CN219017749U

CN219017749U - Battery overturning piece and battery end cover

Info

Publication number: CN219017749U
Application number: CN202222964080.5U
Authority: CN
Inventors: 王得鹏; 韩雪冰; 卢兰光; 路瑶; 毛烁源
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2022-11-08
Filing date: 2022-11-08
Publication date: 2023-05-12
Anticipated expiration: 2032-11-08

Abstract

The utility model relates to a battery overturning piece and a battery end cover, wherein the battery overturning piece is applied to the air pressure detection in a battery, the battery overturning piece comprises a piece body and a detection piece, and the piece body can deform under the action of the air pressure in the battery; the detection piece is connected to the sheet body and is used for detecting the deformation of the sheet body. In the battery overturning sheet, the sheet body is set into a form that the shell deforms under the action of the air pressure in the battery, and the deformation of the sheet body is detected through the detection piece, so that the change condition of the air pressure in the battery can be obtained through the deformation of the sheet body. Through setting the battery upset piece into above structural style, the evolution process of the inside atmospheric pressure of control battery that can be more audio-visual to further carry out accurate estimation to the security performance of battery, refine the atmospheric pressure boundary setting before the battery out of control takes place, can provide the atmospheric pressure monitoring function of full life in-process to high-capacity and high-value battery monomer, safety precaution time in advance.

Description

Battery overturning piece and battery end cover

Technical Field

The utility model relates to the technical field of power batteries, in particular to a battery overturning piece and a battery end cover.

Background

The lithium ion battery also accompanies the use aging and calendar aging of the battery in the use process, and the internal reaction and the gas production of side reaction cause the continuous rising of the gas pressure in the battery. The continuous gas production can reduce the internal structure and density of the battery, correspondingly reduce the capacity of the battery, and even cause the risks of burst of the battery structure, explosion, fire and the like under the condition of excessive gas pressure. To cope with this problem, the current solution is mainly to design explosion-proof valves, overturning plates, etc. on the battery for relieving the internal pressure in advance. The explosion-proof valve (or explosion-proof piece) can generate directional rupture to release internal gas when the internal pressure of the battery is too high. The overturning piece, namely the current short-circuiting device, can deform under the pushing of internal gas; when the air pressure exceeds the deformation threshold of the overturning piece, the overturning piece overturns and is communicated with the anode and the cathode, so that the internal passage of the battery is shorted, and the further progress of the runaway reaction in the battery is stopped. Therefore, the safety effect of the explosion-proof valve is exerted when the internal air pressure reaches the design threshold value, and the air pressure change in the middle process is a state value which is difficult to control.

Disclosure of Invention

Based on this, it is necessary to provide a battery overturning piece and a battery end cover for solving the technical problem that the internal air pressure of the battery in the prior art cannot be effectively monitored.

A battery overturning piece, applied to the inside atmospheric pressure of battery detects, battery overturning piece includes:

the sheet body can deform under the action of air pressure in the battery;

the detection piece is connected to the sheet body and used for detecting the deformation of the sheet body.

In one embodiment, the sheet body is arranged to be recessed along a central axis of the sheet body in a thickness direction to one end of the central axis, the sheet body has a first surface and a second surface arranged opposite to each other in the thickness direction, the second surface is a concave surface, the detecting member is arranged on the concave surface, and the first surface is used for bearing the air pressure.

In one embodiment, the battery overturning sheet further comprises a first insulating member provided between the sheet body and the detecting member.

In one embodiment, the battery roll-over tab further includes an abutment post disposed on the second surface for making electrical connection with a component in the battery end cap.

In one embodiment, an avoidance hole is formed in the abutment post, and one end of the detection member extends along the radial direction of the sheet body through the avoidance hole.

In one embodiment, the peripheral edge of the sheet body is provided as a plane.

In one embodiment, the sensing element is a strain sensor.

A battery end cap comprising a battery inversion sheet as described above, the end cap further comprising:

the battery overturning piece is arranged on the first cover plate and is electrically connected with the first cover plate;

the second cover plate is arranged at intervals with the first cover plate;

the first pole assembly is fixed on the second cover plate and is in insulation abutting connection with the first cover plate;

the second pole assembly is fixed on the second cover plate and is electrically connected with the first cover plate;

when the deformation of the sheet body of the battery overturning sheet exceeds a preset value, the battery overturning sheet is electrically connected with the first pole assembly so that the first pole assembly is electrically connected with the second pole assembly.

In one embodiment, the first cover plate is provided with a first through hole, and the first pole assembly includes:

the first pole body is fixed on the second cover plate and is used for being electrically connected with the winding core inside the battery;

the first sealing piece is at least partially arranged in the first through hole, and the first pole body penetrates through the inner hole of the first sealing piece and extends in a direction away from the first pole body;

the second insulating piece is arranged on one side of the first cover plate, which is away from the second cover plate;

the first conductive piece is arranged on one side of the second insulating piece, which is away from the second cover plate;

when the deformation of the sheet body of the battery overturning sheet exceeds a preset value, the sheet body is conducted with the first conductive piece.

In one embodiment, the first cover plate is provided with a second through hole, and the second post assembly includes:

the second pole body is fixed on the second cover plate and is used for being electrically connected with the winding core in the battery;

the second sealing piece is at least partially arranged in the second through hole, and the second pole body penetrates through the inner hole of the second sealing piece and extends in a direction away from the second pole body;

the second conductive piece is arranged on one side of the first cover plate, which is away from the second cover plate, and is electrically connected with the first cover plate, and the second pole body is electrically connected with the second conductive piece.

In one embodiment, the second post assembly further includes a second post cover, the second post cover is fixed on the second conductive member, and the second post body abuts against the second post cover.

In one embodiment, the battery end cover further comprises an explosion-proof valve assembly, the explosion-proof valve assembly is arranged on the second cover plate, the air pressure in the battery exceeds a preset value, and the explosion-proof valve assembly can be damaged to discharge the air in the battery.

The utility model has the beneficial effects that:

the utility model provides a battery overturning sheet and a battery end cover, wherein in the battery overturning sheet, a sheet body is set into a form that a shell deforms under the action of air pressure in a battery, and the deformation of the sheet body is detected by a detection piece, so that the change condition of the air pressure in the battery can be obtained through the deformation of the sheet body. Through setting the battery upset piece into above structural style, the evolution process of the inside atmospheric pressure of control battery that can be more audio-visual to further carry out accurate estimation to the security performance of battery, refine the atmospheric pressure boundary setting before the battery out of control takes place, can provide the atmospheric pressure monitoring function of full life in-process to high-capacity and high-value battery monomer, safety precaution time in advance.

Drawings

Fig. 1 is a schematic structural diagram of a battery overturning sheet according to an embodiment of the present utility model;

fig. 2 is a schematic cross-sectional view of a battery overturning sheet according to an embodiment of the present utility model;

fig. 3 is an exploded view of a battery end cap according to an embodiment of the present utility model;

fig. 4 is a schematic structural diagram of a first pole assembly end in a battery end cap according to an embodiment of the present utility model;

fig. 5 is a schematic structural diagram of a second post assembly end in a battery end cap according to an embodiment of the present utility model.

A battery overturning sheet 1; a sheet body 11; a first insulating member 12; a detecting member 13; an abutment post 14;

a first pole assembly 2; a first pole body 21; a first seal 22; a second insulating member 23; a first conductive member 24;

a second pole assembly 3; a second pillar body 31; a second seal 32; a second conductive member 33; a second pole cover 34;

an explosion-proof valve assembly 4;

a first cover plate 5;

a second cover plate 6.

Detailed Description

In order that the above objects, features and advantages of the utility model will be readily understood, a more particular description of the utility model will be rendered by reference to the appended drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present utility model. The present utility model may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit of the utility model, whereby the utility model is not limited to the specific embodiments disclosed below.

In the description of the present utility model, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present utility model and simplifying the description, and do not indicate or imply that the device or element being referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the present utility model.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the present utility model, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.

In the present utility model, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the present utility model can be understood by those of ordinary skill in the art according to the specific circumstances.

In the present utility model, unless expressly stated or limited otherwise, a first feature "up" or "down" a second feature may be the first and second features in direct contact, or the first and second features in indirect contact via an intervening medium. Moreover, a first feature being "above," "over" and "on" a second feature may be a first feature being directly above or obliquely above the second feature, or simply indicating that the first feature is level higher than the second feature. The first feature being "under", "below" and "beneath" the second feature may be the first feature being directly under or obliquely below the second feature, or simply indicating that the first feature is less level than the second feature.

It will be understood that when an element is referred to as being "fixed" or "disposed" on another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like are used herein for illustrative purposes only and are not meant to be the only embodiment.

Referring to fig. 1 and 2, an embodiment of the present utility model provides a battery overturning sheet 1, which is applied to air pressure detection in a battery, wherein the battery overturning sheet 1 comprises a sheet body 11 and a detecting piece 13, and the sheet body 11 can deform under the action of air pressure in the battery; the detecting member 13 is connected to the sheet body 11, and the detecting member 13 is used for detecting the deformation amount of the sheet body 11.

In the battery overturning sheet 1, the sheet body 11 is set to be in a form that the shell deforms under the action of the air pressure in the battery, and the deformation amount of the sheet body 11 is detected by the detection piece 13, so that the change condition of the air pressure in the battery can be obtained through the deformation amount of the sheet body 11. Through setting up battery upset piece 1 into above structural style, the evolution process of the inside atmospheric pressure of control battery that can be more audio-visual to further carry out accurate estimation to the security performance of battery, refine the atmospheric pressure boundary setting before the battery out of control takes place, can provide the atmospheric pressure monitoring function of full life in-process to high-capacity and high-value battery monomer, safety precaution time in advance.

The detecting member 13 is connected to a battery management system, the deformation amount of the sheet body 11 detected by the detecting member 13 is transmitted to the battery management system, and the processing unit in the battery management system determines whether the air pressure in the battery is within a preset safety value range according to the deformation amount of the sheet body 11. The detecting member 13 is not limited as long as the deformation amount of the sheet body 11 generated under the internal air pressure of the battery can be detected. In this embodiment, the detecting member 13 is a flexible strain sensor, and since the flexible strain sensor is connected to the sheet body 11, the sheet body 11 is gradually deformed when the air pressure inside the battery is received, and the strain sensor is correspondingly strained. The strain sensor can change its own resistivity along with the micro deformation of the sheet body 11, and the change in resistivity of the strain sensor directly reflects the change in the internal air pressure of the battery. The battery management system estimates the use state of the battery through the change of the resistivity of the strain sensor.

The strain sensor includes electrode connection points at both ends and a strain sensitive material in the middle. The strain sensitive material of the strain sensor is obtained by mixing polymer materials and inorganic nano materials, wherein the polymer materials comprise polyurethane, silane, silicone and the like, and the inorganic conductive materials comprise graphene nano sheets, carbon nano tubes, nano silver wires and the like.

It should be noted that, the structural form of the sheet body 11 is not limited, and the overall structure of the sheet body 11 may be square or circular, as long as the sheet body 11 can elastically deform under the action of the air pressure of the battery. In this embodiment, as shown in fig. 1 and 2, the sheet body 11 may be a circular sheet integrally formed of aluminum, stainless steel, or the like. Specifically, the sheet body 11 is provided to be recessed in the thickness direction along one end of the central axis of the center axis of the sheet body 11, the sheet body 11 has a first surface and a second surface provided opposite to each other in the thickness direction, the second surface is a concave surface, the detecting member 13 is provided on the concave surface, and the first surface is for receiving air pressure. The outer diameter of the sheet body 11 may be in the range of 15-25mm, and the thickness may be in the range of 0.5-1mm, however, in other embodiments, other dimensions may be provided to meet the actual needs. Such an integrally formed circular sheet may be integrally formed by a machining method, or may be formed by cold forming, for example, a press forming method, or the like.

Further, as shown in fig. 1 and 2, the peripheral edge of the sheet body 11 is provided as a plane. The peripheral edge of the sheet body 11 is provided in a planar form, so that when the sheet body 11 is connected with other structures, the contact area between the two is increased, thereby improving the connection strength between the two, and simultaneously, the battery has the advantage of ensuring the tightness of the battery.

In one embodiment, as shown in fig. 1 and 2, the battery roll-over sheet 1 further includes a first insulating member 12, and the first insulating member 12 is provided between the sheet body 11 and the detecting member 13. The first insulating member 12 is arranged between the sheet body 11 and the detecting member 13, so that short circuit between the strain sensor and the sheet body 11 can be prevented, and error measurement of the strain sensor can be avoided, and reliability of monitoring the air pressure in the battery can be improved. In the present embodiment, the first insulating member 12 is a layer of insulating film attached to the sheet body 11 by spraying. The young's modulus of the insulating film is lower than that of the metal material used for the sheet body 11, but is significantly higher than that of the strain sensitive material. The insulating film may have a width of about 1mm, a length of about 13 to 23mm, and a thickness of about 0.03 mm. The insulating layer film may be an insulating polymer material having a shore hardness of less than 50A, including, but not limited to, polyurethanes, silanes, silicones, and the like. The hardness of the insulating layer film is high as that of the strain sensitive material, so that the overturning relaxation caused by the tensile force of the covering material in the deformation process of the overturning sheet is avoided.

In one embodiment, as shown in fig. 1 and 2, the battery inversion sheet 1 further includes an abutment post 14, where the abutment post 14 is disposed on the second surface, and the abutment post 14 is used to make electrical connection with a component in the battery end cap. Wherein the abutment post 14 is disposed in a central portion of the second surface. The abutment post 14 and the sheet body 11 may be molded as one piece, but the abutment post 14 may be fixed to the sheet body 11 by welding, caulking, mechanical fitting, or adhesive.

Further, as shown in fig. 1 and 2, an escape hole is provided in the abutment post 14, and one end of the detection member 13 extends in the radial direction of the sheet body 11 through the escape hole. Specifically, a cross-shaped through groove is provided at an end of the abutment post 14 facing the second surface, and the strain sensor extends in the radial direction of the entire sheet body 11 through the through groove. The abutment post 14 has a cylindrical structure with a height dimension of between 2 and 10mm, directly between 2 and 7 mm; the width of the avoidance hole is between 1 and 3mm, and the depth is between 1 and 3 mm.

For example, the thickness of the sheet body 11 may be set to 0.5mm, the outer diameter to 25mm, and the recessed depth of the second surface of the sheet body 11 to 1.3mm, leaving a flat area of about 1mm width at the periphery of the sheet body 11 for fixing the sheet body 11 while preventing gas leakage. The insulating film and the strain sensor are formed on the sheet body 11 by spraying, and the specific spraying process is not described herein. In the process of preparing the insulating film and the strain sensor by spraying, plasma cleaning can be adopted for the sheet body 11, and after spraying is finished, a rapid annealing process and the like can be adopted to enhance the contact stability of an interface, so that detachment between components is avoided.

As shown in fig. 3-5, the present utility model further provides a battery end cover, where the battery end cover includes the battery overturning piece 1 as described above, and the end cover further includes a first cover plate 5, a second cover plate 6, a first pole component 2, and a second pole component 3, where the battery overturning piece 1 is disposed on the first cover plate 5 and is electrically connected with the first cover plate 5; the second cover plate 6 is arranged at intervals from the first cover plate 5; the first pole assembly 2 is fixed on the second cover plate 6 and is in insulating abutting connection with the first cover plate 5; the second pole assembly 3 is fixed on the second cover plate 6 and is electrically connected with the first cover plate 5; when the deformation of the sheet body 11 of the battery overturning sheet 1 exceeds a preset value, the battery overturning sheet 1 is electrically connected with the first pole assembly 2, so that the first pole assembly 2 is electrically connected with the second pole assembly 3.

In this technical scheme, the first post assembly 2 corresponds to the negative electrode of the battery, and the second post assembly 3 corresponds to the positive electrode of the battery. When gas is generated in the battery, the air pressure pushes the sheet body 11 to deform, and when the air pressure does not reach the set overturning pressure, the tiny deformation of the sheet body 11 is monitored by a riding strain sensor and is converted into a resistance value signal. The resistance value signal is transmitted to an external battery management system through a signal transmission line, so that the real-time detection of the internal pressure of the battery is ensured. When the air pressure in the battery reaches the set overturning pressure, the air pressure in the battery deforms the sheet body 11 to be electrically connected with the first pole assembly 2, so that the first pole assembly 2 and the second pole assembly 3 are short-circuited, further reaction in the battery is avoided, and the use safety of the battery is ensured.

Here, the turning means that when the deformation amount of the sheet body 11 reaches a certain value, the contact post 14 contacts the first pole assembly 2 so that the sheet body 11 is electrically connected to the first pole assembly 2. The first cover plate 5 is made of metal material, such as aluminum, steel and the like; the second cover plate 6 is a polymer insulating material resistant to electrolyte corrosion.

Specifically, as shown in fig. 3 and 4, the first cap plate 5 is provided with a first through hole, the first post assembly 2 includes a first post body 21, a first sealing member 22, a second insulating member 23, and a first conductive member 24, and the first post body 21 is fixed to the second cap plate 6 and is used to maintain electrical connection with a winding core inside the battery; at least part of the first sealing member 22 is arranged in the first through hole, and the first pole body 21 penetrates through the inner hole of the first sealing member 22 to extend in a direction away from the first pole body 21; the second insulating member 23 is arranged on one side of the first cover plate 5 facing away from the second cover plate 6; the first conductive element 24 is arranged on the side of the second insulating element 23 facing away from the second cover plate 6; when the deformation of the sheet body 11 of the battery overturning sheet 1 exceeds a preset value, the sheet body 11 is conducted with the first conductive member 24.

As shown in fig. 3 and 4, the first pole body 21 and the first sealing member 22 are disposed between the first cover plate 5 and the second cover plate 6, the first pole body 21 is electrically connected to the first conductive member 24 at all times, the first pole body 21 is electrically connected to the second cover plate 6 through the first sealing member 22, and the first conductive member is electrically connected to the second cover plate 6 through the second insulating member 23. By the above structural form, the insulating connection of the first pole assembly 2 and the second cover plate 6 is realized. When the pressure inside the battery exceeds the safety value, the air pressure inside the battery makes the convex surface of the sheet body 11 become flatter, so that the abutment post 14 fixed on the sheet body 11 abuts against the first conductive member 24, thereby making the sheet body 11 electrically connect the first conductive member 24 with the second cover plate 6. Since the second pole assembly 3 is electrically connected to the second cover plate 6, the first conductive member 24, that is, the first pole assembly 2 and the second pole assembly 3 are short-circuited, thereby ensuring the safety of the battery.

As shown in fig. 3 and 5, the first cover 5 is provided with a second through hole, the second post assembly 3 includes a second post body 31, a second sealing member 32, and a second conductive member 33, and the second post body 31 is fixed on the second cover 6 and is used for maintaining electrical connection with the winding core inside the battery; at least part of the second sealing element 32 is arranged in the second through hole, and the second post body 31 passes through the inner hole of the second sealing element 32 and extends in a direction away from the second post body 31; the second conductive member 33 is disposed on a side of the first cover 5 facing away from the second cover 6, and is electrically connected to the first cover 5, and the second post body 31 is electrically connected to the second conductive member 33. The positive electrode and the negative electrode of the battery are triggered to be short-circuited through the structural form, and the internal further reaction of the battery is interrupted, so that the use safety of the battery is ensured.

Similarly, as shown in fig. 3 and 5, the second post body 31 and the second sealing member 32 are disposed between the first cover plate 5 and the second cover plate 6, the second post body 31 is electrically connected to the second conductive body at all times, the second post body 31 is electrically connected to the second cover plate 6 through the second sealing member 32, and the second conductive body is electrically connected to the second cover plate 6. When the tab body 11 is electrically connected with the first conductive member 24, a short circuit of the second pole assembly 3 and the first pole assembly 2 is achieved. The second post assembly 3 further includes a second post cover 34, where the second post cover 34 is fixed on the second conductive member 33, and the second post body 31 abuts against the second post cover 34 to electrically connect the second post body 31 and the second conductive member 33. The second cover plate 6, the first sealing member 22 and the second sealing member 32 may be nylon, polyurethane, engineering plastic, etc., and have a certain deformability in addition to sealing performance, so as to ensure that a gap does not occur in the sealing between the components in the case of vibration, etc.

In one embodiment, as shown in fig. 3, the battery end cover further includes an explosion-proof valve assembly 4, the explosion-proof valve assembly 4 is disposed on the second cover plate 6, and the air pressure in the battery exceeds a preset value, and the explosion-proof valve assembly 4 can be destroyed to discharge the air in the battery. In order to avoid the conditions of overheat continuous gas production, heat production and the like of the battery after the battery is internally short-circuited through the battery overturning piece 1, the explosion-proof valve assembly 4 is arranged on the battery cover plate and can be damaged under the overvoltage, so that the high-temperature gas in the battery is discharged to the outside, the explosion of the battery is avoided, and the practical safety of the battery is improved. The explosion proof valve assembly 4 is a metal sheet with preset perforation tracks and perforation threshold pressure.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples illustrate only a few embodiments of the utility model, which are described in detail and are not to be construed as limiting the scope of the utility model. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the utility model, which are all within the scope of the utility model. Accordingly, the scope of protection of the present utility model is to be determined by the appended claims.

Claims

1. The utility model provides a battery upset piece, is applied to in the inside atmospheric pressure of battery detects, its characterized in that, battery upset piece includes:

the sheet body can deform under the action of air pressure in the battery;

2. The battery roll-over sheet according to claim 1, wherein the sheet body is provided with a recess in one end of the central axis along a central axis of the sheet body in a thickness direction, the sheet body has a first surface and a second surface provided opposite to each other in the thickness direction, the second surface is a concave surface, the detecting member is provided on the concave surface, and the first surface is for receiving the air pressure.

3. The battery inversion sheet according to claim 2, further comprising a first insulating member provided between the sheet body and the detecting member.

4. The battery inversion sheet of claim 2 further comprising an abutment post disposed on said second surface for making electrical connection with a component in a battery end cap.

5. The battery turnover sheet according to claim 4, wherein a relief hole is provided on the abutment post, and one end of the detection member extends in a radial direction of the sheet body through the relief hole.

6. The battery inversion sheet according to any one of claims 2 to 5, wherein the peripheral edge of the sheet body is provided as a plane.

7. The battery inversion sheet according to any one of claims 1 to 5, wherein the detecting member is a strain sensor.

8. A battery end cap comprising the battery roll-over tab of any one of claims 1-7, the end cap further comprising:

the second cover plate is arranged at intervals with the first cover plate;

9. The battery end cap of claim 8, wherein the first cover plate is provided with a first through hole, the first post assembly comprising:

10. The battery end cap of claim 8, wherein the first cover plate has a second through hole disposed therein, the second post assembly comprising:

11. The battery end cap of claim 10, wherein the second post assembly further comprises a second post cap secured to the second conductive member, the second post body abutting the second post cap.

12. The battery end cap of any one of claims 8-11, further comprising an explosion-proof valve assembly disposed on the second cover plate, wherein the gas pressure within the battery exceeds a predetermined value, wherein the explosion-proof valve assembly is breakable to vent gas within the battery.