Abstract:
A battery module for enclosing at least one battery cell includes a cooling plate. At least one compressible pad is arranged on the cooling plate. The at least one compressible pad has a first surface in contact with the cooling plate and a second surface opposite the first surface arranged to contact the at least one battery cell. A compression limiting device is arranged adjacent to the at least one compressible pad. The compression limiting device has a first surface facing the cooling plate and a second surface opposite the first surface arranged to contact the at least one battery cell. A compressibility of the compression limiting device is less than a compressibility of the at least one compressible pad.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/640,080 filed on Apr. 30, 2012. The disclosure of the above application is incorporated herein by reference in its entirety. 
     
    
     FIELD 
       [0002]    The present disclosure relates to battery packs for vehicles, and more particularly to battery packs including structures for retaining a plurality of battery 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]    Battery systems may be used to provide power in a wide variety of applications. Exemplary transportation applications include hybrid electric vehicles (HEVs), electric vehicles (EVs), heavy duty vehicles (HDVs) and vehicles with 42-volt electrical systems. Exemplary stationary applications include backup power for telecommunications systems, uninterruptible power supplies (UPS), and distributed power generation applications. 
         [0005]    A battery system may include a battery pack that includes one or more battery modules or subpacks that are connected in series and/or in parallel. Each of the battery modules may include one or more high-voltage battery cells that are electrically connected in parallel and/or in series and mechanically linked together to form a self-supporting assembly. Example battery cells include nickel metal hydride (NiMH) cells, lead-acid cells, lithium ion cells, and other types of battery cells. 
         [0006]    The battery modules may include endplates and sideplates. The endplates and sideplates are placed around a plurality of cells to form an enclosure to band the cells together. One or more of the battery modules may be arranged on a cooling plate within the battery pack. 
       SUMMARY 
       [0007]    A battery module for enclosing at least one battery cell includes a cooling plate. At least one compressible pad is arranged on the cooling plate. The at least one compressible pad has a first surface in contact with the cooling plate and a second surface opposite the first surface arranged to contact the at least one battery cell. A compression limiting device is arranged adjacent to the at least one compressible pad. The compression limiting device has a first surface facing the cooling plate and a second surface opposite the first surface arranged to contact the at least one battery cell. A compressibility of the compression limiting device is less than a compressibility of the at least one compressible pad. 
         [0008]    A method for assembling a battery module for enclosing at least one battery cell includes arranging at least one compressible pad arranged on a cooling plate, the at least one compressible pad having a first surface in contact with the cooling plate and a second surface opposite the first surface arranged to contact the at least one battery cell, and arranging a compression limiting device adjacent to the at least one compressible pad. The compression limiting device has a first surface facing the cooling plate and a second surface opposite the first surface arranged to contact the at least one battery cell. A compressibility of the compression limiting device is less than a compressibility of the at least one compressible pad. 
         [0009]    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 
         [0010]    The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0011]      FIG. 1  is a functional block diagram of an electric vehicle including a battery pack according to the principles of the present disclosure; 
           [0012]      FIG. 2  illustrates a battery module according to the principles of the present disclosure; 
           [0013]      FIGS. 3A and 3B  illustrate a battery module including a compression limiting device according to the principles of the present disclosure; 
           [0014]      FIG. 4  illustrates a compression limiting device according to the principles of the present disclosure; and 
           [0015]      FIG. 5  illustrates a method of assembling a battery module including a compression limiting device according to the principles of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Referring now to  FIG. 1 , an electric vehicle  100  includes a battery pack  104  and an electric vehicle control module (EVCM)  108 . The battery pack  104  includes one or more battery modules  112 , each including one or more battery cells, and a battery control module  116 . The battery control module  116  controls various functions of the battery pack  104  and monitors and collects various characteristics of the battery pack  104 . For example, the battery control module  116  monitors characteristics including, but not limited to, a voltage, a current, and a temperature associated with the battery pack  104 . The battery control module  116  may determine performance variables of the battery pack  104  based on the characteristics. For example only, the battery control module  116  may estimate a state of charge (SOC) of the battery pack  104  based on the voltage, current, and temperature of the battery pack  104 . 
         [0017]    The battery control module  116  may initiate heating and/or cooling of the battery pack  104  based on the temperature. For example, a coolant system  120  may provide liquid coolant that flows through the battery pack  104  to heat and cool the battery pack  104 . The coolant system  120  may include a heater  124  that heats the coolant when the temperature of the battery pack  104  is less than a low temperature threshold, and an air conditioner/compressor  128  that cools the coolant when the temperature of the battery pack  104  is greater than a high temperature threshold. 
         [0018]    The battery control module  116  communicates with battery charger  132 . The battery charger  132  charges the battery pack  104  and may include a user interface (not shown) for providing visual indications of the condition of the battery pack  104  (e.g., the SOC of the battery pack  104 ). The battery charger  132  includes a plug  136  that interfaces with a power source (not shown) to provide charging power to the battery pack  104  via the battery charger  132 . 
         [0019]    The EVCM  108  communicates with the battery pack  104  and the battery control module  116  to control various functions of the vehicle  100 . For example, the EVCM  108  receives a voltage  140  from the battery pack  104 . Conversely, the EVCM  108  receives information from the battery control module  116  related to, for example only, the monitored characteristics of the battery pack  104  and functions of the battery control module  116 , the coolant system  120 , and the battery charger  132 . 
         [0020]    The EVCM  108  controls a motor  144  of the vehicle  100  via a power inverter module (PIM)  148 . The PIM  148  converts a direct current (DC) voltage (e.g., the voltage  140 ) to an alternating current (AC) voltage  152  and provides the AC voltage  152  to the motor  144 . The motor  144  provides rotational force to drive wheels (not shown) of the vehicle  100 . The EVCM  108  may communicate with a user interface module  156  to indicate a status of the vehicle  100  (e.g., a status of the battery pack  104 ). For example, the user interface module  156  may indicate that the vehicle  100  should be plugged in to charge the battery pack  104 . 
         [0021]    Referring now to  FIG. 2 , an example battery module  200  (e.g., the battery modules  112  as shown in  FIG. 1 ) includes a plurality of cells  204 , sideplates  208 , and endplates  212 . The cells  204  may be high-voltage cells (or batteries) such as lithium ion cells. The cells  204  include first terminals  216  and second terminals  220 . The first terminals  216  may be positive and the second terminals  220  may be negative, or the first terminals  216  may be negative and the second terminals  220  may be positive. Although the battery module  200  is shown as including six of the cells  204 , the battery module  200  may include more or less of the cells  204 . 
         [0022]    The cells  204  are compressed and banded together using the sideplates  208  and the endplates  212 . The sideplates  208  may be formed (e.g., molded) from plastic or formed (e.g., stamped) from metal (e.g., high-strength steel. The endplates  212  may also be formed from plastic or metal. The sideplates  208  and the endplates  212  include stiffening ribs or darts  224 . The ribs  224  enable the sideplates  208  and the endplates  212  to restrict swelling or bowing of the cells  204  during service. 
         [0023]    The sideplates  208  further include ramped bases  228 . The ramped bases  228  may be used to secure the battery module  200  in a vertical direction. As shown in  FIG. 1 , when the battery module  200  is installed in a vehicle, the battery module  200  may be placed on a base tray  232  and clamp bars  236  may be placed over the ramped bases  228  and fixed to the base tray  232 . The clamp bars  236  may be fixed to the base tray  232  using fasteners  240 . 
         [0024]    A cooling plate  244  may be arranged between the battery module  200  and the base tray  232 . In some implementations, the cooling plate  244  may be used in place of the base tray  232 . The cooling plate may be electrically cooled or cooled using coolant. In addition, a thermal interface material (not shown in  FIG. 2 ; described in more detail in  FIG. 3 ) such as one or more elastomeric (e.g., compressible) pads may be inserted between the cooling plate  244  and the cells battery module  200  to improve heat transfer between the cells  204  and the cooling plate  244  and to protect the contact interface for a particle that could create an isolation loss. 
         [0025]    When the battery module  200  is compressed in a vertical direction toward the cooling plate  244 , the thermal interface material is compressed. A compression limiting device according to the principles of the present disclosure is arranged between the elastomeric pads, and between the battery module  200  and the cooling plate  244 , to limit an amount the thermal interface material is compressed. 
         [0026]    Referring now to  FIGS. 3A and 3B , a side view of a battery module  300  including battery cells  304  is shown. The cells  304  are arranged on a cooling plate  308 . A thermal interface material such as a plurality of elastomeric pads  312  is arranged between the cells  304  and the cooling plate  308 . The pads  312  are thermally conductive and electrically insulative to electrically isolate the cells  304  from the cooling plate  304  while enabling heat transfer from the cells  304  to the cooling plate  308 . 
         [0027]    When the battery module  300  is compressed in a downward vertical direction toward the cooling plate  308 , the cells  304  compress the pads  312  to maximize thermal contact between the cells  304  and the pads  312 . Excessive compression of the pads  312  may cause excessive wear on the pads  312 . Further, waste particles from manufacturing processes and regular use may interfere with the cells  304  and/or the pads  312 . For example, waste particles between bottom edges of the cells  304  and the cooling plate  308  may cause abrasive contact with the bottom edges of the cells  304 . The abrasive contact may cause excessive wear on an electrically insulative coating on the cells  304 . 
         [0028]    Accordingly, a compression limiting device  316  is arranged between the pads  312 , and between the cells  304  and the cooling plate  308 . The compression limiting device  316  limits an amount that the cells  304  may compress the pads  312  toward the cooling plate  308 . The compression limiting device  316  is significantly less compressible than the pads  312 , and accordingly may be formed (e.g., molded) from high density polypropylene or another suitably rigid, thermally conductive, and electrically insulative material. 
         [0029]    As shown in  FIG. 3A , the battery module  300  is shown without downward compression of the cells  304  toward the cooling plate  308 . Accordingly, a gap  320  is formed between the compression limiting device  316  and the cooling plate  308 . Prior to compression of the cells  304  in the downward direction, a distance between the cells  304  and the cooling plate  308  is A, which may correspond to an uncompressed thickness of the pads  312 . A distance between the cooling plate  308  and the compression limiting device  316  is B. 
         [0030]    As shown in  FIG. 3B , the battery module  300  is shown after the cells  304  are compressed toward the cooling plate  308 . The gap  320  is eliminated or reduced, and the distance between the cells  304  and the cooling plate  308  is now approximately a thickness of the compression limiting device  316 . In other words, the compression of the cells  304  toward the cooling plate  308  compresses (and reduces the thickness of) the pads  312  and displaces the compression limiting device  316  toward the cooling plate  308  to eliminate the gap  320 . When the compression limiting device  316  contacts the cooling plate  308 , the non-compressive properties of the compression limiting device  316  prevent further movement of the cells  304  toward the cooling plate  308  and prevent further compression of the pads  312 . Accordingly, a post-compression distance D between the cells  304  and the cooling plate  308  corresponds approximately to a thickness of the compression limiting device  316  (where A−B=D), which is approximately equal to a post-compression thickness of the pads  312 . 
         [0031]    The thickness of the compression limiting device  316  may be selected according to a desired maximum allowable particle size (e.g., allowable according to manufacturing tolerances) in the battery module  300  between the cells  304  and the cooling plate  308 . In other words, the thickness of the compression limiting device  316  is selected such that a post-compression distance D between the cells  304  and the cooling plate  308  (and, correspondingly, the post-compression thickness of the pads  312 ) is greater than or equal to the maximum allowable particle size. As a result, the compression limiting device  316  prevents the cells  304  from being compressed sufficiently close to the cooling plate  308  to cause contact with any waste particles in the battery module  300 . Before and/or after compression, a conforming foam seal  324  may be applied around a perimeter of the cells  304 , the compression limiting device  316 , and the cooling plate  308 . 
         [0032]    The compression limiting device  316  increases a thermally conductive contact area between the cells  304 . For example, an entire bottom surface of each of the cells  304  may be in thermally conductive contact with one of the pads  312  and adjacent portions of the compression limiting device  316 . For example only, a width of portions of the compression limiting device  316  between the pads  312  may be greater than a distance between flat contact surface portions  328  of adjacent ones of the cells  304 . As shown, bottom portions of the cells  304  may have rounded corners  332 . Accordingly, the width of the compression limiting device  316  should be large enough to extend beyond the rounded corners  332  of adjacent cells  304  to ensure contact with respective flat portions  328  of the adjacent cells  304 . A width of the pads  312  may be selected such that a surface area of each one of the compressed pads  312  is a predetermined minimum size with respect to a total contact area of the flat portions of the cells  304 . For example only, the surface area of each one of the compressed pads  312  is at least 70% of the total contact area of the cells  304 . 
         [0033]    Referring now to  FIG. 4 , a top-down view of an example compression limiting device  400  is shown. Pads  404  are formed on a cooling plate  408 . A foam seal  412  may or may not be applied around a perimeter of the compression limiting device  400 . As shown, the compression limiting device  400  is contiguously formed as a single element from thermally conductive and electrically insulative material. However, in other implementations, the compression limiting device  400  may include a plurality of devices (e.g., a plurality of individual devices each arranged between adjacent ones of the pads  404 ). 
         [0034]    Referring now to  FIG. 5 , a method  500  for assembling a battery module including a thermally conductive and electrically insulative compression limiting device begins at  504 . At  508 , the method  500  determines a thickness of the compression limiting device based on a maximum allowable particle size associated with the battery module. At  512 , one or more compressible, thermally conductive, and electrically insulate pads are arranged on a cooling plate of the battery module. At  516 , the compression limiting device is arranged on the cooling plate. For example, the compression limiting device may be arranged adjacent to and between a plurality of the pads on the cooling plate. At  520 , one or more battery cells are arranged on respective ones of the pads and portions of the compression limiting device adjacent to the pads. At  524 , the battery cells are compressed downward toward the cooling plate, compressing the pads. At  528 , the compression limiting device prevents the battery cells from further compressing the pads toward the cooling plate. The method  500  ends at  532 . 
         [0035]    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. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure. 
         [0036]    As used herein, the term module may refer to, be part of, or include an Application Specific Integrated Circuit (ASIC); an electronic circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor (shared, dedicated, or group) that executes code; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip. The term module may include memory (shared, dedicated, or group) that stores code executed by the processor. 
         [0037]    The term code, as used above, may include software, firmware, and/or microcode, and may refer to programs, routines, functions, classes, and/or objects. The term shared, as used above, means that some or all code from multiple modules may be executed using a single (shared) processor. In addition, some or all code from multiple modules may be stored by a single (shared) memory. The term group, as used above, means that some or all code from a single module may be executed using a group of processors. In addition, some or all code from a single module may be stored using a group of memories.