows of cell blocks.
[0010] In still another embodiment, a battery pack includes a
plurality of electrochemical pouch cells arranged in a plurality of
cell blocks with the cell blocks stacked in at least two rows. A
housing at least partially surrounds the plurality of
electrochemical pouch cells and an intermediate plate is connected
to and extends between at least two opposing sides of the housing.
Additionally, the intermediate plate is disposed between the at
least two rows.
[0011] In another embodiment, a battery pack includes a plurality
of electrochemical cells and a battery monitoring unit (BMU) in
electrically communication with the electrochemical cells. The BMU
includes a processor and a flash memory. In this embodiment, the
flash memory is configured to load updates into the flash memory
prior to reflashing the microprocessor.
[0012] In yet another embodiment, a battery pack includes a
plurality of electrochemical cells and one or more heaters
associated with the plurality of electrochemical cells. The battery
pack also includes a processor and a thermostat associated with the
plurality of electrochemical cells. The thermostat is configured to
open above a threshold temperature. The battery pack also includes
first and second MOSFETs arranged in series and in electrical
communication with the one or more heaters. The processor is
configured to selectively open and close the first MOSFET. The
thermostat is configured to close the second MOSFET when the
plurality of electrochemical cells are below the threshold
temperature, and open the second MOSFET when the plurality of
electrochemical cells are above the threshold temperature.
[0013] In another embodiment, a battery system includes a battery
system controller and at least one battery pack. In this
embodiment, the at least one battery pack includes one or more
electrochemical cells, one or more voltage sensors associated with
the one or more electrochemical cells, and at least one battery
monitoring unit (BMU). The BMU includes a system interface
configured to communicate with the battery system controller and an
interlock MOSFET in electrical communication with the system
interface. The battery system controller is configured so that if
the one or more voltage sensors sense an overvoltage condition in
the one or more electrochemical cells, the MOSFET changes state
causing the system interface to prevent further charging of the at
least one battery pack.
[0014] In yet another embodiment, a method of controlling a system
including one or more electrochemical cells includes: determining a
current threshold of the one or more electrochemical cells based at
least in part on at least one of a temperature and a state of
charge of the one or more electrochemical cells; and controlling an
operation of the system using the current threshold.
[0015] In still another embodiment, a system includes one or more
electrochemical cells, at least one controller associated with the
one or more electrochemical cells, and one or more sensors
constructed and arranged to detect one or more operating conditions
of the one or more electrochemical cells. The sensors may output a
signal to the at least one controller. The at least one controller
may determine a current threshold of the one or more
electrochemical cells based at least in part on at least one of a
temperature and a state of charge of the one or more
electrochemical cells. Additionally, the at least one controller
may control an operation of the system using the current
threshold.
[0016] It should be appreciated that in various embodiments the
foregoing concepts, and additional concepts discussed below, may be
arranged in any suitable combination. Further, other advantages and
novel features of the present disclosure will become apparent from
the following detailed description of various non-limiting
embodiments when considered in conjunction with the accompanying
figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The accompanying drawings are not intended to be drawn to
scale. In the drawings, each identical or nearly identical
component that is illustrated in various figures may be represented
by a like numeral. For purposes of clarity, not every component may
be labeled in every drawing. In the drawings:
[0018] FIG. 1 is a schematic view of a battery pack;
[0019] FIG. 2 is a schematic view of the pack of FIG. 1 prior to
encapsulation;
[0020] FIG. 3 is an exploded schematic view of the pack of FIG. 1
prior to encapsulation;
[0021] FIG. 4 is a schematic view of a heater;
[0022] FIG. 5 is a schematic top perspective view of a battery pack
before encapsulating;
[0023] FIG. 6 is a schematic top perspective view of the heaters
and heater connections of a battery pack assembly;
[0024] FIG. 7 is a schematic top perspective view of the busbars
and cell tab connections battery pack assembly;
[0025] FIG. 8 is a schematic cross-sectional view of a cell module
assembly with the electrode leads extending through the openings of
an associated interconnect board;
[0026] FIG. 9 is a schematic cross sectional view of a battery pack
with an encapsulant delivery tube;
[0027] FIG. 10 is a schematic perspective view of an encapsulated
battery pack prior to encapsulating the BMU housing;
[0028] FIG. 11 is a schematic perspective view of a battery
assembly in an encapsulation mold prior to encapsulation;
[0029] FIG. 12 is a schematic perspective view of a battery
assembly in an encapsulation mold during encapsulation;
[0030] FIG. 13 is a schematic perspective view of an encapsulation
mold;
[0031] FIG. 14 is a schematic perspective cross-sectional view of
the encapsulation mold of FIG. 13;
[0032] FIG. 15 is a schematic perspective cross-sectional view of
the encapsulation mold of FIG. 13;
[0033] FIG. 16 is a schematic perspective view of an encapsulation
mold;
[0034] FIG. 17 is a schematic perspective cross-sectional view of
the encapsulation mold of FIG. 16;
[0035] FIGS. 18A-18B are a flow diagram of a manufacturing
process;
[0036] FIG. 19A is a schematic perspective view of a BMU assembly
installed in a CMA carrier housing;
[0037] FIG. 19B is schematic view of a BMU;
[0038] FIG. 20 is a schematic representation of an encapsulated CMA
including an outer housing;
[0039] FIG. 21 is a schematic representation of an encapsulated CMA
including an outer housing with the BMU housing removed;
[0040] FIG. 22 is a schematic representation of a BMU;
[0041] FIG. 23 is a schematic representation of an overmolded
BMU;
[0042] FIG. 23 A is a cross sectional view of the overmolded BMU of
FIG. 23;
[0043] FIG. 24 is a schematic exploded view of one embodiment of a
housing and other components contained therein;
[0044] FIG. 25 is a schematic exploded view of another embodiment
of a housing and other components contained therein;
[0045] FIG. 26 is a schematic front view of an encapsulated CMA
including an outer housing;
[0046] FIG. 26A is a schematic cross-sectional view of the
encapsulated CMA of FIG. 26;
[0047] FIG. 26B is a schematic cross-sectional view of the
encapsulated CMA of FIG. 26;
[0048] FIG. 27 is a schematic perspective view of a spacer
block;
[0049] FIG. 28 is a schematic perspective view of a tray;
[0050] FIG. 29 is a schematic cross-sectional view of an
encapsulated CMA within an exterior housing and disposed on a
tray;
[0051] FIG. 30 is a block diagram representation of a BMU and
associated CMA;
[0052] FIGS. 31A-31D are a schematic of a BMU Controller including
Cell Voltage, Current, and Temperature measurement circuits;
[0053] FIGS. 32A-32C are a schematic of an electrical system
including Cell Connection, Balance Control, Secondary Overvoltage,
and Power Supply switch over circuits;
[0054] FIG. 33 is a schematic of the circuits used to expand cell
voltage sensing from four cells to six cells for a four cell
BMU;
[0055] FIG. 34 is a schematic of a CMA heater control;
[0056] FIG. 35 is a schematic of a Secondary Overvoltage Protection
and interlock function;
[0057] FIG. 36 is a schematic of an active and standby power supply
switch over circuit;
[0058] FIG. 37 is a flow diagram of one embodiment of a method for
providing over voltage protection for a battery;
[0059] FIG. 38 is a flow diagram of one embodiment of a method for
providing under voltage protection for a battery;
[0060] FIG. 39 is a flow diagram of one embodiment of a method for
providing over temperature protection for a battery;
[0061] FIG. 40 is a flow diagram of one embodiment of a method for
preventing excessive heater temperature;
[0062] FIG. 41 is a schematic of an external Flash Memory used for
more secure program bootloading;
[0063] FIG. 42 is a flow diagram of one embodiment of a method of
using an external flash memory for secure program bootloading;
[0064] FIG. 43 is a flow diagram of one embodiment of a method for
determining and using a current threshold for one or more
electrochemical cells;
[0065] FIG. 44 is a schematic of a system including a power source
with one or more electrochemical cells and a controller that
determines a current threshold for the one or more electrochemical
cells;
[0066] FIG. 45 is a table of exemplary discharge current thresholds
versus temperature and state of charge;
[0067] FIG. 46 is a table of exemplary regenerative charging
current thresholds versus temperature and state of charge; and
[0068] FIG. 47 is a table of exemplary continuous charging current
thresholds versus temperature and state of charge.
DETAILED DESCRIPTION
[0069] The inventors have recognized that typical battery packs
include expensive complicated external enclosures that are
susceptible to water intrusion, damage from shock and vibration, as
well as poor performance at low temperatures. Therefore, the
inventors have developed innovative solutions to provide a low cost
ruggedized battery pack that is easily manufactured while providing
improved shock, vibration, and/or low temperature performance as
well as accommodation of cell swelling in certain embodiments.
[0070] In view of the above, the inventors have developed
encapsulation techniques and at least partially encapsulated
battery pack configurations that, as described below, result in
certain cases in certain benefits and solutions to one or more of
the above noted problems/shortcomings with conventional designs and
methods. For example, in some embodiments, a battery pack including
encapsulated electrochemical cells may not include any additional
external enclosure. In such an embodiment, the encapsulant would
form at least a portion of the exterior surface of the battery
pack. Further, embodiments in which the encapsulant fully
encapsulates the electrochemical cells with the electrode leads of
the cells extending through the encapsulant are also described.
However, embodiments in which the electrochemical cells are at
least partially encapsulated and are located within a rigid outer
housing are also detailed herein. In addition to other benefits,
these various designs including at least partially, and/or fully
encapsulated, electrochemical cells may result in batteries that
exhibit improved shock and vibration performance as compared to
batteries that do not include encapsulated electrochemical
cells.
[0071] The above noted embodiments that do not include a rigid
outer housing may be of benefit in some applications where
electrochemical pouch cells are used. Specifically, flexible
electrochemical pouch cells typically experience swelling during
use due to changes in the state of charge of the cells, temperature
changes, as well as swelling due to aging of the cells.
Consequently, in such an embodiment, the encapsulant may be
flexible enough to accommodate the expected swelling of the
electrochemical pouch cells while maintaining a pressure applied to
an exterior of the electrochemical pouch cells within a
predetermined operating pressure range. Therefore, the battery pack
may include environmental protection while still permitting the
electrochemical pouch cells to expand and/or contract. This
accommodation of swelling while maintaining the desired compression
pressure applied to the cells may help extend the battery life of
the cells.
[0072] The amount of swelling a particular electrochemical pouch
cell will undergo during operation depends on the type of
chemistry, the operating voltage ranges, the age, and other
appropriate parameters used during operation of the cell. However,
in certain embodiments, the amount of swelling an electrochemical
pouch cell undergoes during cycling, and that the encapsulant
flexes to accommodate, is greater than or equal to 2%, 3%, 5%, 10%,
or any other appropriate percentage. Additionally, the amount of
swelling may be less than or equal to about 15%, 10%, 5%, or any
other appropriate percentage. Combinations of the above ranges can
also be used in certain embodiments, including, for example, an
encapsulant flexing to accommodate volumetric swelling of one or
more electrochemical pouch cells between 2% and 15% while
maintaining a compression pressure of the electrodes within a
desired pressure range. In certain embodiments, different
combinations of the above ranges as well as amounts of swelling
both less than, and greater than, those noted above are
employed.
[0073] The inventors have recognized that it may be desirable in
certain embodiments to encapsulate a battery monitoring unit (BMU),
or other component, in a subsequent encapsulation process after the
electrochemical cells have been encapsulated. This may permit cell
module assemblies (CMA's) that are defective to be identified prior
to installing associated electronics thus reducing the overall
manufacturing costs of the battery packs. In such embodiments, a
plurality of electrochemical cells may be encapsulated using a
first encapsulant during a first process. The battery pack may
include a housing that is at least partially embedded in this first
encapsulant and include a housing interior that is isolated from
(i.e. free of contact with) the encapsulant outside of the housing.
After determining the electrochemical cell assembly is not
defective (e.g. excessively imbalanced cells, swollen cells,
excessive self-discharge rates, etc.), a BMU, or other type of
circuitry or component, is assembled into the housing interior.
Depending on the particular embodiment, the housing interior, and
associated component disposed therein, may then be encapsulated
during a second encapsulation process using a second encapsulant.
In some instances, the first and second encapsulant are the same
type of encapsulant. In certain embodiments, however, a different
type of encapsulant is used. In other embodiments, a BMU, or other
type of circuitry, can be overmolded and subsequently assembled
into the housing interior.
[0074] While the embodiments above describe battery packs where the
encapsulant forms an external surface of a battery pack, it should
be understood that in other embodiments, a separate exterior
enclosure, such as the outer housings described further below, may
form the exterior of a battery pack with the encapsulant and the
CMA disposed within the separate exterior enclosure. Additionally,
in certain embodiments, the battery packs described herein may be
used individually, assembled with one another in series and/or
parallel, and/or may be assembled into a separate larger exterior
housing.
[0075] In some embodiments, a battery pack fixture is used to hold
electrochemical cells, the associated busbars, and/or other
electrical interconnects during a welding process. The same battery
pack fixture may then be used as a mold for encapsulating the
entire pack in in an encapsulant during an encapsulating process.
Of course it should be understood that such a battery pack fixture
may be combined/used with any of the battery packs, methods, molds,
and/or fixtures described further below.
[0076] In certain embodiments, it may be desirable to apply a
compressive force to a cell module assembly during an encapsulation
process to ensure that the appropriate compressive pressure is
applied to the electrical cells. In such embodiments, an
encapsulation mold may hold the various portions of an
electrochemical cell module assembly in a desired position and
orientation while applying a pressure to hold the stack of
components together using one or more pressing surfaces during the
encapsulating process. Consequently, after the encapsulant is
introduced into the mold and cured, the encapsulant maintains the
electrochemical cells under a state of compression which applies
the desired compressive pressure to the electrochemical cells'
electroactive surfaces even after removal from the mold. This may
help to extend the life of the electrochemical cells within the
battery pack.
[0077] To help avoid introduction of voids within an encapsulated
battery pack, in some applications, it may be desirable to draw an
encapsulate up and around a CMA which may correspond to one or more
stacks of electrochemical cells which may be arranged in one or
more corresponding cell blocks. While this may be accomplished in
any number of ways, in one embodiment, an encapsulant flow path is
formed between a first portion of a battery pack and/or CMA and a
second opposing portion of the battery pack and/or CMA such as an
upper portion and lower opposing portion of the battery pack and/or
CMA. Encapsulant is then flowed through this flow path such that it
exits the flow path within the second portion of the battery pack
and/or CMA and then flows back towards the first portion of the
battery pack and/or CMA. For example, in one embodiment,
encapsulant is introduced either near or below a bottom surface of
the electrochemical cells of a CMA. The encapsulant then flows up
towards, and in some instances past, the opposing top surface of
the electrochemical cells. While a pressurized flow of encapsulant
may be sufficient to encapsulate a CMA, in some embodiments, a
vacuum applied to the first portion of the battery pack may help
urge the encapsulant to fully encapsulate the battery pack.
Depending on the embodiment, a flow path may be embodied as a tube,
a conduit, a channel formed in a component of the battery pack
and/or CMA, or any other structure capable facilitating flow of an
encapsulant through the battery pack and/or CMA prior to being
introduced to the battery pack and/or CMA interior in the desired
location. Additionally, in some embodiments the structure forming
the flow path may be removable from the battery pack and/or CMA
after encapsulant has been introduced.
[0078] The terms electrochemical cells, cells, and similar terms
are meant to refer to individual battery cells such as coin cells,
prismatic cells of various shape, jelly roll cells, pouch cells, or
any other appropriate electrochemical device capable of acting as a
battery. Additionally, a pouch cell, electrochemical pouch cell,
and other similar terms are meant to refer to cells that include a
deformable outer layer that typically includes layers of laminated
polymers and metal foils surrounding an internal electrode stack or
roll. Typically, pouch cells include larger flat opposing front and
back surfaces and smaller side surfaces. Further, when forming
stacks of pouch cells, the flat surfaces are typically stacked one
on top of the other. However, certain embodiments may use multiple
adjacent cell stacks within a CMA where the cells are either in
series and/or in parallel. In certain embodiments, other ways of
arranging the cells may also be employed.
[0079] While any appropriate material may be used as an
encapsulant, appropriate encapsulants include but are not limited
to elastomers (e.g. silicones), epoxies, and/or any other
appropriate material. In one specific embodiment, an encapsulant is
a flexible polyurethane/polyurea blend.
[0080] In some applications an encapsulant may exhibit one or more
of the following properties: elongation to failure greater or equal
to 250% and in some instances less than 1000%; a glass transition
temperature between or equal to -70.degree. C. and -40.degree. C.;
a dielectric strength greater than or equal to 300 V/mil;
compatibility with Nylon, polybutylene terephthalate (PBT),
polycarbonate, acrylonitrile butadiene styrene (ABS), copper,
aluminum, nickel, and/or tin; a hardness between or equal to shore
60 A and 60 D, stable long term operating temperatures between or
equal to -40.degree. C. to 80.degree. C.; a relatively low
viscosity prior to curing (e.g. less than or equal to 2000 cP/2
Pascal seconds); gel times between or equal to about 4 minutes and
20 minutes; low to no off gassing from the encapsulant; low to no
emission of volatile organic compounds (VOC's) during curing; high
tear resistance; flammability resistance; and other appropriate
properties. While specific properties are noted above, it should be
understood that encapsulants that do not use all of the above noted
properties, and/or have different properties, may also be used for
certain applications.
[0081] In addition to the various battery pack configurations and
arrangements noted above, in some embodiments, a battery pack may
include a battery monitoring unit (BMU) and/or other associated
electronics that provide various types of desired functionality.
For example, in certain embodiments, a BMU may include circuitry
that expands the number of cells for which the BMU may perform cell
voltage sensing and balancing. In certain embodiments, the BMU may
include a secondary overvoltage protection monitoring and interlock
functionality. Additionally, a BMU may include circuitry and/or be
programed to implement a method of active and standby power supply
adaption that provides lower active power dissipation. A BMU may
also include external Flash Memory for more secure program
bootloading. Of course, in certain embodiments BMU's may include
combinations of the above noted functionalities and/or different
functionalities.
[0082] The embodiments described herein may refer to cell module
assemblies and/or battery packs. However, it should be understood
that these terms may be used interchangeably in the various
embodiments to refer to a grouping of one or more electrically
interconnected electrochemical cells.
[0083] Turning now to the figures, several non-limiting embodiments
are described in further detail.
[0084] FIG. 1 presents one embodiment of a battery pack 2. The
battery pack includes an encapsulated cell module assembly 4 (CMA)
that includes a plurality of electrochemical cells that are at
least partially, and in some instances fully, encapsulated in an
appropriate encapsulant. The battery pack includes a housing such
as a battery monitoring unit (BMU) housing 6 that may contain
various components such as a BMU disposed within the BMU housing.
The BMU housing is disposed on an exterior surface 4a of the
encapsulated CMA where the electrode leads of the cells within the
assembly are located. While the BMU housing may be attached to the
encapsulated CMA in any appropriate manner, in some embodiments, at
least a bottom portion of the BMU housing facing the encapsulated
CMA is encapsulated in the same encapsulant material as the
encapsulated CMA. Alternatively, the BMU housing may be attached to
the encapsulated CMA using methods such as threaded fasteners,
clips, mechanically interlocking features, welding, brazing,
adhesives, or in any other appropriate manner.
[0085] In addition to the above, in some embodiments, a housing
such as the depicted BMU housing 6 associated with an encapsulated
CMA 4, may include an interior space 6a that is isolated from the
encapsulant. For example, in the depicted embodiment, the interior
space of the BMU housing corresponds to interconnected walls that
form a depression or cavity that is isolated from the surrounding
encapsulant of the encapsulated CMA. Of course, any other feature
that forms an open topped reservoir that is isolated from the
encapsulant of the encapsulated CMA may also be used. As noted
previously, such an arrangement may enable the testing of the
encapsulated CMA prior to assembling electronics and other
components such as a BMU 18 with the CMA, see FIG. 3. Once the
appropriate components are assembled into the isolated interior
space of the BMU housing, a separate encapsulating step may be
conducted to encapsulate the BMU and open portion of the BMU
housing. In such a secondary encapsulating process the encapsulant
may be added until it fills up to an upper edge of the interior
space or it may extend above or below the BMU housing upper
edge.
[0086] FIGS. 2 and 3 illustrate a cell assembly and the associated
components prior to the battery pack undergoing an encapsulating
process. In the depicted embodiment, the battery pack includes a
plurality of electrochemical cells arranged in one or more cell
stacks to form a CMA. In some instances, and as shown in the
figures, there may be two or more cell stacks arranged side by
side. Further, in instances where flat pouch and/or prismatic cells
are used, the cells may be stacked with their flat sides in contact
with one another, which may aid in building a substantially flat
battery pack assembly. Once appropriately arranged, the CMA 10 may
be positioned between two opposing end plates 16 that are located
on the opposing sides of the CMA. Spacers 12 may then be placed on
one or more of the sides of the CMA. For example, as shown in the
figure, the spacers are placed on the opposing sides and bottom of
the CMA defined between the end plates. As described in more detail
below, the spacers may be used to space the CMA, and the
electrochemical cells therein, from the interior walls of an
encapsulation mold during an encapsulating process which may help
ensure that the encapsulant fully encapsulates the CMA. In some
embodiments, the spacers may include one or more cutouts 12a along
their lengths. As shown in the figures, these cutouts may have
elongated shapes that extend inward from the two opposing elongated
exterior edges of the spacers toward an interior portion of the
spacers. In some instances, the cutouts may be arranged in an
alternating pattern on the opposing sides of the spacer. The
cutouts may help reduce the pressures needed to flow an encapsulant
around the CMA during an encapsulating process due to the increased
area available for flow exposed by these cutouts.
[0087] As best illustrated in FIGS. 3 and 5-7, a cell module
assembly 10 (CMA) may include a number of different components
disposed between two opposing end plates 16. For example, in
certain embodiments, a plurality of planar foam layers 19, heat
distribution plates 20, electrochemical cells 22, and/or heaters 24
may be arranged in alternating fashion within the cell module
assembly. In the particular embodiment shown in the figures, the
cell module assembly includes a foam layer disposed between an end
plate and adjacent heat distribution plate. The heat distribution
plate may then be located between the heat distribution plate and a
layer of one or more electrochemical cells which in turn are
adjacent to a heater that is located between two adjacent
electrochemical cells. This pattern, or another appropriate
pattern, of the components may then be repeated throughout the cell
module assembly until the opposing end plate is reached.
[0088] In the above noted embodiment, any appropriate foam
including both open and closed cell foams may be used for the
plurality of planar foam layers. However, in certain embodiments,
it may be desirable to avoid introducing an encapsulant into the
foam as might occur with an open cell foam subjected to an
encapsulating process. Consequently, in some embodiments, a foam
used for the plurality of planar foam layers in the cell module
assembly may be a closed cell foam. Appropriate materials for the
close cell foam include, but are not limited to, polyurethane,
silicone foam, or any other appropriate foam material.
[0089] While any number of different heaters and heat distribution
plates may be used, in certain embodiments, the heaters and
distribution plates illustrated in the embodiment depicted in the
figures are planar in shape and have a size that covers a majority,
if not all of, the area of an electrochemical cell it is adjacent
to. The inclusion of planar heat distribution plates between
adjacent electrochemical cells may reduce the number of heaters
needed within a CMA. Without wishing to be bound by theory, this
may be due to the heat distribution plates helping to distribute
and equalize temperature gradients between adjacent cells and
different portions of the same cell. Additionally, in some
embodiments, the heaters may generate heat and/or conduct heat
across their faces which may also help to reduce these same
temperature gradients.
[0090] In certain embodiments, a heat distribution plate may
correspond to any thermally conductive planar structure disposed
between two flat cells. For example, a metal plate such as a copper
or aluminum metal plate may be used. Further, in some embodiments,
a thermal conductivity of the heat distribution plates may be
greater than that of the electrochemical cells it is associated
with.
[0091] Depending on the particular embodiment, the one or more
heaters used in a CMA may correspond to any appropriate component
capable of generating heat. In certain embodiments, and as shown in
FIG. 4, a heater 24 may be an etched plate, such as an etched plate
24a including a laminated copper foil heating element 24b. Again,
in instances where flat cells, such as flat electrochemical pouch
cells, are used, the heater may be located between the cell rows
covering a majority, or all, of the large flat surface area of the
one or more associated electrochemical cells. This type of
arrangement may beneficially result in the heater applying heat
directly to the associated cells across their surface areas and in
some embodiments may extend across the faces of multiple cells
arranged in adjacent stacks. For example, two rows of cells 22 may
be used as shown in the figures, though in other embodiments, any
number of cell rows may be used.
[0092] As shown best in FIGS. 5-7, in certain embodiments, a
plurality of heaters 24 located within a CMA may include electrical
connections 24c that are connected to two common busbars 26 located
on opposing sides of the battery pack. In such an arrangement, the
heaters may be electrically connected in parallel with one another;
however, in other embodiments, heaters electrically connected in
series are used. Further, in certain embodiments, by using just a
single pair of busbars, the heaters may be controlled using a
single electrical control which may beneficially simplify both the
control electronics and algorithms associated with the heaters. For
example, one or more temperature sensors may be used to monitor the
temperature of the electrical cells, heaters, and/or battery pack
such that the heaters are operated to maintain a temperature of the
battery pack at a desired threshold temperature. Various
considerations that may also be taken into account when controlling
the amount of heat provided to a cell module assembly by a heater
include, but are not limited to, state of charge of the
electrochemical cells, ambient temperature, and other appropriate
parameters. The one or more temperature sensors may be associated
with any appropriate structure within the battery pack. However, in
certain embodiments, one or more temperature sensors may be
connected to a busbar of the system such a busbar 32 connected to
the electrochemical cells. Appropriate temperature sensors include,
but are not limited to, thermistors, thermocouples, or any other
appropriate sensor capable of being used to detect the temperature
of a battery pack.
[0093] In some instances, during the assembly of a battery pack, it
may be desirable to help control routing and connection of the
electrode leads 28 of the electrochemical cells in a battery pack.
Consequently, in some embodiments, the battery pack may include a
structure such as an insertion plate 36. During the assembly
process, the insertion plate may be assembled onto a top edge of a
cell module assembly from which the electrode leads extend. In the
depicted embodiment, the insertion plate is an elongated plate
structure that includes one or more elongated openings 38 arranged
in rows corresponding to the locations of electrode lead groupings.
As shown in the cross-section of FIG. 8, the electrode leads are
bent towards and are routed upwards through a central region of the
elongated openings towards the corresponding busbars. Once
appropriately arranged together, the electrode leads are
electrically connected to the corresponding busbars in any
appropriate manner including, but not limited to, ultrasonic
welding, soldering, or any other appropriate electrical
connection.
[0094] As noted previously, in some embodiments, it may be
desirable to encapsulate a CMA by flowing encapsulant from a bottom
side of the cell module assembly up and around to a top opposing
side of the CMA. Referring now to FIG. 9, to help facilitate such
an encapsulation process, a battery pack may include an encapsulant
flow path, such as an encapsulant tube 8 received in, and/or in
fluid communication with, an encapsulant tube receiver 40 connected
to the BMU housing described above, which in this embodiment
corresponds to a through hole and associated support structure
formed in or otherwise connected to the BMU housing. The
encapsulant tube may extend from an upper portion of the battery
pack, such as from above the CMA, to a lower portion of the battery
pack, such as a bottom edge of the CMA. While the flow path may be
located in any appropriate location, in the depicted embodiment,
the flow path extends along a central axis of the battery pack. In
certain embodiments, the flow path may be located in a corner of
the battery pack, or any other appropriate location and/or multiple
flow paths in one or multiple locations may be employed.
[0095] Referring now to FIGS. 10-12, one embodiment of an initial
encapsulating process to form an encapsulated cell module assembly
4 with a BMU housing disposed thereon is illustrated. In the
depicted embodiment, a CMA along with the associated spacers, end
plates, and BMU housing, are inserted into a mold 100. The mold
maintains the various components in a desired arrangement during
the encapsulating process. Additionally, the spacers maintain the
cell module assembly and other components spaced from the sides of
the mold. An encapsulant source 102 is then connected to an
encapsulant flow path such as encapsulant tube 8. The encapsulant
source may correspond to any appropriate structure including, but
not limited to, a tube or other structure connected to a
pressurized source of encapsulant and/or a pump capable of
providing pressurized encapsulant. In some embodiments, a mold may
include the use of a vacuum chamber 104 sealed against a sealing
surface 106 of the mold. The vacuum chamber is connected to a pump
108.
[0096] Once appropriately connected to the optional vacuum source
108 and encapsulant source 102, encapsulant is fed through
encapsulant tube 8 and into the mold. The encapsulate tube, or
other flow path, may transfer the encapsulant to a bottom side of
the CMA where it is ejected into the space between the CMA and the
mold wall defined by the associated spacers described above. As
encapsulant continues to be fed into the mold, a vacuum may be
drawn on the vacuum chamber 104 using pump 108. In addition to
helping to reduce the presence of air bubbles within the
encapsulant, the applied vacuum may also help to draw the
encapsulant from a bottom side of the CMA up and around to a top of
the battery pack. This process of feeding encapsulant into the mold
and drawing vacuum may be continued until the CMA is completely
encapsulated and the BMU housing is partially encapsulated without
filling the isolated interior space of the BMU housing. The
encapsulant is then permitted to at least partially cure prior to
ejecting the encapsulated battery pack from the mold.
[0097] FIGS. 13-15 show another embodiment of an encapsulating mold
100. In the figures, the mold includes a chamber 110 that is sized
and shaped to accept an unencapsulated cell module assembly along
with the associated housings, spacers, and other components
described above with the electrode leads extending up and out of
the chamber. While a chamber with a rectangular cross section has
been shown, any other appropriate shape may be used including but
not limited to squares, circles, ovals, etc. To help with
assembling the various components of a battery pack within the
chamber, in some embodiments, a chamber may include one or more
removable, or otherwise openable, covers 112 that may function as
one or more walls of the mold assembly during use. In the depicted
embodiment, the cover is selectively attached to the mold using one
or more connectors 114. Appropriate connectors include the depicted
latches as well as threaded fasteners, interlocking features, quick
release connectors, retractable bolts, or any other appropriate
connector.
[0098] To aid in assembling a battery pack within a mold chamber
110, it may be desirable to include a removable sealing surface
106, similar to the rectangular insert shown in the figures. In
such an embodiment, the assembly and welding of a cell module
assembly and associated components may be completed prior to
assembling the separately formed and removable sealing surface,
which may be in the form of a rectangular gasket, onto a side of
the closed mold chamber including an opening through which the
desired vacuum may be applied to the mold chamber. The
encapsulating process may then be conducted as described
previously.
[0099] In some embodiments it may also be desirable to tilt a mold
to aid in assembling a battery pack within the mold interior.
Therefore, as shown in the embodiment of FIG. 13, a mold may be
connected to a hinge, or other rotation arrangement, that permits
the mold to be tilted during use to aid in assembling the battery
pack components within the mold's interior chamber. For example,
the hinge may permit the mold to tilt between 15.degree. and
60.degree., between 25.degree. and 35.degree., or between or at any
other appropriate angle(s). In certain embodiments, angles both
greater than and larger than those noted above are employed.
[0100] In some embodiments, a mold may include one or more
displaceable pressing surfaces, such as ejector pins 114, and/or
air fittings 116 for aiding in removing an encapsulated battery
pack from a mold chamber. For instance, once an encapsulating
process has been completed, the encapsulated battery pack may be
pressed out of mold by the ejector pins while air is also forced
between an inner surface of the mold and the encapsulated battery
pack using the air fittings. In addition to the above, in some
embodiments the ejector pins may also be used to position and
compress a CMA and the associated components during an
encapsulating process. This may help in creating the appropriate
compression of the electrochemical cells for subsequent use and
operation. In one such embodiment, a cell module assembly and the
associated end plates are positioned between one or more sides of
the mold chamber 110 such that the ejector pins 114 may be
displaced to position the end plates and cell module assembly at a
desired distance from the chamber walls while also applying a
compressive force to the end plates. Once the encapsulant has been
fed into the mold, and the battery pack is encapsulated, the
encapsulant will maintain this compressive force on the end plates
and associated CMA even after the ejection pins and air fittings
have been used to remove the battery pack from the mold.
[0101] While the use of ejector pins for applying a compressive
force to a CMA within a mold is described above, it should be
understood that in other embodiments any appropriate pressing
surface and/or method capable of applying a compressive force to a
battery pack while it is being encapsulated inside of a molding
chamber may be used. For example, in certain embodiments,
protrusions located on opposing inner surfaces of a mold chamber
may compress a cell module assembly there between when the mold is
closed. In certain embodiments, one or more inserts with a
preselected thickness may be positioned between the two end plates
of a cell module assembly and the opposing sides of the mold. In
such embodiments, a preselected thickness of these inserts may be
selected to provide a desired amount of compression when the mold
chamber is closed. Further, the inserts may have any appropriate
shape, size, and/or arrangement. However, in certain embodiments,
the inserts may cover only a portion of the end plates such that
encapsulant covers a majority of the end plate surface. Of course
other methods of creating a compressive force on a cell module
assembly within a mold chamber may also be employed.
[0102] FIGS. 16 and 17 show another embodiment of a mold for
completing an encapsulating process of a battery pack. In the
depicted embodiment, the mold includes three sides that are
attached to hinges 120. This arrangement permits the three sides to
be opened about the hinges after an encapsulating process has been
completed, which may aid in the removal of the battery from the
mold. Additionally, another tiling system for tilting the mold is
depicted in these figures. In this particular embodiment, the
tiling system includes two complementarily shaped curved surfaces
122a and 122b. The tiling system also includes one or more locks
124 that engage corresponding curved channels 126. During
operation, the locks are moved to an unlocked position and the mold
is tilted moving the complementary surfaces relative to one another
to a desired position. As the mold is tilted, the locks move within
the corresponding curved channels to the desired position. Once
appropriately positioned, the locks are moved to a locked position
where they are engaged with the curved channels and/or any other
appropriate feature such as a bearing surface associated with the
channels. Once it is desired to move the mold back to the original
position, such as may be desired after assembling the components
within the mold, the locks may be moved to the unlocked position.
The mold is then moved back to the original orientation. The locks
are then re-engaged to lock the mold in place for the subsequent
encapsulating operation.
[0103] FIGS. 18A-18B are a schematic flow diagram of an exemplary
assembly process for a battery pack according to the above noted
embodiments. As shown in the figure, incoming electrochemical cells
are inspected and are subject to preforming processes and triplets
kitting at 200. Subsequently, cells, thermal plates, heaters, foam
inserts, end plates, and/or the associated interconnect board are
assembled at 202. In step 204, the stack assembly and interconnect
board undergo ultrasonic welding, or any other appropriate
connection process, to connect the electrodes of the
electrochemical cells, heater electrical connections, and/or
sensors with the appropriate busbars, wiring, and/or other
electrical contacts. After forming the electrical connections, the
assembly is placed into a corresponding encapsulating mold for a
first encapsulation process at 206. As noted above, this
encapsulation process may leave an interior of a housing associated
with the CMA, such as a BMU housing, unencapsulated for subsequent
processing steps. Once it is confirmed that the encapsulated CMA is
within desired operating parameters, a BMU, or other component, may
be installed into the unencapsulated interior space of the housing,
at 208. The resulting assemblies are then subjected to electrical
tests at 210 prior to undergoing a second encapsulation process at
212 to encapsulate the BMU and associated interior of the housing.
The resulting encapsulated battery packs are then quarantined for a
predetermined amount of time at 214 prior to undergoing final
electrical testing at 216.
[0104] Having generally described various types of pack geometries
and methods for their manufacture, the layout and operation of an
exemplary battery monitoring unit (BMU) used to control a cell
module assembly (CMA) is described further in regards to FIGS.
19A-27. In these figures, a 6 cell lithium ion battery arranged in
series to provide a nominal 22 V operating voltage is used.
Specifically, each lithium-ion cell operates in the range of 3 Vdc
to 4.15 Vdc for a module voltage ranging from 18V (0% SOC) to 24.9V
(100% SOC). Such an arrangement may be useful for replacing
lead-acid batteries that have 24V nominal operating voltages used
in existing 24V material handling equipment without needing to
alter the functionality of the equipment. While a particular
arrangement of cells and associated electronics are depicted in
these figures, other embodiments may employ a different number of
cells, different types of cell chemistries, and/or different
arrangements of the cells in series and/or parallel to provide
different operating voltages.
[0105] In addition to primary over voltage protection and typical
heater control, in some embodiments, the presently described
battery packs may further include a secondary overvoltage
protection monitoring and interlock circuit and/or a dual redundant
heater control circuit. In addition to the above, the BMU depicted
in the figures may also be used to modify a BMU that is intended to
monitor, balance, and control a first number of cells (e.g. four
cells) to enable it to handle a second larger number of cells (e.g.
six cells, or more). The BMU may also be configured to provide
active and standby power supply adaption capability permitting
lower active power dissipation in some cases. The exemplary BMU
described below may also be used to provide external Flash Memory
for enabling more secure program bootloading. Of course depending
on the embodiment, BMU(s) may be employed that include all, a
combination of some, or in some instances, different
functionalities than those noted above.
[0106] FIG. 19A shows an exemplary embodiment of a BMU assembly 18
installed in a BMU housing 6, such as the depicted CMA carrier.
FIG. 19B shows the BMU by itself. As described previously, the
housing, or CMA carrier, secures the assembly onto the CMA and
provides mechanical support for the interconnecting sense and
heater control wires from the CMA to the BMU assembly. Further,
after installing the BMU and connecting the wires from the CMA, the
BMU and wires may be encapsulated in a secondary encapsulating
process to seal the BMU from the environment. Besides the CMA's
power terminals, the BMU right-angle communication connector shown
in these figures is the only electrical interface to the system.
This connection may be sealed when a system harness is plugged into
the connector.
[0107] In some embodiments, it may be desirable to provide an outer
enclosure for an encapsulated battery pack to either provide
additional physical protection and/or to apply pressures to the
encapsulated battery pack during use. For example, in comparison to
typical electrochemical cells, in some embodiments, the
electrochemical cells used within a battery may include
electrolytes with a relatively low boiling point and/or cell
chemistries that exhibit increased rates of gas generation within
the electrochemical cells due to the presence of side reactions
that occur more rapidly at elevated temperatures. Accordingly, it
may be desirable to apply pressure to such a battery pack during
use to prevent excessive swelling of the electrochemical cells
contained therein which may help the battery pack to pass various
standard tests and/or to improve performance of the battery during
use in environments with elevated temperatures. However, it should
be understood that such an embodiment may be used with any type of
electrochemical cell with any appropriate range of operating
temperatures. One such embodiment is described further in regards
to FIGS. 20-27. In certain embodiments, the various features and
components described in regards to the embodiment described below
may be combined in any appropriate manner with the other
embodiments described herein.
[0108] Referring to FIGS. 20 and 21, an embodiment of a battery
pack 2 including an encapsulated CMA 4 is depicted. As shown in the
figure, the encapsulated CMA is at least partially surrounded by a
rigid outer housing 50 that includes two opposing faces oriented
towards the flattened fronts and backs of the electrochemical cells
as well as at least two other opposing faces oriented towards the
sides of the electrochemical cells. Accordingly, in some
embodiments, the housing may extend around the sides as well as the
opposing front and back portions of the battery pack and/or CMA. In
other embodiments, the housing extends around other portions of the
battery pack, and/or completely surrounds an encapsulated CMA. In
addition to the above, it should be understood that the outer
housing may be made from any appropriate material that is
compatible with the materials used within the battery pack which
may include steel, stainless steel, aluminum, and rigid plastics to
name a few.
[0109] Similar to the other embodiments described herein, a battery
pack 2 may include a BMU housing 6 that includes an interior space
6a that receives a BMU 18. In the depicted embodiment, the BMU has
been over molded with a polymeric material such that one or more
connectors extend out from the overmolded material for attachment
to corresponding connectors on the housing and/or with the CMA
itself. To facilitate the use of the overmolded BMU, the battery
may also include an insertion plate 36 including a plurality of
elongated openings 38 formed therein for routing and connection of
the associated electrical leads 28 and busbars 32 as previously
described. In such an embodiment, the overmolded BMU may be
appropriately isolated from contaminants, and in some instances may
exhibit improved vibration and shock resistance, without the need
for a separate encapsulation procedure. This may also facilitate
both the easy installation and removal of the BMU from a battery
pack if a CMA is discovered to be defective later on during quality
control procedures. However, in certain embodiments, the BMU is
encapsulated using the methods and materials described
previously.
[0110] In the above embodiment, the BMU housing 6 is no longer
encapsulated in a separate encapsulation process. Accordingly, it
may be desirable to seal the housing to a portion of the associated
encapsulated CMA 4 or other portion of the battery pack to provide
additional protection against the intrusion of contaminants to the
battery pack. In one such embodiment, the housing 6 may be sealed
to an exterior surface 4a of the encapsulated CMA and/or to an edge
or surface of the depicted outer housing 50. A seal may be formed
using any number of different techniques and/or materials. For
example, in one embodiment, a seal may be formed using a gasket
sandwiched between opposing surfaces of the BMU housing 6 and outer
housing 50. Alternatively, adhesives, putties, brazing, welds, or
any other appropriate sealing method may be used to form a seal
between the BMU housing and one, or both, of the exterior surface
of the CMA and the outer housing.
[0111] FIGS. 22-23A illustrate one embodiment of an overmolded BMU
18. In the depicted embodiment, the BMU includes a printed circuit
board 18a including one or more connectors 18b that are configured
for connecting to one or more connectors of a CMA and/or battery
pack as previously described. Using any appropriate process
including, for example, positioning the BMU in an appropriately
shaped and sized injection molding cavity, a polymer may be
injection molded, or otherwise applied, to the surface of the PCB
such that the PCB is at least partially, and in some instances
fully, encapsulated with an overmolded material 18c, see the cross
sectional view in FIG. 23A depicting the overmolded material 18c
surrounding the PCB 18a. Additionally, the one or more connectors
may extend out from the overmolded material 18c such that they may
be connected to the one or more connectors of the CMA and/or
battery pack as described above.
[0112] FIG. 24 depicts an exploded view of an outer housing 50 of a
CMA and/or battery pack as well as several interior plates used for
applying pressures to the electrochemical cells during
high-temperature operation where swelling of the electrochemical
cells may occur due to increased gas generation from side reactions
occurring in the cell that may occur more rapidly at higher
temperatures and/or due to boiling of the electrolyte. As
previously discussed, the assembly may include two opposing end
plates 16 positioned on opposing front and back surfaces of the
assembled electrochemical cell blocks, not depicted. The assembly
may also include two or more opposing rigid plates 52 positioned on
opposing sides of the assembly of the electrochemical cell blocks
and rigid plates. Additionally, in this particular embodiment, the
various components of the CMA are disposed between, and in some
instances held in place by, first and second portions 50a and 50b
of the outer housing that surround the noted components and are
attached to each other along two flanges that extend along opposing
sides of the outer housing. The flanges may be attached to each
other in any appropriate fashion including for example, bolts,
welds, brazing, interlocking mechanical features, adhesives, or
using any other appropriate attachment method. Additionally, it
should be understood that in some embodiments the outer housing may
be made from a single unitary piece without the need to attach
separate housing portions together. In such an embodiment, the
electrochemical cells, heaters, heat distribution plates, rigid
plates, and other components may simply be slid into place within
the outer housing during assembly either prior to or after an
encapsulation process.
[0113] In the above embodiment, the rigid plates have been depicted
as including a plurality of ribs 54 that extend in a horizontal
direction relative to a base of the CMA. The ridges may extend
either partially and/or from one side to an opposing side of the
rigid plates (i.e. completely across a face of the rigid plates).
The use of the depicted ribs may increase a bending resistance of
the plate and/or other component they are formed on which may
reduce a deflection of the plate or component when subjected to the
outwardly directed forces from electrochemical cell swelling.
Without wishing to be bound by theory, reducing the amount of
deflection experienced by the components within a battery during
use may help to apply a more uniform pressure to the surfaces of
the associated electrochemical cells sandwiched between the rigid
plates and outer housing. Additionally, while horizontally arranged
ribs have been depicted, in other embodiments, the ribs may be
arranged in other orientations including, for example, a vertical
orientation, and/or a plurality of ribs may be oriented in two or
more directions to provide multiple directions of increased
stiffness. Further, in certain embodiments the ribs are not used,
and a thicker plate, and/or a stiffer material, is used to provide
the desired amount of stiffness.
[0114] FIG. 25 depicts another exploded view of an assembly
including first and second portions of an outer housing that are
attached to one another. The assembly also includes first and
second opposing end plates 16 located on opposing faces of the
electrochemical cellblock assembly as previously described. The
assembly may also include one or more intermediate plates 56
located between two or more adjacent electrochemical cells, not
depicted. While in some embodiments, an intermediate plate may
simply be positioned between adjacent electrochemical cells, in the
depicted embodiment, the intermediate plate 56 extends between, and
is connected to, at least two opposing sides of a first and second
portions of the outer housing 50a and 50b as described further
below. Without wishing to be bound by theory, in some embodiments,
the intermediate plates may help distribute and equalize pressures
applied to electrochemical cells within the battery pack. In this
particular embodiment, the need for separate rigid plates contained
within the outer housing has been eliminated through the use of a
thicker outer housing as well as the use of a plurality of ribs
formed into the opposing surfaces of the housing oriented towards
the flat faces of the associated electrochemical cells. Operation
of such a battery pack is described further below.
[0115] FIGS. 26-26B depict one embodiment of a battery pack 2
including an outer housing 50, along with the opposing end plates
16, and the one or more intermediate plates 56 described above with
regards to FIG. 25. As best seen in the cross-section in FIG. 26A,
this particular CMA includes seven blocks 58a-58g that are located
in series with each block including three electrochemical cells 22
located in parallel which provides a nominal battery pack voltage
of about 26 volts. Though it should be understood that any number
of cell blocks in series may be used to provide any desired
voltage. In this particular embodiment, six of the cell blocks
58a-58f are arranged within the outer housing in two or more stacks
located side-by-side to one another where the cells of one cell
block are located to the side of a corresponding cell of an
adjacent cell block. This forms an arrangement of one or more
complete rows of cells blocks within the CMA. Similar to the
above-described embodiments, one or more heat distribution plates
20 as well as the associated heaters, foams, and/or other
components may be located between the stacked cell blocks as well.
The seventh cellblock 58g is stacked on the complete rows of cell
blocks in an incomplete row within the outer housing. Once the
cells blocks are appropriately arranged, the first and second
portions 50a and 50b of the outer housing are attached to one
another along flanges 50c so that they at least partially enclose
the cell blocks and other components of the CMA within the outer
housing.
[0116] Depending on the specific number of cell blocks used, it
should be understood one or more cell blocks may be located in one
or more incomplete rows of cell blocks that are stacked on one or
more complete rows of cell blocks within the outer housing.
Further, the cell blocks may be located at any position within an
incomplete row. However, in some instances, it may be desirable to
provide a uniform pressure to the cell blocks located within the
complete rows as well as the cell blocks located in the incomplete
row. Correspondingly, as previously described, the assembly may
include one or more intermediate plates that function as pressure
distribution plates. Specifically, in the depicted embodiment, an
intermediate plate 56 is disposed between the portion of the
housing including the seventh cell block and the portion of the
housing including the other cell blocks with the cell blocks in the
adjacent rows of cell blocks pressed either directly, or
indirectly, against the intermediate plate. Further, the seventh
cell block has been positioned within the incomplete row so that it
is positioned at a middle of the row such that it is positioned
equidistant from each of two opposing sides of the outer housing
located to the sides of the cell blocks. Accordingly, the cell
blocks within the complete rows transfer a pressure to the one or
more cell blocks in the incomplete row through the intermediate
plate, which due to its rigidity applies a substantially uniform
pressure to the one or more cell blocks in the incomplete row.
Thus, the intermediate plate may function as a pressure
distribution plate in such an embodiment. Without wishing to be
bound by theory, positioning the seventh cell block along the
centerline of the outer housing between the two stacks of cell
blocks in the complete rows may help to apply a more equal pressure
across a face of the seventh cell block as well. However, in other
embodiments, the cellblock need not be centered within the
housing.
[0117] Applying uniform pressures to the different electrochemical
cells in a CMA may help to extend a useful life of the CMA.
Therefore, in some instances, it may be desirable to limit the
amount of deflection the various components within a battery pack
and/or CMA experience when pressures are applied to them.
Accordingly, in some embodiments, surfaces of the above described
outer housing, one or more rigid plates, an intermediate plate,
and/or any other appropriate component oriented towards a flat face
of a prismatic or pouch electrochemical cell within a battery
and/or CMA may experience a deflection that is less than or equal
to 5%, 4%, 3%, 2%, 1%, or any other appropriate percentage of a
maximum dimension of a portion of the structure oriented towards an
opposing flat surface of the cells when the structure is subjected
to pressures between or equal to 5 pounds per square inch (psi) and
10 psi. For example, in one specific embodiment, a rigid plate,
face of an outer housing, intermediate plate, or other structure,
having an area between or equal to 90 square inches (in 2) and 150
in 2, 100 in 2 and 130 in 2, or other appropriate area may deflect
less than 10 mm, 5 mm, 1 mm, or any other appropriate distance when
subjected to a pressure between or equal to 5 psi and 10 psi. While
particular ranges of deflections, areas, and pressures have been
described above, in other embodiments, a battery pack may include
components that experience any other amount of deflection due to
battery swelling during normal use and/or use at elevated
temperatures.
[0118] In certain embodiments, in addition to providing uniform
pressures across the faces one or more cells within a cell module
assembly, an intermediate plate 56, as depicted in FIGS. 25 and 26A
may function to stiffen an outer enclosure or housing of a cell
module assembly. For example, as described above, the intermediate
plate 56 may extend between, and is attached to at least two
opposing sides of the CMA housing formed by the first and second
portions 50a and 50b of the outer housing. Specifically, as
depicted in the figure, the intermediate plate is sandwiched
between the two flanges 50c located on opposing sides of the first
and second portions of the housing, though in other embodiments the
intermediate plate can be attached at different locations and/or
different ways to the housing. In either case, the intermediate
plate may help to stiffen the closure by resisting displacement
and/or deformation of the portion of the housing it is attached to.
For example, when the cells within a CMA swell, the outwardly
directed faces of the housing may experience an increased outwards
force which may cause the side walls of the housing to deflect
inwards towards an interior of the CMA. This correspondingly places
the one or more intermediate plates located between the two
opposing faces of the CMA housing into a compressive state that
resists this deflection of the sidewalls of the housing.
Correspondingly, the one or more intermediate plates may be
constructed from a material and have appropriate dimensions such
that it is capable of supporting these applied loads during use
without buckling, plastically deforming, and/or experiencing
excessive deformation.
[0119] While a flanged connection to two opposing sides of a CMA
housing has been depicted in the figures and discussed above, it
should be understood that any appropriate type of connection and or
any appropriate arrangement of an intermediate plate relative to
the different sides of a housing may be used to stiffen a CMA
housing. Further, while one or more intermediate plates have been
illustrated, other types of stiffening mechanisms to limit the
amount of relative movement between opposing sides of the housing
may be used including, but not limited to, struts, bolted
connections, rods, braces, cross pieces, and/or any other
appropriate type of support that extends between and is connected
to two or more opposing sides of a CMA housing while being capable
of supporting compressive and/or tensile loads to resist
deformation of the associated portions of the CMA housing.
[0120] In some embodiments, it may be desirable to help maintain a
position of one or more cell blocks located in an incomplete row of
cell blocks. Correspondingly, as depicted in FIG. 26A, one or more
spacer blocks may be located in an incomplete row of
electrochemical cells stacked on, or between, one or more complete
rows of electrochemical cells. For example, two spacer blocks 60
located on either side of one or more cell blocks contained in an
incomplete row, such as the seventh cell block 58g, which may help
maintain the one or more cell blocks in a desired position, such as
in a middle of the outer housing where the cell block is located
equal distance between two opposing sides of the outer housing. In
such an arrangement, a width of the one or more spacer blocks may
be selected to fill a space between the electrochemical cells and a
corresponding side of the outer housing to maintain the cell block
position. Additionally, a thickness of the one or more spacer
blocks may be selected so that the spacer blocks extend between the
outer housing, or an associated rigid plate as discussed above, and
the intermediate plate. Accordingly, pressure may be transmitted
from the other associated cell blocks through the intermediate
plate to the one or more cell blocks and spacer blocks located in
the incomplete cell block row. To help equalize a pressure applied
to the spacer blocks and the corresponding flat face of the
electrochemical cells, a compliance of the spacer blocks may be
substantially equal to that of the cell blocks. For example, a
compliance of the spacer blocks may be within 10%, 20%, 30%, or any
other appropriate percentage of the compliance of the associated
cell blocks.
[0121] The above described spacer blocks may have any appropriate
construction including solid constructions, frames, tubes,
interlocking components, I beams, or any other structure suitable
for locating a cell block and/or electrochemical cell within a
housing. For example, the embodiment depicted in FIGS. 26A and 27
correspond to a hollow rectangular tube that extends from a bottom
surface of the CMA to the opposing top surface of the CMA. The tube
may also include one or more reinforcing structures 60a such as a
strut, brace, cross beam, wall, or other appropriate structure
extending between opposing faces of the tube. In other embodiments,
any other suitable types of reinforcing structures may also be
used.
[0122] In some embodiments, the above described battery pack 2
and/or encapsulated cell module assembly 4 may include an
encapsulant tube receiver 40 formed in a portion of the BMU housing
6 as previously described, see FIG. 20. Therefore, similar to the
prior embodiments, an encapsulation material, such as an
appropriate polymeric resin, may be injected into an encapsulant
tube in fluid communication with the encapsulant tube receiver.
Referring to FIGS. 26-29, to help simplify a CMA manufacturing
process, an encapsulant tube 8 may be integrated with the one or
more spacer blocks 60 located within the encapsulated CMA 4, and
this tube may be placed in fluid communication with the encapsulant
tube receiver in any appropriate way. As also shown in the figures,
in some embodiments, one or more encapsulant tubes may be
integrally formed at two opposing corners of the spacer blocks and
extend from a top to a bottom of the spacer block to provide an
encapsulant flow path extending from a top of the encapsulated CMA
4 to an opposing bottom side of the CMA. Therefore, injected
encapsulant may flow through the encapsulant tube receiver into the
associated encapsulant tube formed in the spacer block to an
opposing bottom surface of the encapsulated CMA 4 adjacent to a
tray 62 the electrochemical cells are disposed on where the tray is
sealed to a bottom of the outer housing 50. Similar to the BMU
housing 6, the tray may be sealed to the outer housing in any
appropriate way. Once the encapsulant is injected the interior
space of the encapsulated CMA 4, the encapsulant may flow out of
the encapsulant tube and then in a reverse direction towards a top
of the CMA as previously described.
[0123] To facilitate the distribution of encapsulant throughout a
CMA and/or battery pack during an encapsulation process, a tray on
which the electrochemical cells are disposed may include one or
more features formed therein that help to guide a flow of
encapsulant from one location within the CMA to another location
within the CMA. As illustrated in FIGS. 28 and 29, a tray may a lip
65 forming an upper outer edge of the tray to define a recessed
cavity 66 within the tray. The recessed cavity may include one or
more raised support surfaces 68 that support the one or more cell
blocks in one or more stacked rows. For example, in the depicted
embodiment, the two stacks of electrochemical cells 22 are disposed
on two adjacent raised support surfaces 68. The tray may also
include one or more grooves 70 that are positioned adjacent to, and
in some instances between, the one or more raised support surfaces.
The grooves 70 extend downwards below a top surface of the raised
support surfaces on which the electrochemical cells are disposed.
Depending on the particular embodiment, the grooves 70 may also
extend at least partially across the tray, and in some embodiments
from one side or lip to an opposing side or lip of the tray. As
shown in FIG. 26B, the pouch cells corresponding to the illustrated
electrochemical cells 22 may include a gap 64 between bottom
portions of the electrochemical cells and the tray support
surfaces. These gaps extend in a different direction than the
grooves 70. Specifically, in the depicted embodiment, the gaps
extend in a direction that is substantially orthogonal to the
grooves 70. As best shown in FIG. 29, an encapsulant tube 8, which
may be integrated with a spacer block as noted above, may also be
aligned with a portion of one of the grooves 70.
[0124] Again referring to FIG. 29, during an encapsulation process,
encapsulant may be injected into the encapsulant tube 8 using any
appropriate arrangement including the above-described encapsulant
tube receptacle formed in a BMU housing, not depicted. The
encapsulant flows through the tube into the corresponding groove 70
formed in the tray. As the encapsulant flows outwards from the
tube, it fills the tray and begins to fill the space between the
electrochemical cells and an adjacent electrochemical cell and/or
the outer housing 50 depending on the particular location of the
tube within the CMA assembly. Simultaneously, the encapsulant may
also flow through the gaps 64 disposed between the bottoms of the
electrochemical cells 22 and tray towards the next groove formed in
the tray. The encapsulant may then begin to fill this groove as
well as the space between the adjacent electrochemical cells. This
process may continue until the encapsulation process has been
completed. Thus, the presence of these grooves in the tray and gaps
between the tray and electrochemical cells may help to aid in
distributing encapsulant across a width and thickness of the CMA
assembly as the encapsulant is filled into the volume contained by
the outer housing and tray.
[0125] While grooves extending in only one direction have been
depicted in the figures and described above, in certain
embodiments, a plurality of grooves extending in two or more
directions along an interior surface of a tray to facilitate
distribution of an encapsulant within a CMA are provided. This may
be of benefit in embodiments, for example, where there is little,
or no, gap located between the bottoms of the electrochemical cells
and the one or more surfaces of the tray supporting the
electrochemical cells. Additionally, while the CMA has been
depicted as being encapsulated while located within an outer
housing, in other embodiments, the CMA is encapsulated and
subsequently placed into a separate rigid outer housing.
[0126] Depending on the particular embodiment, the above described
encapsulant may either fully encapsulate the electrochemical cells
and associated plates, heaters, foam, and/or other structures, or
the CMA may only be partially encapsulated. For instance, in the
embodiments depicted in FIGS. 26-26B, 28, and 29, the encapsulant
may be located between a side of the housing and an exterior side
edge of the stacks of the electrochemical cells. The encapsulant
may also partially encapsulate the bottom and/or top edges of the
electrochemical cells. However, in instances where flat rigid
plates, and/or a flat rigid outer housing have been used, the
encapsulant may not be present between the flat surfaces of the
electrochemical cells and the corresponding rigid plates, end
plates, and/or outer housing that the electrochemical cells are
disposed between. Of course in embodiments in which one or more of
these components include ribs or other structures to increase their
rigidity, the encapsulant may be located in between structures
including the noted ribs. It should also be noted that one or more
spacers as described above may be located between the outer housing
and the electrochemical cells and/or any other appropriate
component of the battery pack to permit encapsulate to flow into a
desired location during an encapsulation process.
[0127] FIG. 30 shows one embodiment of the relationship between a
BMU, an associated primary encapsulated CMA, and an interface to a
system BMC. It should be noted that FIG. 30 is the block diagram
representation of the more detailed full schematics shown in FIGS.
31 and 32. However, all of these figures show the circuits that the
BMU of FIG. 30 uses to measure the CMA's individual cell voltages,
the current, temperature, control cell balancing, and control the
integrated CMA heater. In this embodiment, the measurements are
made using a MM9Z1_638 battery sensor running a custom flash
software program. The BMU also includes a current SHUNT that is
used to coulomb count the energy flowing into and out of the
battery module for performing current measurements. In some
embodiments, the CMA's state of charge (SOC) may be derived from a
combination of individual cell voltage, coulomb count, and/or
temperature.
[0128] In the depicted embodiment, measurements and/or calculations
performed by the BMU are sent over a LINbus physical layer
communication interface using an addressed listener-talker
protocol. The system is designed to have up to two (2) CMA BMUs.
The BMUs are always in a listener mode and only respond to system
BMC commands targeted to a specific BMU's address. A factory option
provision allows the BMU to communicate via the CANbus if the
system application requires. This communication is connected to the
system via the SYSTEM INTERFACE block. In certain embodiments,
active mode BMU's and/or battery packs include more than 2 CMA
BMU's. Additionally, while specific methods for establishing
electrical communication between a CMA, BMU, and BMC are described
above, in other embodiments, any other appropriate methods
including local and/or area network communication link can be
employed.
[0129] As noted previously, in some embodiments, a BMU may include
a Secondary Overvoltage protection circuit as shown by the
Overvoltage Secondary Safety block that works outside the control
of an on board microcontroller (MCU) battery controller to control
a daisy-chained interlock MOSFET switch, see FIGS. 33 and 35. As
seen in these figures, the Overvoltage Secondary Safety controls
the daisy-chain Interlock to the system via the SYSTEM INTERFACE
block. This is more clearly shown in FIG. 35. Specifically, FIG. 35
shows a Secondary Overvoltage Protection circuit using 6 cell
overvoltage supervisory integrated circuit U2. In some instances,
the overvoltage supervisory integrated circuit may be configured to
monitor the overvoltage condition of lithium-ion cells, though
embodiments in which different types of cells are used are also
envisioned. In the depicted embodiment, if any of the voltage sense
inputs (CELL1 to CELL6) rise above a threshold voltage, such as
4.225V, the output OUT (U2 pin 10) will be driven to second voltage
threshold, such as 0V, turning off the interlock MOSFET Q1. When
the interlock MOSFET Q1 is off it will interrupt the system
interlock daisy-chain, providing an alternate communication signal
to the system to indicate a cell, or cells, are overcharged. The
system will react to this signal by preventing any current from
flowing into the battery module until the overcharged cell voltage
is reduced by discharging the battery module.
[0130] In some applications it may also be desirable for a BMU to
include some form of cell balancing to reduce voltage imbalances
between cells located in series and/or parallel. While any number
of different balancing schemes may be used, one exemplary balancing
scheme is illustrated in FIG. 30. In the depicted embodiment, the
BMU includes a cell PASSIVE BALANCE function using an OCTAL POWER
SWITCH to apply 10 ohm cell load resistors (RB 1-RB6) selectively
in order to equalize each cells state of charge relative to the
other cells.
[0131] In some instances it may be desirable to expand the number
cells from which a BMU takes voltage measurements. For example, in
certain embodiments, additional analog MCU ports may be used to
measure additional cell voltages after a resistance divider reduces
the signal to an acceptable input port voltage range. The addition
of voltage gating in the illustrated embodiment is provided by
additional MOSFETs. FIG. 33 shows one embodiment of a circuit that
adds the two additional cell voltage measurements to a BMU that is
configured to measure 4 cells using circuits associated with two
auxiliary input channels. In the depicted embodiment, two N-Channel
MOSFETs (Q2 and Q3) were added to prevent battery current leakage
into the MM9Z1_638 MCU during sleep mode. When the MCU enters sleep
the +5V supply (Vddx) drops to 0V, the MOSFETs are turned off
because the Gate-Source is now 0V. With the MOSFETs open, no
leakage can flow into the MCU unpowered analog port pins PTB0 and
PTB 1. When the MCU is active (Vddx=+5V), each MOSFET's
Source-Drain channel are in a low resistance state allowing the
resistive divider pairs (R34, R36 and R32, R35) to reduce the
sensed battery cell voltages (CELL4S and CELL3S) to within the IV
maximum input range of the analog port. CELL4S is divided down by
22 thus providing a voltage measurement range up to 22V. CELL1S is
divided down by 5 thus providing a voltage measurement range up to
5V. These secondary circuits associated with the auxiliary inputs
in certain embodiments may be configured to both accept and output
different voltages within any suitable voltage range.
[0132] To heat the battery module, a single point failure
protection heater control circuit may be added to a BMU in some
embodiments. In certain such embodiments, the heater may be
controlled by at least one, two or all of at least three mechanisms
including, but not limited to: a MCU, an External System 12V, and
Thermostat as shown in the figures. This type of redundant heater
control system may help to reduce, or even greatly reduce in
certain cases, the probability that a failure of the heater control
circuit would over heat or over discharge the battery. FIG. 34
shows the details of one such embodiment of a single point failure
protection heater control circuit. Power MOSFETs Q4 and Q5 provide
a switchable 25 A current path for the heater. In one exemplary
configuration, the heater's maximum current varies with temperature
from 18 A at 22.degree. C. to 22A at -30.degree. C. Inside the
primary encapsulated CMA, six parallel two terminal heaters are
connected to the most positive voltage (Cell6). The other end of
the parallel heater connection is brought out of the primary
encapsulating compound to connect to the HEATER-(J6)
quick-disconnect PCB mounted terminal. Through this connection, the
heater current passes through a 25 A fuse (F9) and then through the
Q4 and Q5 MOSFET switches. When Q4 and Q5 are activated, this
completes the heater current circuit by connecting to the SHUNT
B-(J7) to the outside terminal after the current shunt. Connecting
to the output terminal allows the heater current to be measured and
coulomb counted so heating can be taken into account when
evaluating various battery properties such as SOC calculations. The
Q4 and Q5 MOSFET switches are each controlled by photo voltaic
MOSFET driver devices U8 and U9 which present a voltage (8V)
between the MOSFETs Source and Gate when activated. A small current
(5 mA) passing through the respective input photo diode activates
the photo voltaic outputs of U8 and U9. U9 controls the on state of
Q5 under the control of the MCU output pin PTB2. U8 controls the on
state of Q4 under the control of both the system active power state
(+12V_BMC) and the bottom PCB mounted bi-metallic thermostat that
has a threshold temperature of an associated CMA below which the
thermostat's contact remains closed allowing the Q4 to be
controlled by the system power state. Further, when the CMA is
above the threshold temperature, the thermostat will open,
effectively not allowing the heater to be turned on. In one
embodiment, a thermostat may have a threshold temperature that is
between or equal to 40.degree. C. and 50.degree. C., and in some
embodiments may be 45.degree. C. In view of the above, it should be
appreciated that having two heater switches in series may help to
mitigate, and/or prevent, the possibility of a single point failure
from overheating or over discharging a battery module including a
heater or heaters.
[0133] In some embodiments, it may be desirable for a BMU to
include a power supply switch over circuit to provide low operating
power when the system is active while still allowing a low power
sleep mode when the system is not active in a full power mode (e.g.
22V-25V nominal operating voltages). FIG. 36 depicts one embodiment
of an active and standby power supply switch-over circuit. When the
system is in standby or sleep, the +12V_BMC signal is not present.
Absence of this signal in standby allows the normally closed (Form
1b) opto-isolated solid state relay (SSR) (U6) to source the full
battery voltage to the VSUP to bias the BMUs sleep circuits. When
the +12V_BMC signal is present in the active system state, the U6
SSR will have a small current flowing through the input opto diode,
opening the SSR (pins 3 and 4) removing the full battery voltage
from the BMU. D2 and D3 diodes on the BMU connect the +12V_BMC to
the same VSUP BMU supply, this then allows the BMU circuits to be
powered by this lower system voltage. This allows a lower power
dissipation from the BMU circuitry when active.
[0134] Having described several different types of circuits for
implementing protections for a cell module assembly and/or battery,
several different types of protection methods for operating a cell
module assembly and/or battery described in further detail below
regards to FIGS. 37-40.
[0135] FIG. 37 illustrates one embodiment of a method for
controlling the over voltage protection of a CMA or battery using
an over voltage protection circuit such as that described above. In
the depicted embodiment, any appropriate type of voltage sensing
circuit may be used to sense a voltage of one or more cells of a
cell module assembly and/or an overall voltage for a CMA at 101. In
either case the detected voltage may be compared to a cell and/or
CMA over voltage threshold at 103. If the sensed voltage is less
than the over voltage threshold, normal operation of the CMA may
continue. Alternatively, if the sensed voltage is greater than the
over voltage threshold, a controller of the CMA may disable an
associated charging circuit to prevent further charging of the CMA
while one or more cells are at the sensed overvoltage, see 105. The
associated controller may then continue to sense the voltage of the
one or more cells and/or the CMA at 107. Once the sensed cell
and/or CMA voltage is less than a reset voltage threshold, which is
less than the over voltage threshold, the associated controller may
re-enable the charging circuit to permit charging of the cells
and/or CMA, at 109 and 111. For example, in one specific
embodiment, voltage level sensing of individual cells may be done
via sensing circuitry located on a BMU. If any of the individual
cell voltages should exceed 4.225 volts, the ground return path of
charging enable relays of a BMC may be opened to prevent charging
of the CMA. Subsequently, when all the monitored cell voltages are
reduced to below a reset voltage threshold of 3.8 volts, the BMC
may re-energize the charging relays, thus enabling the associated
charging circuit. While the over voltage protection described above
uses individual cell voltages, in other embodiments, an average
cell voltage is used
[0136] FIG. 38 illustrates one embodiment of an undervoltage
protection method. In the depicted embodiment, an appropriate
voltage sensing circuit is used to monitor the voltage of one or
more cells and/or a cell module assembly of a battery at 121. An
associated controller may determine if the detected voltage is less
than an under voltage threshold for the one or more cells and/or
CMA at 122. If the detected voltage is less than the noted under
voltage threshold, the associated controller may disable a charging
circuit associated with the one or more cells and/or CMA at 125.
The associated controller may then continue to sense the voltage of
the one or more cells and/or the CMA at 127. Once the sensed cell
and/or CMA voltage is greater than a reset voltage threshold, which
is greater than the under voltage threshold, the associated
controller may re-enable the charging circuit to permit charging of
the cells and CMA, at 128 and 130. However, due to the charging
circuit being disabled, this may involve manual charging, removal
and replacement, and/or other appropriate maintenance of the one or
more cells and/or CMA. In one such embodiment, a lithium ion
battery may have an under voltage threshold of 2.5 V per cell and a
reset voltage threshold of 3.1 V per cell. These thresholds may
either be evaluated as an absolute voltage measurement for each
cell and/or may they may be compared to the average voltage of the
one or more cells by comparing the total CMA voltage to the
expected voltage threshold for that number of cells (i.e. the CMA
threshold is equal to the individual cell threshold multiplied by
the number of cells located in series). For example, if seven cell
blocks were arranged in series for a typical lithium ion battery
this would result in an undervoltage protection system that
disables charging if the CMA voltage falls below a total voltage of
15 V and then re-enables charging once the voltage is above about
22 V.
[0137] While particular voltage thresholds are noted above, it
should be understood that different chemistries and different
operating parameters may be used. Accordingly, different voltage
thresholds than those noted above may also be used in certain
embodiments.
[0138] In addition to the use of physical thermostats, it may be
desirable to enable cell overtemperature protection using one or
more control methods associated with a controller of a CMA and/or
battery. For example, as shown in FIG. 39 one embodiment for a
method of over temperature protection is depicted. In the depicted
embodiment, one or more temperature sensors are used to detect the
temperature of one or more cells of a CMA and/or battery at 131.
Appropriate types of temperature sensors include, but are not
limited to, thermistors, thermocouples, and other any other sensor
capable of detecting a temperature of an object. In one particular
embodiment, the temperature of one or more inner cells, such as
those located towards a center of a CMA and/or battery, may be
measured. Without wishing to be bound by theory, this may
correspond to the highest measured temperature within a CMA and/or
battery during operational cycling. However, it should be
understood that other positions for measuring a temperature of
cells within a CMA and/or battery may also be implemented.
[0139] At 132 the detected temperature of the one or more cells is
compared to an over temperature threshold. If the detected
temperature is less than the over temperature threshold, normal
operation of the CMA and/or battery may continue. However, if the
detected temperature is greater than the over temperature threshold
and/or if the detected temperature is greater than a continuous
operating temperature threshold, an associated controller may
disable the heater and/or charging circuit for the system to avoid
additional heat and/or energy from being input into the CMA and/or
battery, see 134. For example, a solid state temperature sensing
circuit may inhibit the charging enable relays of an associated
charging circuit when the temperature exceeds an over temperature
threshold. Once the charging and/or heater circuits have been
disabled, the associated controller may continue to sense the one
or more cell temperatures at 136 until the detected temperature has
decreased to be less than a desired reset temperature threshold at
138. In some instances, the reset temperature threshold may be less
than the over temperature threshold and continuous operating
temperature threshold 136 and 138. Once the detected temperature is
less than the reset temperature, the controller may re-enable the
charging and/or heater circuits at 140.
[0140] Similar to the thermostat described above, the various
thresholds may correspond to any appropriate temperature dependent
on rated operating temperatures for the particular battery
chemistry and/or application. However, in one embodiment, an over
temperature threshold may be between or equal to 40.degree. C. and
50.degree., and in some embodiments may be 45.degree. C. or any
other temperature corresponding to the maximum rated charging
and/or operating temperature of a particular cell. Correspondingly,
the system may have a continuous operating temperature threshold
that is between or equal to 40.degree. C. and 45.degree. C.
including, for example, 42.degree. C. Additionally, the reset
temperature threshold may be between about 35.degree. C. and
45.degree. C., and in one embodiment may be 40.degree. C. In other
embodiments, temperature thresholds and times both greater and less
than those noted above are employed.
[0141] In some instances, a battery and/or CMA may be exposed to
high operating and/or storage temperatures, after which it may be
desirable to permanently disable operation of the CMA and/or
battery. In such an embodiment, a BMU integrated with a CMA and/or
a BMC associated with the overall battery may include one or more
features that permanently disable an associated charging circuit
when a temperature of the CMA and/or battery exceeds a maximum
operating temperature threshold. While any appropriate method may
be used, in one embodiment, a system may include a thermal cutoff
fuse (TCO) configured to open and permanently disable operation of
a charging circuit when exposed to temperatures above the maximum
operating temperature threshold. Again while any appropriate
maximum operating temperature may be used based on the particular
application and cell type being used, in one embodiment, the
maximum operating temperature threshold may be between or equal to
about 70.degree. C. and 80.degree. C. including, for example,
72.degree. C.
[0142] Similar to controlling the temperature of the one or more
cells within a CMA and/or battery, in some embodiments, it may also
be desirable to monitor and control the temperature of one or more
heaters located within a CMA and/or battery to avoid applying
excessive temperatures to the cells contained therein. For example,
as shown in FIG. 40, at 150 one or more sensors may be used to
monitor the temperature of one or more heaters. In one such
embodiment, the same temperature sensors used to monitor the
temperature of one or more cells may also be used to monitor the
temperature of the heater either directly, or indirectly through
calculation, look up tables, and/or any other appropriate method.
Additionally, in some embodiments, a location of the one or more
sensors may be selected to either directly measure, be correlated
with, or otherwise permit measurement of a surface temperature of
the one or more heaters. In either case, the detected heater
temperature may be compared to a heater threshold temperature at
152. If the detected temperature is greater than the heater
threshold temperature, a controller of the CMA and/or battery may
disable a heater circuit at 154 to prevent additional heating of
the heating elements. For example, in the BMU embodiment previously
described above, two solid state switching elements, which may be
connected in series with the ground return of the heater elements,
may be opened to de-energize the internal heaters, though other
type of control circuits may also be used. The controller may then
continue to sense the heater temperature at 156. Once the sensed
heater temperature is less than the heater threshold temperature at
158, the controller may re-enable the heater circuit at 160.
[0143] In the above embodiment, any appropriate heater threshold
temperature may be used depending on the particular application and
electrochemistry being used. However, in one embodiment, a heater
threshold temperature may be between or equal to 40.degree. C. and
50.degree. C., including for example, 45.degree. C. In other
embodiments, temperature thresholds both greater and less than
those noted above are used.
[0144] The above embodiments of various protection systems such as
overcharge protection, over temperature protection, internal heater
over temperature protection, undervoltage protection and battery
overtemperature protection have been described as using a single
circuit to provide the desired protection. However, in some
embodiments, it may be desirable to include one or more
redundancies to provide more reliable protection for a CMA and/or
battery system. Accordingly, a controller including any one or more
of the above noted protection systems may include two or more
parallel sensing and control circuits. In such an embodiment,
parameters measured by the two or more parallel sensing circuits'
inputs may be processed separately and used to control two or more
redundant control systems such as two or more solid state switching
elements (e.g. switching relays) arranged in a series output
configuration to control operation of a particular circuit and/or
device. These redundant control systems may open their respective
load circuits upon the detection of a fault condition acting on
that particular circuit related to the fault and may remain open
until such time as the fault condition is corrected as previously
described. Thus, the use of redundant protection circuits may help
to minimize the occurrence of a fault without the control system
appropriately responding to the fault.
[0145] In certain embodiments, a separate Flash Memory, such as a
flash memory located externally to a desired controller, may be
used to enable more secure program bootloading in the field. For
example, when releasing firmware updates in the field, it may be
desirable to not interrupt the re-flashing of a software update. If
any disruption of the BMU system serial communications occurs
during the re-flashing, the BMU may become unrecoverable. Referring
to FIG. 42, with the Flash Memory, the updated firmware is first
loaded into the flash memory at 201. The associated controller then
verifies at 209 the accuracy and completeness of the firmware
update located in the flash memory after serial communication has
been completed at 205. Once the downloaded firmware update is
verified at 209, a controller, such as an MCU, of the BMU may then
use the firmware update located on the flash memory to re-flash
itself at 213. FIG. 41 shows an embodiment of a battery pack
including an separate Flash Memory used for a more secure program
bootloading feature. The MM9Z1_638 (U7) MCU communicates with this
external 128k byte Flash Memory U4 via the industry standard Serial
Peripheral Interface (SPI) bus. This SPI bus is also used to
control the cell balancing Octal Power Switch (U2), so the OR gate
(U5) is used to switch which peripheral the MCU controls. While an
embodiment including a particular type of circuit and components
has been illustrated, the above noted concept may be used with any
appropriate circuit and for any desired application where a
controller of a device re-flashes itself.
[0146] Without wishing to be bound by theory, the ability of an
electrochemical cell to either provide (e.g. during discharge) or
accept (e.g. during continuous charge or regenerative charging) a
current may vary with the state of charge and temperature of the
cell. For example, lower temperatures may lower the available
current draw from a cell and/or the ability of the cell to charge
at a given current. This may be due to the reduced mobility of
charge carriers, such as ionic species (e.g. lithium ions within
lithium ion batteries), within the electrolyte and their reduced
ability to intercalate with the electrochemical materials at lower
temperatures. Correspondingly, at higher temperatures more current
may generally be available due to increased mobility of these
charge carriers within the electrolyte and electrochemical
materials of the cells. However, at temperatures approaching a
continuous operating temperature threshold and/or maximum operating
temperature threshold of an electrochemical cell, it may be
desirable to reduce a maximum current during either charge and/or
discharge to prevent excessive heating and/or damage to the cell.
In addition to temperature considerations, larger current draws may
be possible at higher states of charge for an electrochemical cell
due to it being easier to extract charge carriers from the
associated electroactive materials at these higher states of
charge. Conversely, the ability to charge a cell may decrease with
increasing states of charge due to it being more difficult to
intercalate ions into the anode of an electrochemical device at
higher states of charge. Thus, larger states of charge may be
associated with correspondingly reduced charging currents.
[0147] Due to the differences in the ability of an electrochemical
cell to output or accept a desired current at different
temperatures and/or states of charge, in some embodiments, it may
be desirable to limit the current drawn from, or provided to, an
electrochemical cell when exposed to different conditions to avoid
unnecessary damage or degradation of the electrochemical cell.
Accordingly, as depicted in FIG. 43, a controller, such as a BMC,
BMU, and/or any other appropriate controller associated with one or
more electrochemical cells, may sense a temperature of the one or
more electrochemical cells at 203. The controller may then
determine the state of charge (SOC) of the one or more
electrochemical cells at 207 using an operating parameter related
to SOC and/or charge counting methods using voltage and current
measurements. In certain embodiments, however, a controller only
uses one of the above noted states. At 211, the controller may then
determine a current threshold based at least in part on the
temperature and/or SOC of the one or more electrochemical cells.
The current threshold may be determined using any appropriate
method including, but not limited to, functional relationships,
lookup tables, or any other appropriate method capable of
determining a desired current threshold based on the operating
conditions.
[0148] At 215 the controller associated with the one or more
electrochemical cells may output a signal including the determined
current threshold to a separate controller which may control a
system the electrochemical cells are used to power. For example,
the separate controller may correspond to a controller of a
passenger vehicle, a motorcycle, a forklift, an airplane, or any
other appropriate type of device including a battery. Depending on
the particular application, the external controller may take one or
more actions based on the current threshold. For example, the
external controller may simply limit a current drawn from, or
supplied to, the one or more electrochemical cells to be less than
the determined current threshold. However, due to any number of
reasons, including safety and/or performance concerns, in some
embodiments, during at least some modes of operation the separate
controller may not reduce a current to be less than the determined
current thresholds in at least one mode of operation. For example,
it may not be desirable to limit the available current during a
vehicle acceleration, take off or landing of an aircraft, or other
similar type performance or safety driven application. Instead, the
external controller may permit the current to exceed the determined
current threshold during one or modes of operation after which it
may reduce the current to be less than the determined current
thresholds. Alternatively, the external control may not control the
current, and may instead simply output an indication to a user that
the current has exceeded the determined current threshold and
should be reduced to avoid damage to the one or more
electrochemical cells (e.g. an indicator light, dial, text output,
GUI output, or other indicator visible to a user during use).
[0149] FIG. 44 illustrates one embodiment of a system that may
implement the above described method. In the figure, one or more
electrochemical cells are included in a power source 217 such as a
battery and/or CMA. One or more sensors output one or more detected
signals related to one or more operating parameters of the one or
more electrochemical cells to a controller 219, such as a BMC
and/or BMU. While the detected signals may correspond to any
appropriate parameter, in at least one embodiments the signals may
include information related to voltage, current, temperature,
and/or any other appropriate operating parameter of the
electrochemical cells. In embodiments where a controller determines
a state of charge of the one or more electrochemical cells, the
controller may use any appropriate operating parameter or state of
the electrochemical cells. For example, a controller may determine
an SOC of the cells by using the detected parameters to estimate
the state of charge (e.g. an estimated SOC based on measured cell
voltage); tracking power into and out of the one or more
electrochemical cells based on charge counting methods using
voltage and current measurements; and/or using any other
appropriate method of determining a state of charge of the one or
more electrochemical cells. In either case, the controller 219 may
be in electrical communication with an external controller of a
system 221 such as the depicted vehicle in the figure. However, as
noted above, the system 221 may correspond to any appropriate
system or device including a battery.
[0150] In the above described embodiments, different modes of
operation of the one or more electrochemical cells may have
different threshold currents to avoid excessive damage or
degradation to the one or more electrochemical cells. For example,
an acceptable current applied during discharge may be larger than a
corresponding acceptable current provided by an electrochemical
cell during charge. Additionally, due to the intermittent and
short-lived duration of regenerative charging (e.g. charging from
electric braking of a vehicle), acceptable currents from
regenerative charging may be larger than corresponding normal
charging currents which are applied over a longer duration.
Accordingly, a controller associated with the one or more
electrochemical cells described above, may determine, and implement
the use of, different current thresholds from one or more of a
continuous charging operating mode, a regenerative charging
operating mode, and/or a discharging operating mode. However, in
certain embodiments a controller only determines and uses a single
current threshold.
[0151] The above embodiments have been directed to determining a
current threshold for one or more electrochemical cells.
Accordingly, certain embodiments may utilize a single
electrochemical cell used by itself, while certain embodiments
comprise cell module assemblies and full batteries including a
plurality of electrochemical cells.
[0152] The above-described embodiments of the technology described
herein can be implemented in any of numerous ways. For example, the
embodiments may be implemented using hardware, software or a
combination thereof. When implemented in software, the software
code can be executed on any suitable processor or collection of
processors, whether provided in a single computing device or
distributed among multiple computing devices. Such processors may
be implemented as integrated circuits, with one or more processors
in an integrated circuit component, including commercially
available integrated circuit components known in the art by names
such as CPU chips, GPU chips, microprocessor, microcontroller, or
co-processor. Alternatively, a processor may be implemented in
custom circuitry, such as an ASIC, or semicustom circuitry
resulting from configuring a programmable logic device. As yet a
further alternative, a processor may be a portion of a larger
circuit or semiconductor device, whether commercially available,
semi-custom or custom. As a specific example, some commercially
available microprocessors have multiple cores such that one or a
subset of those cores may constitute a processor. Though, a
processor may be implemented using circuitry in any suitable
format.
[0153] Further, it should be appreciated that a computing device
may be embodied in any of a number of forms, such as a rack-mounted
computer, a desktop computer, a laptop computer, or a tablet
computer. Additionally, a computing device may be embedded in a
device not generally regarded as a computing device but with
suitable processing capabilities, including a Personal Digital
Assistant (PDA), a smart phone or any other suitable portable or
fixed electronic device.
[0154] Also, a computing device may have one or more input and
output devices. These devices can be used, among other things, to
present a user interface. Examples of output devices that can be
used to provide a user interface include printers or display
screens for visual presentation of output and speakers or other
sound generating devices for audible presentation of output.
Examples of input devices that can be used for a user interface
include keyboards, and pointing devices, such as mice, touch pads,
and digitizing tablets. As another example, a computing device may
receive input information through speech recognition or in other
audible format.
[0155] Such computing devices may be interconnected by one or more
networks in any suitable form, including as a local area network, a
controller area network, or a wide area network, such as an
enterprise network or the Internet. Such networks may be based on
any suitable technology and may operate according to any suitable
protocol and may include wireless networks, wired networks or fiber
optic networks.
[0156] Also, the various methods or processes outlined herein may
be coded as software that is executable on one or more processors
that employ any one of a variety of operating systems or platforms.
Additionally, such software may be written using any of a number of
suitable programming languages and/or programming or scripting
tools, and also may be compiled as executable machine language code
or intermediate code that is executed on a framework or virtual
machine.
[0157] In this respect, the disclosed embodiments may be embodied
as a computer readable storage medium (or multiple computer
readable media) (e.g., a computer memory, one or more floppy discs,
compact discs (CD), optical discs, digital video disks (DVD),
magnetic tapes, flash memories, circuit configurations in Field
Programmable Gate Arrays or other semiconductor devices, or other
tangible computer storage medium) encoded with one or more programs
that, when executed on one or more computers or other processors,
perform methods that implement the various embodiments of the
disclosure discussed above. As is apparent from the foregoing
examples, a computer readable storage medium may retain information
for a sufficient time to provide computer-executable instructions
in a non-transitory form. Such a computer readable storage medium
or media can be transportable, such that the program or programs
stored thereon can be loaded onto one or more different computers
or other processors to implement various aspects of the present
disclosure as discussed above. As used herein, the term
"computer-readable storage medium" encompasses only a
non-transitory computer-readable medium that can be considered to
be a manufacture (i.e., article of manufacture) or a machine.
Alternatively or additionally, the disclosure may be embodied as a
computer readable medium other than a computer-readable storage
medium, such as a propagating signal.
[0158] The terms "program" or "software" are used herein in a
generic sense to refer to any type of computer code or set of
computer-executable instructions that can be employed to program a
computing device or other processor to implement various aspects of
the present disclosure as discussed above. Additionally, it should
be appreciated that according to one aspect of this embodiment, one
or more computer programs that when executed perform methods of the
present disclosure need not reside on a single computer or
processor, but may be distributed in a modular fashion amongst a
number of different computers or processors to implement various
aspects of the present disclosure.
[0159] Computer-executable instructions may be in many forms, such
as program modules, executed by one or more computers or other
devices. Generally, program modules include routines, programs,
objects, components, data structures, etc. that perform particular
tasks or implement particular abstract data types. Typically the
functionality of the program modules may be combined or distributed
as desired in various embodiments.
[0160] Also, data structures may be stored in computer-readable
media in any suitable form. For simplicity of illustration, data
structures may be shown to have fields that are related through
location in the data structure. Such relationships may likewise be
achieved by assigning storage for the fields with locations in a
computer-readable medium that conveys relationship between the
fields. However, any suitable mechanism may be used to establish a
relationship between information in fields of a data structure,
including through the use of pointers, tags or other mechanisms
that establish relationship between data elements.
Example: Current Versus Operating Condition
[0161] FIGS. 45-46 are tables that illustrate exemplary current
thresholds during discharge, regenerative charging, and continuous
charging for a battery operated at different temperatures and
states of charge. The exemplary currents provided in the tables
correspond to the current thresholds for a lithium ion CMA
including seven cell blocks arranged in series with one another.
Each cell block includes three electrochemical cells each with 26
Ahr capacities.
[0162] Referring to FIG. 45, during discharge, the current
threshold increased with increasing temperature though the current
threshold at lower states of charge decreased again as the
continuous operating temperature and or maximum operating
temperatures were approached at 50.degree. C. Additionally, the
current threshold for discharge increased with increasing state of
charge as expected. Similarly, in FIGS. 46 and 47, the current
threshold during regenerative and continuous charging initially
increased with increasing temperature. However, with further
increases in temperature, the permissible current threshold may be
reduced as the continuous operating temperature is approached
and/or set to 0 at the maximum operating temperature, which in this
embodiment was at 50.degree. C. However, in contrast to the
discharge current thresholds, the permissible regenerative and
continuous charging currents increased with decreasing state of
charge due to it being easier to charge the one or more
electrochemical cells at lower states of charge. As shown in the
tables, the regenerative current thresholds may be less than,
greater than, or approximately the same as the corresponding
discharge current thresholds under the same operating conditions.
However, the depicted continuous charging current thresholds were
generally less than the corresponding regenerative charging and
discharging current thresholds as shown in FIG. 47 though in
certain embodiments only a single current threshold can be used for
all operating modes.
[0163] While the above example provides particular current
thresholds and relationships versus temperature and SOC, it should
be understood that appropriate current thresholds for an
electrochemical device will depend on the specific
electrochemistry, application, cell capacity, number of cells, cell
construction, and pack construction to name a few parameters.
Therefore, it should be understood that the above numbers have been
provided simply as an example and in other embodiments, current
thresholds different from the specifically disclosed current
thresholds above may be employed. Further, the currently disclosed
methods may be applied to the control and use of any number of
different electrochemical devices.
[0164] While the present teachings have been described in
conjunction with various embodiments and examples, it is not
intended that the present teachings be limited to such embodiments
or examples. On the contrary, the present teachings encompass
various alternatives, modifications, and equivalents, as will be
appreciated by those of skill in the art. Accordingly, the
foregoing description and drawings are by way of example only.
* * * * *