Nickel TAB design for cost & weight optimization

Abstract

The present invention relates to a hybrid busbar system (100) for electric vehicle battery packs, designed to optimize material usage and enhance manufacturing efficiency The hybrid busbar system (100) comprises a main conductor (102), preferably copper, and a plurality of button- type bridge metals (104), preferably nickel. Each bridge metal (104) includes a button-shaped tab (202) having a central aperture and a fusible link edge (204) for connection to the main conductor (102). The tab (202) is laser welded to a battery cell terminal such that welding occurs around the aperture, preventing puncture of the cell. The fusible link (204) conducts current under normal operation and disconnects in case of short circuit. The system (100) supports configuration variants for different module layouts and aligns with safe welding zones enabling commonization across cell terminals.

Description

[0001] NICKEL TAB DESIGN FOR COST & WEIGHT OPTIMIZATION

[0002] FIELD OF INVENTION

[0003] [1] The present disclosure generally relates to electric vehicle battery packs utilized in the automobile industry, and specifically relates to optimizing busbars to reduce weight and cost of manufacturing, with additional benefits of manufacturing safety and dissipation of heat generated by cells.

[0004] BACKGROUND

[0005] [2] The subject matter discussed in the background section should not be assumed to be prior art merely as a result of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches, which in and of themselves may also correspond to implementations of the claimed technology.

[0006] [3] Electric vehicles are becoming an increasingly popular segment of the automobile industry across the world due to the many advantages and benefits offered by electric vehicles, some of which include lower running costs, lower maintenance costs, better performance, lack of emissions etc. Due to the increasing popularity of electric vehicles, there is an increasing need of constantly improving upon the different technologies associated with different aspects of such vehicles.

[0007] [4] One such aspect of electric vehicles relates to their battery system. The battery systems used in electric vehicles are integral to their performance, and thereby the improvement of performance, durability and functioning of batteries in electric vehicles is of extreme importance to the automobile industry. Interconnection between cells within the battery pack of electric vehicles is necessary to produce the desired voltage and current, and the cells are required to be connected in either series or parallel in order to generate the appropriate voltage and current. [5] Conventionally, busbars are used for the interconnection of cells and the distribution of power within the battery system of electric vehicles, and such busbars used comprise strips or tabs of a metal, hereafter referred to as bridge metal, welded onto another metal, hereafter referred to as main conductor. The bridge metal used in busbars is generally made of materials having significant electrical conduction such as nickel, and the main conductor is made of materials having a higher electrical conductivity that the bridge metal, such as copper. The materials used for bridge metal and main conductor is selected such that they are chemically compatible for welding.

[0008] [6] For instance, the busbars that are generally used in battery systems of electric vehicles are referred to as sandwich busbars, and comprises a bridge metal constituted by a nickel strip welded onto a main conductor constituted by copper strip. The nickel strip is used in such busbars to overcome the limitation presented by copper strips with respect to welding due to higher reflectivity and lower electrical resistance of copper material. Hence, the nickel strip of lesser thickness is welded to the copper strip to overcome such limitations, and such sandwich busbars are used in high power applications.

[0009] [7] The use of strips or tabs of bridge metals in the existing busbar system as mentioned above pose a plurality of disadvantages relating to wastages of materials, increase of weight and cost of the busbars, and difficulties with respect to welding. Firstly, the use of a complete strip of the bridge metal poses a disadvantage with respect to wastage of materials, since the strip in its entirety does not help in electric and thermal conduction, and only the tab which has been welded onto the cell conducts electricity and heat, and it transfers the same to the main conductor busbar. The additional material utilised in the bridge metal strip is superfluous, as there is an increase in weight as well as cost of manufacturing. Yet another drawback associated with use of bridge metal strips is that a mirror component needs to be created, resulting in more types of busbars which then results in a higher manufacturing cost and adds more child parts while assembling. Such bridge metal strips are being optimised by creating holes as a guide for welding, which did not have much of an impact on the weight reduction.

[0010] [8] Yet another disadvantage associated with existing busbars is that the method of welding generally used for connecting the busbar system to the cells is that of laser welding. While laser welding overcomes the disadvantages presented by wire-binding system of busbars such as the time taken for the manufacturing of an entire battery pack and the reliability issues, there are significant issues that arises with laser welding. For instance, there exists increased risk of cell puncture during laser welding due to the jelly roll in the cylindrical cell's concentration at the centre of the cell and its proximity to the negative tab.

[0011] [9] Hence there is a need for improvement in technology relating to busbars used in electric vehicles to overcome existing issues such as wastage of materials, added weight and cost.

[0012] OBJECT OF THE INVENTION

[0013]

[0010] An objective of the invention is to have an improved and optimized design of busbar or interconnects that connects battery cells to each other, without compromising the functionalities of existing methods.

[0014]

[0011] Another objective of the invention is to reduce the busbar weight and cost of manufacturing, along with the additional benefit of manufacturing safety, where an additional feature provided is the prevention of cell puncture.

[0015] SUMMARY OF THE INVENTION

[0016]

[0012] This summary is provided to introduce aspects related to busbars used in electric vehicles to overcome existing issues such as wastage of materials, added weight and cost and the aspects are further described below in the detailed description. This summary is not intended to identify essential features of the claimed subject matter nor is it intended for use in determining or limiting the scope of the claimed subject matter.

[0017]

[0013] In an embodiment of the present disclosure, a hybrid busbar system for connecting a plurality of battery cells in an electric vehicle battery pack. The hybrid busbar system comprising: a main conductor; and a plurality of button-type bridge metals attached to the main conductor, each button-type bridge metal comprising a button-shaped tab configured to be welded to a terminal of a battery cell and a fusible link edge connecting the button-shaped tab to the main conductor to conduct electrical current and heat from the battery cell to the main conductor and to fuse in response to a short-circuit current.

[0014] In an aspect of the present disclosure, the main conductor is made of copper and the button-type bridge metals are made of nickel.

[0018]

[0015] In an aspect of the present disclosure, each button-shaped tab includes a small opening of a predetermined diameter configured to permit welding of the tab around the opening without puncturing the battery cell.

[0019]

[0016] In an aspect of the present disclosure, the hybrid busbar system is configured to sit on a battery cell holder of the battery pack such that puncturing of the battery cell during welding is avoided.

[0020]

[0017] In an aspect of the present disclosure, each button-type bridge metal is provided with additional tolerances to accommodate differences in height between positive and negative battery cell tabs, thereby enabling a common busbar configuration to be used for both the positive and negative cell tabs.

[0021]

[0018] In an aspect of the present disclosure, the hybrid busbar system is configured in a parallelogram boundary-defined shape.

[0022]

[0019] In an aspect of the present disclosure, the hybrid busbar system is integrated into a battery pack comprising a plurality of battery cells, such that the button-type bridge metals are configured to electrically connect the terminals of the plurality of battery cells.

[0023] BRIEF DESCRIPTION OF DRAWINGS

[0024]

[0020] The accompanying drawings constitute a part of the description and are used to provide further understanding of the present invention. Such accompanying drawings illustrate the embodiments of the present invention, which are used to describe the principles of the present invention. The embodiments are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this invention are not necessarily to the same embodiment, and they mean at least one. In the drawings:

[0021] Fig- 1 illustrates a perspective view of the proposed hybrid busbar system, in accordance with an embodiment of the present invention.

[0025]

[0022] Fig. 2 illustrates a perspective view of a button-shaped bridge metal used in the proposed hybrid busbar system, in accordance with an embodiment of the present invention.

[0026]

[0023] Figs. 3(a) and 3(b) illustrate areas of the top and bottom ends of the cell safe for welding of the proposed hybrid busbar system, in accordance with an embodiment of the present invention.

[0027]

[0024] Fig. 4(a), 4(b), 4(c), and 4(d) illustrate the different configurations of the proposed hybrid busbar system, in accordance with an embodiment of the present invention.

[0028]

[0025] A more complete understanding of the present invention and its embodiments thereof may be acquired by referring to the following description and the accompanying drawings.

[0029] DETAILED DESCRIPTION

[0030]

[0026] The detailed description set forth below in connection with the appended drawings is intended as a description of various embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced. Each embodiment described in this invention is provided merely as an example or illustration of the present invention and should not necessarily be construed as preferred or advantageous over other embodiments. The detailed description includes specific details for the purpose of providing a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.

[0031]

[0027] Exemplary embodiments now will be described with reference to the accompanying drawings. The disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey its scope to those skilled in the art. The terminology used in the detailed description of the particular exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting. In the drawings, like numbers refer to like elements.

[0032]

[0028] It is to be noted, however, that the reference numerals used herein illustrate only typical embodiments of the present subject matter, and are therefore, not to be considered for limiting its scope, for the subject matter may admit to other equally effective embodiments.

[0033]

[0029] The specification may refer to “an”, “another”, “one” or “some” embodiment(s) in several locations.

[0034]

[0030] This does not necessarily imply that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments.

[0035]

[0031] As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms “include”, “comprises”, “including” and / or “comprising” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. Furthermore, “connected” or “coupled” as used herein may include operatively connected or coupled. As used herein, the term “and / or” includes any and all combinations and arrangements of one or more of the associated listed items.

[0036]

[0032] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0033] The detailed description includes specific details for the purpose of providing a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.

[0037]

[0034] Electric automobiles have been growing in popularity and demand due to the several benefits and advantages offered by such vehicles. However, there is a constant need for improving upon technologies associated with various aspects of electric vehicles, and one such aspect that is extremely relevant or significant is that of improvement of battery systems of electric vehicles. An area in which improvement is required is that of busbars currently used in electric vehicles and providing solutions for several of the disadvantages associated with existing busbar systems.

[0038]

[0035] Prior to the boom of the electric vehicle market, regulatory bodies in India did not pay much attention towards the safety and protection of EV battery packs. This led to many short circuits, which then led to vehicle fires. Stringent norms have come into play in recent times regarding short circuit protection. With this regulation, EV manufacturers resorted towards wire-bonding, a welding method designed to blow in case of sudden shorts in the circuit. However, there are certain disadvantages associated with wire-bonding busbar systems, such as the burden of time taken for manufacturing an entire battery pack and poor reliability. For instance, one of the reliability issues that may arise in wire-bonding busbar systems is that some wires that are meant for carrying current may not even be in proper contact with the battery pack. Hence, to overcome such issues, laser welding of busbars may be implemented. However, there is a high chance of puncturing the cells while laser welding as the process itself is non-contact.

[0039]

[0036] Additionally, existing busbar systems comprise a strip of bridge metal of significant conductivity attached to a main conductor of higher conductivity, and is used for interconnectivity of cells. The strip of bridge metal is used to connect the busbar system to the cells, and is generally made of materials like Nickel. Further, the main conductor is used for conducting electricity in the series or parallel connections made by the busbar system. However, there are several disadvantages associated with the existing busbar systems including wastage of materials, and increase of weight and cost.

[0037] The use of complete strips or tabs of bridge metals poses a disadvantage with respect to wastage of materials, since the strip in its entirety does not help in electric and thermal conduction, and only the tab which has been welded onto the cell conducts electricity and heat, and it transfers the same to the main conductor busbar. The additional material utilised in the bridge metal strip is superfluous, as there is an increase in weight as well as cost of manufacturing. Yet another drawback associated with use of bridge metal strips is that a mirror component needs to be created, resulting in more types of busbars which then results in a higher manufacturing cost and adds more child parts while assembling. Such bridge metal strips are being optimised by creating holes as a guide for welding, which did not have much of an impact on the weight reduction

[0040]

[0038] Hence, the present invention relates to a hybrid busbar system that overcomes the above-mentioned disadvantages associated with existing busbar systems. Further, the hybrid busbar systems proposed in this invention serves the same purpose and functionalities as existing busbar systems, and is a more reliable and safe solution for laser welding without puncturing the cell.

[0041]

[0039] Fig. 1 illustrates a perspective view of the proposed hybrid busbar system, in accordance with an embodiment of the present invention. The hybrid busbar system 100 comprises a main conductor 102 and a plurality of button-type bridge metals 104-1 to 104-n (collectively labelled 104). In an embodiment of the present invention, the main conductor 102 is made of copper, and the button-type bridge metals 104 are made of nickel. The button-type bridge metals 104 overcome the disadvantages presented by the bridge metal strips used in the existing busbar systems, as the button-type bridge metals 104 avoid wastage of materials as it is constituted by a button-shaped tab which can be laser welded onto a cell for conducting electricity and heat, and it transfers the same to the main conductor 102. The button-type bridge metals 104 are attached to the main conductor 102 by means of a fusible link of the buttontype bridge metals 104.

[0042]

[0040] Fig. 2 illustrates a perspective view of a button-shaped bridge metal used in the proposed hybrid busbar system, in accordance with an embodiment of the present invention. The button-type bridge metal 200 is constituted by a button-shaped tab 202 having a fusible link edge 204. The button-shaped tab 202 is used for welding the button-type bridge metal 200 of the hybrid busbar system to a cell. The fusible link edge 204 is used for securely connecting the button-type bridge metal 200 to the main conductor of the hybrid busbar, such that the fuse link edge 204 ensures even power and heat transfer, and fuses in case of short circuit current. The button-type bridge metal 200 of the hybrid busbar system is designed such that the hybrid busbar sits on the cell holder, and puncture of cell during laser welding is avoided.

[0043]

[0041] The puncture of the cell is avoided by means of the small opening of a calculated diameter provided in the button-shaped tab 202 to weld around that area, and therefore avoiding cell puncturing. The small opening has been included having an appropriate diameter so that the area around the red zone can be welded without damaging the cells, and the same has been illustrated in Figs. 3(a) and 3(b). The heights of the cell tabs at the positive and negative ends are different, and hence difficult to commonise existing designs of busbars according to the tabs. The present invention overcomes this problem with the help of additional tolerances given to the button-type bridge metal of the hybrid busbar system, which is turn commonises the busbars welded on the positive and negative tabs.

[0044]

[0042] Hence, the button-type bridge metal enables secure and safe connection of the cells with the hybrid busbar system. The purpose of the main conductor is to evenly distribute power across the battery module of an electric vehicle, and the button-type bridge metal aids in the welding process. This is done because the thickness of the cell tab generally ranges from 0.1mm to 0.2mm and since copper is a highly reflective metal with a thickness greater than that of the cell tab, there are high chances of cell puncture and other manufacturing and safety related issues welding due to the jelly roll is concentrated at the centre of the cylindrical cell and its proximity to the negative tab. Hence, nickel is welded onto the cell tab, which then transfers the power to copper, which in turn distributes power to the entire system.

[0045]

[0043] Figs. 3(a) and 3(b) illustrate areas of the top and bottom ends of the cell safe for welding of the proposed hybrid busbar system, in accordance with an embodiment of the present invention. Fig. 3(a) illustrates a top view of a battery cell terminal showing an annular OK area surrounding a central prohibited zone (07). The top terminal includes a safe welding area marked as the OK area and a prohibited region at the center which aligns with the internal jelly roll. The button-shaped tab (202), as shown in fig. 1, of the bridge metal (104), as shown in fig. 1, includes a small opening aligned with this region, allowing welding to be performed annularly around the central aperture, thereby ensuring that no welding energy penetrates the prohibited central zone. Fig. 3(b) illustrates a cross-sectional view of the bottom end of the battery cell. Fig. 3(b) identifies structural layers including the winding, the insulation plate (resin), and the metal can (Fe-Ni). The OK area for welding is denoted, and the button-shaped tab (202) of the bridge metal (104) is designed to avoid direct welding on the central axis by focusing weld placement to peripheral regions as identified. This geometry of the present invention matches the configuration of the tab as described in an embodiment of Fig. 2.

[0046]

[0044] The hybrid busbar systems may be a parallelogram boundary-defined shape to efficiently distribute power throughout the battery pack of an electric vehicle. Different embodiments of the present invention may have different configurations of the hybrid busbar with respect to the configuration of the main conductor and the button-type bridge metal, as illustrated in Figs. 4(a), 4(b), 4(c), and 4(d). Fig. 4(a), 4(b), 4(c), and 4(d) illustrate the different configurations of the proposed hybrid busbar system, in accordance with an embodiment of the present invention. Fig. 4(a) shows an embodiment of the hybrid busbar system (100) where the main conductor (102) is configured in a substantially planar form with button-type bridge metals (104) arranged on its surface. This embodiment demonstrates connection to a matrix of battery cells in a flat module configuration, maintaining electrical interconnectivity across the array. Fig. 4(b) illustrates a variation in which the hybrid busbar system (100) has a stepped or folded geometry at one end. The button-type bridge metals (104) are positioned uniformly along the main conductor (102), enabling series or parallel connections in staggered or offset battery pack arrangements.

[0047]

[0045] Fig. 4(c) shows a configuration where the main conductor (102) is inclined at an edge for mounting, and the bridge metals (104) are placed at an angle. This layout is suitable for battery modules with elevation-differentiated terminals while preserving welding alignment. Fig. 4(d) illustrates a parallelogram-shaped main conductor (102) of the hybrid busbar system (100), where the button-type bridge metals (104) are spaced according to the triangular or diamond cell layout in the battery module. This shape supports uniform power distribution while minimizing track length and material usage.

[0048]

[0046] Technical advantages of present invention: The proposed hybrid busbar system (100) with the button-type bridge element overcomes several of the disadvantages faced by existing busbar systems such as wastage of materials, increase in weight and cost, difficulty with respect to laser welding etc. Further, instead of full nickel busbars, nickel tabs with fuse may be produced in bulk, and the same will be used in respective places, thereby eliminating need of multiple nickel busbars.

[0049]

[0047] The invention has been described above with reference to numerous embodiments and specific examples. Many variations will suggest themselves to those skilled in this art in light of the above detailed description. All such obvious variations are within the full intended scope of the appended claims.

Claims

We Claim:

1. A hybrid busbar system (100) for connecting a plurality of battery cells in an electric vehicle battery pack, the hybrid busbar system comprising: a main conductor (102); and a plurality of button-type bridge metals (104-1 to 104-n) attached to the main conductor (102), each button-type bridge metal (104, 200) comprising a button-shaped tab (202) configured to be welded to a terminal of a battery cell and a fusible link edge (204) connecting the button-shaped tab (202) to the main conductor (102) to conduct electrical current and heat from the battery cell to the main conductor (102) and to fuse in response to a short-circuit current.

2. The hybrid busbar system (100) as claimed in claim 1, wherein the main conductor (102) is made of copper and the button-type bridge metals (104) are made of nickel.

3. The hybrid busbar system (100) as claimed in claim 1, wherein each button-shaped tab (202) includes a small opening of a predetermined diameter configured to permit welding of the tab around the opening without puncturing the battery cell.

4. The hybrid busbar system (100) as claimed in claim 1, wherein the hybrid busbar system (100) is configured to sit on a battery cell holder of the battery pack such that puncturing of the battery cell during welding is avoided.

5. The hybrid busbar system (100) as claimed in claim 1, wherein each button-type bridge metal (104) is provided with additional tolerances to accommodate differences in height between positive and negative battery cell tabs, thereby enabling a common busbar configuration to be used for both the positive and negative cell tabs.

6. The hybrid busbar system (100) as claimed in claim 1, wherein the hybrid busbar system (100) is configured in a parallelogram boundary-defined shape.

7. The hybrid busbar system (100) as claimed in claim 1, wherein the hybrid busbar system (100) is integrated into a battery pack comprising a plurality of battery cells, such thatthe button-type bridge metals (104, 200) are configured to electrically connect the terminals of the plurality of battery cells.

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