Abstract:
A battery pack includes at least one serpentine fluid circulation tube that extends around part of the periphery of a plurality of electric cells. First and second segments of the tube are disposed adjacent a first and a second edge of a first set of the plurality of electric cells. The sets of electric cells are disposed in an alternating arrangement. A first fin and a second fin are provided between each of the electric cells. The fins have a reverse turn wrapped around the segments of the tube. The fins have internal ends that are disposed between the electric cells and the tube segments. The battery pack may be assembled by folding the fins around the electric cells and the tube or by preforming folded sheets that define thermal fins and assembling the folded sheets over segments of the tube from opposite sides of the electric cells.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates to a method of manufacturing a modular battery pack with a plurality of electric cells, fins and tubes to provide a closed loop temperature control system for the battery pack. 
       BACKGROUND 
       [0002]    Batteries for vehicles that have an electrically powered traction motor generally are not provided with a temperature control system for optimum charging and for providing maximum usable energy. Some batteries are air cooled and rely upon air flowing through passages or ducts that are adjacent to the electric cells of the battery. Air cooled systems are difficult to control because variations in ambient temperature impact the ability of such systems to control the temperature of the air provided to the battery. Air cooled batteries are difficult to package compactly while providing efficient temperature control. 
         [0003]    Closed loop liquid temperature control systems for batteries offer the potential of more efficient and compact temperature control systems. One challenge associated with providing a liquid temperature control system is the cost to manufacture such a system. Another challenge is that it is difficult to provide an effective way to evenly control the temperature across individual electric cells throughout the battery pack. 
         [0004]    The manufacturing method and apparatus disclosed herein is directed to solving the above problems and answering the challenges associated with providing closed loop temperature control systems for vehicle battery packs. 
       SUMMARY 
       [0005]    According to one aspect of this disclosure, a battery assembly is provided that is wrapped by a fluid circulating cooling system. A plurality of electric cells each have an outer edge on at least one side. A serpentine fluid tube is disposed adjacent the outer edge of a first set of electric cells. A first fin and a second fin are disposed between each of the electric cells. The first fin has a first reverse turn wrapped around an outer portion of the fluid tube that is on the opposite side of the fluid tube from the outer edge of the electric cells. The second fin has a second reverse turn that is disposed between the fluid tube and each of the first set of electric cells. 
         [0006]    According to other aspects of the disclosure, the serpentine fluid tube of the battery assembly may further comprise a plurality of first segments that are disposed adjacent a first outer edge of a first set of the plurality of electric cells and a plurality of second segments that are disposed adjacent a second outer edge of a second set of the plurality of electric cells. The first and second sets of electric cells may be disposed in an alternating arrangement with the first and second outer edges being disposed on opposite edges of the electric cells. The first fin may have a first reverse turn wrapped around the outer portion of the first segments. The second fin may have a second reverse turn wrapped around the outer portion of the second segments. The second fin may have a first internal end that is disposed between the electric cells and the first segments and the first fin may have a second internal end that is disposed between the electric cells and the second segments. 
         [0007]    According to other aspects of the disclosure, the battery assembly may further comprise a thermal compound provided between the first fin, the first segments and the first internal end. The thermal compound may also be provided between the second fin, the second segments and the second internal end. 
         [0008]    The first fin may be continuous and may extend from between a first cell and a second cell that is adjacent the first cell, around the first segments and between the second cell and a third cell that is adjacent the second cell to the second internal end. The second fin may be continuous and may extend from between a first cell and a second cell that is adjacent the first cell, around the second segments and between the second cell and a third cell that is adjacent the second cell to the first internal end. 
         [0009]    According to an alternative embodiment, a battery assembly is disclosed that includes a fluid circulating cooling system that is assembled to a plurality of electric cells. The plurality of electric cells each have a first outer edge on a first side and a second outer edge on a second side that is oppositely oriented relative to the first side. At least one serpentine fluid tube that may be disposed adjacent the first edge of a first set of electric cells and the second edge of the second set of electric cells. A plurality of folded sheets each includes a first fin and a second fin that are joined by a reversely turned portion. A first set of the folded sheets are assembled over the fluid tube and the first edge of the first set of electric cells and a second set of the folded sheets are assembled over the fluid tube and the second edge of the second set of electric cells. The first fins and the second fins of the first and second sets of folded sheets are interleaved between the electric cells and each other. 
         [0010]    According to other aspects of this embodiment, the first set of folded sheets are U-shaped in cross-section. The first leaf and a second leaf extend from the reverse turn of the first set of folded sheets in a spaced relationship. The second set of folded sheets are U-shaped in cross-section. The first and second leaf extend from the reverse turn of the second set of folded sheets in a spaced relationship. The first and second leafs of the first set of folded sheets are each inserted between a cell and one of the first and second leafs of the second set of folded sheets. The first and second leafs of the first set of folded sheets may each extend to a first internal end and the first and second leaf of the second set of folded sheets may each extend to a second internal end. The first and second leafs of the first set of folded sheets may form a seam at the first internal end and the first and second leafs of the second set of folded sheets may form a seam at the second internal end. 
         [0011]    According to other aspects of this embodiment of the battery assembly, the first fin may have a first surface feature that limits movement of one of the electric cells toward the second internal end and the second fin may have a second surface feature that limits movement of another one of the electric cells toward the first internal end. The first and second retaining surface features may be indentations that engage an outer peripheral edge of the cell. The battery assembly may further include a first electrically insulating layer provided between the electric cells and the first and second fins to electrically insulate the electric cells from the first and second fins. 
         [0012]    The battery assembly includes a liquid that is circulated from a fluid circulation system through the fluid tube and back to the fluid circulation system. 
         [0013]    According to another aspect of the disclosure a fan fold method of manufacturing a battery for an electric vehicle is disclosed wherein a first and a second fin are folded in a fan fold arrangement with a plurality of parallel fins that are joined at a plurality of reversely turned ends. A plurality of electric cells are wrapped with the first and second fins with one cell being disposed between two adjacent parallel fins. A fluid tube is assembled between the first and second fins at the reversely turned ends. 
         [0014]    According to other aspects of the fan fold method, the step of assembling the fluid tube may further comprise wrapping the first fin about the fluid tube on an first reversely turned end and overlapping an outer side of the second fin that encloses one of the electric cells on an inner side of the second fin. The step of assembling the fluid tube may further comprise wrapping the second fin about the fluid tube on a second reversely turned end and overlapping an outer side of the first fin that encloses another one of the electric cells on an inner side of the first fin. 
         [0015]    According to another aspect of the disclosure, an interleaving assembly method of manufacturing a battery is provided. A plurality of electric cells and a serpentine fluid tube are provided that has a plurality of first segments that extend along an first edge of some the electric cells and a plurality of second segments that extend along a second edge of some of the electric cells. A plurality of U-shaped members having two leafs that are joined by a reversely turned portion are assembled each to one of the segments of the fluid tube with each leaf being inserted between two adjacent electric cells. 
         [0016]    According to other aspects of the interleaving assembly method, the plurality of U-shaped members may further comprise a plurality of first U-shaped members and a plurality of second U-shaped members. The assembling step may further comprise assembling the first U-shaped members to the first segments of the fluid tube and assembling the second U-shaped members to the second segments of the fluid tube. The step of assembling the plurality of U-shaped members may further comprise assembling the first U-shaped members over a cell and a leaf of two adjacent second U-shaped members and assembling the second U-shaped members over an adjacent cell and a leaf of two adjacent first U-shaped members. 
         [0017]    According to a further aspect of the disclosure, a battery assembly is sequentially cooled by a fluid circulating cooling system. The battery system comprises a plurality of stacked electric cells that are arranged in a stacking direction. Each electric cell has a first outer edge and a second outer edge on an opposite sides of the electric cells. At least one fluid circulation tube receives a fluid from a supply port, circulates the fluid about the electric cells in a sequence, and drains the fluid into a drain port. The fluid circulation tube includes a first set of segments that each contact one of the outer edges of the electric cell. The fluid transfers thermal energy from the electric cells sequentially as the fluid flows through a first set of segments in the stacking direction and as the fluid flows through a second set of segments counter to the stacking direction. 
         [0018]    According to other aspects of the disclosure relating to the transfer of thermal energy in sequence, the at least one fluid circulation tube may include one fluid circulation tube, wherein the first set of segments contacts the first outer edges and the second set of segments contacts the second outer edges. Alternatively, the at least one fluid circulation tube may include a first fluid circulation tube that includes the first set of segments that contact the first outer edges and a second fluid circulation tube that includes the second set of segments that contact the second outer edges. 
         [0019]    The above aspects and other aspects of the disclosure will be better understood in view of the attached drawings and the following detailed description of the illustrated embodiments. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a fragmentary perspective view of the rear seat in a vehicle and a battery module in a battery storage compartment; 
           [0021]      FIG. 2  is a diagrammatic view of a fluid circulation tube that is routed across two opposite sides of the battery module and is in fluid flow communication with a fluid circulation system; 
           [0022]      FIG. 3  is a diagrammatic view of two fluid circulation tubes that are each routed across one side of the battery module and are both in fluid flow communication with a fluid circulation system; 
           [0023]      FIG. 4  is a fragmentary cross-sectional view of one embodiment of a battery assembly provided with a fluid circulation tube and a plurality of heat conducting fins and electric cells; and 
           [0024]      FIG. 5  is a fragmentary cross-sectional view of an alternative embodiment of a battery assembly provided with a fluid circulation tube and a plurality of heat conducting fins and electric cells. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    A detailed description of the illustrated embodiments of the present invention is provided below. The disclosed embodiments are examples of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale. Some features may be exaggerated or minimized to show details of particular components. The specific structural and functional details disclosed in this application are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art how to practice the invention. 
         [0026]    Referring to  FIG. 1 , a seat  10  for a vehicle  12  is shown in conjunction with a battery assembly  14  of a battery electric vehicle (BEV) or hybrid electric vehicle (HEV). The battery assembly  14  is disposed in a battery compartment  16  located behind the seat  10  of the vehicle  12 . The seat  10  is the rearmost seat of a vehicle which in a vehicle with a single row of seats could be the front seat. The battery compartment  16  of the vehicle  12  is separated from the passengers and seat area by a rear wall  18 . The battery assembly  14  includes an enclosure  20  that encloses a first, or upper, battery stack  22  and a second, or lower, battery stack  26 . It should be understood that a single battery stack could be provided instead of providing a first battery stack  22  and second battery stack  26 . The battery assembly  14  could also be differently oriented in a side-by-side orientation. A fluid supply pipe  28  provides fluid, preferably a liquid coolant, which is circulated through the battery assembly  14  to a fluid return pipe  30 . 
         [0027]    As used throughout the specification and claims of this disclosure, the terms “upper” and “lower” are used with reference to the illustrated embodiments. It should be understood that the battery assembly may be installed in a vehicle with the assembly at an angle, for example, with the upper portions in front of the lower portions or in any other angular orientation. Generally, the upper and lower portions of a part or assembly of parts are on opposite sides of the part. 
         [0028]    Referring to  FIG. 2 , a fluid circulation tube  32  is shown that directs liquid fluid around the battery assembly  14  (shown in  FIG. 1 ) to cool the battery assembly  14 . The fluid circulation tube  32  removes heat or may supply heat to the battery assembly  14 , as needed for optimal battery operation, taking fluid from the fluid supply pipe  28  (shown in  FIG. 1 ) and emptying the liquid into the fluid return pipe  30  (shown in  FIG. 1 ). The fluid circulation tube  32  includes an inlet  33  and an outlet  34  that are connected to a fluid circulation system  35 . Fluid is provided from the fluid circulation system  35  through the inlet  33  and then follows a serpentine path around the top and bottom of either of upper or lower of the battery stacks  22 ,  26  (as shown in  FIG. 1 ). The fluid circulation tube  32  could also follow a serpentine path around the front and rear or left and right sides of the battery assembly  14 . 
         [0029]    In the illustrated embodiment, the fluid circulation tube  32  circulates a liquid coolant around a plurality of battery stacks  22 ,  26  (shown in  FIG. 1 ) prior to being returned to the fluid return pipe  30 . The fluid circulation tube  32  may pass around the top and bottom of a plurality of the electric cells  38  (shown in  FIGS. 4 and 5 ). The temperature of the battery assembly  14  is balanced in the embodiment of  FIG. 2  because the fluid circulating through the fluid circulation tube  32  is heated as it flows sequentially through the top segments  32   a - 32   e  and is continued to be heated as the fluid flows through the bottom segments  32   f - 32   j.  In a cooling mode, an electric cell  38  disposed between segments  32   a  and  32   j  is exposed to the coolest segment and warmest segment. An electric cell  38  disposed next to segments  32   e  and  32   f  is exposed to intermediate temperature segments. Thus the cooling effect is balanced across the module. 
         [0030]    In the embodiment of  FIG. 2 , fewer joints are required for connecting the tube to the coolant supply system. The tube may include a hose  41  shown in dashed lines between the upper and lower sections of the tube. 
         [0031]    Referring to  FIG. 3 , another embodiment is shown that includes on one side, ie. a top side, a serpentine tubular member  37  and on the other side, ie. a lower side, a serpentine tubular member  39 . Coolant is provided through inlets  33   a  and  33   b  to the tubular members  37  and  39 , respectively, from the coolant circulation system  35 . Coolant is returned to the coolant circulation system  35  through the outlets  34   a  and  34   b,  respectively. In this embodiment, coolant passes only around one side of the plurality of electric cells  38  (shown in  FIGS. 4 and 5 ) in a serpentine fluid circulation tube  37  with a second fluid circulation tube  39  passing only around the other side of the plurality of electric cells  38  in a serpentine path. To balance the cooling across the module, the direction of fluid flow in the tubular member  37  is from left to right as shown in  FIG. 3  and the fluid flow through the tubular member  39  is from right to left as shown in  FIG. 3 . 
         [0032]    In the embodiment of either  FIG. 2  or  3 , the inversely symmetrical tube arrangement provides more uniform temperature in all of the cells of a module even though the coolant heats up as it flows through the tubular members. 
         [0033]    Heat created when the electric cells  38  are charged, may be removed by the fluid in the fluid circulation tube  32  and transferred to a fluid circulation system  35 . By removing heat from the electric cells  38  during charging, the battery assembly  14  may be charged more efficiently. Conversely, a cold battery may be heated by circulating warm fluid through the fluid circulation tube  32 . More efficient discharge of the electric cells  38  may also be achieved by warming the battery assembly  14  to a preferred temperature range by circulating the warm fluid through the fluid circulation tube  32  and fluid circulation system  35 . 
         [0034]    Referring to  FIG. 4 , one embodiment of a battery pack  36  is shown in which a plurality of electric cells  38  are wrapped between a first fin layer  42  and a second fin layer  44 . A length of a fluid circulation tube  32  is received between the first and second fin layers  42  and  44 . A void  48  is formed between the first fin layer  42 , second fin layer  44  and the fluid circulation tube  32 . The void  48  may be filled with a thermal compound  50 . The electric cells  38  have a fin  52  formed about their outer periphery. The first fin layer  42  has an outer reverse turn  54  that is formed around and in close contact with the fluid circulation tube  32  in the portion of the battery pack at the bottom of  FIG. 4 , as illustrated. An inner reverse turn  56  is formed in the second fin layer  44 . The inner reverse turn  56  is shown abutting the fluid circulation tube  32  and is also received within the first fin layer  42 . The second fin layer  44  in the leftmost loop shown in  FIG. 4  is shown to be in contact with one of the electric cells  38 . 
         [0035]    In the upper portion of  FIG. 4 , the orientation of the first and second fin layers  42  and  44  is reversed so that the second fin layer  44  extends around the outside of the fluid circulation tube  32  and encloses the first fin layer  42 . The second fin layer  44  is formed into the outer reverse turn  58 . The first fin layer  42  includes an inner reverse turn  57  that is shown to be in contact with the fluid circulation tube  32 . The first fin layer  42  contacts the second electric cell  38  from the left as shown in  FIG. 4 . 
         [0036]    The second fin layer  44  in the first loop on the left side of  FIG. 4  includes an indented rib  59  that limits movement of the cell  38  toward the inner reverse turn  56 . The first fin layer  42  and the second cell from the left in  FIG. 4  includes an indented rib  59  that similarly restricts movement of the cell in the second cell from the left in  FIG. 4 . 
         [0037]    A first surface  60  of the first fin layer  42  contacts one of the electric cells  38 . A second surface  62  of the first fin layer  42  is provided on opposite side of the first fin layer  42  from the outer surface  60 . Similarly, a first surface  64  of the second fin layer  44  contacts one of the electric cells  38  in an alternating fashion while the second surface  66  of the second fin layer  44  is in face-to-face contact with the second surface  62  of the first fin layer  42 . 
         [0038]    To prevent short circuiting through the fins, an electrically insulating layer  68  should be provided between the first surface  60  of the first fin layer  42  and between the first surface  64  of the second fin layer  44 . The electrically insulating layer  68  may be incorporated as an outer covering of the electric cells  38 . The electrically insulating layer, while not shown in  FIG. 4 , may alternatively be a thin layer of plastic or other insulating material that is provided in the areas identified by reference numeral  68  on both sides of the electric cells  38 . 
         [0039]    According to the process for continuous automated assembly, straight lengths of the tubular member  32  denoted  32   a - j  and the bent portions of the tube may be continuously formed as the fins are folded into position around the tube segments  32   a - j.  The electric cells  38  are placed in position as each layer of the tube  32  and fins  42  and  44  are formed into position. The fins  42  and  44  are folded into a tight fit with the tubular member  32  to facilitate heat transfer. 
         [0040]    Referring to  FIG. 5 , an alternative embodiment of the battery pack is generally indicated by reference numeral  70 . In the description of  FIG. 5 , similar components to those shown in  FIG. 4  are identified by the same reference numeral. A plurality of folded sheets  71  are simple pre-formed members that are interleaved with electric cells  38 . A first thermal fin  72  and a second thermal fin  74  are assembled together as a dual leaf structure from opposite directions. The thermal fins  72  and  74  each include an intermediate bend  76  that is assembled to a length of the fluid circulation tube  32 . An end flange  78  is provided on each of the planar fins  72  and  74 . Two adjacent thermal fins  72  are inserted from the same side with one leaf of each fin  72  being received within one of the fins  74 . One leaf of each fin  72  is inserted between the electric cells  38  and one leaf of the fin  74 . A seam  80  is formed at the juncture of the end flanges  78 . The electric cells  38  are captured between each pair of thermal fins  72  and  74  with the electric cells  38  being aligned with the seam  80 . A void  48  is formed between the fluid circulation tube  32  and the end flanges  78  of the thermal fins  72  and  74 . The fin design facilitates forming the fins  72  and  74  into a tight fit to facilitate heat transfer. The process for assembling the fins  72  and  74  to the electric cells  38  may be automated. 
         [0041]    The battery pack  70  shown in  FIG. 5  may be assembled by stacking a plurality of folded sheets  71  with the dual leaf planar thermal fins  72  and  74  being assembled from opposite sides. The dual leaf planar thermal fins  72  and  74  may be assembled with one leaf on each side of the fluid circulation tube  32  and on the outer side of the oppositely oriented planar leaf The electric cells  38  disposed between adjacent thermal fins are inserted from the sides of the assembly as shown in phantom lines in  FIG. 5 . An electrically insulating layer (not shown in  FIG. 5 ) may be provided (either on the electric cells  38  or fins  72  and  74 ) between the electric cells  38  and the dual leaf thermal fins  72  and  74  to prevent electrical contact between the thermal fins  72 ,  74  and the electric cells  38 . 
         [0042]    While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.