U.S. patent application number 11/131930 was filed with the patent office on 2006-01-19 for automated battery cell shunt bypass.
This patent application is currently assigned to Railpower Technologies Corp.. Invention is credited to John David Watson.
Application Number | 20060012334 11/131930 |
Document ID | / |
Family ID | 35428644 |
Filed Date | 2006-01-19 |
United States Patent
Application |
20060012334 |
Kind Code |
A1 |
Watson; John David |
January 19, 2006 |
Automated battery cell shunt bypass
Abstract
A battery pack is provided that includes a plurality of battery
cells electrically connected in series, the plurality of battery
cells including a selected battery cell, and a shorting mechanism
operable, upon the occurrence of a selected event, to automatically
remove electrically the selected battery cell from the electrically
connected battery cells.
Inventors: |
Watson; John David;
(Evergreen, CO) |
Correspondence
Address: |
SHERIDAN ROSS PC
1560 BROADWAY
SUITE 1200
DENVER
CO
80202
US
|
Assignee: |
Railpower Technologies
Corp.
North Vancouver
CA
|
Family ID: |
35428644 |
Appl. No.: |
11/131930 |
Filed: |
May 17, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60572289 |
May 17, 2004 |
|
|
|
Current U.S.
Class: |
320/112 |
Current CPC
Class: |
B60L 58/26 20190201;
H01M 10/625 20150401; H01M 10/613 20150401; Y02T 90/14 20130101;
B60L 50/64 20190201; H02J 7/0016 20130101; B60L 2200/26 20130101;
H01M 50/572 20210101; B60L 2240/547 20130101; H01M 10/482 20130101;
B60L 2240/549 20130101; B60L 53/80 20190201; B60L 58/22 20190201;
H01M 50/578 20210101; B60L 58/15 20190201; H01M 10/06 20130101;
H01M 10/6563 20150401; B60L 58/13 20190201; H01M 10/647 20150401;
H02J 7/007192 20200101; H01M 10/486 20130101; H01M 10/4207
20130101; H01M 50/581 20210101; H01M 10/6557 20150401; H02J 7/0091
20130101; B60L 58/14 20190201; Y02T 90/12 20130101; B60L 3/0046
20130101; B60L 58/25 20190201; H01M 10/635 20150401; Y02E 60/10
20130101; Y02T 10/70 20130101; Y02T 10/7072 20130101; B60L 2240/545
20130101 |
Class at
Publication: |
320/112 |
International
Class: |
H02J 7/00 20060101
H02J007/00 |
Claims
1. A battery pack, comprising: a plurality of battery cells
electrically connected in series, the plurality of battery cells
including a selected battery cell; and a shorting mechanism
operable, upon the occurrence of a selected event, to automatically
remove electrically the selected battery cell from the electrically
connected battery cells.
2. The battery pack of claim 1, wherein the selected event is at
least one of the following: (i) an internal resistance of the
battery cell in excess of a first selected operating threshold;
(ii) an internal pressure of the battery cell in excess of a second
selected operating threshold; (iii) an internal temperature of the
battery cell in excess of a third selected operating threshold;
(iv) a voltage of the battery cell during energy removal in excess
of a fourth selected operating threshold; and (v) a voltage of the
battery cell during charging less than a fifth selected operating
threshold.
3. The battery pack of claim 2, wherein the event is event (i).
4. The battery pack of claim 2, wherein the event is event
(ii).
5. The battery pack of claim 2, wherein the event is event
(iii).
6. The battery pack of claim 2, wherein the event is event
(iv).
7. The battery pack of claim 2, wherein the event is event (v).
8. The battery pack of claim 1, wherein the shorting mechanism
comprises a shorting bar, a sensor that senses the occurrence of
the selected event, a controller in communication with the sensor,
and a shorting bar deployment member, wherein, when the controller
determines from sensor input that the selected event has occurred,
the controller causes the shorting bar deployment member to
position the shorting bar in contact with positive and negative bus
bars of the selected battery cell, thereby shorting out the cell
and forming a shunt bypass of the selected battery cell.
9. The battery pack of claim 4, wherein the shorting mechanism
comprises a piston having a position that changes in response to
the internal pressure, a shorting bar, and a shorting bar
deployment member, wherein, when the internal pressure rises above
the selected operating threshold, the position of the piston causes
the shorting bar deployment member to position the shorting bar in
contact with positive and negative bus bars of the selected battery
cell, thereby shorting out the cell and forming a shunt bypass of
the selected battery cell.
10. The battery pack of claim 5, wherein the shorting mechanism
comprises a thermally expansive material having a length that
increases in direct response to the internal temperature, a
shorting bar, and a shorting bar deployment member, wherein, when
the internal temperature rises above the selected operating
threshold, the length of the thermally expansive material causes
the shorting bar deployment member to position the shorting bar in
contact with positive and negative bus bars of the selected battery
cell, thereby shorting out the cell and forming a shunt bypass of
the selected battery cell.
11. In a battery pack comprising a plurality of battery cells
electrically connected in series, a method, comprising: removing
electrical energy from and/or inputting electrical energy to the
battery pack; and when a selected battery cell in the battery pack
has an operating characteristic beyond a specified operational
limit, automatically removing electrically the selected battery
cell from the battery pack.
12. The method of claim 11, wherein the operating characteristic is
at least one of an internal resistance, an internal pressure, an
internal temperature, and cell voltage.
13. The method of claim 12, wherein the at least one of an internal
resistance, an internal pressure, an internal temperature, and a
cell voltage is internal resistance.
14. The method of claim 12, wherein the at least one of an internal
resistance, an internal pressure, an internal temperature, and a
cell voltage is internal pressure.
15. The method of claim 12, wherein the at least one of an internal
resistance, an internal pressure, an internal temperature, and a
cell voltage is internal temperature.
16. The method of claim 12, wherein the at least one of an internal
resistance, an internal pressure, an internal temperature, and a
cell voltage is cell voltage.
17. The method of claim 12, further comprising: sensing the at
least one of an internal resistance, an internal pressure, an
internal temperature, and a cell voltage; determining that the
sensed at least one of an internal resistance, an internal
pressure, an internal temperature, and a cell voltage of a selected
battery cell is beyond the specified operational limit; in response
to the determining step, repositioning a shorting bar from a first
position out of contact with at least one of the positive bus bar
and negative bus bar of the selected battery cell to a second
position in simultaneous contact with positive and negative bus
bars of the selected battery cell, thereby shorting out the cell
and forming a shunt bypass of the selected battery cell.
18. The method of claim 14, further comprising: when the internal
pressure in a selected battery cell rises above the selected
specified operational limit, a piston is moved from a first to a
second position, wherein, when the piston is in the first position,
a shorting bar is not in contact with at least one of a positive
bus bar and negative bus bar of the selected battery cell and
wherein, when the piston is in the second position, the shorting
bar is in simultaneous contact with positive and negative bus bars
of the selected battery cell, thereby shorting out the cell and
forming a shunt bypass of the selected battery cell.
19. The method of claim 15, further comprising: when the internal
temperature in a selected battery cell rises above the specified
operational limit, a length of a thermally expansive material
lengths from a first length to a second length, wherein, when the
expansive material has the first length, a shorting bar is not in
contact with at least one of a positive bus bar and negative bus
bar of the selected battery cell and wherein, when the expansive
material has the second length, the shorting bar is in simultaneous
contact with the positive and negative bus bars of the selected
battery cell, thereby shorting out the cell and forming a shunt
bypass of the selected battery cell.
20. A system, comprising: a plurality of battery cells electrically
connected in series, the plurality of battery cells including a
selected battery cell; an electric motor in electrical
communication with the battery cells; and a shunting device
operable in a first mode not to shunt a selected battery cell and
in a second mode to shunt the selected battery cell, whereby, in
the first mode, the selected battery cell provides electrical
energy to the electric motor and, in the second mode, the selected
battery cell provides no electrical energy to the electric
motor.
21. The system of claim 20, wherein the shunting device is
operable, when the selected battery cell has at least one of an
internal resistance, an internal pressure, and an internal
temperature in excess of a selected operating threshold, to operate
in the second mode.
22. The system of claim 21, wherein the at least one of an internal
resistance, an internal pressure, and an internal temperature is
internal resistance.
23. The system of claim 21, wherein the at least one of an internal
resistance, an internal pressure, and an internal temperature is
internal pressure.
24. The system of claim 21, wherein the at least one of an internal
resistance, an internal pressure, and an internal temperature is
internal temperature.
25. The system of claim 20, wherein the shunting mechanism
comprises a shorting bar, a sensor that senses the at least one of
an internal resistance, an internal pressure, and an internal
temperature, a controller in communication with the sensor, and a
shorting bar deployment member, wherein, when the controller
determines from sensor input that the at least one of an internal
resistance, an internal pressure, and an internal temperature is
above a selected operating threshold, the controller causes the
shorting bar deployment member to position the shorting bar in
contact with positive and negative bus bars of the selected battery
cell, thereby shorting out the cell and forming a shunt bypass of
the selected battery cell.
26. The system of claim 23, wherein the shunting mechanism
comprises a piston having a position that changes in response to
the internal pressure, a shorting bar, and a shorting bar
deployment member, wherein, when the internal pressure rises above
a selected operating threshold, the position of the piston causes
the shorting bar deployment member to position the shorting bar in
contact with positive and negative bus bars of the selected battery
cell, thereby shorting out the cell and forming a shunt bypass of
the selected battery cell.
27. The system of claim 24, wherein the shunting mechanism
comprises a thermally expansive material having a length that
increases in direct response to the internal temperature, a
shorting bar, and a shorting bar deployment member, wherein, when
the internal temperature rises above a selected operating
threshold, the length of the thermally expansive material causes
the shorting bar deployment member to position the shorting bar in
contact with positive and negative bus bars of the selected battery
cell thereby shorting out the cell and forming a shunt bypass of
the selected battery cell.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] The present application claims the benefits, under 35 U.S.C.
.sctn.119(e), of U.S. Provisional Application Ser. No. 60/572,289
filed May 17, 2004 entitled "Design of a Large Battery Pack" to
Donnelly et al., which is incorporated herein by this
reference.
FIELD
[0002] The present invention relates generally to a method for
automatically electrically removing individual battery cells which
are malfunctioning from a battery pack of cells electrically
connected in series.
BACKGROUND
[0003] Batteries, in particular large lead-acid batteries, are
typically fabricated first by arranging a series of positive and
negative plates separated by a separator material in a stack.
Positive and negative bus bars are typically welded to positive and
negative tabs that extend from the tops of the positive and
negative plates respectively. The positive and negative terminals
of the battery are typically fabricated as part of the bus bar
assembly. The separator material is impregnated with an appropriate
electrolyte and the top of the battery case is installed. Atypical
cell is illustrated in FIG. 1, which is well-known prior art.
[0004] When a large number of cells are used in a series-connected
battery pack configuration (the cell voltages add, the battery pack
current is the same as the individual cell currents), one cell that
begins to degrade or fail can seriously impact or terminate the
operation of the entire battery pack. It is therefore desirable to
have a means where a malfunctioning cell in a series-connected
battery pack can be automatically removed from the battery
pack.
[0005] In a battery pack, degraded or failed plate pairs in a
malfunctioning cell can be open-circuited by utilizing a fuse
mechanism to remove one of more electrode pairs in the affected
cell from service. The open-circuit approach typically applies to
electrode pairs that are in parallel in a cell. This leaves a
smaller number of plate pairs in the cell. This is particularly
effective if the failing electrode pair has a soft short and is
draining the other electrode pairs in the cell. The short causes
local heating which makes the electrode hotter and a thermal fuse
opens-circuits the failing electrode pair. The disadvantage of this
approach is the additional cost and complexity of having a fuse
mechanism on each plate pair, and a reduction in the maximum
current available from the battery pack since all cells must be
derated to the performance parameters of the cell with the shorted
plate pair or pairs. This approach can also cause in imbalance in
the state-of-charge ("SOC") between cells which can lead to loss of
cell lifetimes.
[0006] Another approach is to use a battery management system where
the battery pack performance is reduced to the level of the
degraded or failing cell. This approach limits the maximum
available pack current as well as the available storage capacity
and output voltage of the pack to match the capability of the
malfunctioning cell.
[0007] A third approach is to short-circuit a malfunctioning cell
to eliminate the cell from the battery pack by shunting pack
current around the malfunctioning cell. This approach has the
advantage of not reducing the maximum available battery pack
current. In a large battery pack which may be comprised of several
hundred cells in series, there will be a small reduction in battery
pack voltage and ampere-hour capacity when one or a few cells are
bypassed.
[0008] Thus there is a need for a low cost method to automatically
shunt out malfunctioning cells in a large series connected battery
pack to avoid seriously impacting or terminating the operation of
the entire battery pack.
SUMMARY
[0009] These and other needs are addressed by the various
embodiments and configurations of the present invention which are
directed generally to a method for automatically electrically
removing individual battery cells which are malfunctioning from a
series string of cells.
[0010] In a first embodiment of the present invention, a battery
pack is provided that includes: [0011] (a) a plurality of battery
cells electrically connected in series, the plurality of battery
cells including a selected battery cell, and [0012] (b) a shorting
mechanism operable, upon the occurrence of a selected event, to
automatically remove electrically the selected battery cell from
the electrically connected battery cells.
[0013] The selected event is commonly at least one of the
following: [0014] (i) an internal resistance of the battery cell
being in excess of a first selected operating threshold; [0015]
(ii) an internal pressure of the battery cell being in excess of a
second selected operating threshold; [0016] (iii) an internal
temperature of the battery cell being in excess of a third selected
operating threshold; [0017] (iv) a voltage of the battery cell
during energy removal being in excess of a fourth selected
operating threshold; and [0018] (v) a voltage of the battery cell
during charging being less than a fifth selected operating
threshold.
[0019] By removing individual battery cells from the battery pack
in the event that the internal resistance or other internal
operating characteristic of the battery cell changes beyond
specified limits adversely impacting the operation of the battery,
the present invention can reduce the risk of battery fires,
increase the effective lifetime of the battery pack, and provide a
higher effective battery pack energy output over time. The shorting
mechanism commonly does not reduce the maximum battery peak
current. Depending on the number of cells in the battery pack,
there may be a small reduction in battery pack voltage and battery
pack ampere-hour capacity. The reduced voltage and storage capacity
will commonly not significantly impact battery pack
performance.
[0020] There are number architectures for implementing the present
invention.
[0021] In a first configuration, the shorting mechanism includes a
piston having a position that changes in response to the internal
pressure, a shorting bar, and a shorting bar deployment member.
When the internal pressure rises above a selected operating
threshold, the position of the piston causes the shorting bar
deployment member to position the shorting bar in contact with
positive and negative bus bars of the selected battery cell,
thereby shorting out the cell and forming a shunt bypass of the
selected battery cell.
[0022] In a second configuration, the shorting mechanism includes a
thermally expansive material having a length that increases in
direct response to the internal temperature, a shorting bar, and a
shorting bar deployment member. When the internal temperature rises
above a selected operating threshold, the length of the thermally
expansive material causes the shorting bar deployment member to
position the shorting bar in contact with positive and negative bus
bars of the selected battery cell, thereby shorting out the cell
and forming a shunt bypass of the selected battery cell.
[0023] In a third configuration, the shorting mechanism includes a
shorting bar, a sensor that senses the occurrence of a selected
event, a controller in communication with the sensor, and a
shorting bar deployment member. When the controller determines from
sensor input that the selected event has occurred, the controller
causes the shorting bar deployment member to position the shorting
bar in contact with positive and negative bus bars of the selected
battery cell, thereby shorting out the cell and forming a shunt
bypass of the selected battery cell.
[0024] The first and second configurations are particularly
desirable. They can be low cost, robust, are self-actuating and
have a high degree of reliability.
[0025] These and other advantages will be apparent from the
disclosure of the invention(s) contained herein.
[0026] The above-described embodiments and configurations are
neither complete nor exhaustive. As will be appreciated, other
embodiments of the invention are possible utilizing, alone or in
combination, one or more of the features set forth above or
described in detail below.
[0027] The following definitions are used herein:
[0028] A "battery cell" or "cell" is an individual sealed or vented
cell comprised of one or more internal plate assemblies, each plate
assembly comprised of a negative plate, a separator material and a
positive plate. The battery cell may have one or more external
negative and positive terminals.
[0029] A "plate pair" is the basic unit of a cell and is comprised
of a negative plate, a separator material and a positive plate.
When the separator is impregnated with an appropriate electrolyte,
a voltage typical of the particular battery chemistry is developed
between the positive and negative plates. In a lead-acid battery,
this voltage is typically about 2.13 volts at full charge.
[0030] A "battery rack" is a mechanical structure in which battery
cells are mounted.
[0031] A "battery module" is a collection of cells mounted in a
battery rack frame assembly of convenient size.
[0032] A "battery pack" is an assembly of many individual battery
cells connected electrically. The assembly may be comprised of
subassemblies or modules comprised of individual battery cells. The
battery pack usually, but not always, has one overall positive and
negative terminals for charging and discharging the cells in the
pack.
[0033] A "bus bar" refers to an electrical conductivity path
involving a negative or positive polarity of a plurality of plates
in one or more battery cells. A bus bar may interconnect a number
of battery terminals in one or more battery cells or may be a
single battery terminal of only one battery cell.
[0034] "Float service" as applied to a battery means operating the
battery under rigid voltage conditions to overcome self-discharge
reactions while minimizing overcharge and corrosion of the cell's
positive grid.
[0035] "Cyclical service" as applied to a battery cell means
operating the battery by alternating discharging the cell to a
significantly lower capacity or state-of-charge and then recharging
the cell to at or near its full capacity.
[0036] A "malfunctioning battery cell" is taken to be a cell in
which there is a significant degradation of capacity or significant
change in open-circuit voltage; a significant increase in internal
plate resistance; and/or significant internal shorting in one or
more plate pairs, any of which may cause a cell to degrade in
performance or fail.
[0037] "At least one", "one or more", and "and/or" are open-ended
expressions that are both conjunctive and disjunctive in operation.
For example, each of the expressions "at least one of A, B and C",
"at least one of A, B, or C", "one or more of A, B, and C", "one or
more of A, B, or C" and "A, B, and/or C" means A alone, B alone, C
alone, A and B together, A and C together, B and C together, or A,
B and C together.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] FIG. 1 is an isometric cutaway view of an individual prior
art battery cell;
[0039] FIG. 2 shows a side view of two possible mechanisms for
automatically shorting out battery cells;
[0040] FIG. 3 shows a top view of a mechanism for automatically
shorting out battery cells; and
[0041] FIG. 4 shows a top view of a motorized mechanism for
automatically shorting out battery cells.
DETAILED DESCRIPTION
[0042] FIG. 1 shows a schematic cutaway view of a large energy
storage battery cell 100 that is typical of the cells used in a
large battery pack assemblies. This is prior art. The battery case
101 contains negative plates 102 interleaved with positive plates
103, the latter typically inserted in a pocket 104 of separator
material. The separator 104 is typically impregnated with
electrolyte. The plates 102 and 103 terminate outside the battery
at a negative terminal 105 and a positive terminal 106. The example
of FIG. 1 is that of a single cell where the open circuit voltage
across the terminals 105 and 106 is the same as the open circuit
voltage across any pair of positive and negative plate pairs. Other
batteries, such as for example an automotive starter battery may be
comprised of several plate pairs in series or in parallel or
combinations thereof. In the example of an automotive starter
battery, the open circuit voltage across the terminals is
approximately 12 volts or 6 times the number of internal series
connected plate pairs. The battery cell 100 is shown with a vent
107 which allows excess gas generated for example during an
equalization charge to be discharged when a predetermined internal
pressure is exceeded.
[0043] It is possible to automatically electrically short out one
or more battery cells using an external bus bar that can be
automatically caused to short out the external terminals of a
battery cell. A preferred method of hard shorting a cell would be
outside the cell thus eliminating the resistance of the terminals
and internal bus bars of the cell.
[0044] FIG. 2 shows a side view of two possible mechanisms for
automatically moving an external bus bar to cause a by-pass shunt
of a battery cell. The battery cell is comprised of a case 201
which contains a series 202 of positive and negative plates pairs
separated by electrolyte. The present invention is directed towards
cells in which the internal plate pairs are electrically connected
in parallel although the invention may be applied to cells in which
the internal plate pairs are electrically connected in series or in
combinations of series and parallel groups. It is preferable to
apply the present invention to shunt a cell where the open circuit
voltage is low such as for example a cell where all the plate pairs
are connected electrically in parallel. While the present invention
may be applied to cells with higher terminal-to-terminal open
circuit voltage, the higher the terminal-to-terminal voltage, the
more likely it is for inadvertent shorting to occur due to, for
example, dust and other types of contamination collecting between
the terminals or bus bars and the shorting bar. There is typically
a headroom space 203 above the assembly 202 to allow for gases to
collect. A first shorting mechanism 210 is based on an element 213
that is made of a material that has a large thermal expansion
coefficient relative to the other components so that the element
213 becomes longer relative to the other components as the internal
battery temperature increases. Thus internal battery temperature is
the event that activates this shorting mechanism. The element 213
may be comprised, for example, of a material with an anomalously
high expansion coefficient or it may be a sealed cylinder that
expands when an enclosed liquid or gas lengthens the cylinder as
the enclosed liquid or gas is heated by exposure to the temperature
in the cell. The element 213 is fixed to a housing 212 which is in
turn attached to the top of the battery case 201. When the element
213 expands relative to the other components of the shorting
mechanism, it pushes on a screw mechanism 214 which is attached to
a shorting bar 211. The shorting bar 211 is located on the outside
of the case 201 and is shown in a top view in FIG. 3. When the
element 213 expands, it forces the screw mechanism 214 to rotate a
small amount which in turn rotates the shorting bar. The element
213 is directly exposed to the internal temperature of the battery
and when the internal temperature reaches a predetermined
threshold, the shorting bar 211 is caused to rotate sufficiently to
contact the positive and negative bus bars (as shown in FIG. 3)
thereby shorting out the cell and forming a shunt by-pass. Since
the cell plate pairs are electrically connected preferably in
parallel, there is voltage difference between the positive and
negative bus bars of typically a few volts to a few tens of volts
and the amount of rotation required to short out the battery is
typically between about 5 and 10 degrees.
[0045] A second shorting mechanism 220 is based on a piston 223
that moves in response to internal battery pressure so that the
piston 223 pushes upwards as the internal battery pressure
increases. The piston 223 is free to move within a housing 212
which is in turn attached to the top of the battery case 201. When
the piston 223 moves upward, it pushes on a screw mechanism 224
which is attached to a shorting bar 221. The shorting bar 221 is
located on the outside of the case 201 and is shown in a top view
in FIG. 3. When the piston 223 moves upward, it forces the screw
mechanism 224 to rotate a small amount which in turn rotates the
shorting bar 221. The piston 223 is directly exposed to the
internal pressure of the battery and when the internal pressure
reaches a predetermined threshold, the shorting bar 221 is caused
to rotate enough to contact the positive and negative bus bars (as
shown in FIG. 3) thereby shorting out the battery cell. Thus
internal battery pressure is the event that activates this shorting
mechanism. Since the battery plate pairs are electrically connected
preferably in parallel, there is voltage difference between the
positive and negative bus bars of typically a few volts to a few
tens of volts and the amount of rotation required to short out the
battery is typically between about 5 and 10 degrees. Many batteries
have vents (not shown) to relieve internal pressure that is built
up by evolving gases. Internal pressure is most typically generated
at end of charge cycle due to electrolysis or during normal hybrid
electric vehicle ("HEV") charge-discharge cycling. In these cases,
the change in pressure will be slow. The vents used in the present
invention can be throttled to allow small amounts of gas to escape
slowly. When gas pressure builds up rapidly such as for example
when the internal plate pair resistances increase substantially,
the vents cannot remove gas fast enough to prevent pressure
build-up. The piston 223 is then exposed to enough pressure to
rotate the shorting bar 221 so that it shorts out the battery cell,
thereby substantially reducing the current flow across the
electrode plates where the excess energy is being generated.
Additionally the shorting bars 211 and 221 can contain a fuse
element that would disrupt the short circuit in the event the
battery cell retains a substantial undetected charge.
[0046] FIG. 3 shows a top view of a mechanism for manually or
automatically shorting out large battery cells. In this example, a
bus bar connects several terminals of a given polarity so as to
lower the overall terminal resistance. This view shows battery cell
container 301 which houses three battery cells 306, 307 and 308.
Bus bar 302 forms a positive terminal and connects the positive
plates of battery cell 306. Bus bar 305 connects the negative
plates of battery cell 306 with the positive plates of battery cell
307. Bus bar 304 connects the negative plates of battery cell 307
with the positive plates of battery cell 308. Bus bar 303 forms a
negative terminal and connects the negative plates of battery cell
306. Thus the three battery cells are connected in series in this
example. As can be readily seen, the negative and positive
polarities can be reversed. Shorting bars 311, 312 and 313 are
shown and each can rotate independently about a center post such as
314. The center posts 314 are solidly attached to each shorting bar
and correspond to the screw mechanisms 214 and 224 shown in FIG. 2.
The shorting bar 311 is shown in contact with bus bars 302 and 305
thereby shorting out the battery cell 306. The shorting bars 312
and 313 are shown not in contact with any of the bus bars so that
battery cells 307 and 308 are not shorted out. In this example
therefore, two battery cells 307 and 308 are shown electrically
connected in series with battery cell 306 bypassed by the shorting
bar 311. The shorting bars may be rotated into contact with the
main current carrying bus bars by either of the mechanisms 210 or
220 illustrated in FIG. 2.
[0047] FIG. 4 shows a top view of a motorized mechanism 413 for
automatically shorting out battery cells. The motorized mechanism
413 is preferably mounted on the outside of the battery cell to
avoid exposure to corrosive gases that typically collect in the
interior of the cell. This view shows two cells 401 and 402. Bus
bar 403 forms a positive terminal and connects the positive plates
of battery cell 401. Bus bar 404 connects the negative plates of
battery cell 401 with the positive plates of battery cell 402. Bus
bar 405 connects the negative plates of battery cell 402 with the
positive plates of next battery cell in the series (not shown).
Thus the two battery cells are connected in series in this example.
As can be readily seen, the negative and positive polarities can be
reversed. Shorting bars 411 and 415 are shown and each can rotate
independently about a center post such as 412. The center posts 412
are solidly attached to each shorting bar. A small motor 413 is
shown connected to the center posts 412 in this example by a belt
drive 414. The motor 413 may be powered by any number of electrical
sources including by the power used to operate a battery monitoring
system (not shown) or by power in the cell on which the motor is
mounted or from one or more of the other cells in the battery pack.
The belt drive 414 is one of many well-known means for a motor 413
to rotate a shorting bar 411 about a center post 412. The shorting
bar 411 shown in contact with bus bars 403 and 404 thereby shorting
out the battery cell 401. The shorting bar 415 is shown not in
contact with any of the bus bars so that battery cell 402 is not
shorted out. Alternately, a motorized mechanism may be used to
engage a shorting bar with bus bars by moving the shorting bar in a
linear motion until contact is made with the bus bars.
[0048] The motorized mechanism described above may be actuated by a
sensor which detects any of a number of cell parameters such as for
example an anomalously high internal cell pressure, an anomalously
high internal cell temperature, an anomalously high internal cell
resistance, an anomalously high cell voltage during charging and/or
an anomalously low cell voltage during normal discharging, where
the anomalously low cell voltage during normal discharging may be
of reversed polarity from its normal polarity. Any of these may be
monitored by a sensor placed on or near the cell and the sensor
monitored by a controller which can activate the motorized
mechanism and cause it to short out the cell.
[0049] The above inventions are directed to use in a large battery
pack where all the battery cells are in series. When a cell or
cells develop an anomalously high internal resistances or internal
short or both, this can lead to reduced performance and eventually
cause the battery pack to shut down. Even when the battery pack is
shut down, the defective cell or cells retain enough residual heat
to eventually overheat to the point of causing a cell meltdown or a
battery pack fire.
[0050] A number of variations and modifications of the invention
can be used. It would be possible to provide for some features of
the invention without providing others. For example in one
alternative embodiment, a small amount of propellant can be
contained within in a mechanism, that when a selected temperature
is exceeded, initiates the propellant to generate gases which move
a piston that in turn pushes on a screw mechanism that causes an
external shorting bar to rotate a small amount to short out the
cell. In this embodiment, internal battery temperature is the event
that activates this shorting mechanism. In another alternative
embodiment, a small arms or rifle primer can be contained within in
a mechanism, that when a selected internal cell pressure or
temperature is exceeded, fires the primer to generate gas which
then moves a piston that in turn pushes on a screw mechanism that
causes an external shorting bar to rotate a small amount to short
out the cell. In this embodiment, internal battery temperature
and/or pressure is the event that activates the shorting mechanism.
Alternately, a propellant or primer can be initiated by a
controller that has sensed any of a number of selected events such
as cell pressure, temperature, resistance, or voltage that is out
of its normal range.
[0051] In yet another embodiment, the shorting bar may move in a
nonrotational manner. For example, the bar may move vertically in
any of the above embodiments, such as about a fulcrum. One end of
the bar may always be in contact with the first bus bar while the
other end is moved rotationally or nonrotationally into contact
with the second bus bar.
[0052] In yet a further embodiment, shorting is effected by
activating a switch electrically connected to the opposite polarity
bus bar(s) of one or more battery cells.
[0053] The present invention, in various embodiments, includes
components, methods, processes, systems and/or apparatus
substantially as depicted and described herein, including various
embodiments, subcombinations, and subsets thereof. Those of skill
in the art will understand how to make and use the present
invention after understanding the present disclosure. The present
invention, in various embodiments, includes providing devices and
processes in the absence of items not depicted and/or described
herein or in various embodiments hereof, including in the absence
of such items as may have been used in previous devices or
processes, e.g., for improving performance, achieving ease and\or
reducing cost of implementation.
[0054] The foregoing discussion of the invention has been presented
for purposes of illustration and description. The foregoing is not
intended to limit the invention to the form or forms disclosed
herein. In the foregoing Detailed Description for example, various
features of the invention are grouped together in one or more
embodiments for the purpose of streamlining the disclosure. This
method of disclosure is not to be interpreted as reflecting an
intention that the claimed invention requires more features than
are expressly recited in each claim. Rather, as the following
claims reflect, inventive aspects lie in less than all features of
a single foregoing disclosed embodiment. Thus, the following claims
are hereby incorporated into this Detailed Description, with each
claim standing on its own as a separate preferred embodiment of the
invention.
[0055] Moreover, though the description of the invention has
included description of one or more embodiments and certain
variations and modifications, other variations and modifications
are within the scope of the invention, e.g., as may be within the
skill and knowledge of those in the art, after understanding the
present disclosure. It is intended to obtain rights which include
alternative embodiments to the extent permitted, including
alternate, interchangeable and/or equivalent structures, functions,
ranges or steps to those claimed, whether or not such alternate,
interchangeable and/or equivalent structures, functions, ranges or
steps are disclosed herein, and without intending to publicly
dedicate any patentable subject matter.
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