DESC:TECHNICAL FIELD
[0001] The present invention relates generally to battery packs and, more particularly, to a system for controlling the release of hot gases from a battery pack undergoing thermal runaway.

BACKGROUND
[0002] Existing research in battery technology is directed to rechargeable batteries, such as sealed, starved electrolyte, lead/acid batteries, are commonly used as power sources in different applications, such as, vehicles and the like. However, the lead-acid batteries are heavy, bulky, and have short cycle life, short calendar life, and low turn around efficiency, resulting in limitations in applications.
[0003] Thus, in order to overcome problems associated with conventional energy storage devices including the lead-acid batteries, lithium-ion battery has emerged as a preferred solution which provides an ideal system for high energy-density applications, improved rate capability, and safety. Further, the rechargeable energy storage devices - lithium-ion batteries exhibit one or more beneficial characteristics which makes it useable on powered devices. First, for safety reasons, the lithium-ion battery is constructed of all solid components while still being flexible and compact. Secondly, the energy storage device including the lithium-ion battery exhibits similar conductivity characteristics to primary batteries with liquid electrolytes, i.e., deliver high power and energy density with low rates of self-discharge. Thirdly, the energy storage device as the lithium-ion battery is readily manufacturable in a manner that it is both reliable and cost-efficient. Finally, the energy storage device including the lithium-ion battery is able to maintain a necessary minimum level of conductivity at sub-ambient temperatures.
[0004] In a known structure for an energy storage device, one or more energy storage cells including lithium-ion battery cells are disposed in at least one holder structure in series and parallel combinations using at least one interconnecting structure. The interconnecting structure is adapted for electrically interconnecting the energy storage cells with a battery management system (hereinafter “BMS”). An output voltage and an output current generated by the energy storage device is transmitted to one or more electronic and electrical components configured to be powered by the energy storage device via end connections after being monitored and regulated by the BMS.
BRIEF DESCRIPTION OF DRAWINGS
[0005] The detailed description is described with reference to the accompanying figures, which is related to a two-wheeled hybrid or electric vehicle being one embodiment of the present subject matter. However, the present subject matter is not limited to the depicted embodiment(s) and is applicable to all kinds of hybrid and electric vehicle such as two-wheeled vehicle, three-wheeled vehicle, four-wheeled vehicle and the like. In the figures, the same or similar numbers are used throughout to reference features and components.
[0006] Fig. 1 depicts a typical left-side view of an exemplary two-wheeled vehicle describing the location and orientation of the battery pack in accordance with an embodiment of the present subject matter.
[0007] Fig. 2 illustrates a top view of the location of the battery packs in the exemplary two-wheeled vehicle in accordance with an embodiment of the present subject matter.
[0008] Fig. 3 illustrates an exploded view of the battery pack in the exemplary two-wheeled vehicle in accordance with an embodiment of the present subject matter.
[0009] Fig. 4 illustrates the battery pack without a top cover in the exemplary two-wheeled vehicle in accordance with an embodiment of the present subject matter.
[00010] Fig. 5 illustrates a top view of the battery pack in the engine of the exemplary two-wheeled vehicle in accordance with an embodiment of the present subject matter.
[00011] Fig. 6 illustrates the position of one or more pressure relief feature in the battery pack in accordance with an embodiment of the present subject matter.
[00012] Fig. 7 shows the positions of the cells and one or more pressure relief feature in the exemplary two-wheeled vehicle in accordance with an embodiment of the present subject matter.
[00013] Fig. 8a and Fig. 8b illustrates side view of different types of pressure relief features in the battery pack casing in accordance with an embodiment of the present subject matter.

DETAILED DESCRIPTION
[00014] Exemplary embodiments detailing features of the battery pack thermal management system in a two-wheeled vehicle, in accordance with the present invention will be described hereunder with reference to the accompanying drawings. Various aspects of different embodiments of the present invention will become discernible from the following description set out hereunder. Rather, the following description provides a convenient illustration for implementing exemplary embodiments of the invention. Further, it is to be noted that terms “upper”, “lower”, “right”, “left”, “front”, “forward”, “rearward”, “downward”, “upward”, “top”, “bottom” and like terms are used herein based on the illustrated state or in a standing state of the two-wheeled vehicle with a driver riding thereon. Furthermore, a vehicle longitudinal axis refers to a front to rear axis relative to the two-wheeled vehicle, while a vehicle lateral axis refers to a side to side, or left to right axis relative to the two-wheeled vehicle. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.
[00015] With increased emphasis on reducing emissions emitted by automobiles, currently, there exists a trend of replacing combustion engines with electric motors or a combination of an electric motor and a combustion engine in the form of either using a hybrid vehicle or an electric vehicle. However, such technological shift requires the use of an electric motor that translates into the need for inexpensive Li-ion batteries operable in a wide range of conditions with high energy densities and long operating lifetimes. Additionally, it becomes imperative that the battery pack of such vehicles poses no undue health threats, either during vehicle use or during periods of storage.
[00016] While current rechargeable battery technology is able to meet the evolving demands of the automotive industry, the relatively unstable nature of the chemistries used in such batteries often leads to specialized handling and operating requirements. For example, rechargeable batteries such as lithium-ion cells tend to be more prone to thermal runaway than primary cells, thermal runaway occurring when the internal reaction rate increases to the point that more heat is being generated than can be withdrawn, leading to a further increase in both reaction rate and heat generation. Eventually the amount of generated heat is great enough to lead to the combustion of the battery as well as materials in proximity to the battery. Thermal runaway may be initiated by a short circuit within the cell, improper cell use, physical abuse, manufacturing defects, or exposure of the cell to extreme external temperatures.
[00017] During a thermal runaway event, a large amount of thermal energy is rapidly released, heating the entire cell up to a temperature of 850° C or more. Due to the increased temperature of the cell undergoing thermal runaway, cell starts to vent out poisonous gases such as carbon monoxide, hydro fluoride gases which increases the pressure and temperature of adjacent cells within the battery pack. If the pressure and temperature of these adjacent cells is allowed to increase unchecked, they may also enter into a state of thermal runaway, leading to a cascading effect where the initiation of thermal runaway within a single cell propagates throughout the entire battery pack as the cells are placed nearby to each other in such battery pack. As a result, power from the battery pack is interrupted and the system employing the battery pack is more likely to incur extensive collateral damage due to the scale of thermal runaway and the associated release of thermal energy.
[00018] Certain attempts have been made to address the thermal runaway issue in battery packs. Pressure safety valves have been used to detect the increase in pressure of the cells above a threshold wherein such pressure safety valves have been placed inside the battery pack itself. Hence, for each cell, a pressure safety valve is located inside each cell holder, near to the positive terminal of the cells. A duct having an opening at one end of the battery pack which is open to atmosphere is available through which gases are vent out of the cells. Such gases firstly flow through the entire battery pack through the duct and accumulates therein. Thereafter, once the gases in the duct reaches a predetermined threshold value, the duct is opened and the gases are vented outside the battery pack. However, such accumulation of gases inside the duct results in accumulation of heat and pressure in the battery pack which may result in thermal runaway of cells. While the gases are being flown through air duct, it is possible that thermal runaway from one cell might propagate to the nearby cells, thereby resulting in a cascading effect of nearby cells also going into thermal runaway mode. Further, such battery packs with air ducts require extra space which hampers the compact packaging of the battery pack. Thus, the conventional battery packs with air ducts are expensive with little or no space for thermal management system since the space is being occupied by the air duct.
[00019] Moreover, conventionally, some battery packs are known to have a safety valve at the bottom cover of the casing of the battery pack. Such battery packs have a phase change material or a heat conducting material poured inside the battery pack in a liquid form, which flows through the open spaces and solidifies inside the battery pack. While such phase change material solidifies, the vent out gases from the positive terminal of the cells have to flow through the solidified phase change material to reach to the safety valves located at the bottom cover of the casing of the battery pack. This results in limiting the flow of gases as it is difficult for gases to flow through a solid, thereby resulting in thermal propagation occurring in the nearby cells as well.
[00020] Further, if the battery pack is placed horizontally in the vehicle, there arises no problem in venting out of gases by the cells; however, when the battery pack is vertically placed, gases have the natural property of moving upwards, thereby resulting in safety valve at the bottom cover to not function effectively. This may also result in thermal propagation occurring in nearby cells till the time, the gases from the thermal runaway cell reaches to the safety valve at the bottom cover.
[00021] Additionally, such safety valves are provided on the bottom cover of the casings of the battery packs wherein such bottom cover is made up of plastic. Since plastic has low thermal conductivity, it fails to effectively mitigate the problem of thermal runaway in cells. Moreover, because of the bottom cover being made up of plastic, a lower rating safety valve is placed at the bottom cover since placing a higher rating safety valve will be ineffective as the plastic casing would not be able to withstand high temperature and pressure inside the battery pack.
[00022] Thus, there arises a need for providing a cost-effective and reliable battery pack thermal management system with multiple pressure relief structures in the battery pack that controls the flow of the thermal energy and hot gases created during a cascading thermal runaway event that further addresses the aforementioned and other problems of the prior art.
[00023] Thus, the present subject matter aims to provide a battery pack with a cost-effective thermal management system with one or more pressure relief structures that effectively prevents the thermal runaway event.
[00024] The present subject matter along with all the accompanying embodiments and their other advantages would be described in greater detail in conjunction with the figures in the following paragraphs.
[00025] According to a preferred embodiment, a battery pack is disclosed that comprises a battery pack enclosure which is configured to hold one or more batteries and a thermal management system. Herein the thermal management system comprises one or more end covers that are configured to cover one or more sides of the battery pack enclosure, an external casing configured to cover one or more sides of the battery pack enclosure, a primary pressure relief structure integrated into one or more end covers covering the battery pack enclosure and one or more secondary pressure relief structure integrated into the external casing covering the battery pack enclosure. Herein the primary pressure relief structure and the one or more secondary pressure relief structure remain closed during normal operation of said battery pack. Upon a thermal runaway event of one or more batteries, the secondary pressure relief structure opens up to release the exhaust hot gas from within the battery pack enclosure. Moreover, primary pressure relief structure opens during a thermal runaway event of the battery pack thermal runaway event and provides a flow path for exhausting hot gas from within said battery pack enclosure.
[00026] In yet another embodiment, the one or more end covers are configured to cover a top side and a bottom side of the battery pack enclosure respectively while the battery pack is in a vertical orientation.
[00027] In another embodiment, the primary pressure relief structure is integrated into said one or more end cover on the top side f said battery pack enclosure while said battery pack is in a vertical orientation.
[00028] In yet another embodiment, the external casing is configured to cover a front side and a rear side of the battery pack enclosure while the battery pack is in a vertical orientation.
[00029] In another embodiment, the one or more end covers and the external casing are positioned interchangeably in the battery pack based on either a vertical orientation or a horizontal orientation of the battery pack in a vehicle.
[00030] In yet another embodiment, the primary pressure relief structure integrated into the one or more end covers is of a higher-pressure rating than said one or more secondary pressure relief structures that are integrated into the external casing.
[00031] In another embodiment, the one or more secondary pressure relief structures integrated into said external casing are of different pressure ratings.
[00032] In another embodiment, the one or more secondary pressure relief structures integrated into said external casing are of same pressure ratings.
[00033] In yet another embodiment, the one or more secondary pressure relief structures is placed proximal to a positive terminal of each of the one or more batteries on either side of the external casing inside the battery pack enclosure.
[00034] In another embodiment, the one or more secondary pressure relief structures are placed centrally at equidistant locations from each other proximal to the positive terminal of each of said one or more batteries on either side of the external casing inside the battery pack enclosure.
[00035] The present subject matter is further described with reference to accompanying figures. It should be noted that the description and figures merely illustrate principles of the present subject matter. Various arrangements may be devised that, although not explicitly described or shown herein, encompass the principles of the present subject matter. Moreover, all statements herein reciting principles, aspects, and examples of the present subject matter, as well as specific examples thereof, are intended to encompass equivalents thereof.
[00036] The battery pack thermal management system may be implemented in any type of two-wheeled vehicle, three-wheeled vehicle, four-wheeled vehicle, hybrid or electric vehicle. However, for the purpose of explanation and by no limitation, the battery pack thermal management system, and corresponding additional advantages and features are described through the following embodiments. Arrows wherever provided on top right corner of the figure represent direction with respect to vehicle. Arrow F represents forward direction, arrow R represents rearward direction, arrow UW represents upward direction and arrow DW represents downward direction.
[00037] Fig. 1 depicts a typical left-side view of an exemplary two-wheeled vehicle 100 describing the location and orientation of the battery pack in accordance with an embodiment of the present subject matter. Fig.2 illustrates a top view of the location of the battery packs in the exemplary two-wheeled vehicle in accordance with an embodiment of the present subject matter. For the sake of brevity, Fig. 1 and Fig. 2 will be explained together. Herein, the two-wheeled vehicle 100 has a body frame 111 made up of several tubes welded together which usually supports the body of the said vehicle 100. The vehicle has a steerable front wheel 113 and a driven rear wheel 112. The frame 111 of the vehicle 100 is an elongated structure, which typically extends from a forward end to a rearward end of the vehicle 100. It is generally convex in shape, as viewed from a side elevation view. The frame 111 includes a head tube (not shown), a main frame (not shown) and also may have a sub-frame (not shown). The sub-frame is attached to the main frame using appropriate joining mechanism. The frame 111 is covered by a plurality of vehicle body covers including a front panel (not shown), a rear cover (not shown), a lower side cover (not shown), and a pair of side panel (not shown). A handlebar assembly 114 and a seat assembly (not shown) are supported at opposing ends of the frame 111 and a generally open area is defined there between known as floorboard 116, which functions as a step through space. An under-seat cover (not shown) is disposed under the seat assembly (not shown). A front fender (not shown) is provided above the front wheel 113 to avoid the said vehicle and its occupants from being splashed with mud. Likewise, a rear fender (not shown) is placed to the outer side in the radial direction of rear wheel 112. The rear fender inhibits rain water or the like from being thrown up by rear wheel 112. One or more battery pack (s) 115 is supported by the frame 111 and it is disposed in the front portion of a step through floorboard 116 either in the floorboard or on the rear portion of the vehicle 100.
[00038] Fig. 3 illustrates an exploded view of the battery pack in the exemplary two-wheeled vehicle in accordance with an embodiment of the present subject matter. The battery pack 115 comprises a battery pack enclosure 301 having plurality of battery (s). The battery pack enclosure 301 is enclosed by an external casing 305, and one or more end covers 303, 304. The battery pack enclosure 301 includes a plurality of batteries (not shown) arranged in a particular sequence. The plurality of batteries is lithium-ion cylindrical energy storage cells. The plurality of batteries is electrically connected in series and/or parallel configuration to form an array of batteries disposed inside the battery pack enclosure 301. Such batteries are electrically connected to a battery management system (BMS) (not shown) within the battery pack enclosure 301. In one of the preferred embodiments, the battery pack enclosure 301 is covered by said external casing 305 which is made of a metal, preferably aluminum casing and said one or more end covers 303, 304 which is made up of plastic. The external casing 305 and one or more end covers 303, 304 is placed apart with minimum of 1mm to 5mm air gap. The one or more batteries 410 cells in the battery pack enclosure 301 are placed apart around 1.5 to 2mm in all the directions.
[00039] The external casing 305 encloses the battery pack enclosure 301 from a front side and a rear side while the battery pack enclosure 301 is in a vertical orientation. Further, the one or more end covers 303, 304 encloses a top side and a bottom side of the battery pack enclosure 301 while said battery pack enclosure is in a vertical orientation. Moreover, the said one or more end covers 303, 304 and said external casing 305 is positioned interchangeably inside the battery pack 115 based on said vertical orientation or a horizontal orientation of the battery pack 115 in a vehicle 100.
[00040] Fig. 4 illustrates the battery pack without a top cover in the exemplary two-wheeled vehicle in accordance with an embodiment of the present subject matter. Fig. 5 illustrates a top view of the battery pack in the engine of the exemplary two-wheeled vehicle in accordance with an embodiment of the present subject matter. For brevity purposes, Fig.4 and Fig. 5 will be explained together. Herein, a heat conducting material 405, preferably called a phase change material (PCM) forms a thermal composite poured adjacent to one or more lithium-ion batteries 410. Such heat conducting material 405 are materials that change phase at certain temperatures and are capable of storing and releasing large amounts of energy. Heat is absorbed or released when the materials change phase, from solid to liquid, or liquid to solid, for example. For example, one PCM could change its phase at a low temperature limit, such as about freezing or below (e.g., less than about 0 C, or less than about -5 C, or less than about -10 C, or about -10 C, or in a range of about 0 C to about -10 C), and another at a high temperature limit (e.g., above about 40 C, or above about 45 C). Thermal insulation of batteries 410 using such heat conducting material 305 including PCM can maintain battery cell temperature for longer periods of time under extreme temperature conditions. Additional PCM with different phase change temperatures could also be included, if desired.
[00041] Fig. 6 illustrates the position of one or more pressure relief feature in the battery pack in accordance with an embodiment of the present subject matter. Herein, a thermal management system 600 is disclosed having one or more end covers 303, 304 covering one or more sides of the battery pack enclosure 301. The external casing 305 also covers one or more sides of the battery pack enclosure 301. In an embodiment, a primary pressure relief structure 605, for example, a safety valve is integrated into said one or more end covers 303, 304.
[00042] Herein, in one of the embodiments, the primary pressure relief structure 605 is integrated into said one or more end cover 303 on a top side of said battery pack enclosure 301 while said battery pack 115 is in a vertical orientation. Further, in another embodiment, one or more secondary pressure relief structure 610 is integrated into external casing 305 covering said battery pack enclosure 301. Such primary pressure relief structure 605 that is integrated into said one or more end covers 303, 304 is of a higher-pressure rating than said one or more secondary pressure relief structures 610 that is integrated into said external casing 305.
[00043] In yet another embodiment, such one or more secondary pressure relief structures 610 that are integrated into said external casing 305 are of different pressure ratings. For example, if the primary pressure relief structure 605 is of 24 kPa, the one or more secondary pressure relief structures 610 is of 12 kPa, 6kPa, 4kPa etc.
[00044] However, in yet another embodiment, such one or more secondary pressure relief structures 610 that are integrated into said external casing 305 are of same pressure ratings. For example, if the primary pressure relief structure 605 is of 24 kPa, the one or more secondary pressure relief structures 610 is of 12 kPa, 12kPa, 12kPa etc.
[00045] In another embodiment, referring to Fig 7 which shows the positions of the cells and one or more pressure relief feature in the exemplary two-wheeled vehicle in accordance with an embodiment of the present subject matter, herein said primary pressure relief structure is integrated with said one or more end covers 303 and said one or more secondary pressure relief structures 610 are placed proximal to a positive terminal of each of one or more batteries 410. Herein, the one or more secondary pressure relief structures 610 are integrated with said external casing 305. The one or more secondary pressure relief structures are placed proximal on either side of said external casing 305 inside said battery pack enclosure 301. The battery pack enclosure 301 is parallel to the ground 710 and is placed in a vertical orientation.
[00046] In another embodiment, the one or more secondary pressure relief structures 610 is placed centrally at equidistant locations from each other proximal to said positive terminal of each of said one or more batteries 410 on either side of said external casing 305 inside said battery pack enclosure 301.
[00047] Herein, due to presence of one or more secondary pressure relief structures 610 with different pressure ratings enables in opening of such pressure relief structures depending upon the level of venting that happens in the battery pack enclosure 301. In an embodiment, said primary pressure relief structure 605 and said one or more secondary pressure relief structure 610 remain closed during normal operation of said battery pack 115.
[00048] In another embodiment, in case one or more batteries 410 starts venting out i.e., thermal runaway is initiated, the nearest one or more secondary pressure relief structure 610 will firstly open up to vent out the thermal runaway occurring in the one or more batteries 410. Hence, as soon as pressure and heat builds up in the one or more batteries 410, if it crosses the safety limit of the nearby one or more secondary pressure relief structures 610 such as 12kPa, the nearest one or more secondary pressure relief structures 610 opens up to provide a way out of the battery pack enclosure 301 to flow out.
[00049] Once, the thermal runaway event is propagated to the entire battery pack enclosure 301, the primary pressure relief structure 605 located on the top of said one or more end cover 303 opens up to vent out the heat and excessive pressure generated during thermal runaway of the entire battery pack. Thus, opening up of nearby one or more secondary pressure relief structures 610 ensure that the vent out heat and gases are discharged as soon as the thermal runaway event starts for one or more batteries 410 in a localized region. This results in creating a shortest path for venting out the heat and additional pressure generated during thermal runaway event, thereby avoiding explosion of battery pack due to pressure relief structures being placed at a distant location. The one or more secondary pressure relief structure 610 may be varied based on the number of batteries 410 in the battery pack enclosure 301. Thus, said one or more secondary pressure relief structure 610 opens during a thermal runaway event of one or more batteries 410 and said primary pressure relief structure 605 opens during a thermal runaway event of said battery pack 115 thermal runaway event and provides a flow path for exhausting hot gas from within said battery pack enclosure 301.
[00050] Thus, multiple one or more secondary pressure relief structures 610 are provided near to the one or more batteries 410 being placed centrally at equidistant locations from each other proximal to said positive terminal of each of said one or more batteries 410 on either side of said external casing 305 inside said battery pack enclosure 301.
[00051] Fig. 8a and Fig. 8b illustrates side view of different types of pressure relief features in the battery pack casing in accordance with an embodiment of the present subject matter. For brevity purposes, Fig. 8a and Fig. 8b are explained together. The primary pressure relief structure 605 and one or more secondary pressure relief structures 610 may be of different configuration and dimensions and is not restricted to a particular type of pressure relief structure or valve.
[00052] Thus, the present subject matter improves the battery life by mitigating the thermal runaway of the one or more batteries 410 as one or more secondary pressure relief structure 610 opens up much before the primary pressure relief structures 605, thereby aiding in the exit of the undesirable gases and heat to get emitted from the pack as soon as the thermal runaway event is initiated, thus, preventing the battery pack from getting exploded, thereby improving the vehicle performance and safety of the rider.
[00053] Thus, the present subject matter proposes a novel battery pack with a primary pressure relief structure with a higher-pressure rating (X kPa) located on the top cover of the one or more end covers of the battery pack enclosure, so that the safety of the battery pack gets increased. Moreover, one or more secondary pressure relief structures with multiple lower-pressure ratings (X/2 kPa, X/4kPa etc.) are integrated in the external casing that are proximate to the one or more batteries. This results in early venting out of the gases from the battery pack as soon as the thermal runaway event is initiated, thereby eliminating the chances of battery pack explosion as the undesirable gases are eliminated properly and instantly, thus increasing the lifetime of the battery pack as well. Moreover, the primary pressure relief structures and one or more secondary relief structures are positioned with reference to the movement of the vehicle direction and hence proper ground clearance is maintained with respect to the location of the battery.
[00054] The present subject matter eliminates the problem of accumulation of gases inside the ducts created for venting out of gases which used to result in accumulation of heat and pressure in the battery pack which may result in thermal runaway of cells. Hence, the problem of propagation of thermal runaway from battery to another while the gases are being flown through air duct is avoided, thereby resulting completely eliminating the cascading effect of nearby cells also going into thermal runaway mode. It saves space required by such air ducts in the battery packs, thereby resulting in compact packaging of the battery pack.
[00055] Further, since the battery pack is placed horizontally in the vehicle, there arises no problem in venting out of gases by the cells. The present subject matter eliminates the problem faced by conventional battery packs placed vertically with safety valves located at the bottom of the battery pack since the gases have the natural property of moving upwards, thereby resulting in safety valve at the bottom cover to not function effectively. Since the primary pressure relief structure in the present subject matter is placed at the top of the one of the end covers, the gases can easily move upwards to prevent thermal propagation occurring in nearby cells till the time, the gases from the thermal runaway cell reaches to the safety valve at the bottom cover.
[00056] Also, the problem of limiting the flow of gases due to solidification of heat conducting material or phase change material to reach to the safety valves located in the bottom of the battery pack in the existing prior art is completely eliminated.
[00057] Typically, pressure relief structures are provided on the bottom cover of the casings of the battery packs wherein such bottom cover is made up of plastic. Since plastic has low thermal conductivity, it fails to effectively mitigate the problem of thermal runaway in cells. Moreover, because of the bottom cover being made up of plastic, a lower rating safety valve is placed at the bottom cover since placing a higher rating safety valve will be ineffective as the plastic casing would not be able to withstand high temperature and pressure inside the battery pack. Thus, the present subject matter effectively mitigates the afore-mentioned problems.
[00058] While certain features of the claimed subject matter have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes that fall within the true spirit of the claimed subject matter.

List of reference signs:
100 vehicle
111 frame
112 rear wheel
113 front wheel
114 handle bar
115 battery pack (s)
116 floor board
301 battery pack enclosure
303, 304 one or more end covers
305 external casing
405 heat conducting material
410 one or more batteries
600 thermal management system
605 primary pressure relief structure
610 one or more secondary pressure relief structures
710 ground

,CLAIMS:We claim:
1. A battery pack (115), said battery pack (115) comprising:
a battery pack enclosure (301) configured to hold one or more batteries (410), and
a thermal management system (600), said thermal management system (600) comprising:
one or more end covers (303, 304) being configured to cover one or more sides of said battery pack enclosure (301);
an external casing (305) being configured to cover one or more sides of said battery pack enclosure (301);
a primary pressure relief structure (605) integrated into said one or more end covers (303, 304) covering said battery pack enclosure (301); and
one or more secondary pressure relief structure (610) integrated into said external casing (305) covering said battery pack enclosure (301);
wherein said primary pressure relief structure (605) and said one or more secondary pressure relief structure (610) remain closed during normal operation of said battery pack (115); and
wherein said one or more secondary pressure relief structure (610) opens during a thermal runaway event of one or more batteries (410) and said primary pressure relief structure (605) opens during a thermal runaway event of said battery pack (115) for providing a flow path for exhausting hot gas from within said battery pack enclosure (301).

2. The battery pack (115) as claimed in claim 1, wherein said one or more end covers (303, 304) being configured to cover a top side and a bottom side of said battery pack enclosure (301) while said battery pack (115) is in a vertical orientation.

3. The battery pack (115) as claimed in claim 1, wherein said primary pressure relief structure (605) being integrated into said one or more end cover on the top side (303) of said battery pack enclosure (301) while said battery pack (115) being in a vertical orientation.

4. The battery pack (115) as claimed in claim 1, wherein said external casing (305) being configured for covering a front side and a rear side of said battery pack enclosure (301) while said battery pack (115) being in a vertical orientation.

5. The battery pack (115) as claimed in claim 1, wherein said one or more end covers (303, 304) and said external casing (305) being positioned interchangeably inside said battery pack (115) based on said vertical orientation or a horizontal orientation of said battery pack (115) in a vehicle (100).

6. The battery pack (115) as claimed in claim 1, wherein said primary pressure relief structure (605) integrated into said one or more end covers (303, 304) being of a higher-pressure rating than said one or more secondary pressure relief structures (610) integrated into said external casing (305).

7. The battery pack (115) as claimed in claim 1, wherein said one or more secondary pressure relief structures (610), integrated into said external casing (305), being of different pressure ratings.

8. The battery pack (115) as claimed in claim 1, wherein said one or more secondary pressure relief structures (610), integrated into said external casing (305), beingof same pressure ratings.

9. The battery pack (115) as claimed in claim 1, wherein said one or more secondary pressure relief structures (610) being placed proximal to a positive terminal of each of one or more batteries (410) and on either side of said external casing (305), inside said battery pack enclosure (301).

10. The battery pack (115) as claimed in claim 1, wherein said one or more secondary pressure relief structures (610) being placed centrally at equidistant locations from each other and being proximal to said positive terminal of each of said one or more batteries (410) on either side of said external casing (305) inside said battery pack enclosure (301).