WO2022003716A1

WO2022003716A1 - Exhaust system of a battery module

Info

Publication number: WO2022003716A1
Application number: PCT/IN2021/050627
Authority: WO
Inventors: R Parate TUSHAR; Pramila Rao N; Jabez Dhinagar Samraj
Original assignee: Tvs Motor Company Limited
Priority date: 2020-06-29
Filing date: 2021-06-27
Publication date: 2022-01-06
Also published as: CN115917852A

Abstract

A battery module (100) with an exhaust system (108) is disclosed. The battery module (100) comprises a battery pack (110), comprising a plurality of cells (403), housed in a casing (101), a plurality of end covers (103, 112) for enclosing the battery pack (110) in the casing (101), and a plurality of duct members (301, 310, 304, 314) surrounding the battery pack (110) forming gas holding chambers (601, 603) and downstream gas passages (701, 702) for regulated exhaust of gases released from the battery pack (110). At least one first duct member (301, 310) positioned exterior to a surface (311, 312) of the battery pack (110) and at least two second duct members (304, 314) removably engaged with the first duct member (301, 310) to form the gas holding chamber (601, 603) and downstream gas passages (701, 702) for exhaust of the accumulated gases to atmosphere.

Description

EXHAUST SYSTEM OF A BATTERY MODULE

TECHNICAL FIELD

[0001] The present subject matter relates to battery modules. More particularly, exhaust system of the battery modules is disclosed.

BACKGROUND

[0002] Existing research in battery technology is directed to rechargeable batteries, such as sealed type, starved electrolyte, lead/acid type which 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, a lithium ion battery is ideal for high energy-density applications with improved rate capability, and safety. Further, rechargeable energy storage devices, such as, 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. By virtue of these advantages, the rechargeable energy storage devices, such as, lithium ion battery find applications in rugged environments with increased ambient temperatures.

[0004] However, with some advantages, there are some limitation or challenges like thermal runaway in the lithium ion battery; which occurs due to many reasons such as internal short circuit, overcharging etc. The energy storage devices are susceptible to vibrations during their lifetime, which may lead to functional failure and fatigue damage to the energy storage devices. Due to such issues, the lithium ion battery can undergo critical failure, such as, an explosion due to a cell failure. The gas released from a lithium ion cell is combustible in nature and can catch fire. This induces thermal failure in the adjacent cells and it can start chain of explosion in the lithium ion battery, compromising safety of the battery, other associated components, catastrophic damage to the location of installation of the battery module, such as, a vehicle and ultimately risk the safety of rider and passenger of the vehicle. The construction of the energy storage devices is critical to the longevity, safety, serviceability, and maintainability of the energy storage devices.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Fig.1 exemplarily illustrates a perspective view of a battery module, as per an embodiment of the present invention;

[0006] Fig. 2 exemplarily illustrates a partial exploded view of the battery module exemplarily illustrated in Fig. 1;

[0007] Fig. 3 exemplarily illustrates a partial exploded view of an exhaust system of the battery module along with a battery pack;

[0008] Fig. 4 exemplarily illustrates a partial exploded view of the battery pack exemplarily in Fig. 3;

[0009] Fig. 5 exemplarily illustrates a bottom perspective view of a first end cover of the battery module;

[00010] Fig. 6 exemplarily illustrates a sectional view of the battery module taken along the X-X’ axis in Fig. 1;

[00011] Fig. 7 exemplarily illustrates a sectional view of the exhaust system with the battery pack 110 taken along the axis Y-Y’ in Fig. 2; and [00012] Figs. 8A-8B exemplarily illustrate the perspective views and sectional view of a vent plug taken along the Z-Z’ axis, respectively.

DETAILED DESCRIPTION OF THE INVENTION [00013] During the course of operation, the cells of the lithium ion battery may release gases due to the decomposition of the electrolyte of the cells, short circuit inside the cells, short circuit between cells, etc. The lithium ion cells may swell up due to accumulation of the gases. Further, the electrochemical reactions in the lithium ion cells are highly exothermic and the lithium ion cells tend to heat up during the course of normal operation. Overheating and overcharging of the lithium ion cells increases the pressure of the gases generated in the cells and the cells may vent it in form of an explosion. The accumulation of the gases from the individual cells within the lithium ion battery may swell up the battery. With increase in temperature of the battery, the high-pressure gas may escape from the battery and come in contact with ambient oxygen undergoing spontaneous combustion and leading to catastrophic failure of the lithium ion battery. There is a need to safely vent the accumulated gases from the lithium ion battery with a delay in a regulated manner to decrease the impingement of the high-pressure gases from lithium ion cells on adjacent cells as well as avoid explosion.

[00014] In existing implementations, to monitor conditions of the individual lithium ion cells to prevent a thermal runaway of the lithium ion battery, the lithium ion battery is provided with a battery management system (BMS). However, the BMS may not protect the lithium ion battery from different abuse conditions, such as, overly high temperatures. The BMS mainly consisting of electronic components may itself fail at the elevated temperatures.

[00015] Further, to reduce the probability of explosion due to elevated temperatures of the lithium ion battery, cooling mechanisms, such as, coolant channels around the cells for regulating the temperatures of the cells and/or battery are being employed. However, the cooling mechanisms may make the lithium ion battery large and bulky and not useful in applications with limited space, such as, vehicles. In other implementations, thermal barriers between the lithium ion cells to curtail the propagation of fire within the Li-ion battery are being employed. However, the addition of thermal barriers adds to the weight, volume, manufacturing cost, and maintenance cost of the lithium ion battery and thus undesirable. [00016] In case of accumulation of the gases within the lithium ion battery, the peripheral electronic components of the battery, such as the BMS needs to be shielded from the pressurized gases as they may be sensitive to elevated pressures and temperatures. A dedicated path to accumulate and vent the gases from the lithium ion battery is desirable to mitigate damage caused to the sensitive electronic components.

[00017] Therefore, there exists a need for an improved design of an energy storage device with an exhaust system for regulating the exhaust of the gases from the battery module without hampering functioning of the electronic components of the battery module and offering ease, safety and reliability during assembly, use, maintenance, and servicing of the energy storage device overcoming all problems disclosed above as well as other problems of known art.

[00018] With the above objectives in view, the present invention relates to safety of the battery module, electric components along with rider and passenger in case of thermal runaway by providing a safe venting path for the gases to be released from the battery module.

[00019] In an embodiment, a battery module with an exhaust system is disclosed. The battery module comprises a battery pack, comprising a plurality of cells, housed in a casing and a plurality of end covers for enclosing the battery pack in the casing. Further, the battery module comprises a plurality of duct members surrounding the battery pack forming at least one gas holding chamber and at least two downstream gas passages for regulated exhaust of gases released from the battery pack. The plurality of duct members comprises at least one first duct member positioned exterior to a surface of the battery pack forming at least one gas holding chamber for accumulating the gases released from the battery pack, and at least two second duct members removably and communicatively engaged with the at least one first duct member to form the at least two downstream gas passages for exhaust of the accumulated gases to atmosphere.

[00020] The first duct member comprises a central trough structure with protruding ends on both sides of the central trough structure forming at least one gas holding chamber for accumulating the gases released from the battery pack. Each of the at least two second duct members comprise at least one depression proximal to both ends to accommodate the protruding ends of the at least one first duct member for holding the duct members around the battery pack within the casing forming a continuous and fluidly connected gas passage between at least one gas holding chamber and at least two downstream gas passages. In an embodiment, each of the at least two second duct members further comprises a vent member centrally located in a channel structure that forms at least two downstream gas passages. The vent member comprises a semi-permeable hydrophobic, oleophobic, and dust-proof membrane sheet in each of the at least two second duct members for permeating the gases to pass at a predetermined pressure. The vent member further comprises a grill structure on an outer side of the membrane sheet for allowing a streamlined and distributed flow of the gases from the downstream gas passages to a buffer chamber.

[00021] The battery module further comprises at least two vent plugs on an outer surface of the casing in-line with the vent member on each of the at least two second duct members to vent the exhaust gases from the battery module. The gases generated from the plurality of cells in the battery pack traverses in a first direction towards at least one gas holding chamber defined by the at least one first duct member, further traverses in a second direction towards the at least two downstream gas passages defined by the at least two duct members fluidly connected to the at least one first duct member, and flows out away from the battery pack through the vent member towards exterior of the battery module. The battery module further comprises a buffer chamber formed between the plurality of duct members and the casing for expansion of the gases vented from the plurality of duct members through the vent member in each of the at least two second duct members to protect the battery module from a catastrophic failure. The gases released from the battery pack that are held in the buffer chamber are expelled from the casing through at least two vent plugs on an outer surface of the casing.

[00022] The battery module further comprises a battery management system positioned posterior to one of the plurality of end covers, for monitoring and controlling the plurality of cells in the battery pack. One of the plurality of end covers comprises raised edges along each longer edge of a rectangular opening on a posterior side proximal to the battery management system for abuttingly sealing and removably engaging with the casing to isolate the battery management system from the gases released from the battery pack in the casing. The battery pack comprises at least one interconnect sheet for connecting the plurality of cells in at least one of a series connection and a parallel connection and the at least one interconnect sheet comprises an opening corresponding to each of the plurality of cells for venting of gases from each of the plurality of cells towards the plurality of duct members.

[00023] In another embodiment, an exhaust system of a battery module is disclosed. The exhaust system comprises at least one interconnect sheet comprising an opening corresponding to each of a plurality of cells of the battery module for venting of gases from each of the plurality of cells and at least one gas holding chamber configured in a region surrounding the plurality of cells for accumulating the gases vented from the plurality of cells. The exhaust system further comprises at least two downstream gas passages perpendicular to both ends of the gas holding chamber for routing the accumulated gases from the gas holding chamber away from the plurality of cells and subsequently exhaust the gases through a vent member of each of two downstream gas passages. Further, a buffer chamber is configured between a casing of the battery module and the gas holding chamber for receiving the vented gases from the two downstream gas passages and providing a volume for expansion of the gases as a part of the exhaust system of the battery module. At least two vent plugs are provided on an outer surface of the casing in line with the vent member of each of the two downstream gas passages to vent the exhaust gases from the battery module for protecting the battery module from a catastrophic failure.

[00024] At least one gas holding chamber is defined by at least one first duct member positioned over the interconnect sheet for accumulating the gases released from the plurality of cells. The at least one first duct member comprises a central trough structure holding the gases, with protruding ends on both sides of the central trough structure. At least two downstream gas passages are defined by at least two second duct members removably engaged with the at least one first duct member for exhaust of the accumulated gases to atmosphere. Each of the at least two second duct members comprise at least one depression proximal to both ends to accommodate the protruding ends of the at least one first duct member for forming at least one gas holding chamber and the at least two downstream gas passages thereby forming a continuous and fluidly connected gas passage between the at least one gas holding chamber and the at least two downstream gas passages around the plurality of cells within the casing. Each of the at least two second duct members further comprise the vent member centrally located in a channel structure that forms the at least two downstream gas passages. The vent member comprises a semi- permeable hydrophobic, oleophobic, and dust-proof membrane sheet in each of the at least two second duct members for permeating the gases to pass at a predetermined pressure. The vent member further comprises a grill structure on an outer side of the membrane sheet for allowing a streamlined and distributed flow of the gases from the downstream gas passages to the buffer chamber.

[00025] In an embodiment, the exhaust system further comprises a plurality of raised edges along each longer edge of a rectangular opening of an end cover of the battery module for abuttingly sealing and removably engaging with the casing for isolating electronic components of the battery module from the gases vented from the plurality of cells in the casing. 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.

[00026] Fig.l exemplarily illustrates a perspective view of a battery module 100, as per an embodiment of the present invention. As exemplarily illustrated, the battery module 100 comprises a casing 101 and a first end cover 103. The casing 101 is a hollow rectangular cover enclosing multiple cells and other electrical and electronic components, such as, a BMS board of the battery module 100. The casing

101 comprises enclosing walls, such as, 102 on top and bottom and peripheral walls, such as, 103 between the enclosing walls 102, and open ends (not shown). End covers, such as, 103 of the battery module 100 close the open ends of the casing 101. The casing 101 has mounting provisions (not shown) to mount the end covers, such as, the first end cover 103 and a second end cover (not shown) at the open ends of the casing 101 using attachment means. The first end cover 103 has external electrical connections, such as, 104 of the battery module 100 for charging and discharging of the battery module 100.

[00027] As exemplarily illustrated, on an outer surface of the peripheral walls, such as, 105, a vent plug 106 is provided to vent out the gases from the cells within the battery module 100. In an embodiment, an outer surface of the enclosing walls, such as, 102 may comprise a dovetail pattern that facilitates in easy mounting and unmounting of the battery module 100 in a designated space in a powered device, such as, a vehicle. In an embodiment, both the enclosing walls, such as, 102 have the dovetail pattern. In an embodiment, both the peripheral walls, such as, 105 may also have the dovetail pattern. Corresponding, inner surfaces of the enclosing walls

102 and the peripheral walls 105 also may have a dovetail pattern on them.

[00028] Fig. 2 exemplarily illustrates a partial exploded view of the battery module 100 exemplarily illustrated in Fig. 1. The battery module 100 comprises a battery pack 110 along with an exhaust system 108 positioned within the casing 101. The battery pack 110 comprises the cells located in the cell holders (not shown). The battery pack 110 has mounting provisions for the BMS board 109. The BMS board 109 is screwably attached to the cell holders of the battery pack 110. The BMS board 109 is located between the battery pack 110 and the first end cover 103. On the other side of the casing 101, a second end cover 112 seals the casing 101. The second end cover 112 may be sealed using gaskets and adhesives to ensure the vented gases do not escape through the second end cover 112. The cells in the battery pack 110 may release gases that are to be vented out from the battery module 100 through the casing 101. The gases may be released due to failure of one or more cells, ageing of the cells, etc. The gases are mainly, carbon dioxide, highly flammable hydrocarbons, etc. The exhaust system 108 of the battery module 100 is positioned surrounding the battery pack 110 and in contact with the battery pack 110. The casing 101 further comprises openings, such as, 111 on the peripheral walls, such as, 105 for positioning the vent plugs 106 and 107 for venting of the gases released from the cells to the outside. The vent plugs 106 and 107 are also part of the exhaust system 108. The exhaust system 108 accumulates the gases released from the battery pack 110, and channelizes the gases to exit from the casing 101 through the openings 111 in the peripheral walls 105 of the casing 101. The external electrical connection 104 is plugged into the first end cover 103 at a central location and the electrical contact of the electrical connection 104 extends to the BMS board 109 posterior to the first end cover 103. The construction of the first end cover 103 protects the BMS board 109 and the associated electronics from the exhaust system 108 of the battery module 100 as will be described in the detailed description of Fig. 5.

[00029] Fig. 3 exemplarily illustrates a partial exploded view of the exhaust system 108 of the battery module 100 along with the battery pack 110. As exemplarily illustrated, the exhaust system 108 is positioned surrounding the battery pack 110 of the battery module 100. The exhaust system 108 comprises one or more interconnect sheets 313 in the battery pack 110, one or more gas holding chambers (not shown) surrounding the cells, two downstream gas passages (not shown) formed parallel to the peripheral walls 105 of the casing 101, and a buffer chamber. The cells in the battery pack 110 are interconnected to each other in series and/or parallel connection using at least one interconnect sheet 313 as will be shown in Fig. 4. An interconnect sheet, such as, 313 is positioned below and above the cells in the battery pack 110. The structure of the interconnect sheet 313 allows for every individual cell to vent gases, based on the condition and electrochemical activity in the cell. The gases vented from each of the cells is accumulated in the gas holding chambers formed above and below the cells. The gases from the gas holding chambers are routed away from the battery pack through the downstream gas passages. The gases from the downstream gas passages expand in the buffer chamber as exemplarily illustrated in Figs. 6-7 and vented out from the battery module 100 via the openings 111 in the casing 101 through the vent plugs 106 and 107.

[00030] Each of the gas holding chambers is defined by a first duct member, such as, 301 positioned over the interconnect sheet 313 for accumulating the gases. The first duct member 301 is trapezoidal in shape. The first duct member 301 comprises a central trough structure 301a that gives sufficient volume for the gases to accumulate and expand. The central trough structure 301a avoids pressurising of the gases in the gas holding chamber, as the increased pressure of the gases may exert pressure on the battery pack 110 underneath and cause mechanical damage to the battery pack 110. The central trough structure 301a is hollow and has a predetermined depth for the gases to accumulate. The cross section of the central trough structure 301a may be rectangular, triangular, circular, etc. The first duct member 301 further comprises protruding ends 302 and 303 that extend seamlessly from the central trough structure 301a on both sides. The protruding ends 302 and

303 are also hollow and have a depth that is less than the depth of the central trough structure 301a. As exemplarily illustrated, the cross section of the protruding ends 302 and 303 is semi-circular. The length of the central trough structure 301a of the first duct member 301 covers a top surface 311 of the battery pack 110. The length of the central trough structure 310a of the first duct member 310 covers a bottom surface 312 of the battery pack 110. The top surface 311 and the bottom surface 312 of the battery pack 110 are parallel to the enclosing walls 102 of the casing 101. The first duct members 301 and 310 can be fixed on to the top surface 311 and the bottom surface 312 of the battery pack 110 to the cell holders of the battery pack 110 using attachment means, such as, screws or sealing adhesives.

[00031] The two downstream gas passages are defined by two second duct members 304 and 314 that removably engage with the first duct members 301 and 310. Each of the second duct members 304 and 314 has a hollow channel structure 304a, 314a (not shown) of a predetermined depth. The second duct members 304 and 314 are vertically located and perpendicular to the position of the first duct members 301 and 310. At both ends 305 and 306, each of the second duct members

304 and 314 comprises depressions, such as, 307 that engage with the protruding ends 302 and 303 of the first duct members 301 and 310. That is, the depressions, such as, 307 proximal to the ends, such as, 305 at the top of the second duct members 304 and 314 holds the protruding ends 302 and 303 of the first duct member 301. Similarly, the depressions proximal to the ends, such as, 306 at the bottom of the second duct members 304 and 314 holds the protruding ends of the first duct member 310. The depressions, such as, 307 lock the first duct members 301 and 310 is place on the top and the bottom of the battery pack 110. In an embodiment, the ends 305 and 306 of the second duct member 304 and 314 may have annuli, instead of the depression, where the circumference of the annuli tightly locks the protruding ends 302 and 303 of the first duct members 301 and 310. The engagement of the protruding ends 302 and 303 of the first duct members 301 and 310 with the depressions such as, 307 in the second duct members 304 and 305 forms a continuous and fluidly connected gas passage between the gas holding chambers and the downstream gas passages. Each of the second duct members 304 and 314 further comprises a vent member 308 that is centrally located in the channel structure 304a. The length of the second duct member 304 and 314 is longer than the height of the battery pack 110 and lesser than the height of the peripheral walls 105 of the casing 101.

[00032] The vent member 308 may be a grill structure 309 with a membrane sheet (not shown) that moves in response to a predetermined pressure. The membrane sheet is integral to the channel structure 304a at the central location. On an outer side of the membrane sheet, the grill structure 309 is removably attached to the channel structure 304a. The grill structure 309 comprises fins through which the gases escape from the second duct members 304 and 314. The membrane sheet is semi-permeable, hydrophobic, oleophobic, and dust proof. The membrane sheet arrests entry of dust, water, and any particulate matter in contact with the battery pack 110 and the BMS 109 of the battery module 100. The position of the vent member 308 on the second duct members 304 and 314 is in-line with the openings 111 for the vent plugs 106 and 107 on the casing 101.

[00033] Fig. 4 exemplarily illustrates a partial exploded view of the battery pack 110 exemplarily in Fig. 3. The battery pack 110 comprises the cell holders 404 and 405 for holding the cells 403 and the interconnect sheets 313 and 401 to connect the cells 403 in series and/or parallel combination. The cells 403 are cylindrical in shape. In an embodiment, the cells 403 may be rectangular, triangular, etc. One interconnect sheet 313 is placed above the cell holder 404 on top of the cells 403 and another interconnect sheet 401 is placed below the cell holder 405 at the bottom of the cells 403. The BMS board 109 with associated electronic components is screwably attached to the cell holders 404 and 405. The cells 403 are electrically connected to the BMS board 109. The interconnect sheets 313 and 401 are planar rectangular sheets with edges that electrically connect the cells 403 to the BMS board 109.

[00034] Each interconnect sheet 313 and 401 comprises contact points on the planar surface where the interconnect sheet 313 and 401 bulges to make physical contact with the terminals of the cells 403 to establish an electrical connection between the cells 403 and the interconnect sheet 313 and 401. At these contact points, spot welding of the interconnect sheet 313 and 401 is performed to be in contact with the terminal of the cell 403. In addition to the contact points, the planar surface of the interconnect sheet 313 and 401 comprises vent openings 406. The vent openings 406 are as exemplarily illustrated, C-shaped apertures on the planar surface of the interconnect sheet 313 and 401. The vent openings 406 allow the gases from the cells 403 to escape from the interconnect sheet 313 and 401. The vent openings 406 are provisions provided to avoid accumulation of gases in the cell, such as, 403 in case of a failure and accumulation of gases between the cells 403 in the cell holders 404 and 405. On the edges of the interconnect sheet 313 and 401, there are mounting provisions 402 in-line with the mounting provisions 407 of the cell holders 404 and 405 for mounting the BMS board 109 to the battery pack 110

[00035] Fig. 5 exemplarily illustrates a bottom perspective view of the first end cover 103. The first end cover 103 is a hollow structure of a predetermined depth with a central opening 501 to accommodate the electrical connector 104 of the battery module 100. As exemplarily illustrated, the first end cover 103 is trapezoidal in shape. The first end cover 103 has raised edges, such as, 502 along longer edges 503 of a rectangular opening 504 of the first end cover 103 on an inner side of the hollow structure. The dimensions of the rectangular opening 504 of the first end cover 103 are same as the dimensions of the BMS board 109. When the BMS board 109 is positioned on the cell holders 404 and 405, the BMS board 109 is locked in place with the raised edges 502 of the first end cover 103 behind it. The raised edges 502 prevent the leak of gases towards the BMS board 109 from the first duct members 301 and 310 and the second duct members 304 and 314.

[00036] Fig. 6 exemplarily illustrates a sectional view of the battery module 100 taken along the X-X’ axis in Fig. 1. As exemplarily illustrated, the battery pack 110 is housed within the casing 101 of the battery module 100. The cells 403 are housed in the cell holders 404 and 405. The interconnect sheets 313 and 401 on the cell holders 404 and 405 at the top and bottom are shown. The gas vented through the interconnect sheets 313 and 401 is collected in the gas holding chambers 601 and 603 above and below the cell holders 404 and 405 respectively. The gas holding chambers 601 and 603 are the regions above the top surface 311 and below the bottom surface 313 of the battery pack 110. The first duct members 301 and 310 define the gas holding chambers 601 and 603 respectively. Through the protruding ends 302 and 303 of the first duct members 301 and 310, the gases accumulated in the central trough structure 301a and 310a of the first duct members 301 and 310 flows towards the downstream gas passages (not shown). The downstream gas passages are defined by the second duct members 304 and 314. The protruding ends 302 and 303 of the first duct member 301 and 310 are locked in the depressions 307 at the ends 305 and 306 of the second duct members 304 and 314. As exemplarily illustrated, there is a gap between the casing 101 and the gas holding chambers 601 and 603 and the downstream gas passages. The height of the first duct members 301 and 310 and the second duct members 304 and 314 positioned around the battery pack 110 is lesser than the height of the peripheral walls 105 of the casing 101. The gases from the gas holding chambers 601 and 603 flow out into this gap between the casing 101 and the gas holding chambers 601 and 603. This gap is the buffer chamber 602 for the gases to expand before being expelled from the battery module 101 through the vent plugs 106 and 107 on the peripheral walls 105 of the casing 101.

[00037] Also, can be seen is the raised edges 502 of the first end cover 103 that partitions the region 604 surrounding the BMS board 109 from the buffer chamber

602. In the sectional view, the raised edges 502 may be seen as a step structure extending from the ends of the rectangular opening 504 of the first end cover 103. The raised edges 502 along the longer edge 503 of the rectangular opening 504 extend until the raised edges 502 touch the cell holders 404 and 405. The cell holders 404 and 405 and the raised edges 502 prevent the flow of the vented gases towards the BMS board 109 and the associated electronic components. The vented gases generated due to cell failure do not spread over the BMS board 109 and the raised edges 502 protect it from fire and corrosion due to leaked electrolyte from the cells 402, in case of cell failure. In an embodiment, the raised edges 502 of the first end cover 103 may be sealed with the mounting provisions of the casing 101 using an adhesive.

[00038] Fig. 7 exemplarily illustrates a sectional view of the exhaust system 108 with the battery pack 110 taken along the axis Y-Y’ in Fig. 2. The components of the exhaust system 108 of the battery module 100 shown here are the gas holding chambers 601 and 603, the downstream gas passages 701 and 702, and the vent members 308. The gases from the cells 403 are vented to the gas holding chambers 601 and 603 in a first direction as shown. From the gas holding chambers 601 and

603, the gases flow towards the downstream gas passages 701 and 702 in a second direction as exemplarily illustrated. The protruding ends 302 and 303 of the first duct members 301 and 310 forming the gas holding chambers 601 and 603 and the depressions 307 at the ends 305 and 306 of the second duct members 304 and 314 forming the downstream gas passages 701 and 702 form the fluid connection between the gas holding chambers 601 and 603 and the downstream gas passages 701 and 702. The second duct members 304 and 314 have the vent members 308 centrally located. The vented gases from the downstream gas passages 701 and 702 are vented out through the vent members 308. Each of the vent members 308 comprises the membrane sheet 315 on an inner side of the second duct members 304 and 314 and a grill structure 309 on an outer side of the second duct members 304 and 314. The membrane sheet 315 may be a PTFE membrane supported on a polyester material. The membrane sheet 315 is hydrophobic and oleophobic i.e. it prevents water, oil and dust contaminants to enter inside the battery pack 110. Further, the membrane sheet 315 supports adequate venting rate for a predetermined pressure difference across it. As the pressure difference across the membrane sheet 315 increases, the flowrate of the gases through the membrane sheet also increases. The membrane sheet 315 of the vent member 308 performs pressure equalization i.e. balance pressure inside the battery module 100 with outer atmosphere. This membrane sheet 315 substantially equalizes pressure of the gases in the buffer chamber 602 in the casing 101 with the downstream gas passages 701 and 702 and the gas holding chambers 601 and 603. In case of cell failure, the membrane sheet 315 offers minimum resistance to gas flow thus allows gases to flow at high flowrate through the grill structure 309. This helps to prevent pressure build up inside the gas holding chambers 601 and 603 and the downstream gas passages 701 and 702 to cross its burst pressure and thereby avoid mechanical as well as fire damage in case of cell exploding due to failure. The grill structure 309 of the vent member 308 allows for streamlined and distributed flow of the gases from the downstream gas passages 701 and 702 to the buffer chamber 602.

[00039] Figs. 8A-8B exemplarily illustrate the perspective views and sectional view of the vent plug 106 taken along the Z-Z’ axis, respectively. As exemplarily illustrated, each of the vent plugs, such as, 106 comprises a top portion 801 and a bottom stem 802. The top portion 801 comprises slits 80 la on the sides for the gases to exhaust. The bottom stem 802 is inserted into the opening of the casing 101 in line with the vent member 308. In an embodiment, the bottom stem 802 has threads that allow positioning of the vent plugs 106 and 107 in the openings 111 of the casing 101 with counter threads. The vent plugs 106 and 107 also prevent entry of dirt and moisture into the battery pack 110. In an embodiment, the vent plugs 106 and 107 may be implemented in conjunction with check valves to allow flow of the vented gases through it only in one direction. The vent plugs 106 and 107 also comprise a membrane sheet in the inner side of the slit 801a in the top portion 801. The membrane sheet of the vent plugs 106 and 107 perform pressure equalization i.e. balance pressure inside the battery module 100 with outer atmosphere. This pressure change can happen due to temperature or altitude change or by release of gas inside battery module 100.

[00040] This membrane sheet may equalize pressure by allowing outer gas inside battery pack 110 or vice versa. In case of cell failure, the membrane sheet offers minimum resistance to gas flow thus allows gas to flow at high flowrate through the slits 80 la in the top member 801. This helps to prevent pressure build-up inside the casing 101 to cross its burst pressure and avoid or minimise mechanical as well as fire damage in case of cell exploding due to failure. The membrane sheet, such as, 315 of the vent members 308 and the vent plugs 106 and 107 function until a predetermined temperature. To avoid direct interaction of the vent plugs 106 and 107 and the vent member 308 with the elevated temperatures during the incidence of a fire, the membrane sheets are not in direct contact with the cells 403 in the battery pack 110.

[00041] The embodiments of the battery module with the exhaust system provides a technical advancement in the field of battery technology as follows: Commercial cylindrical cells of format 18650, 26650 or 21700 have inbuild venting system to release gas inside cell to outside. Since exhaust gases coming out from cells is flammable in nature, it is important to allow these gases to be released from the cells without any obstruction. The exhaust system in the battery module creates a volume over cells to accommodate the increased pressure due to gas release from cells. The exhaust system also provides a path to vent the gases out from the battery module to outside ambient atmosphere with minimal damage to other components of the battery module. It also isolates other electronic components of the battery module from getting exposed to these gases which otherwise may get damaged by heat or pressure rise due to the gases.

[00042] The first duct members function as a physical barrier between cell terminals and outer casing of the battery module, in case of cell explosions. The second duct members channelize the gases from cells to outside battery effectively in a pre-defined path to minimize the damage that could occur due to thermal runaway. The use of the membrane sheet in the vent members and the vent plugs prevent dust and water contaminants entry inside the battery module. Also, pressure equalization characteristic of the membrane sheet prevents damages which could occur due to high pressure difference between atmosphere and battery module/battery pack. The exhaust system is designed such that pressure rise inside the cells due to gas released from a single cell under is less and can be vented out in less time with minimal damage to other components of battery module. Collectively, the exhaust system can vent gas released from a single cell failure within a predetermined time duration. The first duct members and the second duct members are made up of metal like Aluminium or stainless steel coated with good thermal and electrical insulation layer to sustain high temperature condition generated due to the failed cell. Also, due to the lightweight ducts that are interlocked with each other using the protruding end and the depressions, the installation of the exhaust system on already available battery pack is feasible and is not bulky. The manufacturability and the serviceability of such a battery module is improved as the modes of the attaching the first duct members and the second duct members to the battery pack does not require fasteners. Such battery modules find use in space constrained applications, such as, electric vehicles or hybrid electric vehicles. [00043] Improvements and modifications may be incorporated herein without deviating from the scope of the invention.

LIST OF REFERENCE NUMERALS

100 Batery module

101 Casing

102 Enclosing wall

103 First end cover

104 Electrical Connector

105 Peripheral wall 106, 107 vent plugs

108 Exhaust system

109 BMS board

110 Batery pack

111 openings in casing

112 second end cover 301, 310 First duct members 30a, 310a central trough structure 302, 303 Protruding ends

304, 314 Second duct members 304a- channel structure

305, 306 ends of second duct members

307 depressions

308 vent members

309 grill structure

311 top surface of batery pack

312 botom surface of batery pack 313, 401 interconnect sheets

315 membrane sheet

402 mounting provision of interconnect sheet

403 cells

404, 405 cell holders

406 apertures in interconnect sheets

407 mounting provision of cell holders 501 opening in first end cover

502 raised edges

503 long edges of the first end cover

504 rectangular opening 601, 603 gas holding chambers

602 buffer chamber 604 region around BMS board 701, 702 downstream gas passages

801 top portion 801a slits in top portion

802 bottom stem

Claims

I/We Claim:

1. A battery module (100) comprising: a battery pack (110), comprising a plurality of cells (403), housed in a casing (101); a plurality of end covers (103, 112) for enclosing the battery pack (110) in the casing (101); and a plurality of duct members (301, 310, 304, 314) surrounding the battery pack (110) forming at least one gas holding chamber (601, 603) and at least two downstream gas passages (701, 702) for regulated exhaust of gases released from the battery pack (110).

2. The battery module (100) of claim 1, wherein the plurality of duct members (301, 310, 304, 314) comprises: at least one first duct member (301, 310) positioned exterior to a surface (311, 312) of the battery pack (110) forming the at least one gas holding chamber (601, 603) for accumulating the gases released from the battery pack (110), and at least two second duct members (304, 314) removably and communicatively engaged with the at least one first duct member (301, 310) form the at least two downstream gas passages (701, 702) for exhaust of the accumulated gases to atmosphere.

3. The battery module ( 100) of claim 2, wherein the at least one first duct member (301, 310) comprises a central trough structure (301a, 310a) with protruding ends (302, 303) on both sides of the central trough structure (301a, 310a) forming the at least one gas holding chamber (601, 603) for accumulating the gases released from the battery pack (110).

4. The battery module (100) of claim 3, wherein each of the at least two second duct members (304, 314) comprises at least one depression (307) proximal to both ends to accommodate the protruding ends (302, 303) of the at least one first duct member (301, 310) for holding the plurality of duct members (301, 310, 304, 314) around the battery pack (110) within the casing (101) to form a continuous and fluidly connected gas passage between the at least one gas holding chamber (601, 603) and the at least two downstream gas passages (701, 702).

5. The battery module ( 100) of claim 4, wherein the each of the at least two second duct members (304, 314) further comprises a vent member (308) centrally located in a channel structure (304a) that forms the at least two downstream gas passages (701,702).

6. The battery module (100) of claim 5, further comprises at least two vent plugs (106, 107) on an outer surface of the casing (101) in-line with the vent member (308) on the each of the at least two second duct members (304, 314) to vent the exhaust gases from the battery module (100).

7. The battery module (100) of claim 5, wherein the vent member (308) comprises a semi-permeable hydrophobic, oleophobic, and dust-proof membrane sheet (315) in the each of the at least two second duct members (304, 314) for permeating the gases to pass at a predetermined pressure.

8. The battery module (100) of claim 7, wherein the vent member (308) further comprises a grill structure (309) on an outer side of the membrane sheet (315) for allowing a streamlined and distributed flow of the gases from the downstream gas passages (701, 702) to a buffer chamber (602).

9. The battery module (100) of claim 5, wherein the gases generated from the plurality of cells (403) in the battery pack (110) traverses in a first direction towards the at least one gas holding chamber (601, 603) defined by the at least one first duct member (301, 310), further traverses in a second direction towards the at least two downstream gas passages (701, 702) defined by the at least two second duct members (304, 314) fluidly connected to the at least one first duct member (301, 310), and flows out away from the battery pack (110) through the vent member (308) towards exterior of the battery module (100).

10. The battery module (100) of claim 4, further comprises a buffer chamber (602) formed between the plurality of duct members (301, 310, 304, 314) and the casing (101) for expansion of the gases vented from the plurality of duct members (301, 310, 304, 314) through the vent member (308) in the each of the at least two second duct members (304, 314) to protect the battery module (100) from a catastrophic failure.

11. The battery module (100) of claim 10, wherein the gases released from the battery pack (110) that are held in the buffer chamber (602) are expelled from the casing (101) through at least two vent plugs (106, 107) on an outer surface of the casing (101).

12. The battery module (100) of claim 1, further comprises a battery management system (109) positioned posterior to one of the plurality of end covers (103), for monitoring and controlling the plurality of cells (403) in the battery pack (110).

13. The battery module (100) of claim 12, wherein the one of the plurality of end covers (103) comprises raised edges (502) along each longer edge (503) of a rectangular opening (504) on a posterior side proximal to the battery management system (109) for abuttingly sealing and removably engaging with the casing (101) to isolate the battery management system (109) from the gases released from the battery pack (110) in the casing (101).

14. The battery module (100) of claim 1, wherein the battery pack (110) comprises at least one interconnect sheet (313, 401) for connecting the plurality of cells (403) in at least one of a series connection and a parallel connection, and wherein the at least one interconnect sheet (313, 401) comprises an opening (406) corresponding to each of the plurality of cells (403) for venting of gases from the each of the plurality of cells (403) towards the plurality of duct members (301, 310, 304, 314).

15. An exhaust system (108) of a battery module (100) comprising: at least one interconnect sheet (313, 401) comprising an opening (406) corresponding to each of a plurality of cells (403) of the battery module (100) for venting of gases from the each of the plurality of cells (403); at least one gas holding chamber (601, 603) configured in a region surrounding the plurality of cells (403) for accumulating the gases vented from the plurality of cells (403); at least two downstream gas passages (701,702) perpendicular to both ends of the at least one holding chamber (601,603) for routing the accumulated gases from the at least one holding chamber (601,603) away from the plurality of cells (403) and subsequently exhaust the gases through a vent member (308) of each of the at least two downstream gas passages (701,702); a buffer chamber (602) configured between a casing (101) of the battery module (100) and the at least one gas holding member (601,603) for receiving the vented gases from the at least two downstream gas passages (701,702) and providing a volume for expansion of the gases; and at least two vent plugs (106, 107) on an outer surface of the casing (101) in-line with the vent member (308) of the each of the at least two downstream gas passages (701,702) to safely vent the exhaust gases from the battery module (100) for protecting the battery module (100) from a catastrophic failure.

16. The exhaust system (108) of claim 15, wherein the at least one gas holding chamber (601,603) is defined by at least one first duct member (301, 310) positioned over the at least one interconnect sheet (313, 401) for accumulating the gases released from the plurality of cells (403).

17. The exhaust system (108) of claim 16, wherein the at least one first duct member (301, 310) comprises a central trough structure (301a, 310a) for holding the gases, and the at least one first duct member (301, 310) is configured with protruding ends (302, 303) on both sides of the central trough structure (301a, 310a).

18. The exhaust system ( 108) of claim 17, wherein the at least two downstream gas passages (701,702) are defined by at least two second duct members (304, 314) removably engaged with the at least one first duct member (301, 310) for exhaust of the accumulated gases to atmosphere.

19. The exhaust system (108) of claim 18, wherein each of the at least two second duct members (304, 314) comprises at least one depression (307) proximal to both ends to accommodate the protruding ends (302, 303) of the at least one first duct member (301, 310) thereby forming a continuous and fluidly connected gas passage between the at least one gas holding chamber (601, 603) and the at least two downstream gas passages (701, 702) around the plurality of cells (403) within the casing (101).

20. The exhaust system (108) of claim 19, wherein the each of the at least two second duct members (304, 314) further comprises the vent member (308) centrally located in a channel structure (304a) that forms the at least two downstream gas passages (701,702).

21. The exhaust system (108) of claim 20, wherein the vent member (308) comprises a semi-permeable hydrophobic, oleophobic, and dust-proof membrane sheet (315) in the each of the at least two second duct members (304, 314) for permeating the gases to pass at a predetermined pressure.

22. The exhaust system (108) of claim 21, wherein the vent member (308) further comprises a grill structure (309) on an outer side of the membrane sheet (315) for allowing a streamlined and distributed flow of the gases from the downstream gas passages (701, 702) to the buffer chamber (602).

23. The exhaust system (108) of claim 15, further comprises a plurality of raised edges (502) along each longer edge (503) of a rectangular opening (504) of an end cover (103) of the battery module (100) for abuttingly sealing and removably engaging with the casing ( 101 ) for isolating a plurality of electronic components of the battery module (100) from the gases vented from the plurality of cells (403) in the casing (101).