U.S. patent application number 11/242273 was filed with the patent office on 2006-01-26 for apparatus for interconnecting battery cells in a battery pack and method thereof.
Invention is credited to Daniele C. Brotto, David A. Carrier, Steven J. Phillips, Andrew E. JR. Seman, Danh T. Trinh, Daniel J. White, Christopher R. Yahnker.
Application Number | 20060019155 11/242273 |
Document ID | / |
Family ID | 34465120 |
Filed Date | 2006-01-26 |
United States Patent
Application |
20060019155 |
Kind Code |
A1 |
Seman; Andrew E. JR. ; et
al. |
January 26, 2006 |
Apparatus for interconnecting battery cells in a battery pack and
method thereof
Abstract
A battery pack for a cordless power has a plurality of battery
cells disposed in a housing. In an embodiment of the invention,
battery cells are interconnected with a laminated plate structure
having non-conductive layers interspersed with conductive layers,
at least one of the conductive layers connected to the battery
cells to interconnect them. In an embodiment of the invention,
battery cells in a battery pack are interconnected with a flexible
printed circuit board having conductive traces thereon that are
attached to the battery cells to interconnect them. In an
embodiment of the invention, a cordless power tool has one or the
other of the foregoing battery packs. In an embodiment of the
invention, the battery cells are Lithium Ion battery cells.
Inventors: |
Seman; Andrew E. JR.; (White
Marsh, MD) ; Yahnker; Christopher R.; (Raleigh,
NC) ; White; Daniel J.; (Baltimore, MD) ;
Brotto; Daniele C.; (Baltimore, MD) ; Carrier; David
A.; (Aberdeen, MD) ; Phillips; Steven J.;
(Ellicott City, MD) ; Trinh; Danh T.; (Parkville,
MD) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Family ID: |
34465120 |
Appl. No.: |
11/242273 |
Filed: |
October 3, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10963367 |
Oct 11, 2004 |
6972544 |
|
|
11242273 |
Oct 3, 2005 |
|
|
|
60510123 |
Oct 14, 2003 |
|
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|
Current U.S.
Class: |
429/159 ; 429/61;
429/62; 429/7 |
Current CPC
Class: |
Y10T 29/49108 20150115;
Y10T 29/49114 20150115; H01M 10/0525 20130101; H01M 10/482
20130101; H01M 10/425 20130101; Y02E 60/10 20130101; H01M 50/502
20210101 |
Class at
Publication: |
429/159 ;
429/007; 429/062; 429/061 |
International
Class: |
H01M 2/24 20060101
H01M002/24; H01M 10/50 20060101 H01M010/50 |
Claims
1. A battery pack for a cordless power tool, comprising a housing
having a plurality of battery cells disposed therein interconnected
by first conductive traces on a flexible printed circuit board
attached to the battery cells.
2. The battery pack of claim 1 wherein the flexible printed circuit
board includes second conductive traces to which electronic
components are attached.
3. The battery pack of claim 2 wherein the electrical components
include at least one thermistor.
4. The battery pack of claim 3 wherein the electric components
include at least one thermistor associated with each battery cell,
each thermistor attached to one of the second conductive traces in
close proximity to the battery cell with which it is
associated.
5. The battery pack of claim 4 wherein the battery cells are
Lithium Ion battery cells and the electronic components include
electronic components configured as a temperature monitoring
circuit and electronic components configured as a cell balance
circuit.
6. The battery pack of claim 2 wherein the electronic components
include electronic components configured in at least one control
circuit.
7. The battery pack of claim 1 wherein the first conductive traces
includes pads that align with terminals of the battery cells, the
pads including slots through which connection tabs extend, the
connection tabs bonded to the battery cell terminals and the
pads.
8. The battery pack of claim 1 further including cell separator
plates in which the battery cells are disposed that hold the
battery cells in position for attachment of the flexible printed
circuit board to the battery cells.
9. The battery pack of claim 1 further including seals disposed
between the flexible printed circuit board and tops and bottoms of
the battery cells.
10. The battery pack of claim 1 wherein the flexible printed
circuit board includes a plurality of substrates with the first
conductive traces on at least one of the substrates.
11. The battery pack of claim 10 wherein at least one of the
substrates has second conductive traces to which electronic
components are attached.
12. The battery pack of claim 11 wherein the electronic components
include at least one thermistor.
13. The battery pack of claim 12 wherein the electric components
include at least one thermistor associated with each battery cell,
each thermistor attached to one of the second conductive traces in
close proximity to the battery cell with which it is
associated.
14. The battery pack of claim 13 wherein the battery cells are
Lithium Ion battery cells and the electronic components include
electronic components configured as a temperature monitoring
circuit and electronic components configured as a cell balance
circuit.
15. The battery pack of claim 10 wherein the electronic components
include electronic components configured in at least one control
circuit.
16. The battery pack of claim 10 wherein the first and second
conductive traces are on separate substrates.
17. The battery pack of claim 10 wherein the flexible printed
circuit board includes respective holes that align with respective
ones of the battery cells and that extend through the substrates
and conductive traces to provide access to terminals of the battery
cells to welding tips.
18. The battery pack of claim 17 further including cell separator
plates in which the battery cells are disposed that hold the
battery cells in position for attachment of the flexible printed
circuit board to the battery cells.
19. The battery pack of claim 1 wherein the flexible printed
circuit board is attached to both tops and bottoms of the battery
cells.
20. The battery pack of claim 2 wherein the flexible printed
circuit board is attached to both tops and bottoms of the battery
cells, the electronic components configured in the at least one
control circuit disposed on a portion of the flexible printed
circuit board that extends between the tops and bottoms of the
battery cells.
21. A cordless power tool, comprising: a. a housing having a motor
disposed therein; and b. a battery pack coupled to the housing, the
battery pack including a battery pack housing with a plurality of
battery cells disposed therein interconnected by first conductive
traces on a flexible printed circuit board attached to the battery
cells.
22. The cordless power tool of claim 21 wherein the flexible
printed circuit board includes second conductive traces to which
electronic components are attached.
23. The cordless power tool of claim 22 wherein -the flexible
printed circuit board includes a plurality of substrates with the
first and second conductive traces on separate substrates.
24. The cordless power tool of claim 23 wherein the electronic
components include at least one thermistor.
25. The cordless power tool of claim 23 wherein the battery cells
are Lithium Ion battery cells, the electric components including at
least one thermistor associated with each battery cell with each
thermistor attached to one of the second conductive traces in close
proximity to the battery cell with which it is associated, the
electronic components also including electronic components
configured as a temperature monitoring circuit and electronic
components configured as a cell balance circuit.
26. The cordless power tool of claim 23 wherein the electronic
components include electronic components configured in at least one
control circuit.
27. The cordless power tool of claim 23 wherein the flexible
circuit board is attached to both tops and bottoms of the battery
cells.
28. The battery pack of claim 21 wherein the first conductive
traces includes pads that align with terminals of the battery
cells, the pads including slots through which connection tabs
extend, the connection tabs bonded to the battery cell terminals
and the pads.
29. The cordless power tool of claim 21 further including cell
separator plates in which the battery cells are disposed that hold
the battery cells in position for attachment of the flexible
printed circuit board to the battery cells.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. patent
application Ser. No. 10/963,367 filed on Oct. 11, 2004, which
claims the benefit of U.S. Provisional Application No. 60/510,123
filed on Oct. 14, 2003.
FIELD OF THE INVENTION
[0002] The present invention relates to battery packs, and more
particularly, to a battery pack having a plurality of battery cells
interconnected by a laminated plate structure or a flexible printed
circuit board.
BACKGROUND OF THE INVENTION
[0003] Cordless products which use rechargeable batteries are
prevalent throughout the workplace as well as in the home. From
housewares to power tools, rechargeable batteries are used in
numerous devices. Ordinarily, nickel-cadium or nickel-metal-hydride
battery cells are used in these devices. Since the devices use a
plurality of battery cells, the battery cells are ordinarily
packaged as battery packs. These battery packs couple with the
cordless devices and secure to the device. The battery pack may be
removed from the cordless device and charged in a battery charger
or charged in the cordless device itself.
[0004] Currently the cells in a battery pack are assembled by
holding them in a fixture and welding individual interconnect
straps between the contact points of cell pairs. This process
involves affixing and restraining each interconnect strap to a
single cell pair and resistance welding the strap onto the contact
points. After this strap is welded, the process is repeated
serially for the next cell. These straps are arranged to produce
strings of cells arranged in series and/or parallel configurations.
One of the difficulties with this process is that the interconnect
straps must be individually affixed and restrained during the
welding process. Another deficiency is that the welding process can
only be completed for one cell pair at a time.
SUMMARY OF THE INVENTION
[0005] In an embodiment of the invention, battery cells in a
battery pack are interconnected with a laminated plate structure
having non-conductive layers interspersed with conductive layers,
at least one of the conductive layers connected to the battery
cells to interconnect them.
[0006] In an embodiment of the invention, battery cells in a
battery pack are interconnected with a flexible printed circuit
board having conductive traces thereon that are attached to the
battery cells to interconnect them.
[0007] In an embodiment of the invention, a cordless power tool has
one or the other of the foregoing battery packs. In an embodiment
of the invention, the battery pack is a Lithium Ion battery pack
with the battery cells being Lithium Ion battery cells.
[0008] Further areas of applicability of the present invention will
become apparent from the detailed description provided hereinafter.
It should be understood that the detailed description and specific
examples, while indicating the preferred embodiment of the
invention, are intended for purposes of illustration only and are
not intended to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The present invention will become more fully understood from
the detailed description and the accompanying drawings,
wherein:
[0010] FIG. 1 is a side sectional view of a cordless power
tool;
[0011] FIG. 2 is an exploded assembly view of a laminated plate
structure interconnecting battery cells in a battery pack in
accordance with an embodiment of the invention;
[0012] FIG. 3 is a top view of the laminated plate structure of
FIG. 2;
[0013] FIG. 4 is a top view of a conductive element grid of the
laminated plate structure of FIG. 2;
[0014] FIG. 5 is a top view of a signal layer of the laminated
plate structure of FIG. 2;
[0015] FIG. 6 is a flow chart of a process to form the laminated
plate structure of FIG. 2;
[0016] FIG. 7 is a flow chart of interconnecting battery cells in a
battery pack with the laminated plate structure of FIG. 2;
[0017] FIG. 8 is a bottom view of a flexible printed circuit board
for interconnecting battery cells in a battery pack in accordance
with an embodiment of the invention;
[0018] FIG. 9 is a side perspective view of an interconnect tab of
the flexible printed circuit board of FIG. 8;
[0019] FIG. 10 is a side perspective view of an end connect tab of
the flexible printed circuit board of FIG. 8;
[0020] FIG. 11 is a side view, broken away, of the flexible printed
circuit board of FIG. 8 interconnecting battery cells in a battery
pack in accordance with an embodiment of the invention;
[0021] FIG. 12 is a side view of a variation of the flexible
printed circuit board interconnecting battery cells in a battery
pack in accordance with an embodiment of the invention;
[0022] FIG. 13 is a flow chart of forming the flexible printed
circuit board of FIG. 8 and using it to interconnect battery cells
of a battery pack in accordance with an embodiment of the
invention;
[0023] FIG. 14 is a top perspective view of a flexible printed
circuit board for interconnecting battery cells using a direct
connection of conductive traces of the flexible printed circuit
board to the battery cells;
[0024] FIG. 15 is a side view of the flexible printed circuit board
of FIG. 14 interconnecting battery cells;
[0025] FIG. 16 is a side perspective view of the flexible printed
circuit board of FIG. 14 interconnecting battery cells; and
[0026] FIG. 17 is a flow chart of forming the flexible printed
circuit board of FIG. 14 and using it to interconnect battery cells
of a battery pack in accordance with an embodiment of the
invention
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0027] The following description of the preferred embodiment(s) is
merely exemplary in nature and is in no way intended to limit the
invention, its application, or uses.
[0028] With reference to FIG. 1, a cordless device, such as a power
tool, is illustrated and designated with reference numeral 1. The
power tool 1 ordinarily includes a clam shell type housing 2. The
housing 2 includes a mechanism 3 to couple the housing 2 with a
battery pack 4. The cordless device 1 includes electrical elements
5 which couple with corresponding electrical elements 6 of the
battery pack 4. The device 1 includes a trigger 7 which is
activated for energizing a motor 8 provided within the housing 2,
as is well known in the art. Normally, a plurality of battery cells
9 are disposed within a housing 11 of battery pack 4. A controller
10 may be provided in housing 2 for controlling motor 8. Controller
10 may alternatively (or additionally) be disposed in battery pack
4 and may also be used for controlling the charge of battery pack
4, as well as its discharge.
[0029] In FIGS. 2 and 3, a laminated plate structure 200 is shown
for interconnecting a plurality of battery cells, such as battery
cells 9 in battery pack 4, and connecting the battery cells 9 to
external devices, such as electrical elements 6. Laminated plate
structure 200 includes a plurality of non-conductive or insulation
layers 202 with one or more "conductive layers" 204 sandwiched
between adjacent non-conductive layers 202. As used herein, the
term "conductive layer" means a layer of conductive elements
disposed in a plane.
[0030] In the embodiment shown in FIGS. 2 and 3, laminated plate
structure 200 includes five layers, three non-conductive layers 202
and two conductive layers 204. Non-conductive layers 202 may
illustratively be stamped from electrically non-conductive
material, such as Mylar, cardboard, or the like. One conductive
layer 204, designated with reference numeral 206 and which will be
referred to as power circuit layer 206, may illustratively provide
power circuit interconnections and the other conductive layer,
designated with reference numeral 208 and which will be referred to
as signal layer 208, may illustratively provide signal
interconnections.
[0031] Power circuit layer 206 includes a plurality of conductive
elements 210. (For clarity, only one of the conductive elements 210
is identified with the reference numeral 210 in FIG. 2.) Conductive
elements 210 may illustratively be conductive metal strips formed
such as by stamping them from a sheet of conductive metal, such as
nickel, plated steel, and the like. Conductive elements 210 may
illustratively be joined together for ease of handling conductive
layer 204 during assembly of laminated plate structure 200, such as
by connecting segments 212 as shown in FIG. 4. Connecting segments
212 may illustratively be formed along with conductive elements
210. For example, if conductive elements 210 are formed by stamping
them from a sheet of conductive metal then connecting segments 212
may be formed at the same time by stamping them from the sheet of
conductive metal.
[0032] Signal layer 208 includes a plurality of terminal pads 214
(only some of which are designated with the reference numeral 214
for clarity) having leads 218. Signal layer 208 may illustratively
be formed by stamping from a sheet of conductive material, such as
metal. It may also be formed as a printed circuit board using
conventional printed circuit board etching techniques, and may
illustratively be a flexible printed circuit board. Power circuit
layer 206 may also illustratively be a printed circuit board, such
as a flexible printed circuit board. In this regard, by forming
power circuit layer 206 as a printed circuit board etched only on
one side, it could act as both a conductive layer 204 and one of
the conductive layers 202. Similarly, forming by forming signal
layer 208 as a printed circuit board etched only on one side, it
too could act as both a conductive layer 204 and a non-conductive
layer 202.
[0033] Each non-conductive layer 202 may illustratively include a
plurality of holes 220 therein (only some of which are identified
with the reference numeral 220 for clarity.) Each hole 220, when
laminated plate structure 200 is affixed to battery cells 9, will
be disposed about a terminal 222 at one end of a battery cell 9.
(For clarity, only some of terminals 222 of battery cells 9 are
identified with the reference numeral 222.) Laminated plate
structures may illustratively be affixed to tops and bottoms of the
battery cells 9 of battery pack 4.
[0034] FIG. 6 is a flow chart of an illustrative method of
assembling laminated plate structure 200. At step 600, one or more
conductive layers 204 are disposed between adjacent non-conductive
layers 202 and at step 602, the non-conductive layers 202 and the
conductive layers 204 compressed together to form laminated plate
structure 200 and illustratively bonded together. Terminal pads 214
of signal layer 208 are illustratively centered in respective holes
220 in non-conductive layers 202 and conductive elements 210 of
power circuit layer 206 extend between respective adjacent holes
220 with an end disposed in axial spaced relation to those holes
220. In the embodiment shown in FIG. 2, laminated plate structure
200 has five layers, three non-conductive layers 202 with a
conductive layer disposed between adjacent non-conductive layers
202. It should be understood that laminated plate structure 200 can
have more or less than five layers but preferably will have an odd
number of layers with a non-conductive layer 202 providing a top
layer 224 and bottom layer 226 of laminated plate structure
200.
[0035] FIG. 7 is a flow chart of an illustrative method of
assembling laminated plate structure 200 to battery cells 9 to
interconnect the battery cells to each other and to electrical
elements 6. At step 700, a laminated plate structure 200 is placed
on the tops and the bottoms of battery cells 9. Holes 220 are
centered over terminals 222 of battery cells 9. A welding tip (not
shown), for example, the welding tip of a spot welder, is inserted
into each hole 220 having a conductive element 210 of power circuit
206 and/or terminal pad 214 disposed therein and presses them
against the terminal 222 of the battery cell 9 disposed in that
hole. The conductive element 210 and/or terminal pad 214 is then
welded to the terminal 222 of that battery cell 9. All welds may
illustratively be done simultaneously, individually, or in sequence
with two or more welds being done simultaneously. Simultaneously
with the welding, or after, the connecting segments 212 are broken,
such as by punching them using a punch press. In this regard, holes
228 (only some of which are shown for clarity) may be provided in
non-conductive layers 202 opening to connecting segments 212 to
facilitate the removal of connecting segments 212.
[0036] Conductive elements 210 connect the terminals 222 of two or
more adjacent battery cells 9 together to connect those battery
cells 9 in series or in parallel and terminal pads 214 provide
signal connections to positive and negative terminals of battery
cells 9. For example, if two adjacent cells are to be connected in
series, one cell is oriented with its positive terminal up and the
other cell is oriented with its negative terminal up. An end of a
conductive element 210 is welded to the positive terminal of the
one cell 9 and the other end welded to the negative terminal 22 of
the other battery cell 9. If two adjacent battery cells 9 are to be
connected in parallel, they are oriented with their positive
terminals up and a conductive element 210 welded to the positive
terminal of each such battery cell 9 and a conductive element 210
welded to the negative terminal of each such battery cell 9.
Similarly, if three or more battery cells 9 are to be connected in
parallel, they are oriented with their positive terminals up and a
conductive element 210 welded to the positive terminal of each such
battery cell 9 and a conductive element 210 welded to the negative
terminal of each such battery terminal 9. In this regard, these
conductive elements 210 would extend between the three or more
adjacent holes 220 that are centered about the terminals of such
battery cells 9. Also, at least one such conductive element may
illustratively be connected to a lead 230 and at least one such
conductive element may illustratively be connected to a lead 232,
which may in turn connected to electrical elements 6 (FIG. 1). From
this discussion, it should be apparent that conductive elements 210
are sized and arranged in power circuit layer 206 to provide the
desired interconnections of battery cells 9 to each other and to
electrical elements 6.
[0037] Also, while signal layer 208 in the embodiment shown in
FIGS. 2, 3 and 5 has a terminal pad 214 for each battery cell 9,
this is by way of example only and it should be understood that
signal layer 208 may illustratively have terminal pads 214 only for
those battery cells that require a signal connection. If for
example, the voltage of the battery pack 4 containing battery cells
9 is being monitored and no other parameter is being monitored,
signal layer 208 may have only two terminals pads, one for positive
and one for negative which would be welded to a positive and to a
negative terminal of the appropriate battery cells 9.
[0038] While in the embodiment shown in FIGS. 2 and 3, each
non-conductive layer 202 has a hole 220 for each battery cell 9, it
should be understood that each non-conductive layer 202 need have a
hole 220 only for those battery cells having terminals that will be
welded to a conductive element 210 and/or a signal terminal pad 214
by a weld tip extending through the hole 220.
[0039] In FIGS. 8-10, a flexible printed circuit board ("PCB") 800
is shown for interconnecting a plurality of battery cells, such as
battery cells 9 in battery pack 4, and connecting the battery cells
9 to external devices, such as electrical elements 6. Flexible PCB
800 includes a substrate 802 made of flexible material, such as
Mylar, having conductive traces 804 thereon. Conductive traces 804
include pads 806, which may illustratively be solder pads.
Substrate 802 has holes 810 therein disposed adjacent solder pads
806. There may illustratively be one hole 810 per battery cell 9
with holes 810 disposed in substrate 802 so that when substrate 802
is placed over battery cells 9, as described below, a hole 810 will
be axially aligned with a terminal 1100 of each battery cell 9.
Each solder pad 806 has a slot 808 therein for receiving a blade
900 of an interconnect tab 902 (FIG. 9) or a blade 1000 of an end
connect tab 1002, as applicable depending whether solder pad 806
interconnects adjacent battery cells 9 or is an end connection that
is connected to external elements, such as electrical elements 6.
Interconnect tabs 902 and end connect tabs 1002 are collectively
referred to herein as connection tabs. Blade 900 of interconnect
tab 902 extends generally normally from a body 904 of interconnect
tab 902. Opposed tabs 906 of body 904 extend outwardly on either
side of blade 900 and provide connection tabs or terminals,
referred to herein as connection pads 906. Blade 1000 extends
generally normally from a body 1004 of end connect tab 1002. Body
1004 provides connection tabs or terminals and which may also be
referred to herein as connection tabs 1004.
[0040] Referring to FIG. 13, flexible PCB 800 is formed as follows.
Conductive traces 804 are formed on substrate 802 in conventional
fashion at 1300. Control electronics may then be optionally
incorporated on PCB 800 to implement one or more control circuits.
These optional control circuits can utilize surface mount
components or through-hole components. The control circuits may
include balancing circuits, battery cell monitoring circuits,
and/or temperature monitoring circuits. Thermistors for sensing the
temperatures of cells 9 may also be directly assembled to PCB 800.
Blades 900 of interconnect tabs 902 and blades 1000 of end connect
tabs 1002 are inserted into slots 808 of respective solder pads 806
and then soldered to solder pads 806 at 1302, such as by wave
soldering or a similar method. Opposed tabs 906 of each
interconnect tab 902 extend over holes 810 that are adjacent either
side of the solder pad 806 to which the blade 900 of that
interconnect tab is soldered. Body 1004 of each end connect tab
1002 extends over the hole 810 that is adjacent the solder pad 806
to which the blade 1000 of that end connect tab 1002 is
soldered.
[0041] Continuing to refer to FIG. 13, at 1304 a resulting flexible
PCB 800 is then placed over the cells 9 of battery pack 4 with body
904 of interconnect tabs 902 and body 1004 of end connect tabs 1002
disposed between substrate 802 and battery cells 9. In this regard,
one flexible PCB 800 may illustratively be placed over the tops of
cells 9 and one flexible PCB 800 may be placed over the bottom of
cells 9. Cell separator plates 1102 (only one of which is shown in
FIG. 11), which may illustratively be made of a rigid
non-conductive plastic, are disposed at generally the top and
bottoms of battery cells 9 and have holes in which battery cells 9
are received. Cell separator plates 1102 hold battery cells 9 in
spaced relation to each other and in the proper position for
placement of flexible PCB 800(s). At 1306, connection pads 906 of
interconnect tabs 902 and connection pads 1004 of end connect tabs
104 are fastened to terminals 1100 of respective battery cells 9,
such as by welding in a manner similar to that described above with
respect to FIG. 2. Conductive traces 804 connect their solder pads
806 in the appropriate configuration so that the flexible PCB(s)
800 thus interconnects battery cells 9 in the desired
configuration, such as connecting the appropriate number of battery
cells 9 in series and/or in parallel to provide the desired voltage
and power, and provides connection points, illustratively at solder
pads 806 to which end connect tabs are soldered, to connect battery
pack 4 to external elements, such as electrical elements 6.
[0042] FIG. 12 shows a variation of flexible PCB 800, designated by
the reference numeral 800'. As shown in FIG. 12, substrate 802'
extends both along the top and bottom of battery cells 9 of battery
pack 4. A portion 1200 of substrate 802' that extends between the
top and bottoms of battery cells 9 may illustratively include an
electronic circuit with electronic devices thereon, such as
controller 10 for controlling battery pack 4 and/or motor 8.
[0043] Substrate 802 may also have a lead portion 1202 that extends
to external devices, such as electrical elements 6 and connects
thereto. Lead portion 1202 thus provides the lead connections
between battery pack 4 and external devices, such as electrical
elements 6.
[0044] In an embodiment of the invention, seals 1204 are provided
between substrate 802' of flexible PCB 800 and the tops and bottoms
of battery cells 9. Seals 1204 may illustratively be made of
synthetic foam or a plastic sheet and have adhesive layers on their
top and bottom surfaces to adhere them to battery cells 9 and
substrate 802' of flexible PCB 800'.
[0045] FIGS. 14-16 show the interconnection of a plurality of cells
9 using direct bonding of a high-current flexible PCB 1400 to
contact surfaces, such as terminals 1100, of cells 9. In this
regard, it should be understood that terminals 1100 may be flat
contact surfaces as opposed to projecting terminal elements. This
method is similar to the method just described and offers many of
the same benefits. The principal difference is that a direct bonded
connection is used instead of the connection tabs. This simplifies
assembly and provides better coupling between any included
temperature sensing thermistors, such as thermistors 1416, and the
cells 9 that are monitored with the thermistors 1416.
[0046] Flexible PCB 1400 includes one or more substrates 1402 made
of a flexible material, such as Mylar, having conductive traces
1404 and 1406 thereon. Where PCB 1400 has more than one substrate
1402, conductive traces 1404, 1406 may be placed on different ones
of the substrates 1402. Portions of the Mylar are removed during
fabrication of PCB 1400 to expose portions of the conductive traces
1404, shown at 1408. PCB 1400 has holes 1410 that extend through
all the substrates 1402 and the conductive traces 1404 thereon to
allow welding tips of resistance welding equipment to contact the
contact surfaces 1100 of the cells 9. Alternatively, non-resistance
welding methods, such as friction or ultrasonic welding, may be
used to bond traces 1404 to contact surfaces 1100 which allows
holes 1410 to be eliminated. Pads 1412 (only one of which is shown
in FIG. 14) for electronic components, shown representatively at
1414, may also be formed on PCB 1400 using standard manufacturing
techniques. As used herein, an electronic component is a component
used in an electronic circuit and includes both passive components,
such as resistors, capacitors, inductors, thermistors, and active
components, such as transistors, operational amplifiers and
integrated circuits. These pads 1412 can be placed in available
space on substrates 1402 and allows for the integration of various
electronic functions of the battery pack 4 by appropriate
configurations of these electronic components. Thermistors 1416 are
assembled onto these pads 1412 in positions in close proximity to
where PCB 1400 connects to the cells 9 to provide for more accurate
temperature readings from cells 9. The electronic components 1414
including thermistors 1416 are assembled onto PCB 1400 using
conventional wave soldering or similar methods.
[0047] To assemble PCB 1400 to cells 9, cell separator plates 1418
are placed on the tops and bottoms of the individual cells 9 to
hold the cells in position during assembly. PCB 1400 is then placed
over the tops of the cells 9 with the exposed areas 1408 aligned
with the contact surfaces 1100 of cells 9. A welding tip, such as
spot welding electrodes (not shown), are placed inserted through
one or more holes 1410 to contact a portion of the contact surface
1100 of the respective cell 9. A second spot welding electrode
contacts the exposed portion 1408 of trace 1404 and applies welding
current to the exposed portion 1408 to weld trace 1404 to the
contact surface 1100 of the cell 9. Exposed portion 1408 may also
be attached to contact surface 1100 of the cell 9 by soldering.
Conductive traces 1408 interconnect the battery cells 9 and the
substrate 1402 having conductive traces 1404 provides a power
circuit layer and the substrate 1402 having conductive traces 1406
provides a signal layer.
[0048] Referring to FIG. 17, flexible PCB 1400 is formed with one
or more substrate layers 1402 of flexible material with conductive
traces 1404, 1406 thereon. During this formation of PCB 1400, the
flexible material is removed around portions 1408 of conductive
traces 1404, 1406. It should be understood, however, that the
flexible material could be removed after PCB 1400 is formed with
one or more substrates 1402 conductive traces 1404, 1406 thereon.
The thermistors 1416 and any other of the electronic components
1414 are then assembled to pads 1412 of conductive traces 1404,
1406. PCB 1400 is then attached to cells 9.
[0049] In a variation, exposed portions 1408 of traces 1404 are
bonded to the contact surfaces 1100 of the cells 9 by conductive
adhesive. The adhesive is placed between the exposed portions 1408
and the contact surfaces 1100 on the tops or bottoms the cells 9.
PCB 1400 is then pressed and held against the cells 9 during the
cure phase. The same process is then used for attaching PCB 1400 to
the other side of cells 9. The assembly of PCB 1400 and cells 9 is
then placed in housing 11.
[0050] Flexible PCB 1400 advantageously provides a thinner package
than a standard printed circuit board as it is comprised of thin
conductive layers encapsulated in any insulating material, such as
Mylar. Using surface mount parts allows for low profile control
circuits. It also provides ease of manufacture in that all
temperature monitoring and balance circuitry is populated on
flexible PCB 1400 before flexible PCB 1400 is attached to cells 9.
Flexible PCB 1400 along with the control circuits in effect becomes
a "plug-in" module. Using all metal connections in the temperature
monitoring circuit (i.e., copper welded to can, surface mount
thermistors soldered to pads 1412) eliminates the need to glue the
thermistors 1416 in place or trying to detect temperature through
paper insulators. The flexible printed circuit board can be
extended, such as described with reference to FIG. 12, to terminate
at terminals for the battery pack eliminating the need for
additional wiring inside the battery pack. This may also eliminate
the need for paper insulation on the top and bottom of cells 9 in
that the Mylar covering on flexible PCB 1400 provides the needed
insulation.
[0051] The above discussed battery packs and techniques for
interconnecting battery cells in them can be advantageously used in
high voltage battery packs, such as when cells 9 are Lithium Ion
battery cells. The interconnections techniques described above can
handle the higher output of Li Ion battery pack. Also, in Li Ion
battery packs the temperature of each cell 9 should be individually
monitored. This is accomplished such as by the use of a thermistor
1416 for each cell 9 as discussed above with reference to FIGS.
14-16. Electronic components 1414 would be configured to provide a
temperature monitoring circuit using thermistors 1416 and
appropriate other electronic components, such as thermal fuses.
Electronic components 1414 would also be configured to provide a
cell balancing circuit and would illustratively include a surface
mount microprocessor and appropriate passive and active surface
mount devices.
[0052] The description of the invention is merely exemplary in
nature and, thus, variations that do not depart from the gist of
the invention are intended to be within the scope of the invention.
Such variations are not to be regarded as a departure from the
spirit and scope of the invention.
* * * * *