Abstract:
An interconnect device enables battery cells having terminals in the form of flexible tabs to be serially interconnected in a stack. The interconnect device comprises a relatively rigid substrate and at least two arrays of pins projecting from opposing first and second surfaces of the substrate. This enables the flexible tabs of the battery cell to be embedded in the pin arrays, providing a quick and easy means of fixing the tabs and enabling them to be interconnected to other cells in a stacked arrangement. A battery module formed from such a stack of cell assemblies is also disclosed.

Description:
[0001]    This application claims the benefits of U.S. Provisional Application No. 61/155,652, filed Feb. 26, 2009. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates generally to the field of batteries, and more particularly to battery modules formed from a plurality of battery cells. 
       BACKGROUND OF THE INVENTION 
       [0003]    The invention relates generally to the field of batteries, and more particularly to battery modules formed from a plurality of battery cells. 
       SUMMARY OF THE INVENTION 
       [0004]    According to a broad aspect of the invention, a cell interconnect device is provided for enabling battery cells having terminals in the form of flexible tabs to be serially interconnected in a stack. The interconnect device comprises a relatively rigid substrate and at least two arrays of pins projecting from opposing first and second surfaces of the substrate. This enables the flexible tabs of the battery cell to be embedded in the pin arrays, providing a quick and easy means of fixing the tabs and enabling them to be interconnected to other cells in a stacked arrangement. 
         [0005]    According to another aspect of the invention, a battery cell assembly is provided. The assembly includes a battery cell having positive and negative terminals and a flexible packaging. The packaging includes a fringe area where the packaging is sealed. The fringe area has a first and an opposing second side, and the positive and negative terminals are in the form of flexible tabs emanating from the fringe area between the first and second sides thereof. An interconnect device including a non-electrically conductive relatively rigid substrate is disposed about the fringe area. The substrate incorporates a first conductive trace adjacent the first side of the flexible packaging and a second conductive trace adjacent the second side of the flexible packaging. The first conductive trace terminates in a first array of pins projecting from the substrate away from the first side of the flexible packaging and the second conductive trace terminates in a second array of pins projecting from the substrate away from the second side of the flexible packaging. The substrate also includes at least one opening for passage of the tabs therethrough. Utilizing the interconnect device, the positive tab is embedded in one of the first and second pin arrays and the negative tab is embedded in the other of the first and second pin arrays. 
         [0006]    Preferably, the first conductive trace also terminates in a third array of pins projecting from the substrate away from the first side of the flexible packaging and the second conductive trace also terminates in a fourth array of pins projecting from the substrate away from the second side of the flexible packaging. The positive tab may be connected to one of (i) either the first or third pin arrays, and (ii) either of the second or fourth pin arrays, and the negative tab may be connected to the other of (i) and (ii). 
         [0007]    Preferably the substrate sandwiches the fringe area of the packaging, and even more preferably the substrate substantially surrounds the fringe area of the packaging. Also, the positions of the pins in the first and second pin arrays are preferably offset from one another. 
         [0008]    According to another aspect of the invention, a battery module is provided. The module includes a housing and a plurality of cell assemblies disposed in the housing in a stacked arrangement. Each cell assembly includes a battery cell having positive and negative terminals and a flexible packaging. The packaging includes a fringe area where the packaging is sealed, and the fringe area has a first and an opposing second side. The positive and negative terminals are in the form of flexible tabs emanating from the fringe area between the first and second sides thereof. An interconnect device including a non-electrically conductive relatively rigid substrate is disposed about the fringe area. The substrate incorporates a first conductive trace adjacent the first side of the flexible packaging and a second conductive trace adjacent the second side of the flexible packaging. The first conductive trace terminates in a first array of pins projecting from the substrate away from the first side of the flexible packaging and the second conductive trace terminates in a second array of pins projecting from the substrate away from the second side of the flexible packaging. The substrate also includes at least one opening for passage of the tabs therethrough. The positive tab is embedded in one of the first and second pin arrays and the negative tab is embedded in the other of the first and second pin arrays. The cell assemblies are serially connected together such that the positive tab from a given cell assembly in the midst of the stack electrically contacts the negative tab of a first neighboring cell assembly and the negative tab from the given cell assembly electrically contacts the positive tab of a second neighboring cell assembly. Terminals mounted on the housing, the terminals being respectively electrically connected to at least one positive tab and one negative tab in the stack. 
         [0009]    The first conductive trace preferably also terminates in a third array of pins projecting from the substrate away from the first side of the flexible packaging and the second conductive trace preferably also terminates in a fourth array of pins projecting from the substrate away from the second side of the flexible packaging. In this case, the positive tab of the given cell assembly may be connected to one of: (i) either the first or third pin arrays, and (ii) either of the second or fourth pin arrays, and the negative tab may be connected to the other of (i) and (ii). 
         [0010]    Preferably, the housing includes at least one coolant chamber and an inlet and outlet thereto for circulation of coolant. And the stack preferably includes heat conductive bodies such as trays inserted in between the cell assemblies that contacting the housing and cooling chambers thereof. 
         [0011]    A spring loaded plate is also preferably mounted in the housing to compress the stack, the stack being expandable in the housing by applying pressure of expansion against the plate. The plate inhibits separation of the stack as a result of the jerkiness experienced by a road-going vehicle. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The present invention will now be described by way of example only with reference to the attached drawings, in which: 
           [0013]      FIG. 1  is an axonometric view of the prior art flexible lithium polymer battery cell; 
           [0014]      FIG. 2  is an exploded axonometric view of a cell assembly according to a preferred embodiment of the invention; 
           [0015]      FIG. 3  is an axonometric view of the cell assembly; 
           [0016]      FIG. 3A  is an axonometric view of another cell assembly, intended to be serially connected with the cell assembly shown in  FIG. 3 ; 
           [0017]      FIG. 4  is an axonometric view of a stack of cell assemblies; 
           [0018]      FIG. 5  is a detail end view of a portion of the stack; 
           [0019]      FIG. 6  is a detail cross-sectional view of a portion of the stack, taken along line VI-VI in  FIG. 4 ; 
           [0020]      FIG. 7  is an axonometric view of a battery module according to the preferred embodiment, comprising the stack; 
           [0021]      FIG. 8  is a fragmentary axonometric view of the battery module, showing the stack with additional electrical interface components installed thereon; 
           [0022]      FIG. 9  is a fragmentary axonometric view of the battery module; and 
           [0023]      FIG. 10  is a detail cross-sectional view of the battery module taken along line X-X in  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]      FIG. 2  shows an exploded axonometric view of a cell assembly  20  according to a preferred embodiment of the invention. The cell assembly  20  includes the cell  10 , which features the flexible tabs  14 , 16  that emanate from a helm  19  of the cell  10  where the flexible packaging  12  is sealed to prevent the leakage of its contents. The helm  19  forms part of a fringe area  18  of the cell  10 , which comprises a relatively thin planar-like region  18   a  incorporating the helm  19 . The relatively thin planar-like region  18   a  flows into a relatively thicker slab portion  18   c  via a concave or tapered transition portion  18   b . The slab portion  18   c  constitutes the bulk of the cell  10 . It should be noted here that, because of its flexibility, the cell  10  may not present these exact shapes in use, but the packing  12  is generally cut, or there is sufficiently excess and loose material, to allow the packaging  12  to achieve such shapes in the fringe area  18 . 
         [0025]    Referring additionally to the assembly view of  FIG. 3 , the cell assembly  20  includes an electrical interconnect  21  which is attached to the cell  10  as discussed in greater detail below. The interconnect  21  is composed of two substantially identical connector halves  22 ,  22 ′ arranged in a mirrored orientation. One side of connector  22  (or  22 ′) features a flat surface  23 , and the opposing side of the connector  22  (or  22 ′) has a more complex shape featuring a rectangular bulbous portion  22   a  that flows into a thinner strip  22   c  via a convex or tapered transition portion  22   b . These portions of the connector  22  (or  22 ′) are shaped to correspondingly mate with the fringe area  18  of the cell  10  so that, when the interconnect  21  is installed, the cell assembly  20  has a substantially uniform thickness d 1  generally equivalent to the thickness of the slab portion  18   c  of the cell  10 . 
         [0026]    Each connector  22  (or  22 ′) has a non-conductive substrate, such as provided by plastic. The substrate is over-molded with a conductive trace  28  (shown in stippled lines). The trace  28  terminates in two groups of pins  32 ,  34  that project from the flat surface  23  of the connector  22  (or  22 ′) opposite the rectangular bulbous portion  22   a  thereof. In addition, each trace  28  also terminates in a pin  36  (seen best in  FIG. 3 ) that is exposed at a projection  37  formed in the connector  22  (or  22 ′). 
         [0027]    Each connector  22  (or  22 ′) also features a small front lip  39  (seen best in  FIG. 3 ). The conductive, flexible tabs  14 ,  16  of the cell  10  are brought out of the interconnect  21  in one ore more openings between the lips  39 . The two connector halves  22 ,  22 ′ may be adhesively bonded to the fringe portion  18  of the cell  18  to form the complete interconnect structure  21 . Additionally or alternatively, the lips  39  may provide a snap fit to attach the two connector halves  22 ,  22 ′ together. 
         [0028]    The cell assembly  20  also includes a shallow, preferably non-electrically conductive but heat conductive tray  40 . The tray include three short sidewalls  40   a ,  40   b ,  40   c , disposed remote from the interconnect  21 . The cell  10  is seated in the tray  40 . The cell  10  may be loosely disposed in the tray  40  or adhesively bonded thereto. 
         [0029]    To form an electrical connection to the interconnect  21 , one tab  16  is folded in first direction over lip  39  to contact pins  32  on one of the connector halves  22 . The pins  32  are embedded in and may pierce the tab  16 . The pins  32  have a footprint sized to accept the breadth of the tab  16 , to ensure maximum conductivity. The other tab  14  is folded over lip  39  in a second direction, opposite the first direction, to contact and be embedded in and/or pierced by the pins  34  on the other connector half  22 ′. The pins  34  also have a footprint sized to accept the breadth of the tab  14 , to ensure maximum conductivity. Thus, in the particular example illustrated in  FIG. 3 , tab  16 /pins  32  of the top connector  22  functions as a positive cell terminal, and tab  14 /pins  34  of the bottom connector  22 ′ functions as a negative cell terminal. The remaining pins  34  on the top connector half  22  and the pins  34  on the bottom connector half  22 ′ are not deployed in the illustrated cell  20 , but are deployed in adjacent cell assemblies as discussed next. 
         [0030]    The pins  32 ,  34  thus provide a quick and easy means to fix the tabs  14 ,  16 , and the interconnect substrate provides a stable platform for interconnecting other cell assemblies. 
         [0031]    Referring additionally to FIGS.  3 A and  4 - 6 , a plurality of cell assemblies  20  may be serially connected together to form a stack  50 . Starting from a first cell assembly  20 A, which is orientated as shown in  FIG. 3 , the next immediately adjacent cell assembly  20 B in the stack  50  is rotated 180 degrees (tray  40  excepted), with its positive tab  16  folded over pins  34  of connector  22  and its negative tab  14  folded over pins  34  of connector  22 ′ (seen best in  FIG. 3A ). As seen best in  FIG. 4 , the second cell assembly  20 B is connected to the first cell assembly  20 A such that the positive tabs/pins  16 / 32  of the first cell assembly  20 A contact the negative tab/pins  14 / 34  of the second cell assembly  20 A. A third cell assembly  20 C is orientated similar to the first cell assembly  20 A, and is electrically connected to the second assembly  20 B. Accordingly, the positive tabs/pins  16 / 34  of the second cell assembly  20 B contacts the negative tabs/pins  14 / 34  of the third cell assembly  20 C. A fourth cell assembly  20 D is orientated similar to the first cell assembly  20 A, and thus it will be apparent that the pattern of alternating cell orientations and tab folds continues in order to serially connect each of the cell assemblies  20  in the stack  50 . 
         [0032]    One tab  14 X on the bottom-most cell assembly  20 A and one tab  16  on the top-most cell assembly  20 Z in the stack  50  is not connected to any pins, but is brought out to function as leads into the stack  50 , as discussed in greater detail below. 
         [0033]    Referring particularly to the detail end and cross-sectional views of  FIGS. 5 and 6 , it will be seen that the pins  32  of cell assembly  201  also pierce the tab  14  of the immediately adjacent cell assembly  20 J and embed into the substrate of its interconnect  21 J. Similarly, the pins  34  of cell assembly  20 J pierce the tab  16  of cell assembly  201  and embed into the substrate of its interconnect  211 . In this manner, good electrical contact can be made, and a physical interlock may be accomplished between adjacent cell assemblies. However, this could cause a short circuit problem where two interconnects  21 J and  21 K abut one another in an interface that is not intended to have an conductive connections, such as between cell assembly  20 J and  20 K. For this reason, the arrays of the pins  32  and  34  on each connector half  22  (or  22 ′) are preferably offset from one another to prevent accidental pin to pin contact where it is not desired. 
         [0034]      FIG. 7  shows a battery module  100  comprising the stack  50 . The module  100  includes a face plate  98  that features a positive terminal  96  and a negative terminal  94 . The terminals  94 , 96  are conventional automotive battery terminals in which a bolt or screw  96   a  is turned to pinch a wire (not shown) between a washer  96   b  and a conductive plate  96   c . The module  100  also includes coolant inlet and outlet  92 ,  93  for the circulation of a coolant flowing within a water jacket  88 . The module  100  also includes a printed circuit board (PCB)  90  that interfaces with the stack  50 , as discussed in greater detail below. 
         [0035]      FIG. 8  shows a fragmentary view of the module  100 , with most of the walls and casing  88  removed from view. As seen in  FIG. 8 , the module  100  includes a first plate  85  that is disposed over the top-most cell assembly  20 Z in the stack  50 . A second plate  86  is mounted over the first plate  85  via a series of springs  84 . The second plate  86  abuts a frame  87  ( FIG. 7 ) formed at the top of the water jacket  88 , keeping the plates  85 ,  86  installed in the module  100 . The spring loaded plate  86  inhibits the separation of individual cell assemblies  20  due to road vibrations and jerkiness experienced by the vehicle, whilst enabling the stack  50  to expand and contract with changes in temperature. 
         [0036]    The PCB  90  is mounted to the stack  50  via the pins  36  exposed at the projections  37  of each interconnect  21 . The PCB preferably includes two components, a first linear board  90   a  which includes mounting sockets for connecting the pins  36 , and a second board  90   b  which is mounted in piggy-back fashion to the first board  90   a . The second board  90  is spaced from the first board  90   a  at a sufficient distance to allow the second board to be flush with the surface of the face plate  98 . 
         [0037]      FIG. 9  shows another fragmentary view of the module  100  including internal walls of the water jacket  88  but with the outside walls thereof removed from view. As will be seen in  FIG. 9 , the water jacket  88  includes left and right internal sidewalls  80   a ,  80   b , internal rear wall  80   c , and an internal bottom wall  80   d . These walls  80   a - d  are joined together and preferably form an integral part of the water jacket  88 , which resembles an open box less top and front, and thus provides coolant-holding chambers on the bottom, sides and rear of the module  100 . In order to maximize heat dissipation, the internal sidewalls  80   a ,  80   b  and internal rear wall  80   c  of the water jacket  88  abut the sidewalls of the trays  40  incorporated in the stack  50  to provide a heat conduction path to the cooling chambers. If desired, heat conductive grease may be applied between the sidewalls of the trays and the internal walls  80   a ,  80   b , and  80   c  to ensure good thermal contact and minimize friction against the water jacket  88  as the stack  50  contracts and expands. 
         [0038]    Referring additionally to the detail cross-sectional view of  FIG. 10 , the module  100  also includes a front wall  78  disposed in the front opening of the water jacket  88  and connected thereto. This illustration also shows how the stack  50  is connected to the negative terminal  94 . More particularly, the tab  14  of the lowermost cell assembly  20 A is not folded onto connector  22 ′, but instead is threaded through a slot  76  in the front wall  78  and sandwiched between the conductive plate  96   c  and the front wall  78 . A similar connection is formed for the positive terminal  96  and tab  16  of the uppermost cell assembly  20 Z. 
         [0039]    While the above description constitutes a plurality of embodiments of the present invention, it will be appreciated that the present invention is susceptible to further modification and change without departing from the fair meaning of the accompanying claims.