Ventilation rate detection method and valve body type selection method

Abstract

The invention provides a ventilation rate detection method and a valve body type selection method.The ventilation rate detection method is used for detecting the ventilation rate of a valve body, the valve body is arranged on a to-be-detected device, the to-be-detected device is provided with a closed inner cavity, the valve body communicates with the inner cavity, and the ventilation rate detection method comprises the steps that the initial internal pressure value of the to-be-detected device is obtained; adjusting the internal pressure of the to-be-tested device to a first threshold value, maintaining the internal pressure for a preset duration, then stopping the adjustment, and recording an adjustment ending moment; continuously detecting the internal pressure of the to-be-detected device, and recording an internal pressure recovery moment when the internal pressure is recovered to the initial internal pressure value; and the actual ventilation rate of the valve body is determined according to the initial internal pressure value, the first threshold value, the adjustment ending moment and the internal pressure recovery moment. Therefore, on one hand, a corresponding detection device for detecting the ventilation rate of the valve body does not need to be manufactured, so that the detection cost is reduced. And on the other hand, the internal pressure of the to-be-detected device is adjusted to the first threshold value and maintained for the preset duration, so that the consistency of the detection result can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of air permeability testing, and in particular to an air permeability testing method and a valve body selection method. Background Art

[0002] In related technologies, the battery pack (PACK) needs to maintain a dynamic balance between internal and external air pressure to ensure the structural stability and long-term reliability of the entire pack. The dynamic balance of internal and external air pressure is closely related to the air permeability of the battery pack. If the air permeability is too large, the gas exchange between the inside and outside of the battery pack will be frequent, which may easily cause condensation in the battery pack and cause poor electrical insulation. If the air permeability is too small, the pressure difference between the inside and outside of the battery pack may also cause the outer shell of the battery pack to deform, which in turn leads to failure of the battery pack seal and the inability to effectively discharge gas during thermal runaway. Currently, there is a lack of a reliable method for detecting the air permeability of battery packs. Summary of the Invention

[0003] The embodiments of the present application provide a method for detecting an air permeability rate and a method for selecting a valve body, which can improve the consistency of the detection results and at least partially solve the above-mentioned technical problems.

[0004] In a first aspect, embodiments of the present application provide a method for detecting an air permeability rate of a valve body, wherein the valve body is disposed on a device to be tested, the device to be tested having a closed inner cavity, and the valve body is in communication with the inner cavity. The method includes:

[0005] Obtaining an initial internal pressure value of the device under test;

[0006] Adjusting the internal pressure of the device under test to a first threshold, maintaining the pressure for a preset time, then stopping the adjustment, and recording the time when the adjustment ends;

[0007] Continuously detect the internal pressure of the device under test and record the internal pressure recovery time when the internal pressure returns to the initial internal pressure value;

[0008] The actual air permeability rate of the valve body is determined according to the initial internal pressure value, the first threshold value, the adjustment end time and the internal pressure recovery time.

[0009] In some embodiments, the valve body further has a valve core, which is configured to open when the internal pressure of the device under test is greater than a first preset threshold value, and adjust the internal pressure of the device under test to the first threshold value, including: reducing the internal air pressure of the device under test to the first threshold value.

[0010] In some embodiments, the device to be tested has a first connection port, which is connected to the inner cavity. Adjusting the internal pressure of the device to be tested to a first threshold value includes: connecting the first connection port to a vacuum device, and using the vacuum device to vacuum the inner cavity to reduce the internal pressure of the device to be tested to the first threshold value.

[0011] In some embodiments, the device to be tested is a battery pack having a high-pressure interface and a low-pressure interface. Connecting the first connection port of the device to be tested to the exhaust device includes: connecting either the high-pressure interface or the low-pressure interface to the exhaust device and sealing the other; or, connecting both the high-pressure interface and the low-pressure interface to the exhaust device.

[0012] In some embodiments, determining the actual air permeability rate of the valve body according to the initial internal pressure value, the first threshold value, the adjustment end time, and the internal pressure recovery time includes:

[0013] The actual air permeability rate is calculated based on the initial internal pressure value, the first threshold value, the adjustment end time, the internal pressure recovery time, and the calculation formula of the actual air permeability rate; the calculation formula of the actual air permeability rate is:

[0014]

[0015] Wherein, v is the actual air permeability, P1 is the initial internal pressure value, P2 is the first threshold value, V is the net volume of the device under test, P0 is the atmospheric pressure, T1 is the adjustment end time, and T2 is the internal pressure recovery time.

[0016] In a second aspect, the present application provides a valve body selection method, comprising:

[0017] Providing a battery pack, the battery pack including a housing and a current test valve body mounted on the housing;

[0018] Get the initial internal pressure value of the battery pack;

[0019] Adjusting the internal pressure of the battery pack to a first threshold, maintaining the pressure for a preset time, then stopping the adjustment, and recording the adjustment end time;

[0020] Continuously detect the internal pressure of the battery pack and record the internal pressure recovery time when the internal pressure returns to the initial internal pressure value;

[0021] Determine the actual air permeability rate of the current test valve body according to the initial internal pressure value, the first threshold value, the adjustment end time and the internal pressure recovery time;

[0022] Obtain the theoretical air permeability rate of the current test valve body;

[0023] When it is determined that the current test valve body meets the design requirements of the battery pack based on the theoretical air permeability rate of the current test valve body and the actual air permeability rate of the current test valve body, the current test valve body is determined as the adapted valve body of the battery pack.

[0024] In some embodiments, determining whether the current test valve body meets the design requirements of the battery pack based on the theoretical air permeation rate of the current test valve body and the actual air permeation rate of the current test valve body includes:

[0025] Calculate the air permeability deviation value σ based on the actual air permeability of the current test valve body and the theoretical air permeability of the current test valve body, σ = (|v-v0|) / v, where v0 is the theoretical air permeability;

[0026] In response to the air permeability rate deviation value being less than or equal to the first deviation threshold, it is determined that the current test valve body meets the design requirements.

[0027] In some embodiments, the method further comprises:

[0028] In response to the current test valve body not meeting the design requirements, the test valve body is replaced according to the theoretical air permeability rate of the current test valve body and the actual air permeability rate of the current test valve body, and it is determined whether the replaced test valve body meets the design requirements.

[0029] In some embodiments, replacing the test valve body according to the theoretical air permeability rate of the current test valve body and the actual air permeability rate of the current test valve body includes:

[0030] Comparing the theoretical air permeability rate of the current test valve body with the actual air permeability rate of the current test valve body;

[0031] If the theoretical air permeability rate of the current test valve body is greater than the actual air permeability rate of the current test valve body, a valve body with a theoretical air permeability rate greater than the theoretical air permeability rate of the current test valve body is selected as the replacement test valve body;

[0032] If the theoretical air permeability rate of the current test valve body is lower than the actual air permeability rate of the current test valve body, a valve body having a theoretical air permeability rate lower than the theoretical air permeability rate of the current test valve body is selected as the replacement test valve body.

[0033] In some embodiments, replacing the test valve body according to the theoretical air permeability rate of the current test valve body and the actual air permeability rate of the current test valve body includes:

[0034] If the theoretical air permeability rate of the current test valve body is less than the actual air permeability rate of the current test valve body, the air tightness of the battery pack is checked.

[0035] Beneficial effects of the embodiments of the present application:

[0036] In an embodiment of the present application, by connecting the valve body to the closed inner cavity of the device to be tested, the air permeability rate of the valve body can be detected by adjusting the internal pressure of the device to be tested and the time it takes for the internal pressure to recover. The valve body in the present application is installed on the device to be tested, and there is no need to make a corresponding detection device for detecting the air permeability rate of the valve body, which reduces the detection cost. At the same time, when the internal pressure of the device to be tested reaches a first threshold value, the present application maintains the internal pressure of the device to be tested at a preset time of the first threshold value, and stops adjusting after the preset time period. The preset time period can be used to make the pressure at various locations inside the device to be tested basically the same, thereby improving the consistency of the detection results. In addition, deformation of the device to be tested due to uneven internal pressure can also be avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0038] Figure 1 This is a flow chart of a method for detecting air permeability provided in an embodiment of the present application;

[0039] Figure 2 This is a flow chart of a valve body selection method provided in an embodiment of the present application;

[0040] Figure 3 This is a flow chart provided by an embodiment of the present application for determining whether the current test valve body meets the design requirements of the battery pack based on the theoretical air permeability rate of the current test valve body and the actual air permeability rate of the current test valve body;

[0041] Figure 4 This is a flow chart of replacing a test valve body according to a theoretical air permeability rate of the current test valve body and an actual air permeability rate of the current test valve body, provided in an embodiment of the present application. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present application. In addition, it should be understood that the specific implementation methods described herein are only used to illustrate and explain the present application, and are not used to limit the present application. In the present application, unless otherwise specified, the directional words used, such as "upper" and "lower", generally refer to the upper and lower parts of the device in actual use or working state, specifically the drawing direction in the accompanying drawings; and "inside" and "outside" refer to the outline of the device.

[0043] The first aspect of this application provides a method for calculating the air permeability rate. Figure 1 , Figure 1 This is a flow chart of a gas permeability detection method provided in an embodiment of the present application. The gas permeability detection method is used to detect the gas permeability of a valve body. The valve body is set on a device to be tested. The device to be tested has a closed inner cavity. The valve body is connected to the inner cavity. The gas permeability detection method includes the following steps.

[0044] S110: Obtaining an initial internal pressure value of the device under test.

[0045] In the embodiments of the present application, the device under test can be connected to a device that regulates air pressure, such as an air pump, and the initial internal pressure of the device under test can be measured using the device. Alternatively, if the device under test has a specification sheet or other document that contains standard values ​​for its various parameters, the initial internal pressure can be directly obtained.

[0046] S120: Adjusting the internal pressure of the device under test to a first threshold value, maintaining the pressure for a preset time, then stopping the adjustment, and recording the adjustment end time.

[0047] In the embodiment of the present application, when the internal pressure of the device under test reaches a first threshold, it is maintained at this level for a preset time period, thereby improving the consistency of the test results.

[0048] S130: Continuously detecting the internal pressure of the device under test, and recording the internal pressure recovery time when the internal pressure returns to the initial internal pressure value.

[0049] The valve body is permeable. Therefore, when the internal pressure of the device under test stops being adjusted, the pressure differential between the inside and outside will cause gas to pass through the valve body and enter the lower pressure side, gradually causing the pressure in the internal cavity of the device under test to equalize with the external pressure. Because the valve body's permeability rate is typically lower than the rate at which the internal pressure of the device under test is adjusted, for example, when using a vacuum device to evacuate the device under test to adjust its internal pressure, the vacuum device's pumping rate is much higher than the valve body's permeability rate. As a result, the amount of gas that passes through the valve body and enters the internal cavity of the device under test during the adjustment of its internal pressure is negligible. Therefore, the valve body is not sealed in the permeability rate detection method provided in the embodiments of the present application.

[0050] S140: Determine the actual air permeability rate of the valve body according to the initial internal pressure value, the first threshold value, the adjustment end time, and the internal pressure recovery time.

[0051] In the embodiment of the present application, by connecting the valve body to the closed inner cavity of the device to be tested, the air permeability rate of the valve body can be detected by adjusting the internal pressure of the device to be tested and the time it takes for the internal pressure to recover. The valve body in the present application is installed on the device to be tested, and there is no need to make a corresponding detection device for detecting the air permeability rate of the valve body, which reduces the detection cost. At the same time, when the internal pressure of the device to be tested reaches a first threshold value, the present application maintains the internal pressure of the device to be tested at a preset time length of the first threshold value, and stops adjusting after the preset time length. The preset time length can be used to make the pressure at various locations inside the device to be tested basically the same, thereby improving the consistency of the detection results. In addition, deformation of the device to be tested due to uneven internal pressure can also be avoided.

[0052] In some embodiments of the present application, the preset duration can be set to 20 to 40 seconds, preferably 30 seconds. In specific implementation, it can also be set to other ranges, which is not limited in this application.

[0053] In some embodiments of the present application, the valve body further has a valve core, which is configured to open when the internal pressure of the device under test is greater than a first preset threshold value. The above-mentioned adjustment of the internal pressure of the device under test to the first threshold value includes: reducing the internal air pressure of the device under test to the first threshold value.

[0054] Valve bodies can be of various types, each with different opening methods. In the present embodiment, the valve body includes a valve core that opens when the internal pressure of the device under test exceeds a first preset threshold value, where the first preset threshold value is greater than a first threshold value. Therefore, to ensure that the valve core does not open when testing the air permeability of the valve body, the internal pressure of the device under test must be controlled to prevent the valve core from opening during testing, thereby affecting the test results. Therefore, in the present embodiment, the air permeability of the valve body is tested by reducing the internal pressure of the device under test. Because the internal pressure of the device under test gradually decreases compared to the initial internal pressure value by evacuating air, the valve core can be prevented from opening. Alternatively, the internal pressure of the device under test can be adjusted by inflating the device under test. However, to prevent the valve core from opening, the adjustable pressure range is limited. However, the evacuation method of the device under test in the present embodiment does not consider the range of air pressure. This increases the difference between the initial internal pressure of the device under test and the first threshold value, thereby increasing the time it takes for the internal pressure to recover from the first threshold value to the initial value, thereby improving the accuracy of the test results.

[0055] In some embodiments of the present application, the device to be tested has a first connection port, which is connected to the inner cavity. Adjusting the internal pressure of the device to be tested to a first threshold value includes: connecting the first connection port to a vacuum device, and using the vacuum device to vacuum the inner cavity to reduce the internal pressure of the device to be tested to the first threshold value.

[0056] In the embodiment of the present application, the first connection port of the device under test is connected to the exhaust device, and the first connection port is used to exhaust the device under test, rather than connecting the valve body to the exhaust device. Therefore, the present application does not need to apply additional mechanical stress to the valve body itself, avoiding valve core wear or seal failure that may occur during the test. In particular, for precision components such as explosion-proof valves, directly exhausting the valve body may accelerate fatigue damage. The functional integrity of the valve body is guaranteed when the internal pressure of the device under test is pumped to the first threshold, thereby ensuring the accuracy of the test results.

[0057] In some embodiments of the present application, the device to be tested is a battery pack, which has a high-pressure interface and a low-pressure interface. Connecting the first connection port of the device to be tested to the exhaust device includes: connecting either the high-pressure interface or the low-pressure interface to the exhaust device and sealing the other; or, connecting both the high-pressure interface and the low-pressure interface to the exhaust device.

[0058] In an embodiment of the present application, when the device to be tested is a battery pack, air is directly extracted using the high-pressure interface and / or low-pressure interface of the battery pack. On the one hand, there is no need to extract air through the valve body, which can improve the accuracy of the test results. On the other hand, the battery pack itself has a high-pressure interface and a low-pressure interface, and there is no need to set up an additional detection interface, which avoids damage to the battery pack structure. At the same time, it can also simplify the detection process.

[0059] In some embodiments of the present application, determining the actual air permeability rate of the valve body according to the initial internal pressure value, the first threshold value, the adjustment end time, and the internal pressure recovery time includes:

[0060] The actual air permeability rate is calculated based on the initial internal pressure value, the first threshold value, the adjustment end time, the internal pressure recovery time, and the calculation formula of the actual air permeability rate; the calculation formula of the actual air permeability rate is:

[0061]

[0062] Wherein, v is the actual air permeability, P1 is the initial internal pressure value, P2 is the first threshold value, V is the net volume of the device under test, P0 is the atmospheric pressure, T1 is the adjustment end time, and T2 is the internal pressure recovery time.

[0063] Secondly, this application provides a valve body selection method, please refer to Figure 2 , Figure 2 1 is a flow chart of a valve body selection method provided in an embodiment of the present application. The valve body selection method includes the following steps.

[0064] S210: Provide a battery pack, where the battery pack includes a shell and a current test valve body installed on the shell.

[0065] S220: Obtaining the initial internal pressure value of the battery pack.

[0066] S230: Regulating the internal pressure of the battery pack to a first threshold, maintaining the pressure for a preset time, then stopping the regulation, and recording the end time of the regulation.

[0067] S240: Continuously detecting the internal pressure of the battery pack and recording the internal pressure recovery time when the internal pressure returns to the initial internal pressure value.

[0068] S250: Determine the actual air permeability rate of the current test valve body according to the initial internal pressure value, the first threshold value, the adjustment end time, and the internal pressure recovery time.

[0069] S260: Obtain the theoretical air permeability rate of the current test valve body.

[0070] S270: When it is determined that the current test valve body meets the design requirements of the battery pack based on the theoretical air permeability rate of the current test valve body and the actual air permeability rate of the current test valve body, the current test valve body is determined as an adapted valve body for the battery pack.

[0071] In an embodiment of the present application, after calculating the air permeability rate of the current test valve body, the theoretical air permeability rate of the current test valve body is combined to determine whether the current test valve body meets the design requirements of the battery pack. Because the actual air permeability rate is generally lower than the theoretical air permeability rate, compared to selecting a valve body based solely on the theoretical air permeability rate or the actual air permeability rate, the selection method of the present application combines the theoretical air permeability rate and the actual air permeability rate to quickly select a valve body that meets the design requirements. For example, if the actual air permeability rate is lower than the theoretical air permeability rate, it indicates that the current test valve body does not meet the battery pack design requirements, and the battery pack requires a valve body with an actual air permeability rate greater than that of the current test valve body. In this case, the valve body can be directly selected from valves with a theoretical air permeability rate greater than that of the current test valve body. This avoids selecting a valve body with a theoretical air permeability rate between the actual and theoretical air permeability rates of the current test valve body, narrowing the range of valve options and facilitating rapid valve body selection.

[0072] See also Figure 3 , Figure 3 This is a flowchart provided by an embodiment of the present application for determining whether the current test valve body meets the design requirements of the battery pack based on the theoretical air permeability rate of the current test valve body and the actual air permeability rate of the current test valve body.

[0073] In some embodiments of the present application, based on the theoretical air permeability rate of the current test valve body and the actual air permeability rate of the current test valve body, determining whether the current test valve body meets the design requirements of the battery pack includes the following steps.

[0074] S271: Calculate an air permeability deviation value σ based on the actual air permeability of the current test valve body and the theoretical air permeability of the current test valve body, σ=(|v-v0|) / v, where v0 is the theoretical air permeability;

[0075] S272: In response to the air permeability rate deviation value being less than or equal to the first deviation threshold, determining that the current test valve body meets the design requirements.

[0076] S273: In response to the air permeability rate deviation value being greater than the first deviation threshold, determining that the current test valve body does not meet the design requirements.

[0077] Because the actual air permeability rate is typically lower than the theoretical air permeability rate, simply comparing the theoretical and actual air permeability rates when determining whether the current test valve body meets design requirements will result in inaccurate valve body selection results. However, in the embodiments of the present application, the deviation between the actual and theoretical air permeability rates is calculated, and then used to determine whether the current test valve body meets design requirements. This deviation allows for a certain degree of fluctuation in the actual air permeability rate compared to the theoretical air permeability rate, making it easier to select a valve body that meets the first deviation threshold, thereby improving the accuracy of the valve body selection results.

[0078] In some embodiments of the present application, the method further includes the following steps.

[0079] S280: In response to the current test valve body not meeting the design requirements, the test valve body is replaced according to the theoretical air permeability rate of the current test valve body and the actual air permeability rate of the current test valve body, and it is determined whether the replaced test valve body meets the design requirements.

[0080] See also Figure 4 , Figure 4 This is a flow chart of replacing a test valve body according to a theoretical air permeability rate of the current test valve body and an actual air permeability rate of the current test valve body, provided in an embodiment of the present application.

[0081] In some embodiments of the present application, replacing the test valve body according to the theoretical air permeability rate of the current test valve body and the actual air permeability rate of the current test valve body includes the following steps.

[0082] S281: Compare the theoretical air permeability rate of the current test valve body and the actual air permeability rate of the current test valve body.

[0083] S282: If the theoretical air permeability rate of the current test valve body is greater than the actual air permeability rate of the current test valve body, a valve body having a theoretical air permeability rate greater than the theoretical air permeability rate of the current test valve body is selected as the replacement test valve body.

[0084] In the embodiments of the present application, if the theoretical air permeability rate of the current test valve body is greater than its actual air permeability rate, it indicates that a valve body with a higher theoretical air permeability rate should be selected as the replacement test valve body. Furthermore, a valve body selection model can be set based on the battery pack parameters. By inputting the relevant battery pack parameters into the model, the model of the valve body compatible with the battery pack can be obtained. Based on this, the present application can also introduce empirical coefficients based on the detected actual air permeability rate. Using these empirical coefficients, the valve body selection model can be modified, thereby improving the accuracy of the valve body selection results.

[0085] S283: If the theoretical air permeability rate of the current test valve body is less than the actual air permeability rate of the current test valve body, a valve body having a theoretical air permeability rate less than the theoretical air permeability rate of the current test valve body is selected as a replacement test valve body.

[0086] In an embodiment of the present application, if the theoretical air permeability rate of the current test valve body is lower than the actual air permeability rate of the current test valve body, a valve body with a lower theoretical air permeability rate can be selected as the replaced test valve body, thereby selecting a valve body that meets the design requirements to reduce the gas exchange between the battery pack and the outside world and reduce the possibility of condensation in the pack.

[0087] In some embodiments of the present application, the test valve body is replaced according to the theoretical air permeability rate of the current test valve body and the actual air permeability rate of the current test valve body, including: if the theoretical air permeability rate of the current test valve body is less than the actual air permeability rate of the current test valve body, the air tightness of the battery pack is checked.

[0088] When there is a problem with the air tightness of the battery pack, that is, there is a leakage point, the gas exchange rate inside and outside the battery pack will be accelerated, which will reduce the time taken for the internal pressure of the battery pack to return to the initial internal pressure value, resulting in an increase in the actual air permeability rate. Therefore, when the above situation occurs, the air tightness of the battery pack can be checked first, which can reduce the number of valve body tests and improve the efficiency of valve body selection.

[0089] The above is a detailed introduction to the embodiments of the present application. Specific examples are used herein to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the method and core idea of ​​the present application. At the same time, for those skilled in the art, based on the ideas of the present application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A method for detecting air permeability, characterized in that: The method is used to detect the air permeability of a valve body, wherein the valve body is provided on a device to be tested, the device to be tested has a closed inner cavity, and the valve body is in communication with the inner cavity. The method comprises: Obtaining an initial internal pressure value of the device under test; Adjusting the internal pressure of the device under test to a first threshold, maintaining the pressure for a preset time, then stopping the adjustment, and recording the end time of the adjustment; Continuously detecting the internal pressure of the device under test, and recording the internal pressure recovery time when the internal pressure returns to the initial internal pressure value; An actual air permeability rate of the valve body is determined according to the initial internal pressure value, the first threshold value, the adjustment end time, and the internal pressure recovery time.

2. The air permeability detection method according to claim 1, characterized in that: The valve body further has a valve core, which is configured to open when the internal pressure of the device under test is greater than a first preset threshold. The adjusting the internal pressure of the device under test to the first threshold includes: reducing the internal air pressure of the device under test to the first threshold.

3. The air permeability detection method according to claim 2, characterized in that: The device under test has a first connection port, which is connected to the inner cavity. The adjusting the internal pressure of the device under test to a first threshold value includes: connecting the first connection port to a vacuum device, and using the vacuum device to vacuum the inner cavity so that the internal pressure of the device under test drops to the first threshold value.

4. The air permeability detection method according to claim 3, characterized in that: The device to be tested is a battery pack, which has a high-pressure interface and a low-pressure interface. Connecting the first connection port of the device to be tested with the exhaust device includes: connecting either the high-pressure interface or the low-pressure interface to the exhaust device and sealing the other; or connecting both the high-pressure interface and the low-pressure interface to the exhaust device.

5. The air permeability detection method according to claim 4, characterized in that: The determining the actual air permeability rate of the valve body according to the initial internal pressure value, the first threshold value, the adjustment end time, and the internal pressure recovery time includes: The actual air permeability rate is calculated according to the initial internal pressure value, the first threshold value, the adjustment end time, the internal pressure recovery time, and the calculation formula of the actual air permeability rate; the calculation formula of the actual air permeability rate is: Wherein, v is the actual air permeability, P1 is the initial internal pressure value, P2 is the first threshold value, V is the net volume of the device under test, P0 is the atmospheric pressure, T1 is the adjustment end time, and T2 is the internal pressure recovery time.

6. A valve body selection method, characterized in that: include: Providing a battery pack, the battery pack comprising a housing and a current test valve body mounted on the housing; Obtaining an initial internal pressure value of the battery pack; regulating the internal pressure of the battery pack to a first threshold, maintaining the pressure for a predetermined period of time, then stopping the regulation, and recording the end time of the regulation; continuously detecting the internal pressure of the battery pack and recording the internal pressure recovery time when the internal pressure returns to the initial internal pressure value; determining an actual air permeability rate of the current test valve body according to the initial internal pressure value, the first threshold value, the adjustment end time, and the internal pressure recovery time; Obtaining a theoretical air permeability rate of the currently tested valve body; When it is determined based on the theoretical air permeability rate of the current test valve body and the actual air permeability rate of the current test valve body that the current test valve body meets the design requirements of the battery pack, the current test valve body is determined as the adapted valve body of the battery pack.

7. The valve body selection method according to claim 6, characterized in that: The determining, based on the theoretical air permeability rate of the current test valve body and the actual air permeability rate of the current test valve body, that the current test valve body meets the design requirements of the battery pack includes: Calculating a permeability deviation value σ based on the actual permeability rate of the current test valve body and the theoretical permeability rate of the current test valve body, σ=(|v-v0|) / v, where v0 is the theoretical permeability rate; In response to the air permeability deviation value being less than or equal to a first deviation threshold, it is determined that the current test valve body meets the design requirement.

8. The valve body selection method according to claim 6, characterized in that: The method further comprises: In response to the current test valve body not meeting the design requirements, the test valve body is replaced according to the theoretical air permeability rate of the current test valve body and the actual air permeability rate of the current test valve body, and it is determined whether the replaced test valve body meets the design requirements.

9. The valve body selection method according to claim 8, characterized in that: The replacing the test valve body according to the theoretical air permeability rate of the current test valve body and the actual air permeability rate of the current test valve body comprises: comparing a theoretical air permeability rate of the current test valve body with an actual air permeability rate of the current test valve body; If the theoretical air permeability rate of the current test valve body is greater than the actual air permeability rate of the current test valve body, selecting a valve body with a theoretical air permeability rate greater than the theoretical air permeability rate of the current test valve body as the replacement test valve body; If the theoretical air permeability of the current test valve body is less than the actual air permeability of the current test valve body, a valve body having a theoretical air permeability less than that of the current test valve body is selected as the replacement test valve body.

10. The valve body selection method according to claim 9, characterized in that: The replacing of the test valve body according to the theoretical air permeability rate of the current test valve body and the actual air permeability rate of the current test valve body further includes: If the theoretical air permeability rate of the current test valve body is less than the actual air permeability rate of the current test valve body, the air tightness of the battery pack is checked.

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