Abstract:
A battery pack for a vehicle may include a cell array defining an upper surface and a housing defining a raised portion extending along and above a length of the array such that the raised portion and upper surface define a vent manifold therebetween which may be configured to collect gases generated by the array. The housing may define a discharge opening configured to allow gases to exit the manifold. A pair of end plates may be disposed at opposing ends of the array. One of the end plates may define a pass through portion in at least partial registration with the discharge opening. An outlet tube may be configured to facilitate fluid communication between the vent manifold and exterior of the vehicle. The battery pack may also include spacers located between upper edges of adjacent cells and may be configured to prevent cooling gases from entering the vent manifold.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of application Ser. No. 13/312,323, filed Dec. 6, 2011, the disclosure of which is hereby incorporated in its entirety be reference herein. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates to battery packs of the type used in motor vehicles powered by a high-voltage electric motor. 
       BACKGROUND 
       [0003]    Depending on its type—e.g., the chemical reactions involved—a power supply such as a battery cell or a battery pack may emit a certain amount of gas during its working life. Providing a ventilation system to allow such byproduct gasses to escape the power supply may be desirable in certain applications, such as when a battery pack is used in a vehicle. To vent battery cells and battery packs carried aboard a wheeled motor vehicle (such as a car, truck, van, SUV, construction vehicle, etc.), an elaborate system may be required to capture the byproduct gases and exhaust them out of the vehicle. Adding to this design challenge is that, in a system of multiple cells in a stack or array, the tolerance stack-up of the cells with its neighboring cells may make it difficult to provide robust sealing for a byproduct gas venting system. 
         [0004]    Many battery packs require a cooling system to maintain proper system operation over the expected range of operating conditions and temperatures. In motor vehicles, cooling is commonly achieved by providing a flow of air through the pack so that it passes over/around the individual cells. The air may be drawn from the interior and/or the exterior of the vehicle, and may likewise be exhausted to the interior and/or exterior of the vehicle. If the battery pack cooling gas is exhausted into the vehicle interior, it is generally desirable for any byproduct gasses that may be emitted by the battery cells to be kept separate from the cooling gas stream so that the byproduct gasses do not enter the passenger compartment. 
       SUMMARY 
       [0005]    A battery pack includes a plurality of interleaved cells and spacers arranged to form a stack having a vent side on which each of the cells has a vent port. The battery pack also includes a pair of end plates disposed at opposing ends of the stack and a plurality of rails spanning between the end plates. The end plates and rails are configured to support and retain the stack. The battery pack also includes a cover including a wall spaced away from the vent side of the stack. The cover is sealed with the end plates and at least some of the rails such that the vent side of the stack, the end plates and the wall form a vent manifold adjacent to the vent side to receive vent gases from the cells. The pair of end plates may each include a surface defining a pass through opening. The vent manifold may be configured to direct the vent gases through the pass through openings of the end plates. An outlet tube may be secured to one of the end plates and at least in partial registration with the respective pass through opening and the outlet tube may be configured to deliver fluid from the vent manifold to an exterior of a vehicle including the battery pack. The vent manifold may be further configured to contain the vent gases. The spacers may define one or more extensions located between upper edges of adjacent cells and may be configured to prevent cooling gases from entering the vent manifold. The spacers may define one or more extensions located between upper edges of adjacent cells and may be configured to prevent vent gases from entering a cabin of a vehicle including the battery pack. 
         [0006]    A battery pack for a vehicle includes a cell array defining an upper surface and a housing defining a raised portion extending along and above a length of the array such that the raised portion and upper surface define a vent manifold therebetween configured to collect gases generated by the array. The housing also defines a discharge opening configured to allow gases to exit the manifold. The vent manifold may be further configured to contain the gases generated by the array. The battery pack may also include a pair of end plates disposed at opposing ends of the array. One of the end plates may define a pass through portion in at least partial registration with the discharge opening. The battery pack may also include a pair of rails arranged with the end plates to retain the cells therebetween. The rails and endplates may be configured to contact the housing and seal the vent manifold therebetween. The housing and the rails may be further configured to generate a compression force at the contact therebetween. The battery pack may also include an outlet tube configured to facilitate fluid communication between the vent manifold and exterior of the vehicle. The battery pack may also include spacers located between upper edges of adjacent cells and may be configured to prevent cooling gases from entering the vent manifold. The housing may further define the discharge opening such that gases exit the manifold when a pressure of the gases exceeds a predefined level. 
         [0007]    A battery pack assembly includes a battery cell array including a plurality of battery cells each defining a vent hole located on portions of the cells that define an upper surface of the array. The battery pack also includes a pair of end plates, at least one of which defines a pass through opening. The battery pack also includes inner and outer support rails arranged with the end plates to retain the cells therebetween and a cover. The cover defines a raised portion extending along a length of the array and above the upper surface, a center portion configured to contact the inner support rail, an outboard portion configured to contact the outer support rail, and a discharge opening. The cover portions and rails are arranged to define a sealed chamber therebetween such that gases exiting the vent holes pass through the chamber en route to the pass through opening and discharge opening. The center portion, outboard portion, and the rails may be further configured to generate a compression force at the contact therebetween. The battery pack may also include an outlet tube secured about the discharge opening and configured for fluid communication with an exterior of the vehicle. The pass through opening and discharge opening may be in at least partial registration with one another. The chamber may be further configured to contain the gases exiting the cells. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a perspective, partially exploded view of a battery pack in accordance with a disclosed embodiments; 
           [0009]      FIG. 2  is a perspective section view of the battery pack of  FIG. 1 , showing the installation of a bridging bar joining the two arrays of the battery pack; 
           [0010]      FIG. 3  is a cross-sectional view showing additional features of the bridging bar and installation of  FIG. 2 ; and 
           [0011]      FIG. 4  is another cross-sectional view of the bridging bar installation of  FIGS. 2 and 3 . 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. 
         [0013]    As shown in  FIG. 1 , a battery pack in accordance with an embodiment of the invention includes a housing made up of a base  10  and a cover  12  that is shown removed to expose the interior of the battery pack. The battery pack interior may be divided into an electronics section  14  and a battery cell section  16 . The battery pack is adapted for use in an automotive vehicle. 
         [0014]    Battery cell section  16  includes two generally parallel arrays  20   a,    20   b  each of which comprises a plurality of voltaic cells  22 . The voltaic cells  22  of each array  20   a,    20   b  are supported in a linear arrangement by a chassis which may, for example, comprise inner and outer support rails  24   a,    24   b  connected at either end to end plates  25 . Spacers  26  (best seen in  FIG. 3 ) may be located between adjacent voltaic cells  22  to allow a flow of cooling gas, usually ambient air, to pass. Spacers  26  may be integrated with the voltaic cells  22  or may be separate components assembled to the cells when the arrays are built up. Spacers  26  may also be utilized as and/or combined with mounting brackets to retain cells  22  in position relative to support rails  24   a,    24   b  and to adjacent cells. 
         [0015]    Seals are provided between the upper edges of adjacent pair of cells  22  within each array. In the depicted embodiment, portions of spacers  26  adjacent the upper edges of cells  22  act as seal. 
         [0016]    When cover  12  is fastened to base  10  to enclose battery cell section  16 , a center portion  12   a  of the cover seals against the top surfaces of inner support rails  24   a.  In a similar fashion, outboard portions  12   b  of the cover seal against the top surfaces of outer support rails  24   b.  These four linear seals combine with the seals between the upper edges of adjacent cells  22  to form a sealed cooling chamber below the upper surfaces of the two arrays  20   a,    20   b.  Clearance is provided between the side walls of cover  12  and the outboard edges of cells  22  (beneath outer rails  24   b ) so that cooling gas is able to flow generally horizontally between cells. 
         [0017]    The surfaces of cells  22  that face one another within each array (the vertical surfaces as viewed in the present figures) are adapted to enable heat transfer between the cells and the cooling gas, as is well known in the art. In  FIG. 1 , flow arrows F indicate a possible direction of the cooling flow. One or more fans or other gas movement devices (not shown) may be provided to force cooling gas through the battery pack, and/or ram air from movement of the vehicle may be used to induce the cooling flow. If air is used as the cooling gas, the air may come from exterior to the vehicle and/or from within the interior of the vehicle. Some or all of the cooling gas exiting the battery pack may be returned to the vehicle interior for climate control purposes, and/or some may be exhausted exterior of the vehicle. 
         [0018]    Cover  12  further comprises two raised portions  12   c,    12   d  located directly above the respective arrays  20   a,    20   b  when the cover is attached to base  10 . Raised portions  12   c,    12   d  sealingly cover the upper surfaces of arrays  20   a,    20   b  to define a pair of vent chambers or manifolds  38   a,    38   b  (see  FIG. 2 ) extending along and above the length of the respective arrays. Since vent holes  32  are located in/on the portions of cells  22  that form the upper surfaces of arrays  20   a,    20   b,  any byproduct gasses issuing from the vent holes will be contained by vent manifolds  38   a,    38   b.    
         [0019]    As best seen in  FIG. 2 , each voltaic cell  22  has a positive terminal  28 , a negative terminal  30 , and a vent hole  32 . Bus-bars, wires, or other electrically conductive connectors (not shown) interconnect the appropriate terminals of adjacent battery cells  22  so that the cells within each array  20   a,    20   b  are connected in electrical series, as is well known in the art. 
         [0020]    In addition to connecting the cells within each array  20   a,    20   b  in series, it may be necessary for the two arrays to be connected in series to achieve a desired voltage level for the battery pack. In this case, a terminal of a cell in array  20   a  is connected with a terminal of a cell in the other array  20   b  having the appropriate (opposite) polarity. This connection may be made by a bridge bar  36  extending between the inboard terminal (closest to the center-line of battery pack dividing the two arrays) at the extreme end of first array  20   a,  and the adjacent inboard terminal of array  20   b.    
         [0021]    During some abnormal operating conditions, such as overheating, the voltaic cells  22  may generate a gaseous byproduct. To prevent an undesirable pressure buildup within the cells, any such byproduct gases are allowed to escape from the cells through vent holes  32 . It is generally desirable that any byproduct gases be exhausted outside of the vehicle rather than being allowed to enter the interior of the vehicle. If the cooling gas circulating through the battery arrays is returned to the vehicle interior, as is commonly the case, this dictates that the byproduct gases must be kept separate from the cooling gas flow. This may be achieved by providing gas-proof seals at appropriate locations in the vicinity of the tops of the cells  22  so that the cooling gas is kept below the upper surface of battery arrays  20   a,    20   b  and a separate manifold is defined above the arrays for collecting any byproduct gases issuing from vent holes  32 . 
         [0022]    Center section  12   a  of the cover seals against the top surfaces of inner support rails  24   a  when the cover is attached to base  10 . In a similar fashion, outboard portions  12   b  of the cover seal against the top surfaces of outer support rails  24   b.  Raised portions  12   c,    12   d  are located directly above the respective arrays  20   a,    20   b  and define first and second vent manifolds  38   a,    38   b  (see  FIG. 2 ) extending along the length of the respective arrays above the voltaic cells  22  to receive any byproduct gasses issuing from vent holes  32 . A tunnel  50  extends between raised portions  12   c,    12   d  and connects the first and second manifolds  38   a,    38   b.  Seals or gaskets  42  may be provided at appropriate locations between cover  12 , support rails  24   a,    24   b  and end plates  25  as necessary to substantially seal the interior of battery pack from its environment. 
         [0023]    A bridge bar  36  connects terminal  28  of the end-most cell in array  20   a  with terminal  30  of the adjacent cell in array  20   b.  Bridge bar  36  comprises a conductive bar  44  (preferably made from copper, aluminum, or other material having good electrical conductivity) and a sealing portion  46  covering the central portion of the conductive bar. Sealing portion  46  may completely surround the center section of conductive bar  44 , as shown, or it may be disposed only at locations where sealing contact is required. Bridge bar  36  may be secured to terminals  28 ,  30  by clips or nuts (not shown) which fit over the top of the terminals. When in the bridging position, sealing portion  46  covers any gap that may exist between inner support rails  24   a  and may have a rib  46   a  projecting downwardly into the gap as shown in  FIG. 4 . 
         [0024]    Sealing portion  46  is preferably made of a resilient material that will achieve an effective gas seal when compressed, such as a polymer or synthetic rubber. Sealing portion  46  may be efficiently formed around the conductive bar  44  by an over-molding process. 
         [0025]    Tunnel  50  is located on cover  12  so as to be positioned over bridge bar  36  to provide clearance for the bar, and also provides a passage through which any gases collecting in first manifold portion  38   a  may flow into the second manifold portion  38   b.  Tunnel  50  may be formed as a part of (integrally with) cover  12 , as a single sheet metal stamping or molded plastic part, for example. Alternatively, tunnel  50  may be fabricated as a separate piece and assembled to cover  12  by welding, adhesive, or a joining technique appropriate for the materials used. 
         [0026]    As best seen in  FIG. 4 , bridge bar sealing portion  46  has flanges  46   b  extending outward from conductive bar  44 . Flanges  46   b  span a width greater than the width of tunnel  50  so that the sealing portion effectively seals off the tunnel from the cooling gas chamber below. Extra seals may be provided, if necessary, in the vicinity of sealing portion  46 , for example, a bead seal  52  disposed above flange  46   b  as shown in  FIG. 4 . 
         [0027]    A vent outlet tube  54  communicates with vent manifold  38   b  so that any byproduct gases generated by the cells of either array  20   a,    20   b  can escape and prevent an undesirable pressure increase inside battery pack. The gases are preferably vented outside of the vehicle via outlet tube  54 . 
         [0028]    While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.