Busbar assembly for the battery pack

Abstract

A busbar assembly (202) for a battery module (200), comprising a first busbar component (208), a second busbar component (210), a positive terminal collection zone (212), and a negative terminal collection zone (214). The first busbar component (208) connects with a positive terminal of cells (204) of a battery module (200). The second busbar component (210) connects with a negative terminal of cells (208) of a battery module (200). The positive terminal collection zone (212) connected through the first busbar component (208) collects positive terminal of each cell (204) of the battery module (200), whereas the negative terminal collection zone (214) connected through the second busbar component (210) collects negative terminal of each cell of the battery module. A cross¬ section area of the first busbar component (208) and the second busbar component (210) increases as the number of cells contributing to the current keeps on increasing.

Description

BUSBAR ASSEMBLY FOR THE BATTERY PACKTECHNICAL FIELD

[0001] The present subject matter relates, in general, to busbars and, particularly, to busbars for battery module to be used in electric vehicles.BACKGROUND

[0002] Electric vehicles use one or more battery packs as a source of power. A battery pack that powers electric vehicles consists of individual battery cells (hereinafter referred as cells) and modules organized in series and parallel. A cell is the smallest unit of a battery pack. The characteristics of the cell play a pivotal role in overall performance of the electric vehicles. A module consists of multiple cells connected in series and / or parallel, encased in a mechanical structure. A battery pack is assembled by connecting multiple modules together in series or parallel with sensors and controllers and then encased in a casing as a final battery pack.

[0003] Electrical connection between cells within the battery pack is typically provided by the busbars. The busbars in battery packs typically consist of flat, conductive metal strips or bars, often made of copper and / or aluminum. These conductive strips connect multiple battery cells in series and parallel configuration, allowing for efficient power distribution and management with the battery pack.BRIEF DESCRIPTION OF DRAWINGS

[0004] The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and components.

[0005] Figure 1 illustrates a top view of battery module utilizing series of busbars, according to a prior art configuration.

[0006] Figure 2 illustrates a top view of a battery module comprising a busbar assembly, in accordance with an implementation of the present subject matter.

[0007] Figure 3A illustrates a first busbar component of the busbar assembly, in accordance with an implementation of the present subject matter.

[0008] Figure 3B illustrates a second busbar component of the busbar assembly, in accordance with an implementation of the present subject matter.SUMMARY OF THE INVENTION

[0009] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0010] In an embodiment of the present invention, a busbar assembly for a battery module is provided. The busbar assembly comprises a first busbar component and a second busbar component. Each of the first busbar component and the second busbar components comprises a substantially longitudinal body having a first end and a second end. Further, the first busbar component comprises a first group of fingers extending from the longitudinal body of the first busbar component. The fingers in the first group of fingers comprise a positive connection tab to connect with a positive terminal of cells of a battery module. Similarly, the second busbar component comprises a second group of fingers extending from the longitudinal body of the second busbar component. The fingers in the second group of fingers comprise a negative connection tab to connect with a negative terminal of cells of the battery module.

[0011] A positive terminal collection zone is formed on the first end of the longitudinal body of the first busbar component to collect positive terminalof each cell of the battery module. Similarly, a negative terminal collection zone is formed on the first end of the longitudinal body of the second busbar component to collect negative terminal of each cell of the battery module.

[0012] In accordance with example embodiments of the present invention, a cross-section area of the first busbar component increases in a direction from the second end to the first end of the longitudinal body of the first busbar component. Similarly, a cross-section area of the second busbar component increases in a direction from the second end to the first end of the longitudinal body of the second busbar component.

[0013] The foregoing general description of the illustrative embodiments and the following detailed description thereof are merely exemplary aspects of the teachings of this disclosure and are not restrictive.DETAILED DESCRIPTION

[0014] The present subject matter relates to optimizing size and performance of busbar assemblies.

[0015] In an electric vehicle (EV), battery packs generally include multiple battery cells to store charge, which is used to drive the EV. Each of the cells includes positive and negative tabs that are electrically connected together. A battery management system (BMS) is connected to busbars for sensing and managing the battery cells.

[0016] The busbar is a metallic strip or bar that conducts electricity and is used to connect cells in series and parallel combination along with power distribution of an electric vehicle. Particularly, the busbar collects the electric current from the battery pack and then transfers the collected electric current to the BMS for facilitating the operation of the electric vehicle.

[0017] Conventional busbars are typically designed with a uniform crosssection area along the length of the busbar. The amount of current flowing through the busbar depends on the number of cells connected to the busbar. As the number of cells varies along the length of the busbar due to parallel and series connection of cells within the battery pack, the amountof current varies along the length of the busbar. Further, due to the uniform cross-section area and varying current along the length of the busbar, the current density varies at various segments in the busbar. This non-uniform current density leads to non-uniform heating along the length of busbar. These losses increase the temperature gradient of the battery pack. Higher temperature gradient in the battery pack lead to non-uniform ageing of the cells, thereby decreasing the overall life of the battery pack.

[0018] To elaborate the technical shortcomings associated with conventional busbars, reference is made to Figure 1 which illustrates the plurality of conventional busbars.

[0019] As shown in Figure 1 , a conventional battery module 100 includes a plurality of non-overlapping busbars 102 arranged in an alternating polarity configuration in accordance with the state of the art. The busbars 102 are of uniform cross-section and fabricated from an electrically conductive material, such as aluminum or copper. The busbars 102 are interposed between every two rows of cells 104 as shown (i.e. , one busbar per every two rows of cells). Thus, for example, the cells 104 within rows 106A and 106B form a first group of cells and the cells within rows 106C and 106D form a second group of cells. In this configuration, all cell terminals of a first polarity corresponding to one group of cell and all cell terminals of a second polarity corresponding to another group of cells are electrically connected to a single busbar.

[0020] Thus, as can be seen from Figure 1 , the busbar 102 with uniform cross-section area leads to overdesign which results in unnecessary extra mass. The excess material not only adds weight of the battery module 100 and in turn of the vehicle, but also increases manufacturing cost.

[0021] Further, the uniform cross-section occupies a significant amount of space on a top cell holder which in turn leaves no space for incorporating other essential features or components, such as additional cells, sensors, etc., on the top cell holder of the battery pack. Furthermore, the uniformcross-section creates non-uniform current density across the busbar which in turn increases thermal gradient of the busbar.

[0022] In accordance with embodiments of the present subject matter, described herein is a busbar assembly with busbars having optimized cross section area, to provide uniform current density across the busbar which in turn decreases the thermal gradient across the busbar. Further, it reduces the overall weight and manufacturing cost of the busbar. Furthermore, it provides extra space to mount other components, such as additional cells, sensors, etc., on the top cell holder of the battery pack.

[0023] In accordance with embodiments of the present subject matter, the busbar assembly comprises a first busbar component and a second busbar component. Each of the first busbar component and the second busbar components comprises a substantially longitudinal body having a first end and a second end. Further, the first busbar component comprises a first group of fingers extending from the longitudinal body of the first busbar component. The fingers in the first group of fingers comprise a positive connection tab to connect with a positive terminal of cells of a battery module. Similarly, the second busbar component comprises a second group of fingers extending from the longitudinal body of the second busbar component. The fingers in the second group of fingers comprise a negative connection tab to connect with a negative terminal of cells of the battery module. A positive collection zone is formed on the first end of the longitudinal body of the first busbar component to collect positive terminal of each cell of the battery module. Similarly, a negative terminal zone is formed on the first end of the longitudinal body of the second busbar component to collect negative terminal of each cell of the battery module.

[0024] In accordance with example embodiments of the present subject matter, a cross-section area of the first busbar component increases in a direction from the second end to the first end of the longitudinal body of the first busbar component. Similarly, a cross-section area of the second busbarcomponent increases in a direction from the second end to the first end of the longitudinal body of the second busbar component.

[0025] In one embodiment, the first busbar component provides for at least one parallel connection of the cells along the length of the first busbar component from second end to the first end of the longitudinal body of the first busbar component. Similarly, the second busbar component provides for at least one parallel connection of the cells along the length of the second busbar component from second end to the first end of the longitudinal body of the second busbar component.

[0026] In an embodiment, a plurality of recess may be formed on longitudinal body of the first busbar component and the second busbar component. The recess may be designed to accommodate fasteners used for securing the top cell holder on the casing. In one example, an insulation layer may be formed around the recess. The insulation layer may serve as an electrical barrier between the busbar assembly and the fasteners passing through the plurality of recesses.

[0027] The cross-section area of the first and the second busbar component of the busbar assembly is optimized based on amount of current flowing through it along its length. Particularly, the section of the first and the second busbar component of the busbar assembly that passes more amount of current have large cross-section area and vice versa.

[0028] The disclosed structure of the busbar assembly of the present invention, by optimizing the cross-section area of the busbar assembly based on the current load, ensures that the overall current density is relatively uniform throughout the first and second busbar components, thereby reducing the overall cost and weight of the busbar assembly and mitigating localized hotspots occurring in the busbar in use which may otherwise adversely affect cells adjacent to those locally hotter regions. Furthermore, the optimized busbar provides extra space on the top cell holder that can be used for mounting other components, such as additional cells, sensors, and mounting of other components, on the top cell holder.Furthermore, the insulated recesses in the longitudinal body accommodate fasteners for attaching the busbar assembly within the battery module in a simple and cost-effective manner. Since the recesses are molded into the longitudinal body, need for machining additional holes for fasteners is avoided.

[0029] The above and other features, aspects, and advantages of the subject matter will be better explained with regard to the following description and accompanying figures. It should be noted that the description and figures merely illustrate the principles of the present subject matter along with examples described herein and should not be construed as a limitation to the present subject matter. It is thus understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and examples thereof, are intended to encompass equivalents thereof. Further, for the sake of simplicity, and without limitation, the same numbers are used throughout the drawings to reference like features and components.

[0030] Figure 2 illustrates a top view of a battery module 200 comprising a busbar assembly 202, in accordance with implementation of present subject matter.

[0031] As depicted in Figure 2, the battery module 200 comprises the group of cells 204 connected by the busbar assembly 202. The group of cells 204 are arranged in parallel and series configuration within the battery module 200. The busbar assembly 202 comprises a pair of terminal busbar components (hereinafter referred as a first busbar component 208 and a second busbar component 210) and a plurality of intermediate busbar components 206. The first busbar component 208, the second busbar component 210, and the plurality of intermediate components 206 are conductive strips, typically made of aluminum or copper, of varying crosssection (described in detail later).

[0032] The first busbar component 208 and the second busbar component 210 are placed at either end of the busbar assembly 202 to connect a group of cells 204 within the battery module 200 to external systems, such as battery management system (BMS), power inverters, vehicle controllers, etc. The plurality of intermediate busbar components 206 are located between the first busbar component 208 and the second busbar component 210. The plurality of intermediate busbar components, together with the terminal busbars, connects the group of cells 204 in series or parallel configuration within the battery module 200.

[0033] In accordance with example embodiments of the present subject matter, the first busbar component 208 comprises a substantially longitudinal body 224. The longitudinal body 224 of the first busbar component 208 includes a first end 224a and a second end 224b. Similarly, the second busbar component 210 comprises a substantially longitudinal body 226. The longitudinal body 226 of the second busbar component 210 includes a first end 226a and a second end 226b.

[0034] Further, the busbar assembly 202 comprises a positive terminal collection zone 212 and a negative terminal collection zone 214. The positive terminal collection zone 212 is formed on the first end 224a of the longitudinal body 224 of the first busbar component 208, wherein the positive terminal collection zone 212 is to connect positive terminals of each of the cells 204 of the battery module 204 (described later). Similarly, the negative terminal collection zone 214 is formed on the first end 226a of the longitudinal body 226 of the second busbar component 210, wherein the negative terminal collection zone 214 is to connect negative terminals of each of the cells 204 of the battery module 204 (described later). From the negative terminal collection zone 214, another busbar may take current out of the battery module 200. Further, parallel and / or series connections are made between the intermediate busbars 206 intervening the terminal busbars of the busbar assembly 202, i.e. , the first busbar component 208and the second busbar component 210, to provide an arrangement having increased voltage and current capacity.

[0035] In one example embodiment, the group of cells 204 within the module 200 are connected to form sub-assemblies that are arranged in x- axis as well as y-axis of the battery module 200. In example embodiments, the cells 204 are grouped in a series configuration in the x-axis of the battery module 200, whereas in the y-axis, the cells 204 are grouped in the parallel configuration.

[0036] In the example embodiment depicted in Figure 2, there are seven series configurations, i.e., S1 to S7, along the x-axis of the battery module 200, and 30 parallel configurations, i.e., P1 to P30, along the y-axis of the battery module 200. Referring to the example embodiment depicted in Figure 2, looking at the group of cells 204 connected in parallel in P30, it is apparent that more cells get connected along the y-axis moving from the second end 224b of the longitudinal body 224 of the first busbar component 208, depicted in the Figure. 2, to the first end 224a of the longitudinal body 224 of the first busbar component 208. As the number of cells connected to the first busbar component 208 increases, their respective current contribution to the first busbar components 208 keeps on adding. Thus, having more cross-sectional area at the first end 224a of the longitudinal body 224 of the first busbar component 208 where more cells contribute their current, allows better handling of current. At the same time, maintaining the cross section of the first busbar components 208 at the second end 224b to be comparatively lower, provides for optimization of space of the subassembly which in turn allows for better accommodation of additional components in the battery module 200. It also reduces the overall cost and weight of the busbar assembly 202. The same is the case with the second busbar component 210.

[0037] In one embodiment, a plurality of recesses 228 may be formed on a surface of the first busbar component 208, the second busbar component 210, and the intermediate busbar components 206. The recess228 are strategically formed to ensure accurate alignment of the busbar assembly 202 with the battery module 200. In one example embodiments, the recess 228 may be formed on either the edge, the center, or both of the first busbar component 208, the second busbar component 210, and the intermediate busbar components 206.

[0038] In an example embodiment, the recesses 228 may be formed during the manufacturing of the busbar assembly 202 through a molding process, thereby eliminating the need for secondary machining, drilling, or stamping operations which in turn reduces the labor and material handling cost.

[0039] In an embodiment, the recesses 228 provide pathways through which fastening elements, such as screws, bolts, etc., can be passed to mount the busbar assembly 202 to the battery module 200. In one example embodiment, an insulation layer (not shown in the Figure) may be formed around the recess 228. In one example embodiment, the insulation layer may be made up of at least one of thermoplastic, rubber, elastomers, ceramics, and glass. The insulation layer around the recess 228 serves as an electric barrier between the fastener and the busbar assembly 202. Thus, the insulation layer around the recess 228 prevents electrical coupling between the fastener and the busbar assembly 202, thereby enhancing the safety of the battery module 200 by minimizing the risk of short circuits.

[0040] Figure 3A illustrates the first busbar component 208 of the busbar assembly 202, in accordance with implementation of the present subject matter.

[0041] As shown in Figure 3A, the first busbar component 208 comprises a first group of fingers 216. The first group of fingers 216 extends from the longitudinal body 224 of the first busbar component 208. Each of the finger 216 in the first group comprises a plurality of positive connection tabs 220. Each of the positive connection tab 220 connect with a positive terminals of cells 204 of the battery module 200. Further, the positive terminal of eachcell 204 within the battery module 200 are connected to the positive terminal collection zone 212 through the first busbar component 208.

[0042] Further, as can be seen from Figure 3A, the cross section area of the first busbar component 208 is greater at the first end 224a of the longitudinal body 224 of the first busbar component 208 than at the second end 224b of the longitudinal body 224 of the first busbar component 208. The cross area of the first busbar component 208 is optimized based on the amount of current load in the busbar section. Since the first end 224a of the longitudinal body 224 of the first busbar component 208 has a large number of group of cells 204, it has more current density. Therefore, cross-section area of the first end 224a of the longitudinal body 224 of the first busbar component 208 is increased.

[0043] In one example embodiment, the cross-section area of the first busbar component 208 at the first end 224a may be more than about 250% of the second end 224b. In another example embodiment, the cross-section area of the first busbar component 208 at the first end 224a may be in range between 50 mm2- 70 mm2, whereas the cross-section area at second end 224b may be in range between 20 mm2- 28 mm2. In yet another example embodiment, the cross-section area of the first busbar component 208 at the first end 224a may be 60 mm2, whereas the cross-section area at second end 224b may be 24 mm2.

[0044] In one embodiment, the plurality of recesses 228 may be formed on the longitudinal body 224 of the first busbar component 208. As can be seen from the Figure 3A, the recesses 228 may be formed about the center of the width of the longitudinal body 224 of the first busbar component 208. In example embodiments, the recesses 228 may also be formed on an outer edge of the longitudinal body 224 of the first busbar component 208. The recesses 228 on the first busbar component 208 ensure accurate alignment of the first busbar component 208 with the battery module 200.

[0045] In an embodiment, the longitudinal body 224 of the first busbar component 208 may be molded with the plurality of recesses 228.

[0046] Figure 3B illustrates the second busbar component 210 of the busbar assembly 202, in accordance with implementation of the present subject matter.

[0047] As shown in Figure 3B, the second busbar component 210 comprises a second group of fingers 218. The second group of fingers 218 extend from the longitudinal body 226 of the second busbar component 210. Each of the finger 218 in the second group comprises a plurality of negative connection tabs 222. Each of the negative connection tab 222 connect with a negative terminals of cells 204 of the battery module 200. Further, the negative terminal of each cell 204 within the battery module 200 are connected to the negative terminal collection zone 214 through the second busbar component 210.

[0048] Furthermore, as can be seen from Figure 3B, the cross-section area of the second busbar component 210 is greater at the first end 226a of the longitudinal body 226 of the second busbar component 210 than at the second end 226b of the longitudinal body 226 of the second busbar component 210. The cross area of the second busbar component 210 is optimized based on the amount of current load in the busbar section. Since the first end 226a of the longitudinal body 226 of the second busbar component 210 has a large number of group of cells 204, it has more current density. Therefore, cross-section area of the first end 226a of the longitudinal body 226 of the second busbar component 210 is increased.

[0049] In one example embodiment, the cross-section area of the second busbar component 210 at the first end 226a may be more than about 250% of the second end 226b. In another example embodiment, the crosssection area of the second busbar component 210 at the first end 226a may be in range between 50 mm2- 70 mm2, whereas the cross-section area at second end 226b may be in range between 20 mm2- 28 mm2. In yet another example embodiment, the cross-section area of the second busbar component 210 at the first end 226a may be 60 mm2, whereas the crosssection area at second end 226b may be 24 mm2.

[0050] In one embodiment, the plurality of recesses 228 may be formed on the longitudinal body 226 of the second busbar component 210. As can be seen from the Figure 3B, the recesses 228 may be formed about the center of width of the longitudinal body 226 of the second busbar component 210. In example embodiments, the recesses 228 may also be formed on an outer edge of the longitudinal body 226 of the second busbar component 210. The recesses 228 on the second busbar component 210 ensure accurate alignment of the second busbar component 210 with the battery module 200.

[0051] In an embodiment, the longitudinal body 226 of the second busbar component 210 may be molded with the plurality of recesses 228.

[0052] In accordance with example embodiments described herein, the busbar assembly 202 design illustrated in Figure 3A and Figure 3B may provide a better optimized distribution of current in the first busbar component 208 and the second busbar component 210. Further, it helps to reduce the overall cost and weight of the busbar assembly 202 and mitigates occurrences of localized hotspots in the first busbar component 208 and the second busbar component 210 during their operation which may otherwise adversely affect cells 204 adjacent to those locally hotter regions. Furthermore, the optimized busbar assembly 202 provides extra space on the top cell holder that can be used for mounting other components, such as additional cells, sensors, etc., on the top cell holder.

[0053] Although the subject matter has been described in considerable detail with reference to certain examples and implementations thereof, other implementations are possible. As such, the present disclosure should not be limited to the description of the preferred examples and implementations contained therein.

Claims

I / We Claim:1 . A busbar assembly (202), comprising: a first busbar component (208) and a second busbar component (210), each comprising a substantially longitudinal body (224, 226) having a first end (224a, 226a) and a second end (224b, 226b), wherein the first busbar component (208) comprises a first group of fingers (216) extending from the longitudinal body (224) of the first busbar component (208), the fingers (216) comprising a positive connection tab (220) to connect with a positive terminal of cells (204) of a battery module (200), wherein the second busbar component (210) comprises a second group of fingers (218) extending from the longitudinal body (226) of the second busbar component (210), the fingers (218) comprising a negative connection tab (22) to connect with a negative terminal of cells (204) of the battery module (200), a positive terminal collection zone (212) formed on the first end (224a) of the longitudinal body (224) of the first busbar component (208) to collect positive terminal of each cell (204) of the battery module (200); a negative terminal collection zone (214) formed on the first end (226a) of the longitudinal body (226) of the second busbar component (210) to collect negative terminal of each cell (204) of the battery module (200); wherein a cross-section area of the first busbar component (208) increases in a direction from the second end (224b) to the first end (224a) of the longitudinal body (224) of the first busbar component (208); and wherein a cross-section area of the second busbar component (210) increases in a direction from the second end (226b) to the first end (226a) of the longitudinal body (226) of the second busbar component (210).

2. The busbar assembly (202) as claimed in claim 1 , wherein a plurality of recesses (228) is formed on the longitudinal body (224, 226) of the first busbar component (208) and the second busbar component (210).

3. The busbar assembly (202) as claimed in claim 2, wherein an insulation layer is formed around each of the plurality of recesses 228.

4. The busbar assembly (202) as claimed in claim 3, wherein the insulation layer is made up of at least one of thermoplastic, rubber, elastomers, ceramics, and glass.

5. The busbar assembly (202) as claimed in claim 2, wherein the longitudinal body (224, 226) of the first busbar component (208) and the second busbar component (210) is molded with the plurality of recesses 228.

6. The busbar assembly (202) as claimed in claim 1 , wherein the cells (204) within the battery module (200) are arranged in a parallel configuration in a direction from the second end (224b) to the first end (224a) of the longitudinal body (224) of the first busbar component (208), and wherein the cells (204) within the battery module (200) are arranged in a parallel configuration in a direction from the second end (226b) to the first end (226a) of the longitudinal body (226) of the second busbar component (210).

7. The busbar assembly (202) as claimed in claim 1 , wherein the cells (204) within the battery module (200) are arranged in a series configuration between the first busbar component (208) and the second busbar component (210).

8. The busbar assembly (202) as claimed in claim 1 , wherein the crosssection area of the longitudinal body (224) of the first busbar component (208) at the first end (224a) is more than 250% of the cross-section area ofthe longitudinal body (224) of the first busbar component (208) at the second end (224b), and wherein the cross-section area of the longitudinal body (226) of the second busbar component (210) at the first end (226a) is more than 250% of the cross-section area of the longitudinal body (226) of the second busbar component (210) at the second end (226b).

9. The busbar assembly (202) as claimed in claim 1 , wherein the crosssection area of the longitudinal body (224) of the first busbar component (208) at the first end (224a) is in range between 50 mm2to 70 mm2; wherein the cross-section area of the longitudinal body (224) of the first busbar component (208) at the second end (224b) is in range between 20 mm2to 28 mm2.

10. The busbar (202) assembly as claimed in claim 1 , wherein the crosssection area of the longitudinal body (226) of the second busbar component (210) at the first end (226a) is in range between 50 mm2to 70 mm2; wherein the cross-section area of the longitudinal body (226) of the second busbar component (210) at the second end (226b) is in range between 20 mm2to 28 mm2.

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