Abstract:
A modular battery pack and method of making a battery pack. The modular structure includes an open box with an interlocking features to allow for flexibility in assembly of numerous battery pack configurations. The design is such that numerous sub-module assemblies are formed that can be fastened, connected or otherwise secured to a tray, frame or other underlying primary support structure. Aligned stacks of individual battery cells can be placed within the volume defined within the box-like structure so that portions of the box-like structure move in response to a spring-like force imparted by the stack of battery cells. Adapter plates facilitate the modular construction by an interlocking connection between the box-like structure and the underlying support structure.

Description:
This application claims priority to U.S. Provisional Application 61/579,204, filed Dec. 22, 2011. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to a mounting strategy for batteries, and more particularly to using such a strategy for various battery modular configurations where the batteries are used to generate motive power for vehicular and related transportation applications. 
     Various batteries, including lithium-ion, lead acid and nickel-metal hydride variants, may be configured to supplement or supplant conventional internal combustion engines (ICEs) for automotive and related transportation applications. The ability to passively store energy from stationary and portable sources, as well as from recaptured kinetic energy provided by the vehicle and its components, makes batteries (in general) and rechargeable batteries (in particular) ideal to serve as part of a propulsion system for cars, trucks, buses, motorcycles and related vehicular platforms. In one form suitable for automotive applications, the batteries are shaped as a generally thin rectangular cell with positive and negative voltage terminals emanating therefrom; several such batteries may typically be combined into larger assemblies—including modules that in turn can be formed into a complete system known as a battery pack—to generate the desired power output. 
     Current modules for holding, mounting or otherwise securing battery cells require numerous components, as well as complicated manufacturing processes to ensure such proper mounting. involving laser welding, spot welding, high part-count fasteners or the like. In the case of welding, such processes involve excessive temperatures, weld flash and related undesirable side effects. Furthermore, the use of compression limiters (along with their associated tie rods) along the stacking dimension of numerous battery cells into a larger battery module may produce tolerance problems during such stacking. Because the compression limiters tend to be made in large batches—where the dimensional consistency from one batch to another may be subject to fairly high tolerances—the stacking of such limiters (which individually may be acceptable) could, upon considering the multiplying effect of placing numerous such limiters into a module, produce unacceptable component size mismatches. Eccentricities in the bores formed in the compression limiters may exacerbate assembly problems, as the tie rods may be intolerant of a misaligned stack of apertures. Other components, such as compression bands (while helpful in ensuring proper dimensions of an assembled stack) and hold-down rails (helpful in providing discrete support of the assembled module onto a tray), introduce increases in overall part count, as well as reduce the overall modularity of the battery system. It is difficult to reconcile different vehicle platforms (where vehicular size, shape and power outputs or battery pack configurations dictate the final configuration of the battery pack) with production and inventory techniques such as those mentioned above, and an attempt to accommodate such a variety of configurations makes an approach based on the above inefficient and expensive. 
     It would be advantageous to have a modular mounting or attachment approach that accommodates number battery pack sizes and configurations. 
     SUMMARY OF THE INVENTION 
     In accordance with the teachings of the present invention, a modular design for securing one or more batteries (i.e., battery cells) into a larger battery assembly (such as a battery module or a battery pack) is disclosed. The design is such that numerous sub-module assemblies are formed that can be fastened, connected or otherwise secured to a tray, frame or other underlying primary support structure. Each of the sub-module assemblies may define an open box made up of two opposing brackets along one axis and two opposing end plates along an orthogonal axis. The box-like structure can be placed on or with the primary support structure in a modular fashion to permit as many battery cells in modular form as needed. Aligned stacks of individual battery cells (that resemble, for example, a stacked deck of playing cards) can be placed within the volume defined within the box-like structure so that the end plates may move along an axis that is substantially normal to theirs (as well as the stacked cells) respective planar dimensions. In this way, at least the corresponding dimension of the box-like structure may move in response to a spring-like force imparted to the end plates by the stack of batteries. Adapter plates facilitate the modular construction by (in one form) including an interlocking connection with the box formed by the brackets and end plates; the construction of the adapter plates promotes an easy and variable attachment to the underlying support structure. This in turn allows for a number of battery pack integrations and variations, especially as they relate to the increased use of common parts in multiple packaging configurations where different numbers of individual batteries may be used to form battery packs of different sizes, shapes, outputs or the like. Such an adaptable configuration is more robust than that used in hoop and compression limiter designs. 
     In the present context, the battery pack is considered to be a substantially complete assembly or system of components necessary for propulsion of the vehicle for which the pack was designed, while battery modules and individual battery cells are (as mentioned above) considered to be subcomponents of the overall system Likewise, an assembly of components for a battery pack used for vehicular applications may include—in addition to numerous battery cells—cooling plates, frames, trays, securing mechanisms and other equipment that, while not contributing to the production of electric power, form an important part of the overall battery system nonetheless. Traditionally, all of these components are stacked and joined together in such a way that weight, cost and complexity are increased. By way of example, the frames alone may be as much as 10% of the total weight of the overall battery pack assembly or system. A further difficulty is that the equipment and fabrication techniques used in such a system do not lend themselves to the formation of modular assemblies that can be modified depending on the particular power needs or layout of the vehicle. 
     According to another aspect of the invention, an automotive battery pack including battery cells, a primary support structure and at least one modular assembly is disclosed. Each modular assembly includes brackets spaced apart from one another along a bracket axis and end plates arranged along an end plate axis such that together, the end plates and the brackets define a box-like structure. The battery cells are either stacked or able to be stacked; in either way, upon placement of the stacked battery cells in the volume defined by the box-like structure, at least one of the end plates can be moved along the end plate axis that is formed along the stacked dimension of the battery cells that is generally orthogonal to the bracket axis. The connection of the adjacent edges of the end plates and brackets is such that a gap or related additional space is formed. One or more adapter plates are also included to provide a secure connection of the modular assembly to the primary support structure via one or more of the brackets. Additional equipment may also be present, including cooling conduit (also referred to herein as heat exchange conduit) to promote heat delivery to or heat removal from the various battery cells. In a particular form, the battery pack is shaped to provide a substantially conformal fit within a corresponding part of a vehicle. As discussed in conjunction with the previous aspect, the brackets define a channel to provide a gap and promote the connection with the end plates. 
     According to yet another aspect of the invention, a method of assembling an automotive battery pack is disclosed. The method includes arranging one or more modular assemblies (such as the aforementioned sub-modules) into generally box-like structures that can expand along one or more dimensions of the box. In this way, each sub-module can accept numerous battery cells that are under a certain amount of compression (although not so much that damage to the structure of any of the battery cells results) such that the stacked cells exert an outward-pushing force along their stacked dimension. As discussed above, the fit between the adjacent plates, brackets or related structure that forms the walls of the box-like structure is such that it permits the relative movement of the end plates relative to the brackets, while the construction of the adapter plates is such that the size, placement or number of modular assemblies may be tailored to coincide with the power, size or shape requirements of the vehicle into which the battery pack is placed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The following detailed description of the preferred embodiments of the present invention can be best understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which: 
         FIG. 1  shows a vehicle with a hybrid propulsion system in the form of a battery pack and an internal combustion engine; 
         FIG. 2A  shows details associated with the battery pack; 
         FIG. 2B  shows a detailed view of a representative stack of individual battery cells highlighting the placement of compression limiters as a way to assemble such a stack according to the prior art; 
         FIG. 3  shows a single battery sub-module according to an aspect of the present invention; 
         FIG. 4  shows a more detailed view of the connection of an adapter plate, bracket and end plate according to an aspect of the present invention; 
         FIG. 5  shows a pair of adjacent battery sub-modules secured to one another through a minimum-width center plate; and 
         FIG. 6  shows the respective placement of a 12-cell stack into a module cage and then compressed into a module through the cooperation of the cage and end plates. 
     
    
    
     DETAILED DESCRIPTION 
     Referring first to  FIGS. 1 ,  2 A and  2 B, a vehicle  1  includes a hybrid propulsion system in the form of an electric power source made up of a conventional ICE  5  and a battery pack  10 . Such a vehicle is known as a hybrid electric vehicle (HEV). It will be appreciated by those skilled in the art that vehicle  1  may not require an ICE  5 , in such case, rather than being an HEV, it is an electric vehicle (EV); either form is within the scope of the present invention. Additional drivetrain components (none of which are shown) useful in providing propulsive power to one or more of the wheels and coupled to one or both of the battery pack  10  and ICE  5  are understood to include electric motors, rotating shafts, axles, transmission, controllers or the like. While vehicle  1  is presently shown as a car, the applicability of the hybrid propulsion system to other such automotive forms (including trucks, buses, aircraft, watercraft, spacecraft and motorcycles) is deemed to be within the scope of the present invention. 
     As shown with particularity in  FIG. 2A , the battery pack  10  is made up of numerous battery modules  100  that in turn are made up of individual battery cells  1000 , companion cooling plates  1100  and (as shown with particularity in  FIG. 2B ) a frame  1200  used to provide structural support. Adjacent individual cells  1000  (which in one form are shaped into generally planar rectangular members) may be stacked such that they (as well as the interspersed cooling plates  1100 ) may face one another as shown. In one typical example, the battery pack  10  may be made up of between about two hundred and three hundred cells  1000 , although it will be appreciated by those skilled in the art that additional or fewer cells  1000  may be needed, depending on the power requirements of vehicle  1 . In one commercial embodiment employed by the Assignee of the present invention, the numerous individual battery cells  1000  are arranged in a combination of serial and parallel connections into nine modules  100  that are arranged in the repeating array as shown to define the generally T-shaped pack  10 . Additional components of battery pack  10  may include coolant delivery conduit  20  (which may be fluidly cooperative with cooling plates  1100  to facilitate the delivery of a coolant (not shown) between the individual battery cells  1000  and a radiator or related heat exchanger (neither of which are shown)), an electronic control unit  30 , bulkhead  40 , battery interface units  50 , manual service disconnect plug  60 , insulation  70  and cover  80  to provide other operational features of battery pack  10 . All of the components mentioned above include undergirding structural support in the form of battery pack tray (also called module tray)  90 , which additionally may include features to enhance vehicular crash-worthiness and other support functions. Hold-down rails  95  are used to clamp a protruding surface of the support frame such that the modules  100  don&#39;t move relative to tray  90  that provides the primary support structure for the individual cells  1000 , modules  100  and other parts of the assembled battery pack  10 . Thus, in one form, tray  90  can provide the support structure of the battery pack such that one or more of the box-like structures that define the shape of the sub-modules can be secured to it. In one preferred form, the securing of the sub-module  110  to the tray  90  is such that it avoids complicated manufacturing processes, such as those involving forming the cage-like structure of the module  100 , as well as those associated with securing the modules  100  to the tray  90 . In a preferred embodiment, the vehicle  1  defines either a body-on-frame construction or a unibody construction; in either configuration, the battery pack  10  of the present invention is shaped to provide a substantially conformal fit within at least one of an automotive body, frame or unibody platform. Such a substantially conformal fit is preferably due to comparable shapes of the outer dimension of the battery pack  10  and complimentary shape in the portion of the body, frame or unibody structure that is designed to form around the battery pack  10 . 
     Referring with particularity to  FIG. 2B , a partial cutaway view shows the various compression limiters  103 , tie rods  105  and supporting flanges or bulkheads  107  (with apertures formed therein for the tie rods  105  and coolant channels) that are used to keep the compression limiters  103  of the prior art properly aligned and stacked. As can be seen, the size and placement of the apertures in the flanges or bulkheads  107  is such that misalignment along the length of the stack is possible unless they are kept to a very tight tolerance. Likewise, the dimensions of the compression limiters  103  along the stacked dimension are such that compressibility and subsequent containment of the stacked fuel cells (not presently shown but represented individually by corresponding frames  1200 ) could be adversely impacted. 
     Referring next to  FIG. 3 , a generally box-shaped cell sub-module  110  is shown (with a group of aligned and stacked battery cells nested therein) resting upon and being connected to tray  90 ; this sub-module  110  includes a generally U-shaped module cage  115  that defines a pair of generally planar upstanding perforate brackets  120  spaced apart by a generally planar base  122  such that the brackets  120  face each other. A pair of slidably-insertable planar end plates  140  can fit within a channel  125  formed by a curvature in the ends of the brackets  120 . The interlocking curls formed by cooperation of the channel  125  and the edges of the generally planar construction of the end plates  140  allows the formation of the box-like structure without the need for welding or fasteners. Furthermore, the size of the channel  125  is such that a gap  135  is formed that permits a relatively loose fit of the end plate  140  within the brackets  120 . This is beneficial in that it can accommodate a spring-like loading of an aligned stack of individual battery cells  1000  (as discussed in more detail below) to ensure a secure fit of cells  1000  within the box-like shape of the sub-module  110 . Thus, the cooperation of the end plate  140  may be placed in an adjacently-faced relationship relative to the adapter plate  130  such that upon placement of numerous battery cells within the box-like structure of cell sub-module  110 , the lateral edges of the stacked cells (not presently shown in  FIG. 3 ) substantially align along the inward-facing surface of the corresponding end plate  140 . In one embodiment, one or both of the end plates  140  and the brackets  20  may have tapered edges to promote an interface that locks together in a manner similar to that of a tapered ball joint design. 
     Adapter plates  130  (which in one preferred form are also of a generally planar construction) may be placed in an adjacently-faced relationship relative to the end plates  140 . In fact, the end plates  140  are designed to accept a number of adaptor plates  130  which can additionally be bolted down directly to the tray  90 . Moreover (as will be discussed in more detail below), these adapter plates  130  can lock two adjoining battery modules together side-to-side or end-to-end. The adapter plates  130  can be combined with features of other pack components, such as a mounting location for a manual service disconnect (not shown). The adapter plate  130  includes unitarily-formed mounting footers  131  as flanged sections to allow a threaded, bolted or related attachment  133  between the cell sub-module  110  and the underlying battery pack tray  90 . Although the present adapter plate  130  is shown with bottom corner mounting locations, it will be appreciated by those skilled in the art that other configurations, such as top flanges with bolt holes formed at end or side locations relative to the box-like structure of sub-module  110  (neither of which are shown) are also within the scope of the present invention. Suffice to state that one of the salient attributes of adapter plate  130  is that its flanged and apertured attachment configuration is of a substantially unitary construction with mounting points sufficient to accommodate complementary locations with tray  90  or other battery pack structure, thereby facilitating a more modular construction than if bound by limited attachment locations. Significantly, the flanged footers  131  permit substantial continuity of attachment of the sub-module  110  to the underlying tray  90 . Upon assembly, a Cartesean coordinate axis defines the three generally orthogonal axes that correspond to a bracket axis  120   A , an adapter plate axis  130   A  (which coincides with an end plate axis  140   A  as shown in  FIG. 6 ) and a vertical axis V A . As can be seen, each axis defines a linear dimension that extends in a direction that is substantially normal to the planar dimensions of their respective brackets or plates. 
     Referring next to  FIG. 4  in conjunction with  FIG. 3 , as with the relationship between the brackets  120  and the end plates  140 , there is a nested arrangement of the generally planar edge of the adapter plate  130  within the C-shaped channel  125  formed in the end of the bracket  120 . The adapter plate  130 , bracket  120  and module end plate  140  are shown in more detail in their assembled form, where the battery pack tray  90  of  FIG. 3  has been removed from the present figure for viewing clarity. In one form, numerous individual generally rectangular, planar cells and cooling plates (neither of which are shown) are stacked within the assembled module sub-module  110 ; in the process, they are compressed along their stacked dimension, after which the stack of cells and cooling plates is allowed to expand. This expansion presses against the adjacent face of the end plate  140 , causing it to more securely cooperate with bracket  120 . An additional flat plate  150  is optionally present as a cooling plate which—in this configuration—is placed between the end plate  140  and the cells (not presently shown). As shown in the figure, the lateral edges of the end plates  140  may also be formed into a generally C-shaped channel such that the C-shaped portion of each end plate  140  may nest inside the C-shaped portion of the adjoining bracket  120 . Once the end plate  140  is in place, the adapter plate  130  may then be slid down into the channel  125 . The top-down slidable engagement of the adapter plates  130  within the channel  125  permits the stacked sequence of numerous individual cells to be secured or otherwise attached to the tray  90 . Other components of the sub-module  110 , including cell monitoring electronics  160 , positive and negative terminals  170  and sub-module cover  180  are shown in  FIG. 3  as being contained within the sub-module  110 . In configurations where top flanges (similar to flanged footers  131 ) are employed, battery cell sub-modules  110  may be placed in a vertically-stacked arrangement, thereby further contributing to the flexibility of the battery packs to fit within a particular vehicle configuration. 
     Referring next to  FIG. 6 , a group of twelve individual cells  1000  are stacked—along with end plates  140  and the top section defined by the battery interface unit  160  that includes (among other things) positive and negative battery terminals  170 —into the spaced brackets  120  to form the box-like structure of the sub-module  110 . The combined effect of the brackets  120  and the end plates  140  is that the cage  115  that is formed into the box-like structure holds the end plates  140  and the stacked cells in compression, while the end plates  140  hold in the sides of the cage  115  that extend along the stacked axis of the cells. In general, the cells  1000  are stacked in a face-to-face relationship such that their edges substantially align to define a generally rectangular shape. End plates  140  are added to the opposing ends of the stacked cells  1000 , while the battery interface unit  160  is mounted at the top so that three of the six sides of the sub-module  110  are in place. The slightly compressive properties of the cells  1000  tend to push along the end plate axis  140   A  so that the end plates  140  are likewise pushed outward. This subassembly is then lowered into the spaced defined by cage  115  so that once engaged, the edges of the end plates  140  are slid into the channels  125  of the brackets  120 . As mentioned above, the gaps present within the channels  125  permit a certain amount of movement in order to accommodate the compressive forces exerted by the stacked cells  1000  on the end plates  140 . At As assembled, the sub-modules  110  define all six sides of the box-like structure to provide containment and support for the numerous individual battery cells  1000  that are in turn supported by tray  90 . Upon inclusion of one or more adapter plates (not presently shown) along one of the various mounting locations on tray  90 , the sub-modules  110  may be arranged such that they make up the modules  100  that are shown in  FIG. 2A . 
     Referring next to  FIG. 5 , an interlocking adapter plate (now called a center plate)  230  can be designed such that it can lock two sub-modules  110  together side-to-side or end-to-end. The interlocking adapter plate  230  interfaces the bracket  120  in a manner generally similar to that of the module end plate  140  and the interlocking adapter plate  130 , but is designed to interface two sub-modules  110  in this manner at the same time. This promotes a minimum-width to accommodate dimensional variations, as well as the diameter of the fastener used between the adjacent sub-modules  110 . The end plates  140  can be combined with features of other components, such as a mounting location for a manual service disconnect. Moreover, the end plates  140  can be designed to accommodate additional battery pack configurations not shown in the figures. The center plate configuration between two adjacent sub-modules  110  not only reduces the overall assembly footprint by reducing the distance between adjoining sub-modules  110 , but also can double on some of the ends as a close-out plate at the end of a battery pack. This is the case regardless of whether the adapter plates  130  or center plates  230  are configured for bottom (i.e., tray  90 ) securing (such as that through the aforementioned bolted relationship) or top securing (which would be especially useful in stacked module configurations). 
     Although not shown, the modular nature of the sub-module construction is such that the adapter plates not only promote flexibility in tray mounting and module stacking options as a way to accommodate various vehicular power and shape configurations, they also have the effect of further reducing part count by removing the need for an end plate on the closed-out end of the battery pack  10 . 
     It is noted that terms like “preferably,” “commonly,” and “typically” are not utilized herein to limit the scope of the claimed invention or to imply that certain features are critical, essential, or even important to the structure or function of the claimed invention. Rather, these terms are merely intended to highlight alternative or additional features that may or may not be utilized in a particular embodiment of the present invention. Likewise, terms such as “substantially” are utilized to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. It is also utilized to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue. 
     For the purposes of describing and defining the present invention it is noted that the term “device” is utilized herein to represent a combination of components and individual components, regardless of whether the components are combined with other components. For example, a device according to the present invention may comprise a battery or related source of electric power that in turn may be used to provide motive power. A device may also refer to a vehicle incorporating the source of motive power or other equipment that may make up, or be used in conjunction with, the vehicle or source of motive power; the nature of the device will be clear from the context. Furthermore, variations on the terms “automobile”, “automotive”, “vehicular” or the like are meant to be construed generically unless the context dictates otherwise. As such, reference to an automobile will be understood to cover cars, trucks, buses, motorcycles and other similar modes of transportation unless more particularly recited in context Likewise, the invention may be used in conjunction with battery cells unrelated to automotive applications, where temperature-sensitive equipment may need added thermal protection; such additional configurations are understood as being within the scope of the present invention. 
     Having described the invention in detail and by reference to specific embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims. More specifically, although some aspects of the present invention are identified herein as preferred or particularly advantageous, it is contemplated that the present invention is not necessarily limited to these preferred aspects of the invention.