Abstract:
A battery assembly according to an exemplary aspect of the present disclosure includes, among other things, an array frame including a frame body and a slot formed through the frame body. A heat exchanger is received within the slot.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates to a battery assembly for an electrified vehicle. The battery assembly includes a battery array and an integrated heat exchanger. The battery assembly may include various retention features for retaining the heat exchanger relative to the battery array. 
       BACKGROUND 
       [0002]    The need to reduce automotive fuel consumption and emissions is well known. Therefore, vehicles are being developed that either reduce or completely eliminate reliance on internal combustion engines. Electrified vehicles are one type of vehicle being developed for this purpose. In general, electrified vehicles differ from conventional motor vehicles in that they are selectively driven by one or more battery powered electric machines. Conventional motor vehicles, by contrast, rely exclusively on the internal combustion engine to drive the vehicle. 
         [0003]    A high voltage battery assembly for powering electric machines of an electrified vehicle typically includes multiple battery arrays. Each battery array includes a plurality of battery cells and a support structure that generally surrounds the battery cells to build the battery array. A heat exchanger, such as a cold plate, may be positioned beneath the battery cells to thermally manage heat generated by the battery cells. Typically, the heat exchanger is clamped between the battery array and a tray to ensure robust contact between the heat exchanger and the battery cells. 
       SUMMARY 
       [0004]    A battery assembly according to an exemplary aspect of the present disclosure includes, among other things, an array frame including a frame body and a slot formed through the frame body. A heat exchanger is received within the slot. 
         [0005]    In a further non-limiting embodiment of the foregoing assembly, the frame body extends along a longitudinal axis and includes a top portion, a bottom portion and frame arms that extend between the top portion and the bottom portion. 
         [0006]    In a further non-limiting embodiment of either of the foregoing assemblies, the top portion includes a first side and a second side that each include an alternating pattern of rigid snap arms and flexible snaps arms. 
         [0007]    In a further non-limiting embodiment of any of the foregoing assemblies, the slot is formed in the bottom portion of the frame body. 
         [0008]    In a further non-limiting embodiment of any of the foregoing assemblies, a thermal fin extends within the frame body. The thermal fin includes a body and a leg that extends to a position outside of the frame body. 
         [0009]    In a further non-limiting embodiment of any of the foregoing assemblies, the heat exchanger is biased against the leg of the thermal fin. 
         [0010]    In a further non-limiting embodiment of any of the foregoing assemblies, the frame body includes a bottom portion including a top wall and a bottom wall that extend between opposing ends, the slot extending horizontally between the opposing ends and vertically between the top wall and the bottom wall. 
         [0011]    In a further non-limiting embodiment of any of the foregoing assemblies, a spring feature protrudes upwardly from the bottom wall. 
         [0012]    In a further non-limiting embodiment of any of the foregoing assemblies, the spring feature is angled relative to the bottom wall. 
         [0013]    In a further non-limiting embodiment of any of the foregoing assemblies, the spring feature is corrugated. 
         [0014]    A battery assembly according to another exemplary aspect of the present disclosure includes, among other things, an array frame including at least one retention arm and a heat exchanger connected to the array frame by the at least one retention arm. 
         [0015]    In a further non-limiting embodiment of the foregoing assembly, the array frame houses a battery cell, and comprising a thermal interface material between the battery cell and the heat exchanger. 
         [0016]    In a further non-limiting embodiment of either of the foregoing assemblies, the array frame includes an open bottom that establishes a pocket bound by side walls and a top wall. The at least one retention arm protrudes from at least one of the side walls and the top wall. 
         [0017]    In a further non-limiting embodiment of any of the foregoing assemblies, the array frame is mounted to a tray. 
         [0018]    In a further non-limiting embodiment of any of the foregoing assemblies, an air gap is between the heat exchanger and the tray. 
         [0019]    A battery assembly according to another exemplary aspect of the present disclosure includes, among other things, a battery array including a plurality of array frames, a lower cover connected to at least a portion of the plurality of array frames, and a heat exchanger secured between the battery array and the lower cover. 
         [0020]    In a further non-limiting embodiment of the foregoing assembly, a thermal interface material is between the heat exchanger and the plurality of array frames. 
         [0021]    In a further non-limiting embodiment of either of the foregoing assemblies, one of the portion of the plurality of array frames and the lower cover includes a rigid retention arm and the other of the portion of the plurality of array frames and the lower cover includes a flexible retention arm that engages the rigid retention arm to secure the lower cover to the portion of the plurality of array frames. 
         [0022]    In a further non-limiting embodiment of any of the foregoing assemblies, the flexible retention arm includes an extension that overlaps a second extension of the rigid retention arm. 
         [0023]    In a further non-limiting embodiment of any of the foregoing assemblies, the battery array is mounted to a tray. 
         [0024]    The embodiments, examples and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible. 
         [0025]    The various features and advantages of this disclosure will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]      FIG. 1  schematically illustrates a powertrain of an electrified vehicle. 
           [0027]      FIGS. 2A and 2B  illustrate an array frame of a battery array. 
           [0028]      FIG. 3  illustrates a battery array built from stacked array frames. 
           [0029]      FIG. 4  illustrates a retention feature of an array frame. 
           [0030]      FIGS. 5A and 5B  illustrate a spring feature of an array frame. 
           [0031]      FIG. 5C  is a blown-up view of encircled area AR 1  of  FIG. 5A . 
           [0032]      FIGS. 5D and 5E  illustrate additional exemplary spring features of an array frame. 
           [0033]      FIG. 6  illustrates a battery assembly according to a first embodiment of this disclosure. 
           [0034]      FIG. 7  illustrates a cross-sectional view of a battery assembly. 
           [0035]      FIG. 8  schematically illustrates positioning of a heat exchanger relative to a plurality of array frames of a battery assembly. 
           [0036]      FIG. 9  illustrates a battery assembly according to another embodiment of this disclosure. 
           [0037]      FIG. 10  illustrates a cross-sectional view of a battery assembly. 
           [0038]      FIG. 11  illustrates a battery assembly according to yet another embodiment of this disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0039]    This disclosure describes exemplary battery assemblies that may be employed within electrified vehicles. The battery assemblies include one or more array frames that may be stacked and connected together to build a battery array. A heat exchanger is connectable to the battery array to thermally manage the heat generated by the battery cells of the battery array and also heat the battery cells during low environmental temperatures. The battery assembly may employ various retention features to secure the heat exchanger relative to the battery array. For example, in one embodiment, the array frames of the battery array include slots that establish a channel for receiving the heat exchanger beneath the battery cells. In another embodiment, the array frames include flexible retention arms for securing the heat exchanger to the battery array. In yet another embodiment, a lower cover connects to the array frames to secure the heat exchanger to the battery array. These and other features are discussed in greater detail in the paragraphs that follow. 
         [0040]      FIG. 1  schematically illustrates a powertrain  10  for an electrified vehicle  12 . Although depicted as a HEV, it should be understood that the concepts described herein are not limited to HEV&#39;s and could extend to other electrified vehicles, including, but not limited to, plug-in hybrid electric vehicles (PHEV&#39;s) and battery electric vehicles (BEV&#39;s). 
         [0041]    In one embodiment, the powertrain  10  is a power-split powertrain system that employs a first drive system and a second drive system. The first drive system includes a combination of an engine  14  and a generator  18  (i.e., a first electric machine). The second drive system includes at least a motor  22  (i.e., a second electric machine), the generator  18 , and a battery assembly  24 . In this example, the second drive system is considered an electric drive system of the powertrain  10 . The first and second drive systems generate torque to drive one or more sets of vehicle drive wheels  28  of the electrified vehicle  12 . 
         [0042]    The engine  14 , such as an internal combustion engine, and the generator  18  may be connected through a power transfer unit  30 , such as a planetary gear set. Of course, other types of power transfer units, including other gear sets and transmissions, may be used to connect the engine  14  to the generator  18 . In one non-limiting embodiment, the power transfer unit  30  is a planetary gear set that includes a ring gear  32 , a sun gear  34 , and a carrier assembly  36 . 
         [0043]    The generator  18  can be driven by the engine  14  through the power transfer unit  30  to convert kinetic energy to electrical energy. The generator  18  can alternatively function as a motor to convert electrical energy into kinetic energy, thereby outputting torque to a shaft  38  connected to the power transfer unit  30 . Because the generator  18  is operatively connected to the engine  14 , the speed of the engine  14  can be controlled by the generator  18 . 
         [0044]    The ring gear  32  of the power transfer unit  30  may be connected to a shaft  40 , which is connected to vehicle drive wheels  28  through a second power transfer unit  44 . The second power transfer unit  44  may include a gear set having a plurality of gears  46 . Other power transfer units may also be suitable. The gears  46  transfer torque from the engine  14  to a differential  48  to ultimately provide traction to the vehicle drive wheels  28 . The differential  48  may include a plurality of gears that enable the transfer of torque to the vehicle drive wheels  28 . In one embodiment, the second power transfer unit  44  is mechanically coupled to an axle  50  through the differential  48  to distribute torque to the vehicle drive wheels  28 . 
         [0045]    The motor  22  can also be employed to drive the vehicle drive wheels  28  by outputting torque to a shaft  52  that is also connected to the second power transfer unit  44 . In one embodiment, the motor  22  and the generator  18  cooperate as part of a regenerative braking system in which both the motor  22  and the generator  18  can be employed as motors to output torque. For example, the motor  22  and the generator  18  can each output electrical power to the battery assembly  24 . 
         [0046]    The battery assembly  24  is an example type of electrified vehicle battery assembly. The battery assembly  24  may include a high voltage battery pack that includes a plurality of battery arrays capable of outputting electrical power to operate the motor  22  and the generator  18 . Other types of energy storage devices and/or output devices can also be used to electrically power the electrified vehicle  12 . 
         [0047]    In one non-limiting embodiment, the electrified vehicle  12  has two basic operating modes. The electrified vehicle  12  may operate in an Electric Vehicle (EV) mode where the motor  22  is used (generally without assistance from the engine  14 ) for vehicle propulsion, thereby depleting the battery assembly  24  state of charge up to its maximum allowable discharging rate under certain driving patterns/cycles. The EV mode is an example of a charge depleting mode of operation for the electrified vehicle  12 . During EV mode, the state of charge of the battery assembly  24  may increase in some circumstances, for example due to a period of regenerative braking. The engine  14  is generally OFF under a default EV mode but could be operated as necessary based on a vehicle system state or as permitted by the operator. 
         [0048]    The electrified vehicle  12  may additionally be operated in a Hybrid (HEV) mode in which the engine  14  and the motor  22  are both used for vehicle propulsion. The HEV mode is an example of a charge sustaining mode of operation for the electrified vehicle  12 . During the HEV mode, the electrified vehicle  12  may reduce the motor  22  propulsion usage in order to maintain the state of charge of the battery assembly  24  at a constant or approximately constant level by increasing the engine  14  propulsion usage. The electrified vehicle  12  may be operated in other operating modes in addition to the EV and HEV modes within the scope of this disclosure. 
         [0049]      FIGS. 2A and 2B  illustrate an array frame  54  that houses at least two battery cells  56 . A plurality of array frames  54  may be stacked side-by-side to build a battery array (see, e.g., battery array  78  of  FIGS. 3 and 6 ). One or more battery arrays that include multiple array frames  54  and battery cells  56  can be assembled and mounted inside a battery assembly, such as the battery assembly  24  of the electrified vehicle  12  of  FIG. 1 , to electrically power an electrified vehicle. 
         [0050]    In one embodiment, the battery cells  56  are pouch cells for a high voltage battery assembly. One non-limiting example of a suitable pouch battery cell is a lithium-ion polymer battery. However, other types of battery cells are also contemplated, and it should be understood that this disclosure is not limited to pouch type battery cells. 
         [0051]    The array frame  54  includes a frame body  58  that extends along a longitudinal axis A (see  FIG. 2A ). The frame body  58  includes a top portion  60 , a bottom portion  62  and frame arms  64  that connect between the top portion  60  and the bottom portion  62 . In one embodiment, the top portion  60  and the bottom portion  62  extend in parallel with the longitudinal axis A, and the frame arms  64  are transverse to the longitudinal axis A. In another embodiment, the frame body  58  is a unitary, plastic structure. 
         [0052]    In one non-limiting embodiment, a thermal fin  66  may be at least partially embedded within the frame body  58  and extend between the top portion  60  and the bottom portion  62 . In one embodiment, the thermal fin  66  is an aluminum thermal fin. However, other materials are additionally contemplated. The thermal fin  66  separates the battery cells  56  and may contact side faces  55  of the battery cells  56 . During certain conditions, the thermal fin  66  removes heat from the battery cells  56 . In other conditions, the thermal fin  66  may add heat to the battery cells  56 . The frame body  58  establishes pockets  76  on both sides of the thermal fin  66 . The battery cells  56  may be received within the pockets  76  to house the battery cells  56  within the array frame  54 . 
         [0053]    The thermal fin  66  may include a body  74  and a leg  72  that extends from the body  74  (see  FIG. 2B ). The body  74  may be embedded or molded into the frame body  58 , while the leg  72  extends outside of the frame body  58 . In another embodiment, the thermal fin  66  may be inserted into the frame body  58  such that one end of the body  74  is located within a groove  68  formed in the top portion  60  of the frame body  58 , and an opposite end of the body  74  may extend through a passage  70  formed through the bottom portion  62  of the frame body  58 . The leg  72  of the thermal fin  66  may be oriented transversely to the body  74  so it extends underneath the bottom portion  62  to the position outside of the frame body  58 . In one embodiment, the leg  72  extends to a position that is beyond the side face  55  of the battery cell  56  housed substantially above the leg  72 . 
         [0054]    The frame body  58  may further include a plurality of retention features  80  that are integrated into the top portion  60 . The bottom portion  62  could similarly include integrated retention features, although not shown in this embodiment. The retention features  80  may engage corresponding retention features of adjacent array frames  54  to build a battery array. In yet another embodiment, the frame arms  64  could include retention features similar to the retention features  80  for connecting adjacent array frames  54 . 
         [0055]    Referring to  FIG. 3 , a plurality of array frames  54  may be stacked side-by-side to construct a battery array  78 . Two array frames  54  are depicted in  FIG. 3 , which omits the battery cells for clarity. This disclosure is not limited to any specific number of array frames  54  and/or battery cells  56  and is not intended to be limited to the specific configurations that are illustrated by the various Figures. 
         [0056]    In one embodiment, the top portion  60  of the frame body  58  of each array frame  54  is rotationally symmetric about a vertical axis V that is transverse to the longitudinal axis A. In another embodiment, the bottom portion  62  is rotationally symmetric about the vertical axis V. In yet another embodiment, both the top portion  60  and the bottom portion  62  are rotationally symmetric about the vertical axis V. In this way, the array frames  54  can be provided in a repeating fashion to construct the battery array  78 . The symmetry of the top portion  60  and/or the bottom portion  62  permits the use of common array end plates, thereby reducing cost and complexity of the battery array  78 . In other words, unique left hand and right hand array end plates are not required to construct the battery array  78 . 
         [0057]    The top portion  60  of the frame body  58  includes a first side  84  and a second side  86  that both extend between opposing ends  96 ,  98 . The first side  84  and the second side  86  both include a plurality of retention features  80  for connecting the array frame  54  to an adjacent array frame  54 . In one embodiment, the retention features  80  protrude from both the first side  84  and the second side  86  of the top portion  60 . In another embodiment, the top portion  60  of each array frame  54  is substantially flat. 
         [0058]    In another non-limiting embodiment, the retention features  80  of the top portion  60  include a plurality of rigid snap arms  82 A and a plurality of flexible snap arms  82 B oriented in an alternating pattern along each of the first side  84  and the second side  86  of the top portion  60 . Because the top portion  60  is rotationally symmetric about the vertical axis V, each flexible snap arm  82 B of the first and second sides  84 ,  86  are aligned directly across the top portion  60  from a rigid snap arm  82 A on the opposite side  84 ,  86 . Thus, the array frames  54  provide a repeating design that simplifies assembly and reduces complexity of the battery array  78 . 
         [0059]    The rigid snap arms  82 A and the flexible snap arms  82 B of both the first side  84  and the second side  86  are oriented to engage corresponding features of an adjacent array frame  54  to connect the array frames  54  together. For example, the flexible snap arms  82 B may be received over top of the rigid snap arms  82 A to connect adjacent array frames  54 . The flexible snap arms  82 B may flex slightly as the rigid snap arms  82 A are pushed toward the flexible snap arms  82 B. 
         [0060]    The top portion  60  of each array frame  54  may additionally include one or more recessed grooves  92 . In one embodiment, each recessed groove  92  extends between the first side  84  and the second side  86  of the top portion  60  and is disposed between a rigid snap arm  82 A and a flexible snap arm  82 B on the first side  84  and the second side  86 . The recessed grooves  92  of adjacent array frames  54  align with one another and can accommodate tension straps that bind the battery array  78  in a lengthwise direction to maintain a consistent array length and resist bulging of the battery cells  56  during certain conditions. 
         [0061]      FIG. 4  illustrates features associated with the bottom portion  62  of an array frame  54 . The bottom portion  62  may include a top wall  88  and a bottom wall  90  that extend between opposing ends  89 ,  91 . Each of the opposing ends  89 ,  91  includes a foot  93 . Additional feet  95  may protrude from the bottom wall  90  between the feet  93 . The feet  93 ,  95  provide a substantially flat surface for positioning the array frame  54  on a supporting surface, such as a tray (see, for example, tray  27  of  FIGS. 6-7 ). 
         [0062]    In one embodiment, a slot  94  extends through the bottom portion  62  of the array frame  54 . In other words, the slot  94  is an opening that extends across a thickness T of the array frame  54  (see  FIG. 5B ). The slot  94  may extend horizontally between the opposing ends  89 ,  91  and vertically between the top wall  88  and the bottom wall  90 , in one embodiment. The slot  94  is configured to receive a heat exchanger, as is further discussed below (see, for example, heat exchanger  25  of  FIGS. 6-8 ). In one non-limiting embodiment, the slot  94  is molded into the array frame  54 . 
         [0063]    Referring to  FIGS. 5A, 5B and 5C , the bottom wall  90  of the array frame  54  may include one or more spring features  21 . In one embodiment, the spring feature  21  protrudes upwardly from the bottom wall  90  and may be angled relative to the bottom wall  90 . The spring feature  21  may extend across an entire length or only portions of the length of the slot  94 , and may be configured as a continuous piece or multiple spaced apart pieces. The spring feature  21  may be a plastic, flexible member that flexes in response to contacting a heat exchanger  25  that is inserted into the slot  94  in a slot insertion direction D 1  (see  FIG. 5C ). The spring feature  21  is designed to maintain robust contact between the heat exchanger  25  and the thermal fin  66  of the array frame  54 . Additional details concerning the relationship between the spring feature  21 , the heat exchanger  25  and the thermal fin  66  are discussed in greater detail below. 
         [0064]    In another embodiment, the spring feature  21  is positioned within the slot  94  such that it is aligned beneath a bend  23  of the thermal fin  66  (see  FIGS. 5B and 5C ). The bend  23  is a curved portion of the thermal fin  66  located between the body  74  and the leg  72 . However, in other embodiments, the spring feature  21  could be positioned beneath any portion of the leg  72  of the thermal fin  66 . 
         [0065]    Referring to  FIG. 5D , the bottom wall  90  of each array frame  54  may include a spring feature  21 . The spring features  21  deflect upon insertion of a heat exchanger  25  to apply an upwards force against the heat exchanger  25  and facilitate improved contact between the heat exchanger  25  and the thermal fin  66 . In another embodiment, shown in  FIG. 5E , the spring features  21  may be corrugated to increase the upward force against the heat exchanger  25 . An angle a between platforms  19  of the corrugated spring features  21  may be greater than or equal to 90 degrees. 
         [0066]      FIGS. 6 and 7  illustrate a battery assembly  99  that includes a battery array  78 , a heat exchanger  25  and a tray  27 . The battery array  78  is constructed of a plurality of array frames  54  that are connected together and house battery cells  56 . Each array frame  54  includes a slot  94 . Once connected together, the slots  94  of the array frames  54  align to establish a channel  29  (see  FIG. 6 ) that extends through the battery array  78 . 
         [0067]    The heat exchanger  25  may be inserted into the channel  29  to connect it to the array frames  54 , and thus, to the battery array  78 . In this way, the heat exchanger  25  is substantially integrated with the battery array  78 . The heat exchanger  25  functions to remove heat generated by the battery cells  56  during certain conditions, or alternatively to heat the battery cells  56  during other conditions. In one embodiment, the heat exchanger  25  is configured as a cold plate. However, other implementations are also contemplated. The spring features  21  bias the heat exchanger  25  against the leg  72  of each thermal fin  66  within the channel  29  (see  FIG. 8 ). Therefore, in this embodiment, a thermal interface material (TIM) may not be necessary to achieve sufficient heat transfer. 
         [0068]    Referring now primarily to  FIG. 7 , the battery array  78  may be fixedly secured to the tray  27 . In one embodiment, the battery array  78  is secured to the tray using one or more fasteners  31  that are inserted through openings  33  of the array frames  54 . Other mechanical attachments are also contemplated as within the scope of this disclosure. 
         [0069]    In the assembled position shown in  FIG. 7 , the heat exchanger  25  is supported between the battery cells  56  and the tray  27 . In one embodiment, the bottom wall  90  of the array frames  54  thermally isolates the heat exchanger  25  from the tray  27  so that heat from the battery cells  56  is not conducted through the tray  27 . 
         [0070]    Another battery assembly  199  is illustrated in  FIGS. 9 and 10 . In this disclosure, like reference numbers designate like elements where appropriate and reference numerals with the addition of  100  or multiples thereof designate modified elements that are understood to incorporate the same features and benefits of the corresponding original elements. Like the battery assembly  99  discussed above, the exemplary battery assembly  199  includes a battery array  178 , a heat exchanger  125  and a tray  127 . The battery array  178  is constructed of a plurality of array frames  154  that are connected together and house battery cells  156 . The array frames  154  of this embodiment include open bottoms  151  rather than slots. A lower cover  153  is connectable to the array frames  154  at the open bottoms  151  to position the heat exchanger  125  between the battery cells  156  and the lower cover  153 . 
         [0071]    In one embodiment, as best illustrated in  FIG. 10 , the array frames  154  include first retention arms  161  and the lower cover  153  includes second retention arms  163 . The first and second retention arms  161 ,  163  engage one another to secure the lower cover  153  to the array frames  154  of the battery array  178 . The array frames  154  and the lower cover  153  may each include two or more retention arms that are molded portions of these components. One of the first retention arms  161  and the second retention arms  163  may act as a male retention arm, while the other of the first retention arms  161  and the second retention arms  163  acts as female retention arm to secure the lower cover  153  to the array frames  154 . 
         [0072]    In another embodiment, extensions  165  of the second retention arms  163  overlap corresponding extensions  167  of the first retention arms  161  to secure the lower cover  153  to the array frames  154 . The second retention arms  163  may flex inwardly and then flex outwardly to overlap the extensions  167  of the rigid first retention arms  161 . Of course, an opposite configuration is also contemplated in which the first retention arms  161  are flexible and the second retention arms  163  are rigid. 
         [0073]    Once the lower cover  153  is secured to the array frames  154 , the heat exchanger  125  is considered “integrated” with the battery array  178 . In one embodiment, the lower cover  153  thermally isolates the heat exchanger  125  from the tray  127  so that heat from the battery cells  156  is not conducted through the tray  127 . In another non-limiting embodiment, the lower cover  153  includes spring features  121  that bias the heat exchanger  125  toward the battery cells  156 , or optionally, toward a TIM  171  disposed between the battery cells  156  and the heat exchanger  125 . The TIM  171  may be made from a material having a relatively high thermal conductivity and is configured to maintain thermal contact between the battery cells  156  and the heat exchanger  125  to increase the thermal conductivity between these neighboring components during a heat transfer event. 
         [0074]      FIG. 11  illustrates yet another exemplary battery assembly  299 . The battery assembly  299  of this embodiment includes a battery array  278 , a heat exchanger  225  and a tray  227 . The battery array  278  is constructed of one or more array frames  254  that are connected together and house battery cells  256 . The array frames  254  of this embodiment include open bottoms  251  that establish a pocket  253  at a bottom portion  262  of the array frames  254 . 
         [0075]    In one non-limiting embodiment, the pockets  253  include a perimeter bounded by a first side wall  281 , a second side wall  283  and a top wall  285  that extends between the first side wall  281  and the second side wall  283 . One or more retention arms  287  for connecting the heat exchanger  225  to the battery array  278  may protrude into the pockets  253 . The retention arms  287  may protrude into the pocket  253  from the side walls  281 ,  283 , the top wall  285 , or from a junction between the first side wall  281 /second side wall  283  and the top wall  285 . The retention arms  287  are flexible and include extensions  289  for receiving the heat exchanger  225 . For example, the heat exchanger  225  may rest atop the extensions  289  to secure it to the battery array  278 . A TIM  271  may be positioned between the battery cells  256  and the heat exchanger  225 . In addition, an air gap  295 , which is part of the pocket  253 , may thermally isolate the heat exchanger  225  from the tray  227 . 
         [0076]    Although the different non-limiting embodiments are illustrated as having specific components or steps, the embodiments of this disclosure are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting embodiments in combination with features or components from any of the other non-limiting embodiments. 
         [0077]    It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should be understood that although a particular component arrangement is disclosed and illustrated in these exemplary embodiments, other arrangements could also benefit from the teachings of this disclosure. 
         [0078]    The foregoing description shall be interpreted as illustrative and not in any limiting sense. A worker of ordinary skill in the art would understand that certain modifications could come within the scope of this disclosure. For these reasons, the following claims should be studied to determine the true scope and content of this disclosure.