Equivalent testing device and testing method for expansion force of battery

Abstract

The invention discloses a battery expansive force equivalent test device and a test method. The battery expansive force equivalent test method comprises the following steps: step 1, setting independent operation parameters; step 2, performing loading, load holding and unloading tests on a battery pack shell by a loading unit according to the operation parameters; step 3, according to the cycle index in the step 1, circularly executing the step 2 and forming a maximum displacement curve of the cycle index; 4, obtaining a detection result according to the maximum displacement curve of the cycle index in the step 3; by extracting the maximum value of a displacement time curve and associating the maximum value with the cycle index, a maximum displacement curve of the cycle index is formed, and a detection result is obtained according to the maximum displacement curve, so that the limitation of traditional judgment depending on scattered and single cycle data is broken through, the maximum load-holding deformation of each cycle is systematically presented, and the deformation evolution characteristics of the shell are accurately captured; and full-cycle period visualization analysis is realized, and an actual cycle stress scene of the shell is fitted.

Description

Technical Field

[0001] This invention relates to the technical field of battery expansion force equivalent testing devices, and more particularly to a battery expansion force equivalent testing device and testing method. Background Technology

[0002] With the rapid development of power battery technology, the stability of the battery pack's casing structure, as the core carrier of power batteries, directly affects the safety and lifespan of the battery pack. During the charge and discharge cycle, the cells will undergo irreversible volume expansion. The continuous expansion force acting on the battery pack casing can easily cause problems such as casing deformation and cracking. Therefore, conducting equivalent expansion force tests on the battery pack casing to verify its resistance to expansion deformation has become a key link in battery pack R&D and mass production testing. The practicality and accuracy of related testing methods have also become a focus of industry attention.

[0003] Currently, there are existing methods in the industry for testing the expansion force of battery pack casings. Generally, a loading device is used to apply force to the casing to simulate the expansion of the battery cell. After completing simple loading, holding, and unloading operations, the passability is judged based on the deformation value of the casing. In the existing testing methods, each loading unit usually uses uniform operating parameters, which cannot differentiate parameters such as loading rate, holding time, and unloading rate according to the actual expansion characteristics of the battery cell. It is difficult to accurately simulate the real working process of battery cell expansion, full charge holding, and discharge contraction, resulting in poor working condition equivalence. Summary of the Invention

[0004] The purpose of this invention is to provide an equivalent test method for battery expansion force, in order to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: a battery expansion force equivalent test method, comprising the following steps:

[0006] Step 1: Set independent operating parameters for each loading unit. The operating parameters include loading rate, holding time, unloading rate, target force value, and number of cycles. The target force value is the expansion force acting on the battery pack casing. The loading rate is used to simulate the rate of cell expansion, the unloading rate is used to simulate the rate of cell volume contraction after discharge, and the holding time is used to simulate the continuous expansion time of the cell in a fully charged state.

[0007] Step 2: The loading unit performs loading, load holding, and unloading tests on the battery pack casing according to the operating parameters;

[0008] Step 3: Based on the number of iterations in Step 1, repeat Step 2 repeatedly and generate the maximum displacement curve for the maximum number of iterations.

[0009] Step 4: Obtain the test results based on the maximum displacement curve of the number of cycles in Step 3; if the first part of the maximum displacement curve of the number of cycles gradually increases and the second part of the curve tends to be stable, and the maximum value of the maximum displacement curve of the number of cycles does not exceed the design deformation limit of the battery pack shell, then the battery pack shell is qualified; otherwise, the battery pack shell is unqualified.

[0010] Compared with existing technologies, the beneficial effects of this solution are: 1) This technical solution configures independent operating parameters for each loading unit, and the operating parameters can be specifically matched to the actual working characteristics of cell expansion rate, full charge holding time, and discharge contraction rate, realizing the equivalent simulation of the real working condition of the battery pack shell under the action of expansion force, solving the technical problem of distortion in traditional test condition simulation and disconnection from actual use scenarios, and greatly improving the authenticity and accuracy of expansion force test.

[0011] 2) The cyclic test of loading, holding, and unloading generates the maximum displacement curve after the number of cycles. Based on the trend of the curve increasing at the beginning and stabilizing at the end, and the dual judgment criteria that the maximum value does not exceed the design deformation limit, the passability test is completed. This breaks through the limitations of traditional tests that rely on a single numerical judgment and cannot reflect the deformation evolution law of the shell under the action of cyclic expansion force. It can accurately capture the deformation characteristics of the shell in multiple expansion and contraction cycles, effectively avoid the misjudgment and omission problems caused by single judgment, and significantly improve the comprehensiveness and reliability of the test results.

[0012] In a preferred embodiment of the present invention, during the loading process in step two, the pressure sensor in the loading unit collects the pressure value acting on the battery pack casing and the time point corresponding to the pressure value collected by the pressure sensor in real time. The actual loading rate is obtained by the pressure change and the time change. The actual loading rate is compared with the loading rate, and the running speed of the driver in the loading unit is adjusted according to the comparison result so that the actual loading rate and the loading rate are matched.

[0013] Compared with existing technologies, the beneficial effects of this solution are as follows: 1) During the loading process, this technical solution collects pressure values ​​and corresponding time points in real time through pressure sensors, calculates the actual loading rate, compares it with the set loading rate, and adjusts the driver's running speed, thereby achieving dynamic and precise control of the loading rate. This solves the problem that the loading unit is prone to deviation from the set value due to equipment deviation and shell force feedback in traditional testing, and allows the actual loading rate to be precisely matched with the set loading rate for simulating cell expansion, greatly improving the accuracy of the working condition simulation of the battery expansion force equivalent test.

[0014] 2) This technical solution constructs a closed-loop control mechanism for the loading process, which includes real-time acquisition, rate calculation, comparison and adjustment. It breaks through the technical limitation that open-loop loading in traditional expansion force testing cannot be corrected in real time. It effectively avoids loading rate fluctuations caused by equipment operation deviations, external interference and other factors, and ensures the rate stability of the entire loading process. This makes the loading process of the battery pack casing subjected to expansion force more closely match the actual expansion rate change characteristics of the battery cell.

[0015] In a preferred embodiment of the present invention, when the pressure value collected by the pressure sensor in the loading unit matches the target force value, the load holding step in step two is executed. During the load holding process, the displacement sensor in the loading unit collects the offset value of the battery pack housing in real time, and forms a displacement-time curve based on the load holding time and the offset value. At the same time, the pressure sensor in the loading unit collects the actual force value acting on the battery pack housing in real time, and forms a force-time curve based on the load holding time and the actual force value.

[0016] Compared to existing technologies, the advantages of this solution are that the displacement-time curve and force-time curve generated by this solution can supplement the generation of the maximum displacement curve for subsequent cycles with refined measured data during the load-holding stage, making the overall deformation analysis of the battery pack casing more consistent with actual usage scenarios. It can also provide multi-dimensional data support for judging the structural stability and deformation trend of the casing under continuous expansion force, and provide accurate measured basis for the structural optimization and expansion force tolerance design of the battery pack casing, further enhancing the technical reference value of the entire battery expansion force equivalent test.

[0017] In a preferred embodiment of the present invention, the force deviation rate is obtained based on the force-time curve, and the driver in the loading unit is adjusted in a timely manner to keep the force deviation rate within the range of ±1%.

[0018] Compared to existing technologies, the advantages of this solution are that it precisely controls the load-bearing force deviation rate within ±1%, ensuring that the deformation data acquisition of the battery pack casing during the load-bearing stage is based on a stable and accurate force value. This avoids displacement detection errors caused by force fluctuations, further improving the authenticity of the displacement-time curve and the reliability of the detection data. It provides high-precision data support for the generation of the maximum displacement curve for subsequent cycles and the determination of casing qualification. At the same time, the standardized deviation rate control method is compatible with automated testing processes, improving the standardization level of the entire battery expansion force equivalent test and the reference value of the test results.

[0019] In a preferred embodiment of the present invention, when the load reaches the set time, the unloading in step two is performed. During the unloading process, the pressure sensor in the loading unit collects the pressure value in real time. The actual unloading rate is obtained by the pressure change and the time change. The actual unloading rate and the loading rate are compared, and the running speed of the driver is adjusted according to the comparison result.

[0020] Compared to existing technologies, this solution offers several advantages. It achieves automated and precise control of the unloading rate, enabling rate correction without manual intervention. This reduces control errors caused by human operation, improves the automation level and efficiency of the entire battery expansion force equivalent test, and ensures that the loading-holding-unloading rate precisely matches the actual expansion and contraction characteristics of the battery cell. This avoids detection errors in casing deformation recovery caused by unloading rate deviations, further enhancing the authenticity of the maximum displacement curve over the number of cycles. This provides more reliable full-process measured data support for determining the qualification of the battery pack casing.

[0021] In a preferred embodiment of the present invention, a maximum displacement curve with a maximum number of cycles is formed based on the maximum value in the displacement-time curve and the number of cycles, and the detection result is obtained based on the maximum displacement curve with a maximum number of cycles.

[0022] Compared with existing technologies, the beneficial effects of this solution are as follows: 1) This technical solution extracts the maximum value in the displacement-time curve and correlates it with the number of cycles to form the maximum displacement curve of the number of cycles, and directly obtains the detection results based on this curve. This solves the problems of lack of specificity in the selection of detection data in traditional tests, lack of focus on the core deformation data in the load-holding stage, and low correlation between the data and the number of cycles. It realizes the accurate coupling modeling of core deformation data and the number of cyclic tests, so that the curve can truly reflect the core deformation law of the battery pack shell under multiple expansion and contraction cycles, which greatly improves the specificity and authenticity of the detection data modeling.

[0023] 2) This technical solution breaks through the limitations of traditional battery expansion force testing, which relies on scattered deformation data and single cycle data to determine the qualification of the casing. By using the maximum displacement curve of the number of cycles, the maximum deformation of the battery pack casing in each cycle of load holding stage is systematically presented. It can accurately capture the deformation evolution characteristics of the casing under repeated expansion force, and realize the full cycle visualization analysis of the casing deformation law, making the detection dimension more in line with the actual cyclic stress scenario of the casing.

[0024] In a preferred embodiment of the present invention, if the maximum value in the displacement-time curve exceeds the design deformation limit of the battery pack housing during step three, it indicates that the battery pack housing is unqualified, and subsequent testing should be stopped immediately.

[0025] Compared with existing technologies, the beneficial effects of this solution are: 1) This technical solution monitors the maximum value of the displacement-time curve in real time during the cyclic test. Once the value exceeds the design deformation limit of the battery pack casing, it is judged as unqualified and subsequent tests are stopped immediately. This solves the problems of traditional tests that require all cycles to be completed before the qualification judgment is made, which easily generates a large number of invalid tests and cannot identify early failures of the casing in time. It realizes the real-time and accurate judgment of the unqualified state of the casing, greatly improves the timeliness and pertinence of the test judgment, and can quickly screen out casings with structural defects.

[0026] 2) This technical solution, through its design of immediate stop testing at the extreme limit, directly eliminates the meaningless subsequent cyclic testing process for unqualified casings, significantly reducing invalid testing time, equipment operating losses and testing energy consumption, effectively improving the overall efficiency of batch testing of battery pack casings, while avoiding secondary damage to the casings, making the conclusions of structural failure analysis more in line with the essence of the actual problem, and providing more valuable experimental basis for structural defect investigation and design optimization of battery pack casings, adapting to the actual needs of industrial-scale batch testing.

[0027] In a preferred embodiment of the present invention, before performing step one, the force sensor in the loading unit is calibrated using standard weights and the displacement sensor in the loading unit is zeroed.

[0028] Compared to existing technologies, the beneficial effects of this solution are that the force sensor of the loading unit is calibrated with standard weights before the test, and the displacement sensor is zeroed. This solves the problem that traditional tests do not perform accurate pre-calibration of the core sensors, and the test data acquisition is easily distorted due to sensor zero drift and accuracy deviation. It realizes the standardized pre-calibration of the two types of core sensors, force and displacement, and eliminates system errors from the source of data acquisition, which greatly improves the accuracy and authenticity of the test basic data acquisition.

[0029] The present invention also provides a battery expansion force equivalent testing device for performing the battery expansion force equivalent testing method according to any one of claims 1-8, characterized in that: it includes a fixed platform and a support frame installed on the fixed platform, the fixed platform is provided with a pressure plate clamp for fixing the battery casing, and a plurality of loading units are slidably installed on the support frame.

[0030] Compared to existing technologies, the advantages of this solution are that the test device is designed as a fixed platform with a supporting frame as its basic structure. The battery pack housing is stably fixed by a pressure plate clamp, and several loading units are slidably configured on the supporting frame. This solves the problems of poor housing stability and fixed and inflexible loading unit placement in traditional test devices. It ensures the positioning accuracy of the battery pack housing during testing and enables flexible adaptation of the loading unit installation position, greatly improving the adaptability of the device to battery pack housings of different specifications and with different stress distribution requirements.

[0031] In a preferred embodiment of the present invention, the loading unit includes a planetary reducer, an electric cylinder is fixedly installed at one end of the planetary reducer, a front pressure head is fixedly installed at the other end of the planetary reducer, a driver is fixedly installed at the input end of the planetary reducer, a hinge pressure head is fixedly installed at the output end of the electric cylinder, a pressure sensor is installed between the hinge pressure head and the output end of the electric cylinder, and four fixed columns are fixedly connected between the front pressure head and the electric cylinder.

[0032] Compared to existing technologies, this solution offers several advantages. The loading unit is equipped with a planetary reducer and a driver. A pressure sensor is installed between the output end of the electric cylinder and the hinge pressure head. Four fixed columns connect the front pressure head and the electric cylinder. This solves the problems of low transmission accuracy, easy interference from installation gaps in force value acquisition, and insufficient structural rigidity in traditional loading units. It achieves precise transmission of loading power and direct and accurate acquisition of the force value acting on the housing. At the same time, it enhances the structural stability of the loading unit and significantly improves the dual accuracy of force loading and acquisition.

[0033] In addition to the technical problems solved by the present invention, the technical features constituting the technical solutions, and the advantages brought about by the technical features of these technical solutions as described above, other technical problems that the present invention can solve, other technical features contained in the technical solutions, and the advantages brought about by these technical features will be further described in detail with reference to the accompanying drawings. Attached Figure Description

[0034] Figure 1 This is a perspective view of the battery expansion force equivalent testing device of the present invention.

[0035] Figure 2 This is a cross-sectional view of the loading unit in the battery expansion force equivalent testing device of the present invention.

[0036] Figure 3 This is a flowchart of the battery expansion force equivalent test method of the present invention.

[0037] Figure 4 This is a schematic diagram of the force-time curve in the battery expansion force equivalent test method of the present invention.

[0038] Figure 5This is a schematic diagram of the displacement-time curve in the battery expansion force equivalent test method of the present invention.

[0039] Figure 6 This is a schematic diagram of the maximum displacement curve after a number of cycles in the battery expansion force equivalent test method of the present invention.

[0040] The following are the reference numerals: 01. Fixed platform, 02. Support frame, 03. Loading unit, 04. Electric cylinder, 05. Planetary reducer, 06. Front pressure head, 07. Driver, 08. Hinge pressure head, 09. Pressure sensor, 10. Fixed column, 11. Pressure plate, 12. Connecting ball, 13. Spherical cavity. Detailed Implementation

[0041] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings.

[0042] Please see Figure 1 As shown, the battery expansion force equivalent testing device provided in this embodiment includes a fixed platform 01 and a support frame 02 installed on the fixed platform 01. The fixed platform 01 is equipped with a pressure plate clamp for fixing the battery casing. The pressure plate clamp is prior art and will not be described in detail here; for example, it is disclosed in publication number CN216695450U, entitled "A Clamp for a Battery Pack Casing Leak Detection Device." The support frame 02 is equipped with multiple loading units 03; in this embodiment, three loading units 03 are provided, located between the fixed platform 01 and the support frame 02. In use, the battery pack casing to be tested is fixed to the fixed platform 01 using the pressure plate clamp, and then the loading unit 03 is placed inside the battery pack casing and connected to the support frame 02. Once the loading unit 03 is installed, the expansion force equivalent test of the battery pack casing can be performed.

[0043] Please see Figure 2As shown, the loading unit 03 includes a planetary reducer 05. An electric cylinder 04 is fixedly mounted at one end of the planetary reducer 05, and a front pressure head 06 is fixedly mounted at the other end. The lead screw inside the electric cylinder 04 is fixedly connected to the output end of the planetary reducer 05. A driver 07, preferably a servo motor, is fixedly mounted on the input end of the planetary reducer 05. A hinge pressure head 08 is fixedly mounted at the output end of the electric cylinder 04. A pressure sensor 09 is installed between the hinge pressure head 08 and the output end of the electric cylinder 04. Four fixed posts 10 are fixedly connected between the front pressure head 06 and the electric cylinder 04. The hinge pressure head 08 includes a pressure plate 11 and a connecting ball 12 installed within the pressure plate 11. A spherical cavity 13 adapted to the connecting ball 12 is provided within the pressure plate 11, and a connecting post fixedly connected to the pressure sensor 09 is provided on the connecting ball 12. The power of the driver 07 is amplified and reduced by the reducer and then transmitted to the lead screw in the electric cylinder. The rotational motion of the lead screw is converted into the linear motion of the nut, thereby pushing the piston rod and the hinge pressure head 08 at the end to move towards the battery pack housing.

[0044] A slide rail is fixedly mounted on the outer surface of the electric cylinder 04, and a slider is slidably mounted on the slide rail. Stops are fixed at both ends of the slide rail to prevent the slider from detaching from it. The support frame 02 has two parallel elongated holes. After the loading unit 03 is placed inside the battery pack housing, fasteners are passed through the elongated holes on the support frame 02 and connected to the slider, thus fixing the loading unit 03 to the support frame 02. Because the slider and slide rail are slidably connected, when the loading unit 03 is working, regardless of whether the front pressure head 06 or the hinge pressure head 08 contacts the battery pack housing first, the loading unit 03 can move in the opposite direction. For example, if the hinge pressure head 08 contacts the battery pack housing first, the loading unit 03 continues to work, moving in the opposite direction to the hinge pressure head 08 until the front pressure head 06 contacts the battery pack housing.

[0045] Please see Figure 3 As shown, this embodiment also provides a battery expansion force equivalent test method, including the following steps:

[0046] Step 1: Calibrate the pressure sensor and displacement sensor on loading unit 03. Use standard weights to calibrate the force sensor (ensure the force value accuracy is ≤ ±0.5%FS); perform zero calibration on the displacement sensor (ensure the displacement accuracy is ≤ 0.1%FS).

[0047] Based on the different test locations within the battery pack casing, corresponding operating parameters are set. These parameters include loading rate, holding time, unloading rate, target force value, and number of cycles. For example, to perform equivalent battery expansion force tests at three locations within a battery pack casing, three loading units 03 are placed inside the battery pack casing. Corresponding operating parameters are then set for each of the three loading units 03. The operating parameters for each loading unit 03 may be the same or different. The target force value is the expansion force acting on the battery pack casing; the loading rate simulates the rate of cell expansion; the unloading rate simulates the rate of cell volume contraction after discharge; and the holding time simulates the continuous expansion time of the cell in a fully charged state.

[0048] Step 2: Load the battery pack casing under test. During the loading process, the pressure sensor 09 in the loading unit 03 collects the pressure value acting on the battery pack casing in real time and the time point corresponding to the pressure value collected by the pressure sensor. The actual loading rate is obtained by the pressure change and the time change. The actual loading rate is compared with the loading rate, and the running speed of the driver 07 in the loading unit 03 is adjusted according to the comparison result.

[0049] The actual loading rate is calculated using the following formula: Actual loading rate = Pressure change / Time change. Pressure change = Final pressure - Initial pressure; Time change = Final time - Initial time. For example, if the time point corresponding to the pressure value collected by the pressure sensor is t1, and the pressure value collected by the pressure sensor at this time is P0 (when the loading unit just contacts the battery pack casing), and the next pressure value collected by the pressure sensor is P1, then the time point corresponding to pressure value P1 is t2. Therefore, pressure change = P1 - P0; time change = t2 - t1.

[0050] When the pressure value collected by the pressure sensor 09 in the loading unit 03 matches the target force value, during the load holding phase, the displacement sensor in the loading unit 03 collects the offset value of the battery pack casing in real time, and a displacement-time curve is formed by the load holding time and the offset value (e.g., ...). Figure 5 As shown), the actual force acting on the battery pack casing is collected in real time by pressure sensor 09, and a force-time curve is generated based on the load holding time and the actual force value (as shown). Figure 4 (As shown). The force deviation rate is obtained from the force value time curve. Force deviation rate = (actual force value - target force value) / target force value × 100%. Ensure that the force deviation rate is always ≤ ±1%. If the force deviation rate is > ±1%, the actual force value is adjusted in time by the driver 07 in the loading unit 03.

[0051] It should be noted that during the load holding phase, the force value acting on the battery pack casing is collected in real time by the pressure sensor 09. The purpose is to ensure that the actual force value acting on the battery pack casing matches the target force value.

[0052] When the load reaches the set time, the load is unloaded. During the unloading process, the pressure value is collected in real time by the pressure sensor 09. The actual unloading rate is obtained by the pressure change and the time change. The actual unloading rate is compared with the loading rate, and the running speed of the driver is adjusted according to the comparison result.

[0053] Step 3: Repeat Step 2 based on the number of iterations; obtain the maximum displacement curve based on the maximum value in the displacement-time curve from Step 2 and the number of iterations from Step 1 (e.g., ...). Figure 6 (as shown)

[0054] Step 4: Obtain the test results based on the maximum displacement curve obtained in Step 3 after the number of cycles. If the first part of the maximum displacement curve gradually increases and the second part tends to stabilize, and the maximum displacement does not exceed the design deformation limit of the battery pack casing, it indicates that the battery pack casing structure has good creep resistance. If the displacement continues to increase and exceeds the limit value, it indicates that there is a durability risk in the structure. During the execution of Step 3, if the maximum value in the displacement-time curve exceeds the design deformation limit of the battery pack casing, it indicates that the battery pack casing is unqualified, and subsequent testing should be stopped immediately. For example, if the number of cycles is 1000, during the execution of Step 3, when the maximum value of the displacement-time curve is found to exceed the design deformation limit of the battery pack casing after 600 cycles of Step 2, subsequent testing should be stopped immediately.

[0055] If the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indications will also change accordingly.

[0056] The above embodiments are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for equivalent testing of battery expansion force, characterized in that, Includes the following steps: Step 1: Set independent operating parameters for each loading unit. The operating parameters include loading rate, holding time, unloading rate, target force value, and number of cycles. The target force value is the expansion force acting on the battery pack casing. The loading rate is used to simulate the rate of cell expansion, the unloading rate is used to simulate the rate of cell volume contraction after discharge, and the holding time is used to simulate the continuous expansion time of the cell in a fully charged state. Step 2: The loading unit performs loading, load holding, and unloading tests on the battery pack casing according to the operating parameters; Step 3: Based on the number of iterations in Step 1, repeat Step 2 repeatedly and generate the maximum displacement curve for the maximum number of iterations. Step 4: Obtain the test results based on the maximum displacement curve of the number of cycles in Step 3; if the first part of the maximum displacement curve of the number of cycles gradually increases and the second part of the curve tends to be stable, and the maximum value of the maximum displacement curve of the number of cycles does not exceed the design deformation limit of the battery pack shell, then the battery pack shell is qualified; otherwise, the battery pack shell is unqualified.

2. The battery expansion force equivalent test method according to claim 1, characterized in that: During the loading process in step two, the pressure sensor in the loading unit collects the pressure value acting on the battery pack casing in real time and the time point corresponding to the pressure value collected by the pressure sensor. The actual loading rate is obtained by the pressure change and the time change. By comparing the actual loading rate with the loading rate, the running speed of the driver in the loading unit is adjusted according to the comparison result to make the actual loading rate match the loading rate.

3. The battery expansion force equivalent test method according to claim 2, characterized in that: When the pressure value collected by the pressure sensor in the loading unit matches the target force value, the load holding process in step two is executed. During the load holding process, the displacement sensor in the loading unit collects the offset value of the battery pack housing in real time and forms a displacement-time curve based on the load holding time and the offset value. At the same time, the pressure sensor in the loading unit collects the actual force value acting on the battery pack housing in real time and forms a force-time curve based on the load holding time and the actual force value.

4. The battery expansion force equivalent test method according to claim 3, characterized in that: The force deviation rate is obtained from the force-time curve, and the driver in the loading unit is adjusted in time to keep the force deviation rate within ±1%.

5. The battery expansion force equivalent test method according to claim 3, characterized in that: Once the load has been maintained for the set time, the unloading process in step two is executed. During the unloading process, the pressure sensor in the loading unit collects the pressure value in real time. The actual unloading rate is obtained by measuring the pressure change and the time change. The actual unloading rate is compared with the loading rate, and the running speed of the driver is adjusted according to the comparison result.

6. The battery expansion force equivalent test method according to claim 3, characterized in that: The maximum displacement curve with the number of cycles is formed based on the maximum value in the displacement-time curve and the number of cycles. The detection result is obtained based on the maximum displacement curve with the number of cycles.

7. The battery expansion force equivalent test method according to claim 3, characterized in that: If the maximum value in the displacement-time curve exceeds the design deformation limit of the battery pack casing during step three, it indicates that the battery pack casing is unqualified, and subsequent tests should be stopped immediately.

8. The battery expansion force equivalent test method according to claim 1, characterized in that: Before performing step one, the force sensor in the loading unit is calibrated using standard weights, and the displacement sensor in the loading unit is zeroed.

9. A battery expansion force equivalent testing device, used to perform the battery expansion force equivalent testing method according to any one of claims 1-8, characterized in that: It includes a fixed platform and a support frame installed on the fixed platform. The fixed platform is equipped with a pressure plate clamp for fixing the battery casing, and several loading units are slidably installed on the support frame.

10. The battery expansion force equivalent testing device according to claim 9, characterized in that: The loading unit includes a planetary reducer, an electric cylinder is fixedly mounted on one end of the planetary reducer, a front pressure head is fixedly mounted on the other end of the planetary reducer, a driver is fixedly mounted on the input end of the planetary reducer, a hinge pressure head is fixedly mounted on the output end of the electric cylinder, a pressure sensor is installed between the hinge pressure head and the output end of the electric cylinder, and four fixed columns are fixedly connected between the front pressure head and the electric cylinder.

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