Prismatic battery module with scalable architecture

Abstract

A battery system comprising: a plurality of sub-units, each comprising a heat sink and a battery cell having an upper end and first and second voltage poles, both extending from the upper end of the battery cell, the first and second voltage poles of each battery cell being arranged symmetrically with respect to a center line of that battery cell, wherein all battery cells in the plurality of sub-units are arranged such that their first voltage poles are aligned in a first row and their second voltage poles are aligned in a second row; a plurality of identical busbar supports in the same number as the plurality of sub-units, each busbar support of the plurality of busbar supports having two slots and being mounted on a corresponding different one of the sub-units, each of the first and second terminals of the battery cell for that sub-unit extending upwardly through a corresponding different one of the two slots; and a plurality of bimetallic busbars, each supported by a different corresponding subset of busbar supports and electrically directly connected to either a first or second pole of each of the battery cells of each of the modules on which those busbar supports are mounted, wherein each of the plurality of subunits further comprises a second battery cell having an upper end and first and second voltage poles both extending from the upper end of the second battery cell, wherein the first and second poles of each second battery cell are arranged symmetrically with respect to the centerline of that battery cell, and wherein each of the second battery cells in the plurality of sub-units is arranged such that its first voltage poles are aligned in the first row and its second voltage poles are aligned in the second row.

Description

TECHNICAL FIELD

[0001] The present invention relates to battery modules and scalable architectures for manufacturing battery modules. BACKGROUND OF THE INVENTION

[0002] A "battery module" is a subassembly typically installed within a "battery pack," which is a unit installed in a land, sea, or air vehicle. These vehicles typically have a variety of high-power electrical loads, such as computer-controlled inverters that power an electric motor used for vehicle propulsion or some form of mechanical actuation.

[0003] A large group of battery modules can also be used by an electric utility to help offset the worst cases of power fluctuations in a local power distribution grid. The modules are installed in a "battery station," which is a large, fixed, weatherproof, climate-controlled enclosure fixed to a concrete foundation. The modules are mounted and electrically connected using racks and couplings, allowing each module to be quickly connected or disconnected.

[0004] Other subassemblies and components are typically installed in battery packs and battery stations to deliver complete, ready-to-use battery packs to vehicle manufacturers or complete, ready-to-use battery stations to electric utilities. These subassemblies and components include electronic sensor modules, electronic control modules, electrical charging modules, electrical interface connectors, electrical fuses, electrical wiring harnesses, and thermal management devices. BRIEF SUMMARY OF THE INVENTION

[0005] Generally, from one aspect, a battery system having a scalable architecture comprises a group of sub-assemblies, each of which comprises a heat sink and a battery cell having a top end and first and second voltage terminals extending from the top end of the battery cell, wherein the first and second voltage terminals of each battery cell are arranged symmetrically with respect to a centerline of the battery cell, and wherein all battery cells in the plurality of sub-assemblies are arranged such that their first voltage terminals are aligned in a first row and their second voltage terminals are aligned in a second row.The system further comprises a set of identical busbar supports equal in number to the plurality of sub-assemblies, each busbar support having two slots and mounted on a corresponding sub-assembly, each of the first and second battery cell terminals for that sub-assembly extending upwardly through a correspondingly different one of the two slots. The system also comprises a group of bimetallic busbars, each supported by the busbar supports and electrically directly connected to either a first or second terminal of each of the battery cells of each of the modules on which those busbar supports are mounted.

[0006] Other embodiments include one or more of the following features. The battery cells used in the system are prismatic battery cells. Both the first and second rows of terminals are located on the same side of the battery system. All subunits are identical to each other, except for the orientation of each of the battery cells of the subunit relative to the cell centerline. All heat sinks are identical to each other except for one or two heat sinks. Each of the bus bars is electrically connected to at least two adjacent terminals in the same row of terminals.

[0007] In certain embodiments, the battery system comprises two pressure plates, with the subassemblies arranged as a stack between the pressure plates. In one such embodiment, one or more compliant pads are located between the first pressure plate and the adjacent subassembly. In another such embodiment, a band encloses the first and second pressure plates and the subassemblies.

[0008] In embodiments of the battery system, each of the plurality of sub-units further comprises a second battery cell having a top end and first and second voltage poles both extending from the top end of the second battery cell, wherein the first and second poles of each second battery cell are arranged symmetrically with respect to the centerline of that battery cell, and wherein all second battery cells in the plurality of sub-units are arranged such that their first voltage poles are aligned in the first row and their second voltage poles are aligned in the second row.

[0009] In general, from another aspect, a battery system comprises a plurality of battery sub-units, each sub-unit comprising a heat sink and at least one battery cell having a positive terminal and a negative terminal; a plurality of bus bar supports equal in number to the plurality of battery sub-units, and each mounted on the heat sink of a corresponding different one of the plurality of sub-units, each bus bar support comprising a first slot through which the positive terminal of the at least one battery cell for that sub-unit passes and a second slot through which the negative terminal for the at least one battery cell for that sub-unit passes, said plurality of bus bar supports comprising a first bus bar support;a first busbar located above and at least partially supported by the first busbar support and electrically connected to the negative pole passing through the first slot in the first busbar support; and a second busbar located above and at least partially supported by the first busbar support and electrically connected to the positive pole passing through the second slot in the first busbar support.

[0010] Other embodiments include one or more of the following features. Wherein the first bus bar support comprises a latch to engage a slot in a heat sink. Wherein the first bus bar support comprises a thermistor and a socket in which a thermistor is at least partially disposed. Wherein the battery system further comprises a bus bar shell, the first bus bar support comprising a container to which the bus bar shell is attached. Wherein the first bus bar support comprises a groove in which wiring is disposed and a flexible finger that at least partially retains the wiring within the groove. Wherein the first bus bar support comprises two latches between which a bus bar is at least partially retained. Wherein the first bus bar support comprises a main body located between the first bus bar and the positive terminal of the battery cell of the corresponding sub-unit.The battery cell is a prismatic battery cell.

[0011] Generally, from another aspect, a method of manufacturing a battery comprises: mounting a first battery cell on a heat sink, the battery cell having a first terminal; attaching a bus bar support to the heat sink, the bus bar support including a first slot through which the first terminal passes; providing a bus bar having a U-shaped portion defining a groove and characterized by a bend corner at one end of the U-shaped portion, the bus bar also having a treatment for reducing reflectivity at least near the bend corner; mounting the bus bar on the bus bar support, the bus bar support fixing the bus bar such that the first battery terminal is disposed in the groove formed by the U-shaped portion such that the upper end of the terminal is immediately adjacent to the bend corner; directing a laser beam onto the bend corner of the U-shaped portion;and melting the bus bar at the bend corner by means of the laser beam and forming a metallurgical connection between the bus bar and the upper end of the first battery terminal;

[0012] In certain embodiments, the laser beam is directed at a substantially frontal angle toward the end of the battery cell terminal. In some such particular embodiments, the laser beam travels in a direction of travel parallel to the groove, where in some embodiments the laser beam is directed at a slightly less than perpendicular angle to the direction of travel. In some other such particular embodiments, the treatment comprises a coating of one or more of nickel and tin.Still other such particular embodiments further include forming the bus bar by joining a first bus bar segment to a second bus bar segment, the first segment being made of a first metal and the second segment being made of a second metal different from the first metal, where in some embodiments the first bus bar segment is ultrasonically welded to the second bus bar segment before the bus bar is attached to the pole.

[0013] In general, in yet another aspect, a battery system comprises a plurality of battery subassemblies arranged in a stack, each battery subassembly of the plurality of battery subassemblies comprising a first battery cell, a heat sink, a second battery cell, and a compliant pad, in that order, with the heat sink between and in thermal contact with the first and second battery cells, and with the compliant pad adjacent to the second battery cell. In some embodiments, the battery cells are prismatic batteries.

[0014] In embodiments of the battery system, the plurality of battery subunits are arranged in a stack, wherein the compliant pad of one subunit is in contact with the first battery cell of an adjacent subunit.

[0015] In certain embodiments of the system, each of the heat sinks is substantially identical to each of the other heat sinks.

[0016] In embodiments, the battery system further comprises a heat sink disposed at the first end of the stack in thermal contact with the first battery cell of the adjacent battery sub-unit.

[0017] In embodiments, the heat sink of a first battery sub-unit of the plurality of battery sub-units comprises a bottom surface and a side connected to the bottom surface, the side being at approximately a right angle to the bottom surface. Some such embodiments include the following features: Wherein the side is formed by an approximately ninety-degree bend in the heat sink. Wherein the side is formed by three parallel approximately ninety-degree bends in the heat sink, and where the three bends form a notch that receives a top edge of the side of an adjacent heat sink.

[0018] In some embodiments of the system, the first battery cell of a first sub-assembly comprises a flexible sidewall, wherein the heat sink of the first sub-assembly comprises a tooth structure extending from the heat sink toward the sidewall of the first battery cell, and wherein the tooth structure comprises a distal end sufficiently sharp to pierce the flexible sidewall of the first battery cell if the flexible sidewall of the first battery cell is forced against the tooth structure due to the buildup of excess pressure within the first battery cell.

[0019] Certain embodiments further comprise a bus bar support mounted to the heat sink of the first sub-assembly, wherein the first battery cell of a first sub-assembly comprises a flexible sidewall, and wherein the bus bar support comprises a tooth structure extending from the heat sink toward the sidewall of the first battery cell, and wherein the tooth structure comprises a distal end that is sufficiently sharp to pierce the flexible sidewall of the first battery cell if the flexible sidewall of the first battery cell is forced against the tooth structure due to the buildup of excess pressure within the first battery cell.

[0020] The details of one or more embodiments of the invention are set forth in the accompanying drawings and the following description. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. SHORT DESCRIPTION OF THE CHARACTERS

[0021] For a more complete understanding of the nature and objects of the present invention, the following detailed description should be taken in conjunction with the accompanying drawings, in which the same reference numerals are used to identify the same or similar parts, wherein: Fig. 1 shows a battery module. Fig. 2 shows a battery module with busbar covers and busbars removed and subassemblies exposed. Fig. 3 shows a prismatic battery cell. Fig. 4 shows a zipper lock of a prismatic battery cell. Fig. Figure 5 shows a more detailed view of a cell subaggregate. Fig. 6 shows another view of a cell subaggregate. Fig. 7 shows an alternative heat sink and cell subassembly. Fig. 8 shows another alternative heat sink and cell subassembly. Fig. 9 shows a heat sink with attached pressure relief teeth. Fig. 10 shows a view of a battery module pressure plate. Fig. 11 shows a portion of a belt component of a battery module. Fig. 12 shows several busbar supports attached to cell subassemblies in a battery module, including a cell subassembly with reduced height. Fig. 13A shows a busbar support attached to a heat sink. Fig. 13B shows an alternative busbar support for supporting a battery cell. Fig. 14 shows a plurality of busbar supports attached to cell subassemblies in a battery module, each supporting at least a portion of a busbar jumper. Fig. 15 shows a side profile of a busbar jumper. Fig. 16 shows a busbar pole in relation to a pressure plate and cell subassemblies. Fig. 17 shows a busbar pole attached to a pressure plate and a busbar bridge. Fig. 18 shows a busbar pole with two variations of clamps for securing wiring. Fig. 19 shows a side view of a wiring fixing bracket. Fig. 20 shows a support bracket for mounting a thermistor. Fig. 21 shows a sectional view of a busbar sleeve. Fig. 22 shows a family of battery modules incorporating scalable architecture. Fig. Shows 23 pressure relief teeth. Fig. 24 shows several arrangements of bus bar components that can be used to achieve different configurations of battery modules. Fig. Showing 25 views of a welding laser configuration in relation to a busbar component. Fig. 26 before and after views of the attachment of a busbar component to a battery cell terminal. DETAILED DESCRIPTION OF THE INVENTION

[0022] A battery module consists of an assembly of cell subassemblies, each containing a prismatic battery cell, with the cells electrically connected to the other cells in the module to form the battery module. The term "prismatic" refers to the shape of the battery cell described herein and differentiates this module from other modules with cylindrical battery cells.

[0023] Fig. 1 shows a battery module 10 with a negative terminal 20 and a positive terminal 21. The battery module 10 contains one or more cell subassemblies 30. As described in more detail below, the cell subassemblies are a fundamental building block from which battery modules of arbitrary sizes can be constructed. The cell subassemblies contain prismatic battery cells (not shown), each of which provides a portion of the battery's electrical power and storage capacity. The cell subassemblies 30 are held together by compression plates 50 and straps 51. Compression plates 50 serve as a mounting mechanism for the battery module and include one or more mounting ports 52 to allow the module to receive devices (not shown) for mounting the battery module 10, for example, in a battery pack enclosure or on the rack of a battery station in various mounting orientations.The individual battery cells are electrically connected in parallel and / or series by bus bars (described below) that connect the cells to each other and to the battery terminals, all located on one side of the battery module. The side of battery module 10 is covered with one or more bus bar covers 40.

[0024] Fig. Figure 2 shows a battery module 10 with the bus bars and bus bar shrouds removed to reveal a view of the interior of cell subassemblies 30. Each subassembly contains one or two prismatic battery cells 300, each cell with a positive terminal 301 and a negative terminal 302. Terminals 301 and 302 are electrically connected in series and / or parallel via bus bar jumpers (not shown). Bus bar terminals (also not shown) connect some of the battery terminals to either the negative terminal 20 or the positive terminal 21 of the battery module.

[0025] The prismatic battery module described herein has a group of identical cells. The number of cells per module and the module's electrical connection configuration (parallel count versus series count) define the module's electrical characteristics and performance. For example, a module with a "2353P" configuration has sixty-nine (69) cells, twenty-three (23) subgroups electrically connected in series, and three (3) cells in each subgroup electrically connected in parallel. Depending on the configuration, battery modules can contain either an even or an odd number of battery cells. PRISMATIC BATTERY CELL

[0026] Fig. Figure 3 shows a prismatic battery cell 300. A prismatic cell has two large flat surfaces, top surface 306 and bottom surface 307 (not visible), which are essentially parallel to each other and are used for mechanical attachment and thermal management within the module. The cell's casing can be referred to as a "pouch" because it is a non-rigid, flexible sheet that is folded and bound to create a cost-effective and environmentally sealed package. The material of the pouch is a thin aluminum foil with a polymer coating applied to both surfaces. The pouch is folded at the bottom edge, creating sealing boundary 303. The polymer-coated pouch is formed into a thermally consolidated flange on the two sides, creating two further sealing boundaries 304 and 305. This arrangement reduces the physical volume of the module without a decrease in net power.The size of the side flange is selected to ensure long-term robustness. The cell's side flanges are folded to create a compact width.

[0027] The cell's two flat electrical poles, positive pole 301 and negative pole 302, protrude from one of the edges of the pouch, and the poles are sealed from the environment by means of electrically insulating polymeric perimeter seals. The remaining portion of the pouch's pole edge is thermally solidified to create a fourth environmentally sealed boundary, completing the cell's perimeter seal. The poles are symmetrically arranged with respect to the central axis 315, and preferably, the poles are in the center plane of the battery cell. Accordingly, battery cell 300 can be "tilted" 180 degrees about the central axis 315, with the result that each pole is in the same position as the opposite pole held prior to the cell being "tilted" (relative to viewing the cell along axis 315 looking toward the edge containing the cell poles).This symmetry allows one to stack a row of cells regardless of whether the negative terminal is on the left or right side (as viewed along the central axis 315), and in either orientation, the resulting rows of terminals are each aligned in a straight line and can thus be easily connected to each other. In particular, battery modules can be built with various combinations of series and parallel connections by (1) selectively orienting the battery cells so that the terminals on the same left / right side of adjacent battery cells have either the same or opposite polarity; and (2) electrically connecting groups of these adjacent terminals using bus bar components (described below), with connections between opposite polarity terminals forming series configurations and connections between like polarity terminals forming parallel configurations.The negative terminal material is copper, and the positive terminal material is aluminum, to complement the cell's chemistry and internal structure. The terminal length is short compared to other commercially available designs. The possibility of using compact terminals is explained in the subsection titled "Busbar Components." For the purposes of explanation, the cell from . Fig. 3 additional minus and plus symbols have been added.

[0028] The non-rigid, flexible pouch of the battery cell will physically expand if a worst-case electrical overload event occurs. Pressure relief (also known as outgassing) during an electrical overload event can be enabled by using a "tooth" mounted externally to the cell, either as an alternative to or in conjunction with pressure relief valve feature 309. The tooth pierces the cell in a controlled manner should the cell expand to the point of contact with it. This tooth is further described below.

[0029] Fig. Figure 4 shows zipper fuse 308 integrated into an electrical terminal 302 of battery cell 300. Zipper fuse 308 comprises two rows, each row consisting of a slotted hole 310 at one end of the row and circular holes 311 between the slotted hole 310 and the other end of the row. This fuse is referred to as a "zipper fuse" because of its appearance. The zipper fuse is integrated into the negative terminal of the cell. The geometry, number, and position of the zipper fuse slotted holes 310 and circular holes 311 are selected so that the fuse will trip within a specified time period, preventing a cascade failure mode with the neighboring or possibly all cells of the module.In particular, the fuse slot holes help ensure a consistent fuse activation pattern by concentrating current "hot spots" near the area surrounding the holes to promote the onset of fuse operation in those areas. The use of circular holes in addition to the slots helps, among other things, maintain the structural integrity of the pole prior to fuse operation. The arrangement of the two parallel rows of slot holes and circular holes creates an area 312 between the rows that is partially thermally isolated from the rest of the pole, concentrating the heat generated during fuse operation and helping to make the operation more complete and consistent. BATTERY SUB-GENERATION

[0030] Fig. 5 shows a group of cell subassemblies, including subassemblies 30a and 30b. Subassembly 30a includes heat sink 400a having two large, flat surfaces, and a battery cell 300a that also has two large, flat surfaces. Battery cell 300a is mounted adjacent to heat sink 400a such that the second large, flat surface of battery cell 300a is adjacent to the first large, flat surface of heat sink 400a. Subassembly 30a also includes compliant pad 401a having two large, flat surfaces and a second battery cell 310a having two large, flat surfaces. Compliant pad 401a is mounted adjacent to battery cell 300a such that the first large, flat surface of battery cell 300a is adjacent to the second large, flat surface of compliant pad 401a.Compliant pad 401a is also mounted adjacent to battery cell 310a, such that the first large, flat surface of compliant pad 401a is adjacent to the second large, flat surface of second battery cell 310a. This arrangement forms a repeating "cassette" configuration of a battery cell, a heat sink, another battery cell, and a compliant pad, followed by another grouping of a battery cell, a heat sink, another battery cell, and a compliant pad, and so on. Compliant pad 401a helps distribute pressure between the subassemblies when they are sandwiched between the pressure plates, as well as allows for cell expansion / contraction during use. Similarly, subassembly 30b is mounted adjacent to subassembly 30a. Subassembly 30b includes heat sink 400b with two large, flat surfaces, and a battery cell 300b that also has two large, flat surfaces.Heat sink 400b is mounted adjacent to battery cell 310a such that the first large, flat surface of battery cell 310a is adjacent to the second large, flat surface of heat sink 400b. Battery cell 300b is mounted adjacent to heat sink 400b such that the second large, flat surface of battery cell 300b is adjacent to the first large, flat surface of heat sink 400b. Subassembly 30b also includes compliant pad 401b having two large, flat surfaces and a second battery cell 310b having two large, flat surfaces. Compliant pad 401b is mounted adjacent to battery cell 300b such that the first large, flat surface of battery cell 300b is adjacent to the second large, flat surface of compliant pad 401b.

[0031] As in both Fig. 5 as well as in Fig. As shown in Figure 2, all heat sinks are bonded to the adjacent cells during the module assembly process using a dispensed, post-assembly curing adhesive, which is also used to bond the compliant pads to the adjacent cells. The assembly of cells, pads, and heat sinks creates the main stack subassembly for each module, promoting a scalable architecture. In other words, the module size can be easily changed by simply adding or removing identical subassemblies. The subassemblies may or may not be pre-assembled as such and then later assembled as subunits in the main stack of the battery module. The assembly of the main stack can be realized as a one-step process, with all battery cells, heat sinks, and compliant pads being assembled together in one process.The concept of a “subassembly” is used as a convenient term for a logical group of components when describing the overall structure of the battery module.

[0032] Also as in Fig. As shown in Figure 5, all battery cells (e.g., 300a, 310a, 300b, and 310b) are mounted on corresponding heat sinks (e.g., 400a and 400b) with their positive poles oriented to the left or right, as viewed from the end toward the poles. For example, in Fig. 5 battery cells 300a, 310a and 300b all with their negative poles to the right from the perspective of Fig. 5, while battery cell 310b is mounted with its positive terminal facing the right. Other orientations of groups of battery cells (e.g., tilting battery cell 310b 180 degrees so that its positive and negative terminals switch positions) allow various combinations of series or parallel connections between the terminals, depending on which groups of adjacent terminals are electrically connected via the busbar jumpers and terminals described below.

[0033] Fig. 6 shows a view of a cell subassembly 30 from which battery module 10 is constructed. Fig. 6 shows a heat sink 400 connected to a battery cell 300, which in turn is connected to a compliant pad 401. Fig. 6 does not show the adjacent cell that would be connected to compliant pad 401 as above and in Fig. 5. Still in relation to Fig. 6, the metallic heat sink 400 contacts two cells 300 and 310 when sub-assembly 30 is stacked next to another sub-assembly. Each cell contacts the heat sink through one of the cell's two flat surfaces to facilitate thermal management through heat transfer via conduction or forced convection. This results in only about half the number of heat sinks being required per module compared to using one heat sink for each cell. The advantage is a compact module that has an improved power output-to-physical volume ratio compared to commercially available modules, some of which have larger and more elaborate heat sinks.

[0034] The heat sink is constructed from aluminum sheet, stamped and formed using standard tooling practices. The heat sink has an electrically insulating coating to ensure that a worst-case electrical overload event does not create an electrical short-circuit path to any or all of the heat sinks. The coating thickness is preferably selected so that it does not significantly impede heat transfer. Protective coatings and application methods can be selected to simultaneously provide protection against electrical short circuits during a worst-case electrical overload event, enable effective heat transfer, and reduce costs.

[0035] Another function of the heat sink is to protect the cells from foreign objects during a severe vehicle collision. As previously discussed, the heat sink's molded wings 403 blend into the profile of an adjacent heat sink, providing a satisfactory level of cell protection considering the complexity, cost, and physical volume of the module. These wings are created by folding three edges of the heat sink at approximately right angles to the heat sink's large flat surfaces.

[0036] In relation to Fig. 5, a notch (404a, 404b) is formed by the heat sink using additional curvatures near the area of ​​the wing that meets the large flat surfaces of the heat sink to accommodate a portion of the wings of an adjacent heat sink. For example, notch 404b is formed to accommodate a portion of wing 403a. This makes it easier to stack the heat sinks with their internal components on top of each other. The battery pack housing may be the primary protective barrier during a crash, so the heat sinks provide another barrier to enhance the safety capabilities of the battery module.

[0037] A second type of heat sink with short, shaped wings that enclose only one battery cell (as opposed to "full-height" heat sinks that enclose two cells) is used when the module has an odd number of cells, with the second type of heat sink located at one end of the stack of subassemblies. In these odd-cell configurations, no battery cell is attached to the bottom of the lowest heat sink, as shown in Fig. 5 shown.

[0038] Fig. Figure 7 shows this second type of heat sink 420 integrating into an adjacent cell subassembly 421. Heat sink 420 is connected to battery cell 320 in the same manner as the full-height heat sinks are attached to the adjacent cells. Fig. Figure 7 also illustrates the use of two compliant pads, 422a and 422b, which are used at either end of a module's main stack to distribute and equalize the clamping force imparted to the stack by the pressure plates. This second type of heat sink is also used when the module has an even cell count, but even-cell modules also utilize a third type of heat sink.

[0039] A third type of heat sink with mid-height shaped wings that enclose only one battery cell can also be used when the module has an even cell count, where the third type of heat sink is located at one end of the stack of subassemblies opposite the end with the second type of heat sink. In these even-cell configurations, this third type of heat sink fits adjacent to a heat sink that would otherwise have an exposed battery cell. For example, with reference to Fig. 8, this third type of heat sink 430 rests beneath the bottom heat sink 429 to help protect a single battery cell 321 located between heat sinks 429 and 430. Two compliant pads (not shown) are mounted adjacent to each other, and one side of one of the compliant pads is mounted adjacent to heat sink 430 at the end of the module's main stack of subassemblies.

[0040] While these additional types of heat sinks cause the release and production of additional components in the manufacturing process, they fully respect the principle that a heat sink contacts each cell via one of the cell's two large flat surfaces and that each cell is protected from foreign objects during a severe collision.

[0041] Fig. Figure 9 shows a heat sink 400 with pressure relief teeth 410 and 411 mounted through holes in the heat sink. One tooth 410 is oriented so that its pointed end points toward one of the heat sink's attached battery cells, and when a second cell is attached to the heat sink, the other tooth 411 faces that cell. An additional pair of teeth may be mounted elsewhere on the heat sink 400 or on the bus bar support connected to the heat sink. The tooth material is molded plastic, and it is either heat-staked or ultrasonically welded to a simple hole in the stamped aluminum heat sink. If an electrical overload event occurs, the non-rigid, pliable cell bag physically expands due to rapid internal gassing. As it expands, the force of the internal pressure pushes the bag against the tooth, puncturing the cell and providing controlled relief of the internal pressure.The battery cell has an opening that helps define a specific region in which the pouch can expand, and within which the sharp tip or edge of the tooth is at least partially located to puncture the pouch as it expands. Although the battery cell can expand along multiple expansion paths, the opening helps define and promote expansion along at least one such path. Expansion of the pouch can also be partially controlled by creating a region of the pouch with increased extensibility relative to the rest of the battery cell. In some embodiments, the opening can expose a region of increased extensibility. In each of these embodiments, the sharp tip of the tooth is located along at least one of the pouch's expansion paths.

[0042] Fig. Figure 23 shows two additional alternative embodiments of pressure relief teeth. Tooth 450 includes a tip 451 and two channels 452. Tooth 455 includes two tips 456 and two channels 457 extending from the tip region. The structure of tooth 455 (along with other embodiments that utilize a sharp edge instead of a tip) can help promote the formation of a "slit" or tear in the pouch to promote gas escape. In each of these types of teeth, the channels help provide a path for gases to escape from the battery cell and ensure that the pouch does not inadvertently reseal against the tooth (despite the hole). Other orientations and combinations of sharp tips and channels may also be used, as may other combinations of sharp edges and / or channels.

[0043] The tooth is made of a non-conductive material to help prevent a short circuit between the interior of the battery cell and the heat sink.

[0044] As in Fig. 5 and Fig. 6, a compliant pad contacts each cell via one of the two large flat surfaces of the cell to provide the following functions: (a) provide uniform pressure distribution for the life and performance of the cell, (b) provide constant pressure on the active area of ​​the cell throughout the lifetime of the cell, (c) compensate for changes in cell thickness due to its inherent properties during charge and discharge cycles, and (d) compensate for changes in module length due to thermal expansion and contraction of the cell and other module components such as the heat sinks, pressure plates, and clamping bands. PRINTING PLATE COMPONENT

[0045] FIG: 10 shows a compression plate 50. Compression plate 50 is a rigid structure that applies a static clamping force to the module's main stack of cells, compliant pads, and heat sinks. The structure also provides a means by which the module can be secured within the enclosure of a battery pack. This component may be referred to as a "compression plate" to emphasize its primary function. The plate material is a molded plastic polymer with defined temperature exposure and flammability ratings. The plate has a prominent flat surface for contacting one end of the module's main stack, which has two compliant pads at either end to help distribute and equalize the clamping force.

[0046] The side of pressure plate 50 facing away from the subassemblies has a matrix of reinforcing ribs 520 to increase its structural rigidity and complement the design practice for molded parts to achieve a uniform wall thickness. The matrix has a non-uniform pattern because the ribs also form pockets that accommodate large electronic components that are soldered to the module's active control printed circuit board (PCB) subassembly (not shown). The PCB subassembly includes a printed circuit board and components, with the majority of the components on one side of the plates. The PCB subassembly is mounted component-side down on pressure plate 50. Inserting the electronic components saves valuable space and contributes to a compact module length on the plate, helping to achieve an excellent power output-to-physical volume ratio.The plate's pockets are also valuable because they can be used as receptacles for vibration-damping elements (not shown) to grip the top surfaces of large electronic components soldered to the module's active PCB subassembly. The elements prevent excessive stress and fatigue at the solder joints on the PCB. The preferred vibration-damping element is a stamped block with an elastomeric, closed-cell, non-hygroscopic polyurethane foam material and a pressure-sensitive adhesive material on one side, both of which have defined temperature exposure and flammability ratings.

[0047] The PCB assembly can be either passive or active. Passive PCB assemblies may be sufficient for smaller battery modules, while larger modules utilize one or two active PCB assemblies, with one mounted on each of the pressure plates at either end of the module. The active PCB control subassembly has three right-angled PCB electrical connector headers selectively soldered to industry-standard plates through holes in the PCB. All other electronic components are SMT (surface mount technology) devices reflow-soldered to industry-standard blocks on both sides of the PCB. Precautions are taken to ensure proper electrical insulation between the module's steel strips and the PCB, as the strips pass in close proximity. PCB trace, via, and component keep-in and keep-out zones are carefully defined for both sides of the PCB to avoid electrical interference.Module viability can be improved by applying a silicone-based or polyurethane-based conformal coating on both sides of the PCB, which reduces the growth of dendrites between adjacent low-current, high-impedance copper traces.

[0048] Side 510 of pressure plate 50 is opposite the side with the matrix of reinforcing ribs 520 and faces the stack of subassemblies. Side 510 can be flat, or it can form a non-flat, shallow convex or concave arched profile to further optimize force distribution within the main stack of the module.

[0049] Pressure plate 50 has two flat rails 501 to accommodate thin steel retaining bands that provide the static clamping force to the module's main stack. The rails have a curved profile to help distribute and equalize the clamping force. Suitable curvature profiles can be determined by measurements taken with existing measurement products specifically designed and marketed for this type of instrumentation application.

[0050] Pressure plate 50 also has four apertures with recessed bushings 503, 504, 505, and 506 (also known as counterbores) for receiving steel mounting components, such as cylindrical sleeves, washers, bushings, and retaining bolts, to promote a flexible mounting strategy. The present configuration enables mounting of a module within the enclosure of a battery pack or on the rack of a battery station using one of three mounting orientations, appropriate for the majority of existing and anticipated applications and customer requirements.

[0051] The pressure plate can be formed from two separate sections joined by vibration welding. Each section would have half the profile of the mounting holes and recessed bushings. After welding, fully circular holes and bushings would be formed. The advantage of this approach is that the two sections could be formed without long active slides in the mold, which are perpendicular to the main drawing direction of the mold.

[0052] Pressure plate 50 has two recessed areas 508 to accommodate a steel busbar nut or nuts (not shown). The design of the nuts is intentionally simple to provide a cost-effective solution. The nut has three threaded holes for attachment. The center hole engages a steel fastener (not shown) that holds the busbar nut to the pressure plate. The other two holes engage steel fasteners that secure an outer power lug and a wire harness to the module's negative or positive power rail, which are explained in subsequent sections. TAPE COMPONENT

[0053] Fig. Figure 11 shows steel band 530, which is one of two steel bands used to wrap the module's main stack of cells, compliant pads, heat sinks, and pressure plates. Each steel band 530 sits in one of the flat rails 501 of pressure plate 50. Two bands are sufficient, and three bands are not necessary if the module has seventy-six (76) cells or fewer. More bands may be used if desired. The length of steel band 530 is determined by the clamping force required to properly compress all of the compliant pads in the main stack, and it is held in place by an existing, published, and suitable steel buckle 531 that is permanently crimped to the band.A handheld pneumatic tool with a pneumatic actuator can be used to tension the strap and crimp buckle 531, and the tool can also have a mechanism for trimming the excess tail of the strap after buckle 531 is crimped. Compared to an alternative approach that uses very long steel tie rods and retaining nuts at both ends, the use of the straps and buckles is a more compact approach. Using the same strap, buckle, and installation process for each module promotes a scalable architecture. Another approach is to tension and weld the strap instead of using the crimped buckle. The pressure plate 50 can incorporate flat or notched areas within the flat rails 501 to accommodate the buckles of the clamping straps and to more evenly distribute the pressure in the buckle area.Pressure plate 50 may also have four corner roundings along each rail 501 to ensure that the clamping forces in the straight areas of the two bands are balanced.

[0054] An existing, published and suitable handheld computer-controlled power tool with closed-loop servo control can be used instead of a standard pneumatic actuator. This can increase the precision of the applied static clamping force and reduce the cycle times of the strap installation and buckle crimping process. While the pressure plates and straps help physically hold the battery module together, the module's bus bars (described next) electrically connect the system. Conductor rail support component

[0055] The electrical connection between the adjacent cells of the module is an important feature, which includes the registration of the flexible and brittle cell terminals relative to each other, and includes the prevention of accidental contact between adjacent terminals that are not electrically connected for the intended application. Fig. Figure 2 shows how all cells in the main stack of the module are securely held and locked relative to each other, except for the cell poles, e.g. 101 and 102.

[0056] Fig. Figure 12 shows a robust, compact, and cost-effective solution using a molded plastic component. The component can be referred to as a "busbar carrier" to emphasize its primary function. The standard busbar carrier 600a contacts the upper edge of a heat sink 600a and also encloses the two cells 300a and 310a. Cells 300a and 310a are both fixed to a respective side of the heat sink, and each has two electrical terminals (the negative terminals of each battery cell 300a and 310a are in Fig. 12), which extend through openings in the busbar support. One busbar support is used for each subassembly and promotes a scalable architecture. For example, busbar support 600b contacts the edge of the second type of heat sink, heat sink 400b.

[0057] Fig. Figure 13A shows another view of a busbar carrier 600 mounted on a heat sink 400. The standard busbar carrier has nine features / functions: 1. Seven flexible tongues 608 (four shown) and two wedge-shaped latches 609 to define two slots (component 406 in Fig. 5) to grip into a heat sink. 2. Rectangular central opening 604 to couple to a thermistor 605 having an over-molded elastomeric handle. 3. Four tapered openings 601 to allow the simultaneous introduction and registration of four cell poles. 4. Main body 610 supporting a bus bar during a zipper fuse tripping event in a cell. By maintaining separation between any remainder of the terminal and the bus bar, the bus bar support prevents accidental reconnection of the faulty cell to the bus bar, which could cause a cascade failure mode with neighboring cells. 5. Two fixed snap locks 602 and two flexible snap locks 603 for gripping two separate bus bar components (not shown) during laser welding of the bus bars to the cell terminals. This feature helps eliminate the need for a special laser welding fixture. As described below, it acts as a mounting fixture, securing the bus bar components in registration with the cell terminals before and during welding. These snap locks hold each bus bar component in a substantially fixed position relative to the heat sink and the attached battery cells. The tapered openings and the main body hold the terminals of each of the battery cells in a substantially fixed position relative to the heat sink and the bus bar component. 6. Eighteen recesses 607 to provide sufficient clearance for each electrical connecting rivet of a busbar. 7. Central groove 606 to allow routing of the module's voltage sensor harness and thermistor harness. 8. Four flexible fingers 611 to hold the two cable harnesses (not shown) before the bus bar sleeves are installed. 9. Two screw domes 612 at the ends for fastening the busbar covers.

[0058] Additionally show Fig. 13B and Fig. 16, a second bus bar support 650, designed to enclose only one cell when the module has an odd number of cells. While this decision results in the release and production of a different component, it fully respects the principle that each cell terminal is registered and protected from accidental contact with a neighboring terminal. The module's vibration endurance can be improved by adding two or more slots in the heat sink near the center and / or adding two additional wedge-shaped snap locks in the bus bar support. BUTTERY RAIL COMPONENTS

[0059] Busbar components consist of busbar jumpers, which electrically connect the adjacent cells of the module, and busbar terminals, which connect the one or more battery cell terminals to the outer terminals of the battery module. Fig. Figure 14 shows a robust, compact, and cost-effective interconnection approach using these busbar components to increase module viability. This approach avoids the use of threaded fasteners for any of the electrical connections inside the module, instead employing precision welds manufactured using adaptive, automated computer-controlled processes.

[0060] Fig. Figure 14 shows several busbar jumpers 700, each held by busbar supports 600. For each busbar support through which the terminal of a battery cell extends, the busbar jumper connected to that terminal is held between the fixed latch of the support and its opposite flexible latch. The latches hold the busbar jumper against the terminal and prevent its movement.

[0061] Fig. Figure 15 shows a bimetallic busbar jumper 700. The battery module uses a group of busbar jumpers 700, each comprising a copper region 701 laser-welded to a group of negative cell terminals made of copper material, and an aluminum region 702 laser-welded to a group of positive cell terminals made of aluminum material. The 180-degree bends 703 of the busbar jumper define an inner surface 704 into which the cell terminals are inserted during assembly. The regions of the busbar that have bends are continuous pieces of metal. Precision laser welding is used to partially melt the busbar jumpers and metallurgically bond them to the terminals, avoiding ultrasonic welding, which could conduct too much energy into a cell terminal and, in turn, damage a cell's internal electrical connections.A liquid welding treatment is applied to the outer surface (opposite the inner surface 704) of the bends of the busbar jumper 703. During welding, laser energy is directed onto this surface. This treatment creates a surface finish that reduces the reflectivity of the laser beam during laser welding of highly reflective surfaces, both aluminum and copper. This treatment can be a nickel or tin coating, which allows for better absorption of the Nd-YAG laser beam wavelength. This minimizes the energy required for welding and allows cell terminal welding to be performed without exceeding a maximum temperature limit for the cell terminal seal. The energy of the laser beam penetrates the 180-degree bend 703 of the busbar and creates a molten bead within the bend of the busbar 704 and at the tip of the cell terminal (not shown).The welding laser is directed onto the bend 703 of the bus bar at an angle that is substantially frontal to the end of the battery post and toward the outer surface of the bend, as shown at angle of attack 708.

[0062] Fig. Figure 25 shows an additional view 735 of the configuration of a welding laser 730 and a bimetallic busbar jumper 700, with the laser beam 733 directed at the bend of the busbar at an angle of attack 708 that is substantially frontal to the end of the battery post. A second view 740 shows the configuration of view 735 as seen along a reference line 736 (i.e., view 735 rotated 90 degrees about the vertical z-axis). View 740 shows laser 730 moving from the right side end of the bend 742 of the bus bar to the left, where the laser beam 733 moves in a direction of travel parallel to the trough, with the laser beam 733 directed at a slight angle 741 with respect to the bend 742, where angle 741 is opposite to the direction of travel of the laser 730 to prevent the laser beam from reflecting back into the laser optics and causing damage.This results in laser beam 733 being directed at a slightly less than perpendicular angle to the direction of travel of the laser beam. During welding, the laser 730 may move relative to the bus bar and battery post being welded, the bus bar and battery post assembly may move relative to the laser, or both may move relative to each other. The result in each case is that the bus bar and battery post are secured together along the length of the groove in which the battery post lies.

[0063] Fig. Figure 26 shows side views of the attachment of a bus bar component to a battery cell post, both before and after attachment. View 770 shows a bend 704 in bus bar 700 forming a groove in which battery post 771 is located. View 775 shows these components after welding, with battery post 776 secured by a resolidified metal pool 778 at an inner corner of the bend in bus bar 777.

[0064] Welding processes such as laser welding or conventional welding methods may be impractical when used to join the two sections of a bimetallic jumper bus bar due to dissimilar materials and known metallurgical limitations. Instead, bus bar jumper 700 uses an ultrasonic roll seam welding process to create linear weld 705. The ultrasonic welding of the two components of the jumper bus bar is performed separately from the module, so that no ultrasonic energy is directed into a cell terminal, risking damage to a cell's internal electrical connections. As noted above, the bus bar supports act as welding fixtures.The busbar supports hold the busbar components in place, with the cell poles inserted into the slots defined by the bends in the busbars until the busbars are laser welded to the poles as discussed above.

[0065] To further balance and optimize the electrical current characteristics of the bimetallic jumpers, the cross-sections, widths, and / or thicknesses of the two sections of the jumper busbar—made of aluminum and copper—can be independently cut to achieve similar resistances in each section. To reduce costs, extruded, cut-to-length profiles can be used for one or both of the two sections of the bimetallic jumper busbars, instead of sheet metal stamping and forming processes. In one configuration, the copper section of the busbar jumper is stamped, and the aluminum section is extruded.

[0066] Fig. Figure 16 shows a bus bar terminal 750 partially secured by bus bar supports 600 and 650. Bus bar supports secure the bus bar terminals in the same way the supports secure the bus bar jumpers. Bus bar terminal 750 is laser welded to a corresponding terminal of battery cells 300a, 310a, and 320. Battery modules utilize a monometallic bus bar negative terminal made of copper material at one end of the module's main stack and a monometallic bus bar positive terminal made of aluminum material at the other end of the module's main stack. The bus bar terminals are secured by steel bus bar nuts 760 attached to the bushings 508 of the pressure plate 50. The bus bar terminal 750 has a tapered central portion 751 that serves as a module fuse in the event of a worst-case electrical overload event. The fuse has a tendency to melt in the thin area where the current density is highest.The safety capability of the module can be improved by adjusting the tripping response time of the two module fuses by installing zipper fuse holes and slots on the busbar terminals in a similar manner to how the zipper fuses are integrated into the battery cell terminals.

[0067] Fig. 17 shows the installation of busbar pole 750 on pressure plate 50. Busbar pole 750 is mounted on a steel busbar nut (not visible under busbar pole in Fig. 17). The bus bar nut is attached to one of the pressure plate sockets 508a. Bus bar terminal 750 is attached to an outer power lug and a wire harness (not shown) as described earlier. Additionally, a stamped copper bus bar nut jumper 780 may be connected to bus bar terminal 750 and also connected to pressure plate socket 508b via bus bar nut 760b. Bus bar nut 760b is secured to pressure plate 50 via a central hole that engages a steel fastener mounted in pressure plate socket 508b. The jumper is an accessory that provides an optional attachment location for the module-to-module heavy-duty wire harness. WIRING FIXTURES

[0068] Fig. Figure 18 shows a bus bar pole 750 with two variations of clamps for attaching wiring, such as voltage sensor wire harnesses, to bus bar poles and bus bar jumpers. From one side, clamp 791 is U-shaped and substantially convex, while clamp 790 is W-shaped. Either or both clamps 790 and 791 can be used to connect wiring. Voltage sensor wires are ultrasonically welded to the clamps before the clamps are attached to the bus bar components. The clamps have one or more teeth 793 that bite into the bus bar jumpers or poles, allowing the clamps to be positioned and held until a laser welding operation secures the clamps to the bus bar. The clamps can be made of stamped copper or aluminum, appropriate and compatible with the type of bus bar to which they are connected.The clamps have 792 notches for a metal type to indicate the clamp type during manufacturing using automatic image inspection. These clamps can be laser welded to the bus bar components at the same time the bus bar components are welded to the battery cell posts, sharing a common weld. Using the same welding technique described above for attaching the bus bar components to the battery posts, a laser is steered through the clamp and the underlying bus bar component and directed toward the end of the post located in the U-shaped bend of the bus bar component. Using this procedure, a single welding operation welds all three components (the clamp, the bus bar component, and the battery post) at the same time.The U-shaped brackets can also be laser welded to the busbar components without sharing a common weld.

[0069] Fig. Figure 19 shows a side view of a W-shaped clamp 790, with the teeth 793 of the clamp slightly bent inward for installation on a busbar. Teeth may or may not be required to secure the clamp to the busbar until it is welded if the clamp is designed with an interference fit, so that the interference would provide the holding function.

[0070] Fig. Figure 20 shows a busbar terminal 750 with a clamp 794 for securing a thermistor 795 to the busbar terminal. The thermistor head is bonded within the bracket of the clamp with an applied, post-assembly curing epoxy adhesive. The neck of the thermistor head contacts the adjacent die 796, ensuring the head has a defined, reproducible position. Embossed chamfers 797 on the upper edges of the bracket help prevent damage to the thermistor head during installation. Busbar covers

[0071] Fig. 1 shows three bus bar shrouds 40. Battery modules use a group of molded plastic shrouds to protect the bus bars and other internal components of the module, such as the voltage sensor harness and the thermistor harness, from any accidental contact with external foreign objects, especially if they are metallic.

[0072] Fig. Figure 21 shows a bus bar sleeve 40a without the flat main skin of the sleeve so that the relative fits can be seen. Bus bar sleeve 40b is also shown, including the flat main skin of the sleeve. Each of the sleeves has a matrix of reinforcing ribs, including 801, 802, and 803, to increase its structural rigidity and also to redirect and distribute any damaging external forces to the module's bus bar supports and heat sinks rather than to the bus bar terminals 750, bus bar jumpers 700, and / or cell terminals. Bus bar sleeves enclose the module's bus bars to help prevent adjacent bus bars from contacting each other and causing electrical short circuit paths during a worst-case electrical overload incident or a severe vehicle collision. Certain ribs, e.g., rib 802, extend deeper into the battery module than other ribs and between the bus bar jumpers, e.g.,803 to help prevent contact between adjacent busbars, while ribs such as 803 are shallower to prevent the distribution of forces to the busbar terminals, busbar jumpers, or cell terminals. Alternatively, the battery module can use lower-cost, simpler shells that have a lap joint and fewer perpendicular contact pads. The disadvantage of this latter approach is that the module's robustness to withstand external perpendicular forces may be reduced. SCALABLE ARCHITECTURE

[0073] The features described above result in a scalable architecture. The term “scalable architecture” refers to a flexible configuration that facilitates the rapid design, development, qualification, and production of battery modules with different quantities of battery cells, sub-assemblies with cells electrically connected in parallel, and sub-assemblies with cells electrically connected in series. This flexibility allows a battery supplier to tailor the electrical characteristics of many different modules and satisfy different customer performance specifications. For example, the current prismatic battery module family from A123Systems with the “3P” configuration is available in Fig. 22. The seven members of this family are the 23S3P, 22S3P, 16S3P, 13S3P, 11S3P, 6S3P and 1S3P modules, in Fig. 22 identified as 907, 906, 905, 904, 903, 902 and 901 respectively.

[0074] Fig. Figure 24 shows various configurations of busbar components for the following members of the A123Systems prismatic battery module family, 13S3P, 23S2P, 4S2P and 4S6P, in Fig. 23 identified as 950, 951, 952 and 953 respectively.

Claims

[1] A battery system comprising: a plurality of sub-units, each comprising a heat sink and a battery cell having an upper end and first and second voltage poles, both extending from the upper end of the battery cell, the first and second voltage poles of each battery cell being arranged symmetrically with respect to a center line of that battery cell, wherein all battery cells in the plurality of sub-units are arranged such that their first voltage poles are aligned in a first row and their second voltage poles are aligned in a second row; a plurality of identical busbar supports in the same number as the plurality of sub-units, each busbar support of the plurality of busbar supports having two slots and being mounted on a corresponding different one of the sub-units, each of the first and second terminals of the battery cell for that sub-unit extending upwardly through a corresponding different one of the two slots; and a plurality of bimetallic busbars, each supported by a different corresponding subset of busbar supports and electrically directly connected to either a first or second pole of each of the battery cells of each of the modules on which those busbar supports are mounted, wherein each of the plurality of subunits further comprises a second battery cell having an upper end and first and second voltage poles both extending from the upper end of the second battery cell, wherein the first and second poles of each second battery cell are arranged symmetrically with respect to the centerline of that battery cell, and wherein each of the second battery cells in the plurality of sub-units is arranged such that its first voltage poles are aligned in the first row and its second voltage poles are aligned in the second row. [2] The battery system of claim 1, wherein the battery cells are prismatic battery cells. [3] The battery system of claim 2, wherein both the first row and the second rows are on the same side of the battery system. [4] The battery system of claim 3, wherein each of the plurality of sub-units is identical to each other except for the orientation of each of the battery cells of the sub-units with respect to the battery cell centerline. [5] The battery system of claim 3, wherein all heat sinks are identical to each other. [6] The battery system of claim 3, wherein all but two of the heat sinks are identical to each other. [7] The battery system of claim 3, wherein each of the plurality of bus bars interconnects at least two adjacent poles of the same row. [8] The battery system of claim 3, further comprising a first pressure plate and a second pressure plate, wherein the plurality of sub-units are arranged as a stack of sub-units, and wherein the stack of sub-units is located between the first pressure plate and the second pressure plate. [9] The battery system of claim 8, wherein one or more compliant pads are located between the first pressure plate and the adjacent subassembly. [10] The battery system of claim 8, further comprising a band, the band enclosing the first and second pressure plates and the plurality of subassemblies. [11] A battery system comprising: a plurality of battery subunits, each subunit comprising a heat sink and at least one battery cell having a positive terminal and a negative terminal; a plurality of busbar supports in the same number as the plurality of battery sub-units, and each of which is mounted on the heat sink of a corresponding different one of the plurality of sub-units, each bus bar support comprising a first slot through which the positive pole of the at least one battery cell for that sub-unit passes and a second slot through which the negative pole for the at least one battery cell for that sub-unit passes, said plurality of bus bar supports comprising a first bus bar support; a first busbar located above and at least partially supported by the first busbar support and electrically connected to the negative terminal passing through the first slot in the first busbar support; and a second busbar located above and at least partially supported by the first busbar support and electrically connected to the positive pole passing through the second slot in the first busbar support, wherein the first bus bar support includes a latch to engage a slot in a heat sink. [12] The battery system of claim 11, wherein the first bus bar support comprises a thermistor and a socket in which a thermistor is at least partially located. [13] The battery system of claim 11, wherein the battery system further comprises a bus bar shell, wherein the first bus bar support comprises a container to which the bus bar shell is attached. [14] The battery system of claim 11, wherein the first bus bar support comprises a groove in which wiring is located and a flexible finger that at least partially retains the wiring within the groove. [15] The battery system of claim 11, wherein the first busbar support comprises two snap locks between which a busbar is at least partially held. [16] The battery system of claim 11, wherein the first bus bar support comprises a main body located between the first bus bar and the positive terminal of the battery of the corresponding sub-unit. [17] The battery system of claim 11, wherein the battery cell is a prismatic battery cell. [18] A method of manufacturing a battery comprising: Mounting a first battery cell on a heat sink, the battery cell having a first terminal; Attaching a bus bar carrier to the heat sink, the bus bar carrier having a latch to engage a slot in the heat sink, and the bus bar carrier further comprising a first slot through which the first pole passes; Providing a busbar having a U-shaped region defining a groove and characterized by a bend corner at one end of the U-shaped region, the busbar also having a treatment for reduced reflectivity at least near the bend corner; Mounting the busbar on the busbar support, wherein the busbar support fixes the busbar such that the first battery pole is arranged in the groove formed by the U-shaped region so that the upper end of the pole is directly at the bend corner; Directing a laser beam onto the curved corner of the U-shaped area; and using the laser beam to melt the busbar at the bend corner and form a metallurgical connection between the busbar and the upper end of the first battery terminal. [19] The method of claim 18, wherein the laser beam is directed at a substantially frontal angle toward the end of the battery cell terminal. [20] The method of claim 19, wherein the laser beam moves in a direction of movement parallel to the trough. [21] The method of claim 20, wherein the laser beam is directed at an angle slightly less than perpendicular to the direction of travel. [22] The method of claim 18, wherein the treatment comprises a coating of one or more of nickel and tin. [23] The method of claim 18, further comprising forming the bus bar by joining a first bus bar segment to a second bus bar segment, the first segment being made of a first metal and the second segment being made of a second metal different from the first metal. [24] The method of claim 23, wherein the first busbar segment is ultrasonically welded to the second busbar segment before the busbar is attached to the pole. [25] A battery system comprising: a plurality of battery sub-assemblies arranged in a stack, each battery sub-assembly of the plurality of battery sub-assemblies comprising a first battery cell, a heat sink, a second battery cell, and a compliant pad, in that order, with the heat sink between and in thermal contact with the first and second battery cells and with the compliant pad adjacent to the second battery cell. [26] The battery system of claim 25, wherein the battery cells are prismatic batteries. [27] The battery system of claim 26, wherein the plurality of battery sub-units are arranged in a stack, with the compliant pad of one sub-unit in contact with the first battery cell of an adjacent sub-unit. [28] The battery system of claim 27, wherein each of the heat sinks is substantially identical to each of the other heat sinks. [29] The battery system of claim 27, further comprising an end subassembly, the end subassembly comprising a heat sink, a battery cell, and a compliant pad stacked in that order, and the compliant pad of the alternative subassembly being in contact with the first battery cell of an adjacent battery subassembly. [30] The battery system of claim 27, wherein the battery system further comprises: a heat sink disposed at the first end of the stack in thermal contact with the first battery cell of the adjacent battery sub-unit. [31] The battery system of claim 27, wherein the heat sink of a first battery sub-unit of the plurality of battery sub-units comprises a bottom surface and a side connected to the bottom surface, the side being at approximately a right angle to the bottom surface. [32] The battery system of claim 31, wherein the side is formed by a bend of approximately ninety degrees in the heat sink. [33] The battery system of claim 31, wherein the side is formed by three parallel bends of approximately ninety degrees in the heat sink, and wherein the three bends form a notch that receives an upper edge of the side of an adjacent heat sink. [34] The battery system of claim 25, wherein the first battery cell of a first sub-assembly comprises a flexible sidewall, and wherein the heat sink of the first sub-assembly comprises a tooth structure extending from the heat sink toward the sidewall of the first battery cell, and wherein the tooth structure includes a distal end sufficiently sharp to pierce the flexible sidewall of the first battery cell if the flexible sidewall of the first battery cell is forced against the tooth structure due to the buildup of excess pressure within the first battery cell. [35] The battery system of claim 25, further comprising a bus bar support mounted to the heat sink of the first sub-assembly, and wherein the first battery cell of a first sub-assembly comprises a flexible sidewall, and wherein the bus bar support comprises a tooth structure extending from the heat sink toward the sidewall of the first battery cell, and wherein the tooth structure comprises a distal end sufficiently sharp to pierce the flexible sidewall of the first battery cell if the flexible sidewall of the first battery cell is forced against the tooth structure due to the buildup of excess pressure within the first battery cell.

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