Abstract:
A framed lithium battery cell group includes a first frame member ( 20 ) and a second frame member ( 30 ). The frame members are locked together, clamping the lithium battery cell pack ( 10 ) on the seal edge surfaces ( 13, 16 ), thereby providing structural rigidity and protection from damage due to handling and vibration. Each of the frame members ( 20, 30 ) has multiple pins ( 25 ) and sockets ( 26 ) on the side opposite the clamping surface ( 33 ) to facilitate aligning and stacking multiple lithium battery cell pack and frame assemblies to form a lithium battery cell group ( 50 ). Each of the frame members ( 20, 30 ) include a buss bar capture feature ( 22, 32 ) having a bus bar ( 40 ) inserted therein for electrically connecting all of the terminals for a given lithium battery pack group to the buss bar ( 40 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     Not applicable.  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not applicable.  
       FIELD OF THE INVENTION  
       [0003]     The invention relates to battery group assembly.  
       BACKGROUND OF THE INVENTION  
       [0004]     Packaging lithium battery cells in a metallic case is known in the art as can be seen in U.S. Pat. No. 6,406,815. These metallic cases have the advantage of protecting the cells from handling and vibration damage. They are also dimensionally consistent, allowing for combining of multiple cases into a single large pack as disclosed in U.S. Pat. No. 6,368,743.  
         [0005]     However, the metallic cases are expensive to manufacture and each different configuration requires new dies to produce the various components and new tools to assemble those components. Consequently, techniques and materials for enclosing lithium battery cells in envelopes creating lithium battery cell packs have been developed, one type of which can be seen in U.S. Pat. No. 6,729,908. Unfortunately, these packages do not provide structural rigidity or protection from handling and vibration nearly as well as the metallic cases, nor can they be combined into consistently sized groups of cells because of the inherent variation in the thickness of a lithium battery cell pack.  
       SUMMARY OF THE INVENTION  
       [0006]     A cell frame clamps the packaging envelope of a lithium battery cell pack around the perimeter from opposing sides, creating a lithium battery pack and frame assembly. If the packaging envelope is of the folded type, the frame can clamp on the three seal edges of the packaging envelope and provide a concave feature on the fourth or bottom edge to cradle and protect the packaging envelope bottom edge. If the packaging envelope is manufactured from two separate pieces and therefore sealed on all four sides, the cell frame may be designed to clamp on all four seal edges. The frame members have a buss bar capture feature which holds a buss bar securely in place to facilitate mechanically and electrically connecting all of the terminals for a given lithium battery pack group to the buss bar.  
         [0007]     In another aspect of the present invention, the two frame members may be identical, thereby being manufacturable from a single mold cavity.  
         [0008]     In another aspect of the present invention the frame members have a pin and socket configuration on the side facing away from the clamping surfaces in order to mate and align with one or more additional lithium battery cell pack and frame assemblies to create a lithium battery pack group.  
         [0009]     In another inventive aspect, a housing is provided which encloses at least one cell group. The housing providing additional compressive force to the cell group. In one embodiment, the housing comprises a top and a bottom section, which are fastened together with fasteners. In an alternate embodiment, a pair of compression plates sandwich the cell group, the compression plates being fastened together to provide additional compressive force to the cell group. In yet another embodiment, at least one compression strap is provided. The compression strap wraps around the cell group to apply compressive stress.  
         [0010]     For purposes of simplicity, the term “cells” is used herein to mean unicells, bicells, or any other basic battery cell construction.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:  
         [0012]      FIG. 1  illustrates an exemplary prior art lithium battery cell enclosed in a packaging envelope making a lithium battery cell pack.  
         [0013]      FIG. 2  illustrates two frame members in position before clamping on the seal edges of a lithium battery cell pack.  
         [0014]      FIG. 3  illustrates a multiple lithium battery cell pack stack with anode and cathode buss bars, forming a lithium battery cell group.  
         [0015]     FIGS.  4 ( a ) and ( b ) show an exploded view of an external compressive force providing structure where the enclosure halves are separated and the enclosure halves after being fastened together using bolts, respectively.  
         [0016]      FIG. 5 ( a ) shows an internal compression system which utilizes compression plates and compression bolts, while  FIG. 5 ( b ) shows an another internal compression system which utilizes compression straps which wrap around the cell group.  
         [0017]      FIG. 6 ( a )-( d ) shows steps in an exemplary framed cell module assembly according to the invention.  
         [0018]      FIG. 7 ( a )-( d ) shows steps in an exemplary assembly process showing insertion of a plurality of framed cells according to the invention into an external protective case. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0019]     Referring initially to  FIG. 1 , a typical lithium battery cell pack is shown and is generally designated  10 .  FIG. 1  shows that the lithium battery cell pack includes an anode terminal  11 , a cathode terminal  12 , a packaging envelope  15 , side seal edges  13 , top seal edge  16 , and bottom edge  14 . The actual anode and cathode assembly (battery cell) is shown in hidden lines, being hidden inside the packaging envelope  15 .  
         [0020]     In a preferred embodiment, packaging envelope  15  is made from a single piece of polymer coated aluminum foil and is folded around the lithium battery cell at the bottom edge  14  of the cell, and subsequently sealed to itself on side seal edges  13  and top seal edge  16 . The packaging envelope could also be made from two or more separate pieces and subsequently sealed on all four edges.  
         [0021]      FIG. 2  shows first frame member  20  and second frame member  30  in position to be clamped on a lithium battery cell pack  10  shown disposed therebetween, according to an embodiment of the invention. Frame members  20  and  30  are preferably plastic frames, such as from readily moldable plastics. An exemplary readily moldable plastic that is relatively inexpensive and structurally sufficient is ABS plastic. If there is a requirement for a fire resistant plastic, a plastic having intumescent properties is preferably used, such as the elastomeric intumescent material disclosed in U.S. Pat. No. 6,809,129 to Abu-Isa.  
         [0022]     As first frame member  20  and second frame member  30  are pressed together thereby clamping on side seal edges  13  and top seal edge  16  of lithium battery cell pack  10 , snap tangs  31  engage with tang receivers  21  at multiple points around the periphery of the frame members  30  and  20 , respectively, to lock the frame members together, thus securing lithium battery cell pack  10  in the frame assembly. Tangs  31 , around the periphery, also serves as an a alignment features for the lithium cell as it is inserted into the cell frame. Both the first frame member  20  and the second frame member  30  include terminal clearance feature  37 , allowing clearance on the clamp surface  33  at the portion of the frame where the terminals  11  and  12  protrude from the packaging envelope so the clamp surface  33  will not be clamped on the terminals. In a preferred embodiment, the bottom edge  14  of lithium battery cell pack  10  is held in position by a trough which is formed by the two concave surfaces  34  coming together when the two frame members are locked together. This trough helps to protect the bottom edge  14  of the lithium battery cell pack  10 .  
         [0023]      FIG. 2  also shows anode terminal  11  and cathode terminal  12  in the straight position as they would be after the two frame members  20  and  30  are locked together.  FIG. 2  further shows buss bar capture feature  22  on the first frame member  20  and buss bar capture feature  32  on the second frame member  30 . The function of these features will be described below relative to  FIG. 3 .  
         [0024]     Referring now to  FIG. 3 , a multiplicity of lithium battery cell pack and frame assemblies are shown stacked together to make lithium battery cell group  50 . The frame structure facilitates this grouping by incorporating pin  25  and socket  26  features on the sides of the frame members opposite clamping surfaces  33 . Pin  25  and socket  26  secure adjacent framed cells to one another. The number of lithium battery cell packs in the group  50  depends on the desired electrical properties of the group.  
         [0025]      FIG. 3  further shows the terminal buss bars  40 , one for anodes and one for cathodes, located in the buss bar capture features  22 ,  32  shown in  FIG. 2 . In the preferred embodiment, the terminals  11 ,  12  of a first lithium battery cell pack and frame assembly are folded over into the terminal troughs  26 ,  36  and then the desired length of buss bars are inserted in the first lithium battery cell pack and frame assembly. The terminals  11  and  12  are then preferably ultrasonically welded to respective buss bars  40 . Subsequently, the terminals of a second lithium battery cell pack and frame assembly are folded over into the troughs  26 ,  36  and then the second lithium battery cell pack and frame assembly is placed on the first lithium battery cell pack and frame assembly in such a manner as to align the buss bars  40  with the buss bar capture feature of the second lithium battery cell pack and frame assembly and align pins  25  and sockets  26  of the first assembly with the corresponding sockets  26  and pins  25  of the second assembly. Of course, the geometry shown for the pin and socket feature is not meant to be limiting as numerous other mating shapes could be utilized to accomplish the same function. The cylindrical shapes shown are merely for illustrative purposes. As noted above, the terminals  11 ,  12  of the second assembly are then welded, such as ultrasonically welded, to respective buss bars  40 . This process continues until the desired number of lithium battery cell pack and frame assemblies are stacked together to make lithium battery cell group  50 .  
         [0026]     While lithium cell frames according to the invention surrounding the cells provides protection to cell group  50  during handling, once packaged inside the battery pack, additional compressive force beyond that provided by the snap features  25  and  26  or other interlocking features may not supply enough compressive force to grip the cells for certain intended applications. Relative movement between the frames and the cells can result in fractured terminals as they generally consist of delicate foil gauge metals.  
         [0027]     Thus, additional compressive clamping force may be required to clamp down on the lithium cells. A sufficient clamping force ensures little or no relative movement between the frames and the cells.  
         [0028]     The invention provides arrangements which provide additional compressive force to the cells comprising the cell group. In one embodiment, cell group  50  can be subsequently installed in an external protective case which can be sized to hold the group in such a way as to securely hold all of the lithium battery cell pack and frame assemblies in place, providing additional clamping force on the frame members, further securing the lithium battery cell packs. Alternatively, cell group  50  can be securely held by suitable internal structures.  
         [0029]     FIGS.  4 ( a ) and ( b ) show an exploded view of an external compressive force providing structure where the enclosure halves  410  and  420  are separated, while  FIG. 4 ( b ) shows the enclosure halves  410  and  420  fastened together using bolts, respectively. A typical material used in battery pack enclosures is a plastic. If additional strength is needed, additives to the plastic can be applied to obtain the needed physical characteristics. If the additives do not provide sufficient strength and stiffness to the enclosure, hybrid metal and plastic components can be manufactured to add additional strength.  
         [0030]     The (3) cell groups  50  are shown disposed on enclosure half  420  in  FIG. 4 ( a ). The buss bars are preferably attached to the center bussing structure as seen in  FIG. 4 ( a ) before the lid is closed and the compressive force is applied to the cell stacks. The bolted features  411  together with bolts  412  of the battery enclosure supply the desired force which minimizes or eliminates relative movement between the frames and the cells comprising cell group  50 . Although bolts  412  are shown in FIGS.  4 ( a ) and ( b ), other fasteners may be used.  
         [0031]     The battery pack enclosure shown in  FIG. 4 ( a ) contains 7 cell stacks connected in series. The remaining empty quadrant shown can be used to package battery pack accessory hardware, such as protection electronics, fuse(s), connector(s), and an internal wiring harness. The battery pack enclosure can also contain features to form fit around the cell stacks, and preferably also includes the same socket and pin features that will interface with the outside cells.  
         [0032]     Cell groups  50  can also be configured to include compression system hardware as part of the battery internal sub-assembly. In an alternative force providing structure shown in FIGS.  5 ( a ) and ( b ), an internal structure is used to supply the compressive force. This can be accomplished using a variety of structures.  FIG. 5 ( a ) shows an internal compression system which utilizes compression plates  510  and compression bolts (not shown) which fit in bolted features  511  which minimize or eliminate relative movement between the frames and the cells comprising cell group  50 .  FIG. 5 ( b ) shows an internal compression system which utilizes compression plates  510  in combination with compression straps  540 . Although two (2) straps  540  are shown in  FIG. 5 ( b ), a single strap or more than two ( 20  straps can be used.  
         [0033]     The above-described FIGS.  4 ( a ), ( b ) and  5 ( a ) and ( b ) are only examples some preferred compressive force supplying structures. Those having ordinary skill in the art will appreciate numerous variations of this inventive arrangement are possible.  
         [0034]      FIG. 6 ( a )-( d ) shows steps in an exemplary framed cell module assembly according to the invention having four (4) cells to form a 4 V module. In step (a), a first cell/frame assembly is placed over a buss bar. The weld tabs of the cell are preferably ultrasonically welded to the buss. In steps (b)-(d) successive cell/frame assemblies are placed over the buss bar, then each ultrasonically welded to the buss to form the 4 V framed module.  
         [0035]      FIG. 7 ( a )-( d ) shows steps in an exemplary assembly process showing insertion of a plurality of framed cells according to the invention into an external protective case. In  FIG. 7 ( a ), a first cell frame stack is inserted into the bottom half of the external frame.  FIG. 7 ( b ) shows four stacks inserted into the bottom half of the external frame.  FIG. 7 ( c ) shows the resulting structure after placement of a center buss plate on the four stacks shown in  FIG. 7 ( b ), and after an additional three stacks placed on the buss bar.  FIG. 7 ( d ) shows the resulting battery assembly after attaching all bussing bolts and the final bus bar. The assembly shown in  FIG. 7 ( d ) is the same as that shown inserted into the bottom frame half shown in  FIG. 4 ( a ).  
         [0036]     While the particular METHOD AND APPARATUS FOR SECURING BATTERY CELLS as herein shown and described in detail is fully capable of attaining the above-described objects of the invention, it is to be understood that it is the presently preferred embodiment of the present invention and thus, is representative of the subject matter which is broadly contemplated by the present invention, that the scope of the present invention fully encompasses other embodiments which may become obvious to those skilled in the art, and that the scope of the present invention is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather one or more.” All structural and functional equivalents to the elements of the above-described preferred embodiment that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it is to be encompassed by the present claims. Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. section 112, sixth paragraph, unless the element is expressly recited using the phrase “means for.”