Claims:WE CLAIM:
1. A busbar (200) for connecting a plurality of cells (110) of a battery (100), each of the plurality of cells (110) having a pair of terminals (112a, 112b), the busbar (200) comprising:
a plurality of first busbar segments (210 and 220), each of the plurality of first busbar segments (210 and 220) having an opening (230) for connecting to one of the pair of terminals (112a, 112b) of one of the cells (110), the opening (230) having an opening edge portion (234) adjacent to a periphery of the opening (230), wherein a thickness of at least some of the opening edge portion (234) varies by a predetermined value from a busbar thickness D of rest portion (222) of the plurality of busbar segments (210 and 220); and
a second busbar segment (240) protruding between the plurality of first busbar segments (210 and 220), the second busbar segment (240) connecting edges of the plurality of first busbar segments (210 and 220).

2. The busbar (200) as claimed in claim 1, wherein the plurality of first busbar segments (210 and 220) includes a left busbar segment (210) and a right busbar segment (220), the second busbar segment (240) being located between the left busbar segment (210) and the right busbar segment (220).
3. The busbar (200) as claimed in claim 2, wherein the left busbar segment (210) and the right busbar segment (220) have a substantially flat profile.

4. The busbar (200) as claimed in claim 1, wherein the second busbar segment 240 has a curved profile.

5. The busbar (200) as claimed in claim 1, wherein the opening (230) is adapted to the terminals (112a,112b), the opening (230) being circular depending upon the terminals (112a,112b), the opening edge portion (234) being concentric with the opening (230).\

6. The busbar (200) as claimed in claim 1, wherein the thickness of the opening edge portion (234) is less than the busbar thickness, the busbar thickness being uniform throughout the rest portion (222).

7. The busbar (200) as claimed in claim 7, wherein the thickness of the opening edge portion (234) is equal to one third of the busbar thickness of the rest portion (222).

8. A battery (100) comprising:
a plurality of cells (110), each of the plurality of cells (110) having a first terminal (112a) at a first end and a second terminal (112b) at a second end of the respective plurality of cells (110), the plurality of cells (110) being arranged in an array; and
a plurality of busbars (200) for connecting the plurality of cells (110) to one another, each of the plurality of busbars (200) having:
a plurality of first busbar segments (210 and 220), the plurality of first busbar segments (210 and 220) including a left busbar segment (210) and a right busbar segment (220), each of the plurality of first busbar segments (210 and 220) having an opening (230) for connecting to one of the terminals (112a,112b) of the respective plurality of cells (110), the opening (230) having an opening edge portion (234) adjacent to a periphery of the opening (230), wherein a thickness of at least some of the opening edge portion (234) varies by a predetermined value from a busbar thickness of rest portion (222) of the plurality of first busbar segments (210 and 220); and
a second busbar segment (240) protruding between the plurality of first busbar segments (210 and 220), the second busbar segment connecting edges of the plurality of first busbar segments (210 and 220).

9. The battery (100) as claimed in claim 8, wherein the opening (230) is adapted to the terminals (112a, 112b), the opening (230) being circular depending upon the terminals (112a,112b), the opening edge portion (234) being concentric with the opening (230), the location of the opening (230) on the plurality of first busbar segments (210 and 220) depending upon the arrangement of the array of the plurality of cells (110) .

10. The battery (100) as claimed in claim 9, wherein the thickness of the opening edge portion (234) is equal to one third of the busbar thickness, the busbar thickness being uniform throughout the rest portion (222).

11. A busbar (200A) for connecting to one terminal (112t) of a pair of terminals (112a,b) of a cell (110t) of a battery (100), the busbar (200A) comprising a first busbar segments (210a) and a terminal busbar segment (310) extending from the first busbar segment (210a) at an angle, the first busbar segment (210a) having an opening (230) for connecting to the terminal (112t) of the cell (110t), the opening (230) having an opening edge portion (234) adjacent to a periphery of the opening (230), wherein a thickness of at least some of the opening edge portion (234) is less than a busbar thickness D of rest portion (222) of the substantially flat profiled first busbar segment (210a) and of the substantially flat profiled terminal busbar segment (310), the terminal busbar segment (310) providing connection for an external device.

Dated this 31st day of March 2022
TVS MOTOR COMPANY LIMITED
By their Agent & Attorney

(Nikhil Ranjan)
of Khaitan & Co
Reg No IN/PA-1471 , Description:FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]

TITLE OF INVENTION
Busbar for Connecting Cells in a Battery

APPLICANT
TVS MOTOR COMPANY LIMITED, an Indian company, having its address at “Chaitanya”, No.12 Khader Nawaz Khan Road, Nungambakkam, Chennai 600 006.

PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed.
FIELD OF THE INVENTION
[001] The present invention relates to a battery pack and more particularly to a busbar design for connecting cells of a battery pack.

BACKGROUND OF THE INVENTION
[002] It is known in the art to connect multiple cells such as Lithium-ion or Nickel metal hydride cells in series or parallel to obtain any desired voltage or current in a battery pack. For example, a set of cells may be arranged in parallel to obtain a desired current. Consequently, many of the parallel sets may be coupled in series to obtain a desired voltage of the larger set. The larger set may be electrically coupled in series or parallel with other similarly sized sets to obtain an even higher voltage or current.
[003] A bus bar is a metal strip or a bar that conducts electricity and is used for electrical power distribution. Battery cells can be connected in a battery pack with bus bars to make battery packs.
[004] In conventional battery modules and specially in prismatic battery, a plurality of cells are joined electrically in parallel or series using busbars. The busbars are joined to the terminals of cells using various welding techniques known in the art.
[005] Aluminium is a good conductor of electricity and has been a preferred known choice as a material for manufacturing the terminals of the battery. For similar reasons, aluminium is also preferred for making busbars. A reason for this is because other metals create alloys and get oxidized which creates insulation thereby causing poor flow of electricity, while aluminium does not.
[006] Since aluminium forms an electrically insulating oxide layer on its surface when exposed to air, a consistently good electrical contact between the two aluminium poles/terminals can only be ensured by a welded connection if no other additional measures are taken.
[007] The designs of busbars and welding joints as known in the art, have higher electrical contact resistance. Further, aluminium is a soft metal and poses problems of strong welding and mounting although it is comparatively easier to weld.
[008] Alternatively, it is also known in the art to replace aluminium with other metals with high electrical conductivity such as copper and the like but due to alloy formation this leads to a non-homogeneous temperature distribution under current load.
[009] As per known art, screw mounting is sometimes preferred to connect the busbar to the terminal of the battery. However, this is not a universal solution and can only be used in case of some special kind of cells which can be screw welded. Further, screw welding adds to the weight and is a time-consuming manufacturing process.
[010] Further, existing busbar designs do not provide provisions for deep penetration of laser beam through the busbar and the cell terminal. This may lead to terminal damage.
[011] Thus, there is a need in the art for stable and reproducible electrical connections for cells in a battery pack, which addresses at least the aforementioned problems.

SUMMARY OF THE INVENTION
[012] In one aspect, the present invention is directed at a busbar for connecting a plurality of cells in a battery. Each of the plurality of cells has a pair of terminals. In another aspect, the invention is directed to a battery pack having cells with their terminals connected using the busbars.
[013] The busbar includes a plurality of first busbar segments and a second busbar segment protruding between the plurality of first busbar segments. Each of the plurality of first busbar segments has an opening for connecting to one of the pair of terminals of one of the cells. The opening has an opening edge portion adjacent to a periphery of the opening. A thickness of at least some of the opening edge portion varies by a predetermined value from a busbar thickness of rest portion of the plurality of busbar segments. The second busbar segment protrudes between the plurality of first busbar segments and connects edges of the plurality of first busbar segments.
[014] In an embodiment, the plurality of first busbar segments includes a left busbar segment and a right busbar segment. The second busbar segment is located between the left busbar segment and the right busbar segment. The left busbar segment and the right busbar segment have a substantially flat profile.
[015] In an embodiment, the second busbar segment has a curved profile.
[016] In an embodiment, the plurality of first busbar segments are at the edge portions of the busbar.
[017] In an embodiment, the opening is adapted to the pair of terminals and is circular depending upon the terminals. The opening edge portion is concentric with the opening.
[018] In an embodiment, the thickness of the opening edge portion is less than the uniform thickness of the rest portion of the busbar.
[019] In another embodiment, the thickness of all of the opening edge portion is uniform and less compared to the busbar thickness.
[020] In another embodiment, the thickness of the opening edge portion is equal to one third of the busbar thickness of the rest portion.
[021] In another embodiment, the busbar includes a first busbar segments and a terminal busbar segment disposed at an angle with the first busbar segment. The first busbar segment has the opening for connecting to the terminal of the cell. The opening having the opening edge portion with a thickness less than a busbar thickness of the rest portion of the substantially flat profiled first busbar segment the terminal busbar segment. The terminal busbar segment provides connection for an external device to the cell.
[022] In various embodiments, the busbar is made of 1000 series grade aluminium.

BRIEF DESCRIPTION OF THE DRAWINGS
[023] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Figures 1A, 1B and 1C illustrate a battery pack in various views, in accordance with an embodiment of the invention, wherein,
Figure 1A illustrates the battery pack in a perspective view;
Figure 1B illustrates the batter pack in the same perspective view with a top cover of the batter pack removed; and
Figure 1C illustrates the battery pack in an exploded perspective view.
Figures 2A and 2B illustrate the busbar, in accordance with an embodiment of the invention, wherein,
Figure 2A illustrates the busbar in a front view; and
Figure 2B illustrates the busbar in a top view.
Figure 3 illustrates the busbar in top view, in accordance with another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION
[024] The present invention relates to a battery pack (battery) comprising a plurality of cells connected to one another and arranged in an array. More particularly, the present invention relates to a bus bar design for accurate and precise joining between the cells of the battery pack.
[025] Figures 1A, 1B and 1C illustrate a battery pack 100 in various views, in accordance with an embodiment of the invention. Figure 1A illustrates the battery pack 100 in a perspective view and Figure 1B illustrates the battery pack 100 in the same perspective view with a top cover 150 of the batter pack 100 removed. Figure 1C illustrates the battery pack 100 in an exploded perspective view.
[026] The battery pack 100 includes a plurality of cells 110 packed and arranged in an array between the top cover 150 and a bottom cover 152. As an example, the battery pack 100 includes two sets of cells (110a and 110b). Each set of cells (110a and 110b) has four cells out of the plurality of cells 110. All of the plurality of cells 110 are connected in series to form the battery pack 100. In another embodiment, the plurality of cells 110 are connected in parallel and series or combination of both to achieve the desired volt and amperes. Each of the plurality of cells 110 has a pair of terminals (112a, 112b). A terminal 112a of the cell 110a of the battery pack 100 is connected to a terminal 112b of the cell 110b of the battery pack 100 through a busbar 200. In various embodiments, the shape of the plurality of cells 110 varies. For example, may be cylindrical, cuboidal, prismatic and the like.
[027] Figures 2A and 2B illustrate the busbar 200, in accordance with an embodiment of the invention. Figure 2A illustrates the busbar 200 in a front view and Figure 2B illustrates the busbar 200 in a top view. The busbar 200 includes a plurality of first busbar segments (210 and 220) and a second busbar segment 240 protruding between the plurality of first busbar segments (210 and 220). Each of the plurality of first busbar segments (210 and 220) has an opening 230 for connecting to one of the pair of terminals 112a, 112b of one of the cells 110. The opening 230 has an opening edge portion 234 adjacent to a periphery of the opening 230. A thickness of at least some of the opening edge portion 234 varies by a predetermined value from a busbar thickness D of a rest portion 222 of the plurality of busbar segments (210 and 220). The rest portion 222 is a portion of the busbar 200 excluding the opening edge portion 234. The second busbar segment 240 connects edges of the plurality of first busbar segments (210 and 220).
[028] During a welding process such as laser welding, the opening 230 along with the edge portion 234 melt to get stuck with cell terminals (112a,b).
[029] In an embodiment, the plurality of first busbar segments (210 and 220) includes a left busbar segment 210 and a right busbar segment 220. The second busbar segment 240 is located between the left busbar segment 210 and the right busbar segment 220. The left busbar segment 210 and the right busbar segment 220 have a substantially flat profile.
[030] In an embodiment the second busbar segment 240 has a curved profile. The radius of curvature of the curved portion depends upon the design consideration and size and form factor of the cells. For example, in an embodiment, the length of the busbar is about 50mm, the uniform thickness D is 1.5 mm, the thickness of the opening portion is 0.4 mm. The radius of curvature R is chosen so that the height of the curved portion top over and above the lower surface of the busbar may be 3.5mm, that is the curved portion protrudes about 2 mm from the uniformly flat busbar. The diameter of the opening may be in the order of five to ten mm.
[031] In an embodiment, the plurality of first busbar segments (210 and 220) are at the edge portions of the busbar 200.
[032] In an embodiment, the opening 230 is adapted to the terminals (112a,112b) and is circular depending upon the terminals (112a,112b). The opening edge portion 234 is concentric with the opening 230.
[033] In an embodiment, the thickness of the opening edge portion 234 is less than the uniform busbar thickness D of the rest portion 222. In another embodiment, the thickness of all of the opening edge portion 234 is uniform and less compared to the busbar thickness D. In another embodiment, the thickness of the opening edge portion 234 is equal to one third of the busbar thickness D of the rest portion 222.
[034] For example, in an embodiment, busbar 200 has a length of 50mm and uniform busbar thickness D of 1.5mm. In accordance with an embodiment of the invention, the thickness of the opening edge portion 234 is about 0.5 mm. In another embodiment, the thickness of the opening edge portion 234 is 0.4mm. In another embodiment, the thickness of the opening edge portion 234 varies form 0.4 mm to 0.5mm at different portions within the same embodiment. The thickness of the opening edge portion 234 is 0.4mm at some portion of the opening edge portion 234 and 0.5 mm at some other portion of the opening edge portion 234.
[035] Figure 3 illustrates a busbar 200A (also shown in Figures 1A-C) for a cell 110t of the battery 100, in accordance with another embodiment of the invention. Busbar 200A connects to only one terminal 112t of the pair of terminals (112a,b) of the cell 110t of the battery 100. Busbar 200A includes a first busbar segments 210a and a terminal busbar segment 310 extending at an angle from the first busbar segment 210a. The first busbar segment 210a has an opening 230 for connecting to the terminal 112t of the cell 110t. The opening 230 has an opening edge portion 234 adjacent to a periphery of the opening 230. A thickness of at least some of the opening edge portion 234 is less than a busbar thickness D of the rest portion 222 of the substantially flat profiled first busbar segment 210a and of the substantially flat profiled terminal busbar segment 310. The terminal busbar segment 310 is solid and does not have an opening or hole. The terminal busbar 310 does not connect to terminal of a cell but is for providing connection for an external device.
[036] Busbar 200A is a terminal busbar connecting to only one of the pair of terminals (112a and 112b) at one end having only one opening 230. In an embodiment, the terminal busbar segment 310 is disposed at a substantially right angle with respect to the first busbar segment 210 and provides connection for one of the polarities of the battery 100 to an external device such as another battery, an external load and the like.
[037] In various embodiments, the busbar 200 is made of 1000 series grade aluminium.
[038] Advantageously, the busbar design of the invention provides highly stable and rigid electrical connections for the cells in the battery pack. The curved portion of the busbar of the invention adds more tensile strength to the bus bar and helps to prevent failure and breakage of the busbars under harsh mechanical testing including vibration test.
[039] Due to the provision of the lower thickness of about 0.5mm of the opening edge portion, laser welding becomes easy, and the welded aluminium can easily stick to the terminals of the cells through the opening. This kind of welding is known as fillet laser welding. The design of the busbar provided by the invention enables welding with less heat input which prevents the cell terminals from being damaged. Additionally, the joint so formed can be checked visually as well for quality checks.
[040] Additionally, the busbar of the invention also offers lower electrical resistance, and involves lesser manufacturing time, is lighter in weight and reduces the temperature difference within the battery.
[041] While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims.