Abstract:
A battery module according to the principles of the present disclosure includes a plurality of battery cells, a pair of sideplates, and a pair of endplates. The sideplates are disposed on opposite sides of the plurality of battery cells and the endplates are disposed at opposite ends of the battery module. The sideplates include a first mating portion and the endplates include a second mating portion that engages the first mating portion to provide an interference fit. The interference fit joins the sideplates and the endplates together and bands the plurality of cells together between the sideplates and the endplates.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/638,144, filed on Apr. 25, 2012. The disclosure of the above application is incorporated herein by reference in its entirety. 
     
    
     FIELD 
       [0002]    The present disclosure relates to batteries for vehicles and more specifically to battery modules including structures for retaining a plurality of electrochemical cells. 
       BACKGROUND 
       [0003]    The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
         [0004]    Electric vehicles (EVs), hybrid electric vehicles (HEVs) and plug-in HEVs use multiple propulsion systems to provide motive power. The propulsion systems include electric systems that receive power from a battery pack. A battery pack includes one or more battery modules, and a battery module includes a plurality of high-voltage cells (or batteries) such as lithium ion cells. The cells are electrically connected to one another and mechanically linked together to form a self-supporting assembly. 
         [0005]    Battery modules have been developed that include stainless steel endplates and sideplates. The endplates and sideplates are placed around a plurality of cells and are laser welded to each other to band the cells together. However, the cost and mass of stainless steel is relatively high, and the module is not serviceable once the endplates and sideplates are welded together. In addition, it is difficult to inspect the quality of the laser welds between the endplates and sideplates without destructive testing. 
       SUMMARY 
       [0006]    A battery module according to the principles of the present disclosure includes a plurality of battery cells, a pair of sideplates, and a pair of endplates. The sideplates are disposed on opposite sides of the plurality of battery cells and the endplates are disposed at opposite ends of the battery module. The sideplates include a first mating portion and the endplates include a second mating portion that engages the first mating portion to provide an interference fit. The interference fit joins the sideplates and the endplates together and bands the plurality of cells together between the sideplates and the endplates. 
         [0007]    Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0009]      FIG. 1  is a perspective view of a battery module with a terminal cover of the battery module disassembled from the remainder of the battery module; 
           [0010]      FIG. 2  is a perspective view of a portion of the battery module of  FIG. 1  within circle  2  shown in  FIG. 1 ; 
           [0011]      FIG. 3  is an exploded perspective view of the battery module of  FIG. 1 ; 
           [0012]      FIG. 4  is a perspective view of two battery modules aligned end-to-end and secured to a base tray; 
           [0013]      FIG. 5  is a perspective view of portions of the battery modules of  FIG. 4  rotated to illustrate ribs in endplates of the battery modules that nest together; 
           [0014]      FIG. 5A  is a section view of the battery modules of  FIG. 4  taken along line  5 A- 5 A shown in  FIG. 4 ; and 
           [0015]      FIG. 6  is a perspective view of a battery module with a portion of a sideplate of the battery module removed to show a retaining feature extending from the sideplate. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    A battery module according to the principles of the present disclosure may include high-strength steel endplates and plastic sideplates. The endplates and sideplates may include a snap feature that allows the endplates and sideplates to snap together, and thereby eliminate the need for fasteners or a mechanical joining process. The snap feature may be referred to as a detent, catch, or stop, and may include a ramped projection molded into the sideplates. The endplates may include flanges that wrap around the sideplates, and the flanges may define slots that receive the ramped projection. 
         [0017]    When the battery module is assembled, a person may position the sideplates on opposite sides of high-voltage cells using fixtures. The person may then slide the endplates over the sideplates. As the person slides the endplates over the ramped projections on the sideplates, the flanges of the endplates deflect outward until the ramped projections are received into the slots in the flanges. At that point, the flanges snap back to their original positions to lock the endplates in place. Once the snap features engage, the cells are held in place by compression and frictional sliding forces. 
         [0018]    The cost and mass of high-strength steel endplates and plastic sideplates is less than the cost and mass of stainless steel endplates and sideplates. In addition, joining the endplates and sideplates using snap features instead of laser welding the endplates to the sideplates is a simpler process that does not require equipment such as a robot and a laser. To further reduce cost, common endplates (front to back) and common sideplates (left to right) may be used. Overall, the cost and mass of the battery module may be approximately 40 percent less than that of a battery module which includes stainless steel endplates and sideplates that are laser welded together. 
         [0019]    Referring now to  FIGS. 1 through 3 , a battery module  10  includes a plurality of cells  12 , sideplates  14 , sideplate inserts  16 , endplates  18 , an interconnect assembly  20 , and a terminal cover  22 . The cells  12  may be high-voltage cells (or batteries) such as lithium ion cells. The cells  12  include first terminals  24  and second terminals  26 . The first terminals  24  may be positive and the second terminals  26  may be negative, or the first terminals  24  may be negative and the second terminals  26  may be positive. Although the battery module  10  is depicted as including twelve of the cells  12 , the battery module  10  may include additional or fewer cells. 
         [0020]    The cells  12  are compressed and banded together using the sideplates  14  and the endplates  18 . The sideplates  14  may be formed (e.g., molded) from plastic. The inserts  16  and the endplates  18  may be formed (e.g., stamped) from metal (e.g., high-strength steel). The sideplates  14  include stiffening ribs  28 , and the endplates  18  include stiffening ribs  30 . The inserts  16  are positioned between adjacent pairs of the ribs  28 . The ribs  28 ,  30  and the inserts  16  enable the sideplates  14  and the endplates  18  to restrict swelling or bowing of the cells  12  during service. 
         [0021]    The sideplates  14  further include ramped bases  32 , lips  34 , and ramped projections  36 . The ramped bases  32  may be used to secure the battery module  10  in the vertical direction. As shown in  FIG. 1 , when the battery module  10  is installed in a vehicle, the battery module  10  may be placed on a base tray  38  and clamp bars  40  may be placed over the ramped bases  32  and fixed to the base tray  38 . The clamp bars  40  may be fixed to the base tray  38  using fasteners  42 . The lips  34  on the sideplates  14  extend over the top of the cells to prevent the cells  12  from moving vertically during shock or vibration events. 
         [0022]    A cooling plate (not shown) may be used in place of the base tray  38 . The cooling plate may be electrically cooled or cooled using coolant. In addition, a thermal interface material such as thermal grease may be inserted between the cooling plate and the cells  12  to improve heat transfer therebetween. 
         [0023]    The endplates  18  include angled flanges  44  that wrap around the sideplates  14  when the endplates  18  are assembled to the sideplates  14 . The flanges  44  may extend perpendicularly from the remainder of the endplates  18 . The flanges  44  define slots  46  that receive the ramped projections  36  on the sideplates  14 . The endplates  18  may be coated with electrically insulating material using electrophoretic deposition. 
         [0024]    During assembly, a person may position the sideplates  14  on opposite sides of the cells  12  using fixtures. The person may then slide the endplates  18  over the sideplates  14 . As the person slides the endplates  18  over the ramped projections  36  on the sideplates  14 , the flanges  44  of the endplates  18  deflect outward until the ramped projections  36  are received into the slots  46  in the flanges  44 . At that point, the flanges  44  snap back to their original positions to lock the endplates  18  in place. 
         [0025]    As best shown in  FIG. 2 , the inserts  16  include angled tabs  47  that extend through the slots  46  in the endplates  18  when the inserts  16  are assembled to the sideplates  14  and the endplates  18 . The tabs  47  may extend perpendicularly from the remainder of the inserts  16 . The tabs  47  are held between the ramped projections  36  on the sideplates  14  and the slots  46  in the endplates  18 . Thus, the inserts  16  counteract tension forces that may be applied to the sideplates  14  as the cells  12  swell due to charging and/or aging. In addition, the ribs  28 , the ramped projections  36 , and the slots  46  engage the inserts  16  to hold the inserts  16  in place. 
         [0026]    The interconnect assembly  20  electrically connects the first terminals  24  and the second terminals  26  to one another. The interconnect assembly  20  includes bus bars  48 , a bus bar carrier  50 , a wiring harness  52 , and terminal nuts  54 . The wiring harness  52  includes a main connector  56  and terminal connectors  58 . 
         [0027]    During assembly, the bus bar carrier  50  is positioned on top of the cells  12  around the first terminals  24  and the second terminals  26 . The bus bars  48  are placed over the first terminals  24  and the second terminals  26 , and the terminal connectors  58  of the wiring harness  52  are placed over the bus bars  48 . The terminal nuts  54  are threaded onto the first terminals  24  and the second terminals  26  to secure the bus bars  48  and the terminal connectors  58  to the first terminals  24  and the second terminals  26 . 
         [0028]    The terminal cover  22  is then placed over the first terminals  24  and the second terminals  26  to electrically insulate the first terminals  24  and the second terminals  26 . 
         [0029]    Referring now to  FIGS. 4 ,  5 , and  5 A, the battery module  10  is shown positioned end-to-end with a battery module  10 ′ that is similar to the battery module  10 . The base tray  38  and the clamp bar  40  have been replaced with a base tray  38 ′ and a clamp bar  40 ′ that is sized to secure two battery modules positioned end-to-end. Although two battery modules are shown, a battery pack for a vehicle may include only one battery module or more than two battery modules positioned end-to-end. 
         [0030]    As best shown in  FIGS. 5 and 5A , the ribs  30 ,  30 ′ of the battery modules  10 ,  10 ′ are configured to allow the battery modules  10 ,  10 ′ to be placed end-to-end without losing space for the ribs  30 ,  30 ′. The ribs  30  of the endplate  18  are offset from the ribs  30 ′ of the endplate  18  so that the ribs  30 ,  30 ′ of the endplates  18 ,  18 ′ are nested together as shown in  FIG. 5A  when the battery modules  10 ,  10 ′ are positioned end-to-end. If the ribs  30 ,  30 ′ are not offset relative to one another as shown in  FIG. 5A , one of the endplates  18 ,  18 ′ may be rotated  180  degrees about the longitudinal axis X of the battery module  10  in the direction of arrow A to offset the ribs  30 ,  30 ′ as shown. 
         [0031]    Referring now to  FIG. 6 , the sideplates  14  may include one or more retaining features that retain auxiliary components such as a high-voltage cable, a wiring harness, a cell supervisory circuit (CSC), and/or cooling tubes or hoses.  FIG. 6  shows a retaining feature  60  that includes walls  62  extending inward from one of the sideplates  14  to secure a CSC  64 . The CSC  64  measures the open-circuit voltage of each of the cells  12  and includes an enclosure that houses a printed circuit board (PCB)  68  therein. 
         [0032]    The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical OR.