Claims:WE CLAIM:
1. A battery pack (100) for a motor vehicle (200), the battery pack (100) comprising: a housing (110); a battery module (130) having a plurality of cells (132) disposed inside the housing (110) and extending between a top end (130a) and a bottom end (130b); plurality of first busbars (136a) disposed between the top end (130a) and a top wall (112) of the housing (110); plurality of second busbars (136b) disposed between the bottom end (130b) and a bottom wall (114) of the housing (110); and a thermally conductive material applied between the plurality of first busbars (136a) and the top wall (112), and the plurality of second busbars (136b) and the bottom wall (114).

2. The battery pack (100) as claimed in claim 1, wherein the thermally conductive material dissipates heat generated by the cells (132).

3. The battery pack (100) as claimed in claim 1, wherein the thermally conductive material is a viscous fluid.

4. The battery pack (100) as claimed in claims 1 and 3, wherein a hard material is formed by curing the thermally conductive material.

5. The battery pack (100) as claimed in claims 1 and 4, wherein the thermally conductive material is selected from a group consisting of silicone, urethane, acrylic and an epoxy-based material.

6. The battery pack (100) as claimed in claim 1, wherein the plurality of busbars (136a, 136b) comprises at least a provision each for channelization and dissipation of gases generated from the battery module (130).

7. The battery pack (100) as claimed in claims 1 and 6, wherein each layer of the thermally conductive material comprises at least a through- corresponding to the provisions of the respective busbars (136a, 136b) for channelization and dissipation of gases generated from the battery module (130).

8. The battery pack (100) as claimed in claim 1, wherein the top wall (112) of the housing (110) comprises plurality of fins (120) for dissipation of heat generated from the battery module (130).
, Description:FIELD OF THE INVENTION
[001] The present invention relates to a battery pack for a motor vehicle.

BACKGROUND OF THE INVENTION
[002] Batteries are a useful source of stored energy that can be incorporated into several devices and systems. Rechargeable lithium-ion batteries have emerged as a preferred choice for usage in energy storage technology because of their high specific energy compared to other electrochemical energy storage devices. Lithium-ion battery packs essentially have a battery module which includes plurality of interconnected individual lithium-ion batteries. The lithium-ion battery packs are thus used in almost all consumer electronics devices, industrial equipment, transportation, automobile industry, etc.
[003] Owing to the nature of the lithium-ion batteries, storing and operating the battery pack at an optimal operating temperature is very important to allow the battery pack to maintain a charge for an extended period of time. However, one of the primary disadvantages in operating lithium-ion battery packs is that individual battery cells in the battery packs are prone to thermal management issues which occur when elevated temperatures trigger heat-generating exothermic reactions which in turn further increase temperatures and potentially trigger deleterious reactions. During such an event an individual cell heats up to 850°C or more consequently increasing the temperature of adjacent cells within the battery pack as well. As a result, power from the battery pack is interrupted due to the overall damage caused.
[004] Hence, there have been several attempts made for channelizing and dissipating the heat generated from the individual cells in order to mitigate all damage causing reactions. In one such attempts, thermal conductive resilient pads are intimately sandwiched between a metallic sheet and top or bottom common electrodes. The metallic sheets are secured to a retaining frame via screw bolts. Heat generated by the battery cells during operation is thus dissipated via their top and bottom portions to the metallic sheets, then to the thermal conductive pads and subsequently to ambient air. However, since the metallic sheets are rigid in nature, full contact with cell connecting surface cannot be established due to which complete dissipation of the heat cannot be achieved.
[005] In another attempt, silicone rubber syntactic foam is used as a potting material. The silicone rubber syntactic material is disposed in the battery module to partially encapsulate the battery cells, and a heat exchange member integrally interconnecting the heat dissipation members is mounted to one side of the battery module. Accordingly, heat generated from the battery cells during charge and discharge stage is removed by the silicone rubber syntactic material. However, filling the battery pack entirely with the silicone rubber syntactic foam drastically increases battery weight which is directly linked to performance of the motor vehicle. Thus, leading to a lower vehicle performance. Further, a phenomenon of thermal expansion is prevented in this type of arrangement, because of which structural stresses on the cells are created, which eventually degrades life of the cells.
[006] Thus, there is a need in the art for a battery pack which addresses at least the aforementioned problems.

SUMMARY OF THE INVENTION
[007] The present invention is directed to a battery pack for a motor vehicle. The battery pack has a housing; a battery module having a plurality of cells disposed inside the housing and extending between a top end and a bottom end; plurality of first busbars disposed between the top end and a top wall of the housing; plurality of second busbars disposed between the bottom end and a bottom wall of the housing; and a thermally conductive material applied between the plurality of first busbars and the top wall, and the plurality of second busbars and the bottom wall; wherein the thermally conductive material dissipates heat generated by the cells.
[008] In an embodiment of the invention, the thermally conductive material is a viscous fluid. In a further embodiment, a hard material is formed by curing the thermally conductive material. In yet another embodiment, the thermally conductive material is selected from a group consisting of silicone, urethane, acrylic and an epoxy-based material.
[009] In an embodiment of the invention, the busbars have at least a provision each for channelization and dissipation of gases generated from the battery module. In a further embodiment, each layer of the thermally conductive material has at least a through-hole corresponding to the through-holes of the respective busbars for channelization and dissipation of gases generated from the battery module.
[010] In another embodiment of the invention, the top wall of the housing comprises plurality of fins for dissipation of heat generated from the battery module.

BRIEF DESCRIPTION OF THE DRAWINGS
[011] 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.
Figure 1 shows a body of a saddle type two-wheeler vehicle in accordance with an embodiment of the invention.
Figure 2 shows a perspective view of a battery pack in accordance with an embodiment of the invention.
Figure 3 shows an exploded view of the battery pack in accordance with an embodiment of the invention.
Figure 4 shows a top view of the battery pack in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION
[012] The present invention relates to a battery pack for motor vehicles.
[013] Figure 1 shows a perspective view of a saddle type motor vehicle 200. The motor vehicle 200 is a two-wheeler which seats two persons. The motor vehicle 200 has a front end 10 and a rear end 20, and between the front end 10 and the rear end 20, the motor vehicle 200 has a body 60. The motor vehicle 200 has a wiring system (not shown in the figure) extending between the front end 10 and the rear end 20 connected to a battery 100 (shown in Figures 2, 3, and 4) disposed generally inside the body 60. The motor vehicle 200 has a floorboard 30 which acts as a foot rest for a rider. On the rear end 20, the motor vehicle 200 has a rear taillight 40. Further, the motor vehicle 200 has a front cover typically below a handle (not shown).
[014] Referring to Figure 2, the battery pack 100 of the present invention has a housing 110 which essentially functions as a protective casing of the battery pack 100. Thus, the housing 110 has a top wall 112, a bottom wall 114 (not visible in the present figure), opposing side walls 116a, 116b (not visible in the present figure), 118a, and 118b (not visible in the present figure). In an embodiment as shown in Figure 2, the housing 110 has an upper casing 110a and a lower casing 110b. Thus, the top wall 112 resides in the upper casing 110a and the bottom wall 114 resides in the lower casing 110b. The upper casing 110a and the lower casing 110b are detachably attached to each other by a plurality of affixing means X. In an embodiment of the invention, the affixing means X are either screws, or nuts and bolts, etc. In the embodiment shown in Figures 2 and 3, the top wall 112 of the housing has plurality of fins 120. Accordingly, surface area of the top wall 112 increases thereby facilitating dissipation of heat generated from inside the battery pack.
[015] Referring now to Figure 3, the battery pack 100 of the present invention has a battery module 130 disposed inside the housing 110. The battery module 130 has a plurality of cells 132 arranged in rows and columns. In the present invention, the battery module 130 extends between a top end 130a and a bottom end 130b. As shown in the Figure, in an embodiment, the plurality of cells 130 are interconnected serially and/ or parallelly through a first interconnect 134a disposed adjacent to the top end 130a of the battery module 130 and a second interconnect 134b disposed adjacent to the bottom end 130b of the battery module 130.
[016] Further, as shown in Figure 3, the battery pack 100 has plurality of first busbars 136a and plurality of second bus bars 136b. The busbars are metallic strips or bars used to distribute power received from the plurality of cells 132 through the interconnects 134a and 134b. Accordingly, the plurality of first bus bars 136a is disposed between the top end 130a of the battery module 130 and the top wall 112 of the housing 110. Further, the plurality of second bus bars 136b is disposed between the bottom end 130b of the battery module 130 and the bottom wall 114 of the housing 110. In an embodiment as shown in Figure 3, the plurality of first bus bars 136a is disposed between the first interconnect 134a and the top wall 112 of the housing 110, and the plurality of second bus bars 136b is disposed between the second interconnect 134b and the bottom wall 114 of the housing 110. Referring now to Figure 4, in an embodiment, the plurality of first busbars 136a has at least one provision 138. Similarly, the plurality of second busbars 136b also has at least one provision (not shown). The provisions on the plurality of first busbars 136a and the plurality of second busbars 136b are made for channelization and dissipation of gases generated from the plurality of cells 132 in the battery module 130.
[017] In order to dissipate heat generated from the plurality of cells 132, the present invention has a thermally conductive material (not shown in the Figures). The thermally conductive material also provides an electric insulation. The thermally conductive material is applied between the plurality of first busbars 136a and the top wall 112 of the housing 110 and between the plurality of second busbars 136b and the bottom wall 114 of the housing 110. In an embodiment, the thermally conductive material is a viscous fluid. Thus, the thermally conductive material can be conveniently spread over entire surface of the first plurality of busbars 136a facing the top wall 112 of the housing 110. Similarly, the thermally conductive material can be also spread over entire surface of the plurality of second busbars 136b facing the bottom wall 114 of the housing 110. In an embodiment of the invention, the thermally conductive material is selected from a group including, but not limited to silicone, urethane, acrylic or an epoxy-based material. In another embodiment, the thermally conductive material is a flame retardant thus arresting propagation of flames inside the battery module in event of accidents.
[018] In an embodiment, the thermally conductive material is cured to form a hard material. The hard material is elastic in nature and functions as a damper. The hard material thereby provides a cushion to the plurality of first busbars 136a and the plurality of second busbars 136b and protects the busbars and the battery module from structural loads. In a further embodiment, respective layers of the thermally elastic material also have at least one through-hole (not shown). Accordingly, the through-holes of the layers of the thermally conductive material present on the plurality of first busbars 136a and the plurality of second busbars 136b respectively, correspond to the provisions 138 of the plurality of first busbars 136a and the provisions (not shown) of the plurality of second busbars 136b. The through-holes and the provisions thereby function as channels/ passages for dissipation of the gases released from the plurality of cells 132.
[019] Advantageously, the battery pack of the present invention provides ample surface areas at the top wall of the housing and at the layers of the thermally conductive material for dissipation of the heat generated from the battery module. Further, provision of the through-holes which function as channels for gas dissipation, prevents accidents like cell explosions happening due to trapped gasses. The thermally conductive material being viscous in nature is spread evenly over the surfaces of the busbars thus removing trapped air pockets. This ensures a complete solid contact between the interconnects and the top and the bottom wall of the housing. Therefore, parts of the entire battery pack remain intact resulting in structural integrity of the battery pack.
[020] 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.