Abstract:
A battery pack according to an exemplary aspect of the present disclosure includes, among other things, an enclosure including a monolithic body with at least a first sidewall and a base connected to the first sidewall and a fluid channel extending inside of at least one of the first sidewall and the base.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates to a battery pack for an electrified vehicle. The battery pack includes a monolithic enclosure body having at least a sidewall and a base. The sidewall, the base, or both include one or more fluid channels for thermally managing battery cells of the battery pack. 
       BACKGROUND 
       [0002]    The need to reduce automotive fuel consumption and emissions is well known. Therefore, vehicles are being developed that reduce or completely eliminate reliance on internal combustion engines. Electrified vehicles are one type of vehicle currently being developed for this purpose. In general, electrified vehicles differ from conventional motor vehicles because 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 pack for powering electric machines and other electrical loads typically includes multiple battery cells. An array structure binds the battery cells together. A separate enclosure houses and seals the battery cells from the exterior environment. Yet another separate structure, typically configured as a cold plate, is commonly positioned in contact with the battery cells to thermally manage the heat generated by the cells. 
       SUMMARY 
       [0004]    A battery pack according to an exemplary aspect of the present disclosure includes, among other things, an enclosure including a monolithic body with at least a first sidewall and a base connected to the first sidewall and a fluid channel extending inside of at least one of the first sidewall and the base. 
         [0005]    In a further non-limiting embodiment of the foregoing battery pack, the fluid channel is formed inside the base. 
         [0006]    In a further non-limiting embodiment of either of the foregoing battery packs, the fluid channel is formed inside the first sidewall. 
         [0007]    In a further non-limiting embodiment of any of the foregoing battery packs, the fluid channel is formed inside the base and a second fluid channel is formed inside the first sidewall. 
         [0008]    In a further non-limiting embodiment of any of the foregoing battery packs, the monolithic body includes the first sidewall, the base, a second sidewall and a cover. 
         [0009]    In a further non-limiting embodiment of any of the foregoing battery packs, the battery pack includes a plurality of fluid channels inside the monolithic body, the plurality of fluid channels connecting to establish a serpentine passage. 
         [0010]    In a further non-limiting embodiment of any of the foregoing battery packs, the battery pack includes a plurality of fluid channels inside the monolithic body, the plurality of fluid channels arranged to establish a parallel, U-flow scheme. 
         [0011]    In a further non-limiting embodiment of any of the foregoing battery packs, a first end cap is attached to a first end of the base and a second end cap is attached to a second end of the base. 
         [0012]    In a further non-limiting embodiment of any of the foregoing battery packs, each of the first end cap and the second end cap include a manifold. 
         [0013]    In a further non-limiting embodiment of any of the foregoing battery packs, both an inlet and an outlet are disposed in either the first end cap or the second end cap. 
         [0014]    In a further non-limiting embodiment of any of the foregoing battery packs, a plurality of fluid channels are inside the monolithic body, and a plurality of walls are positioned to divide the plurality of fluid channels from one another. 
         [0015]    In a further non-limiting embodiment of any of the foregoing battery packs, at least one of the plurality of walls extends from a first end of the base but terminates short of a second end of the base. 
         [0016]    In a further non-limiting embodiment of any of the foregoing battery packs, an end plate or a cover is attached to the monolithic body. 
         [0017]    In a further non-limiting embodiment of any of the foregoing battery packs, a plurality of ribs protrude from surfaces that surround the fluid channel. 
         [0018]    In a further non-limiting embodiment of any of the foregoing battery packs, at least one battery array is positioned atop the base. 
         [0019]    A method according to another exemplary aspect of the present disclosure includes, among other things, forming an enclosure for enclosing a battery array of a battery pack, the enclosure including a monolithic body that includes at least a first sidewall integrated with a base. 
         [0020]    In a further non-limiting embodiment of the foregoing method, the forming step includes extruding the enclosure. 
         [0021]    In a further non-limiting embodiment of either of the foregoing methods, the forming step includes manufacturing the enclosure such that at least one of the first sidewall and the base includes a fluid channel. 
         [0022]    In a further non-limiting embodiment of any of the foregoing methods, the forming step includes manufacturing the enclosure to include the first sidewall, the base and at least one of a second sidewall or a cover. 
         [0023]    In a further non-limiting embodiment of any of the foregoing methods, the method includes positioning the battery array atop the base. The base is configured to simultaneously support the battery array and thermally manage heat generated by battery cells of the battery array. 
         [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]      FIG. 2  illustrates portions of a battery pack of an electrified vehicle. 
           [0028]      FIG. 3  is a cross-sectional view through section A-A of the battery pack of  FIG. 2 . 
           [0029]      FIG. 4  illustrates an exemplary thermal management scheme of a battery pack enclosure. 
           [0030]      FIG. 5  illustrates another exemplary thermal management scheme of a battery pack enclosure. 
           [0031]      FIG. 6  illustrates an exemplary battery pack enclosure. 
           [0032]      FIG. 7  illustrates a battery pack enclosure according to another embodiment of this disclosure. 
           [0033]      FIG. 8  illustrates a battery pack enclosure according to yet another embodiment of this disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0034]    This disclosure details exemplary battery pack designs for an electrified vehicle. The battery pack includes a monolithic enclosure body having at least a first sidewall that extends from a base. A fluid channel is formed inside the monolithic enclosure body and is configured to communicate a coolant. The coolant may be circulated through the fluid channel to thermally manage heat generated by battery cells of the battery pack. Fluid channels may be disposed through the base, the first sidewall and/or any other wall of the monolithic enclosure body. These and other features are discussed in greater detail in the following paragraphs of this detailed description. 
         [0035]      FIG. 1  schematically illustrates a powertrain  10  for an electrified vehicle  12 . Although depicted as a hybrid electric vehicle (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), battery electric vehicles (BEV&#39;s) and fuel cell vehicles. 
         [0036]    In one non-limiting 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 pack  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 . Although a power-split configuration is shown, this disclosure extends to any hybrid or electric vehicle including full hybrids, parallel hybrids, series hybrids, mild hybrids or micro hybrids. 
         [0037]    The engine  14 , which in one embodiment is 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 . 
         [0038]    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 . 
         [0039]    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 . 
         [0040]    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 pack  24 . 
         [0041]    The battery pack  24  is an exemplary electrified vehicle battery. The battery pack  24  may be a high voltage traction battery pack that includes a plurality of battery assemblies  25  (i.e., battery arrays or groupings of battery cells) capable of outputting electrical power to operate the motor  22 , the generator  18  and/or other electrical loads of the electrified vehicle  12 . Other types of energy storage devices and/or output devices can also be used to electrically power the electrified vehicle  12 . 
         [0042]    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 pack  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 pack  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. 
         [0043]    The electrified vehicle  12  may additionally operate 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 pack  24  at a constant or approximately constant level by increasing the engine  14  propulsion. 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. 
         [0044]      FIG. 2  illustrates portions of a battery pack  24  that can be employed within an electrified vehicle. For example, the battery pack  24  could be part of the electrified vehicle  12  of  FIG. 1 . The battery pack  24  includes a plurality of battery cells  56  for supplying electrical power to various electrical loads of the electrified vehicle  12 . Although a specific number of battery cells  56  are depicted in  FIG. 2 , the battery pack  24  could employ a fewer or a greater number of battery cells within the scope of this disclosure. In other words, this disclosure is not limited to the specific configurations shown in  FIGS. 2 and 3 . 
         [0045]    The battery cells  56  may be stacked side-by-side along a longitudinal axis A to construct a grouping of battery cells  56 , sometimes referred to as a “cell stack.” In one non-limiting embodiment, the battery pack  24  includes two separate groupings of battery cells  56  (i.e., two cell stacks). 
         [0046]    In another non-limiting embodiment, the battery cells  56  are prismatic, lithium-ion cells. However, battery cells having other geometries (cylindrical, pouch, etc.), other chemistries (nickel-metal hydride, lead-acid, etc.), or both could alternatively be utilized within the scope of this disclosure. 
         [0047]    In another non-limiting embodiment, spacers  58 , which can alternatively be referred to as separators or dividers, may be positioned between adjacent battery cells  56  of each grouping of battery cells  56 . The spacers  58  may include thermally resistant and electrically isolating plastics and/or foams. The battery cells  56  and the spacers  58  may together be referred to as a battery array  60 . Two battery arrays  60  are shown in  FIG. 2 ; however, the battery pack  24  could include only a single battery array or greater than two battery arrays. The battery cells  56  could be held together by a friction force generated as a result of compressing the cells during assembly of each battery array  60 . In another embodiment, an adhesive is used to aid in holding the battery cells  56  together. 
         [0048]    An enclosure  62  generally surrounds each battery array  60  of the battery pack  24 . In one non-limiting embodiment, the enclosure  62  includes a monolithic body  64  that includes a base  66 , a first sidewall  68  and a second sidewall  70 . The first sidewall  68  and the second sidewall  70  are connected to the base  66  and, in one embodiment, extend upwardly at opposing sides of the base  66 . The battery arrays  60  are positioned atop the base  66 , and the first sidewall  68  and the second sidewall  70  extend adjacent to the sides of the battery arrays  60  along an axis that is parallel to the longitudinal axis A. In one non-limiting embodiment, the monolithic body  64  is an extruded, single-piece component with no mechanical connections. 
         [0049]    The enclosure  62  may additionally include a cover  72  and end walls  74  (both shown in phantom to better illustrate other features of the battery pack  24 ) that may be attached to the monolithic body  64  to fully assembly the enclosure  62  and enclose the battery arrays  60 . The cover  72  and the end walls  74  may be welded, bonded or mechanically fastened to the monolithic body  64 . In another non-limiting embodiment, the enclosure  62  is made of aluminum, although other materials are also contemplated within the scope of this disclosure. 
         [0050]    The enclosure  62  is configured to perform multiple functions. For example, in one embodiment, the enclosure  62  is configured to apply a compressive load against the battery arrays  60 . In another embodiment, the enclosure  62  is configured to at least partially enclose and seal the battery arrays  60  from the exterior environment. In yet another embodiment, the enclosure  62 , and more particularly the monolithic body  64  of the enclosure  62 , is equipped with features for thermally managing the battery cells  56  of each battery array  60 . For example, heat may be generated and released by the battery cells  56  during charging operations, discharging operations, extreme ambient conditions, or other conditions. It is often desirable to remove the heat from the battery pack  24  to improve capacity and life of the battery cells  56 . In one non-limiting embodiment, the base  66  of the monolithic body  64  of the enclosure  62  acts as a cold plate, or heat exchanger plate, to conduct the heat out of the battery cells  56 . In other words, the base  66  acts as a heat sink to remove heat from a heat source (i.e., the battery cells  56 ). Incorporating the cold plate functionality into the enclosure  62  in this manner can reduce the vertical footprint of the battery pack  24 . 
         [0051]    Referring now to  FIGS. 2 and 3 , the base  66  of the monolithic body  64  of the enclosure  62  may include one or more fluid channels  76  for circulating a coolant C to thermally condition the battery cells  56 . The first sidewall  68 , the second sidewall  70 , or both may alternatively or additionally include similar fluid channels (see, for example,  FIGS. 6 and 7 ). The coolant C may be a conventional type of coolant mixture such as water mixed with ethylene glycol. However, other coolants, including gases, are also contemplated within the scope of this disclosure. 
         [0052]    In one non-limiting embodiment, the fluid channels  76  connect to establish a serpentine passage  78  for communicating the coolant C through the base  66 . The serpentine passage  78  extends between an inlet  86  and an outlet  88 . A plurality of walls  80  may separate the fluid channels  76  from one another. The walls  80  may extend between opposing ends  84 A,  84 B of the base  66 . In one non-limiting embodiment, each wall  80  extends from one of the opposing ends  84 A,  84 B toward the other opposing end  84 A,  84 B but terminates prior to reaching the opposing end  84 A,  84 B. For example, the walls  80  may terminate by a distance D inwardly from the opposing end  84 A,  84 B. In this way, the flow of the coolant C is not blocked by the walls  80  and can turn from one fluid channel  76  to another as it travels along the serpentine passage  78 . Portions of the walls  80  may be removed by trimming or machining to facilitate the continuous flow of the coolant C. 
         [0053]    In yet another non-limiting embodiment, a plurality of ribs  82  protrude from surfaces  85  of the base  66  that circumscribe the fluid channels  76 . The ribs  82  are configured to increase the surface area, and therefore the heat exchange capabilities, of the fluid channels  76 . 
         [0054]    The fluid channels  76  can be configured in different sizes and shapes to help meter and balance the flow of the coolant C through the serpentine passage  78 . The size and shape of each fluid channel  76  and the total number of fluid channels  76  are not intended to limit this disclosure and can be specifically tuned to the cooling requirements of the battery pack  24 . 
         [0055]    In use, the coolant C is communicated into the inlet  86  of the serpentine passage  78  and is then communicated through the fluid channels  76  that define the serpentine passage  78  before exiting through the outlet  88 . The coolant C picks up the heat conducted through the base  66  from the battery cells  56  as it meanders along its path. Although not shown, the coolant C exiting the outlet  88  may be delivered to a radiator or some other heat exchanging device, be cooled, and then returned to the inlet  86  in a closed loop. 
         [0056]      FIG. 4  illustrates another exemplary thermal management scheme that may be incorporated inside the enclosure  62 . In one non-limiting embodiment, the exemplary thermal management scheme is disposed inside the base  66  of the monolithic body  64  of the enclosure  62 . However, the thermal management scheme could be disposed inside other portions of the enclosure  62 . 
         [0057]    In this embodiment, a first end cap  90 A is attached at a first end  84 A of the base  66  and a second end cap  90 B is attached at a second end  84 B of the base  66 . The first end cap  90 A and the second end cap  90 B may be attached to the base in any known manner. 
         [0058]    Each end cap  90 A,  90 B includes a manifold  92 , or passage, for directing the coolant C through the serpentine passage  78 . For example, coolant C from a first fluid channel  76 A may be communicated into the manifold  92  of the second end cap  90 B prior to entering a second fluid channel  76 B. The coolant C may then be communicated through the second fluid channel  76 B and into the manifold  92  of the first end cap  90 A prior to entering a third fluid channel  76 C and so on. 
         [0059]    A plurality of walls  80  may separate the fluid channels  76 A,  76 B,  76 C and  76 D from one another in order to establish the serpentine passage  78 . In one non-limiting embodiment, the walls  80  extend inside the base  66  and stretch from the first end  84 A to the second end  84 B. The manifolds  92  of the first end cap  90 A and the second end cap  90 B establish passages for allowing the coolant C to pass around each wall  80  as it is communicated along the serpentine passage  78 . 
         [0060]      FIG. 5  illustrates yet another exemplary thermal management scheme that may be incorporated into the enclosure  62 . In this embodiment, the thermal management scheme provides a parallel, U-flow design for communicating the coolant C through the enclosure  62  so simultaneously cool two battery arrays (not shown in  FIG. 5 ) in parallel. Similar to the  FIG. 4  embodiment, a first end cap  90 A is attached at a first end  84 A of the base  66  and a second end cap  90 B is attached at a second end  84 B of the base  66 . Each end cap  90 A,  90 B includes a manifold  92  for directing the coolant C into the parallel U-flow scheme. In one non-limiting embodiment, the first end cap  90 A includes both an inlet  86  for directing the coolant C into the enclosure  62  and an outlet  88  for expelling the coolant C from the enclosure  62 . 
         [0061]    In operation, coolant C enters through the inlet  86  into the manifold  92  of the first end cap  90 A. The coolant C may then simultaneously enter into both a first fluid channel  76 A and a second fluid channel  76 B inside the base  66 . The coolant C is communicated across the lengths of the first and second fluid channels  76 A,  76 B prior to entering into the manifold  92  of the second end cap  90 B. The coolant C may then turn around walls  80  and enter a third fluid channel  76 C from the first fluid channel  76 A and enter a fourth fluid channel  76 D from the second fluid channel  76 B. The portions of the coolant C that are communicated within the first and third fluid channels  76 A,  76 C and the second and fourth fluid channels  76 B,  76 D both travel along a U-shaped path. In this non-limiting embodiment, the coolant C communicated through the first and third fluid channels  76 A,  76 C may cool a first battery array and the coolant C communicated through the second and fourth fluid channels  76 B,  76 D may communicate a second battery array. The coolant C exiting the third and fourth fluid channels  76 C,  76 D may be expelled from the enclosure  62  through the outlet  88 . 
         [0062]      FIGS. 6, 7 and 8  illustrate various alternative configurations of the monolithic body  64  of the enclosure  62  of the battery pack  24 . Referring first to  FIG. 6 , the fluid channels  76  may be formed in one or both of the first and second sidewalls  68 ,  70  of the monolithic body  64  rather than in the base  66 . Therefore, the first and second sidewalls  68 ,  70  can act as a cold plate instead of the base  66 . 
         [0063]    In another embodiment, shown in  FIG. 7 , fluid channels  76  may be formed through each of the base  66 , the first sidewall  68  and the second sidewall  70  of the monolithic body  64 . In this manner, thermal management of the battery arrays can be achieved at multiple locations of the monolithic body  64 . 
         [0064]    In yet another non-limiting embodiment, shown in  FIG. 8 , the monolithic body  64  of the enclosure  62  includes a base  66 , a cover  72 , a first sidewall  68  and a second sidewall  70 . In other words, the base  66 , the cover  72 , the first sidewall  68  and the second sidewall  70  define a single-piece enclosure structure in which the first sidewall  68  and the second sidewall  70  connect, without any mechanical connections, between the base  66  and the cover  72 . 
         [0065]    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. 
         [0066]    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. 
         [0067]    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.