Battery cell cycle test tool design method, test tool and test method

Abstract

The invention relates to the technical field of batteries, in particular to a battery cell cycle test tool design method, a test tool and a test method.The battery cell cycle test tool design method comprises the following steps that cycle test is conducted on a battery pack, and the constraint rigidity of a battery cell in the battery pack in the cycle process is obtained; determining the equivalent stiffness of the cycle test tool of the battery cell according to the constraint stiffness; and designing a cycle test tool according to the equivalent stiffness. Thus, the designed cycle test tool can provide the extrusion force with the same change as that in the battery pack for the to-be-tested battery cell in the cycle test process, the cycle test state of the battery cell in the battery pack is simulated, and therefore the cycle test stress state of the single battery cell is kept consistent with the stress state of the single battery cell in the battery pack; and the test result of the single battery cell can more accurately represent the cycle performance of the battery cell in the battery pack.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery cell cycle test fixture design method, a test fixture and a test method. Background Art

[0002] With the development of the new energy vehicle industry, the performance of its important component, batteries, has received increasing attention. The research on battery performance is often achieved through testing. Testing the entire battery pack requires a certain number of cells, and the testing cost is relatively high. In order to reduce the testing cost, battery manufacturers estimate the performance of single cells in the battery pack through performance testing of single cells. Ensuring that the stress state of the single cell in the cycle test is consistent with its stress state in the battery pack is an important prerequisite for the single cell test results to characterize its performance in the battery pack.

[0003] The magnitude of the force applied during the cycle test of a single battery cell is closely related to the stiffness of the cycle test fixture. The greater the stiffness of the fixture, the greater the cycle force applied to the battery cell. It is critical to design a suitable fixture to restore the force applied to the battery cell in the battery pack. Currently, the existing technical solutions do not design and select the stiffness of the battery cell cycle test. Steel or aluminum fixtures with a uniform structural type are used as cycle test fixtures for different single battery cells. The fixture only considers whether the size of the fixture can accommodate the battery cell to be tested. Therefore, during the cycle test of a single battery cell using the existing battery cell cycle test fixture, the battery cell often has the problem of excessive restraint. Summary of the invention

[0004] The present application provides a battery cell cycle test tool design method, a test tool and a test method, which are used to solve the problem in the prior art that the single battery cell cycle test tool cannot accurately simulate the stress state of the battery cell in the battery pack.

[0005] On the one hand, the present application provides a battery cell cycle test fixture design method, comprising:

[0006] Perform cycle tests on the battery pack to obtain the constraint stiffness of the cells in the battery pack during the cycle;

[0007] Determine the equivalent stiffness of the battery cell's cyclic test fixture based on the constraint stiffness;

[0008] Design the cyclic test fixture based on the equivalent stiffness.

[0009] In one possible design, the battery pack is subjected to a cycle test to obtain the restraint stiffness of the cells in the battery pack during the cycle, including:

[0010] Perform cycle test on the battery pack for a preset time;

[0011] Determine the pressure change of a single cell in the battery pack before and after the cycle;

[0012] Determine the thickness change of a single cell in a battery pack before and after cycling;

[0013] The constraint stiffness is determined according to the pressure change value and the thickness change value.

[0014] In one possible design, the pressure change value of a single cell in the battery pack before and after the cycle is determined, including:

[0015] Measure the initial pressure of the battery cell located in the center of the battery pack before cycling;

[0016] Measure the current pressure of the battery cell located at the center of the battery pack after cycling;

[0017] The pressure change value is determined based on the initial pressure and the current pressure.

[0018] In one possible design, the thickness change of a single cell in the battery pack before and after cycling is determined, including:

[0019] Measure the initial average thickness of the cells in the battery pack before cycling;

[0020] Measure the current average thickness of the cells in the battery pack after cycling;

[0021] The thickness change value is determined according to the initial average thickness and the current average thickness.

[0022] In one possible design, a cyclic test fixture is designed according to the equivalent stiffness, including: determining an elastic coefficient of the cyclic test fixture according to the equivalent stiffness.

[0023] In one possible design, the cyclic test fixture is designed according to the equivalent stiffness, and the method further includes: determining an initial position of the cyclic test fixture according to an initial pressure.

[0024] In one possible design, the cyclic test fixture is designed based on the equivalent stiffness, and further includes: determining the elastic limit of the cyclic test fixture based on the current pressure.

[0025] On the other hand, the present application also provides a battery cell cycle test tool, which is manufactured by the battery cell cycle test tool design method as described above, and the tool includes:

[0026] A pressing plate, used to abut against the surface of the battery cell to be tested;

[0027] The spring, one end of which is connected to the pressure plate, can change the extrusion force between the pressure plate and the battery cell to be tested through expansion and contraction deformation. The elastic coefficient of the spring is the equivalent stiffness of the tooling.

[0028] In one possible design, the tooling also includes:

[0029] Support seat, used to place the battery cell to be tested;

[0030] A guide rod is arranged on the support seat, and the guide rod is slidably connected with the pressure plate;

[0031] The base plate is detachably mounted on the guide rod and is connected to the other end of the spring.

[0032] On the other hand, the present application also provides a battery cell cycle testing method, which uses the battery cell cycle testing tooling as described above to perform cycle testing on the battery cell.

[0033] The beneficial effects of this application are as follows:

[0034] The battery cell cycle test fixture design method of the present application obtains the constraint stiffness of the battery cells in the battery pack during the cycle process, determines the equivalent stiffness of the battery cell cycle test fixture according to the constraint stiffness, and then designs the cycle test fixture according to the equivalent stiffness. In this way, the designed cycle test fixture can provide the battery cell to be tested with the same varying extrusion force as in the battery pack during the cycle test, simulate the state of the battery cell undergoing cycle test in the battery pack, thereby keeping the stress state of the single battery cell during the cycle test consistent with its stress state in the battery pack, which is conducive to making the test results of the single battery cell more accurately characterize its cycle performance in the battery pack.

[0035] The battery cell cycle test tool provided in the present application is manufactured by the battery cell cycle test tool design method in the present application, and therefore, it also includes all the above-mentioned advantages of the battery cell cycle test tool design method.

[0036] The battery cell cycle testing method provided in the present application uses the battery cell cycle testing tooling of the present application to perform cycle testing on the battery cells, and therefore includes all the above-mentioned advantages of the battery cell cycle testing tooling. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0038] Figure 1 A flow chart of a battery cell cycle test fixture design method provided in an embodiment of the present application;

[0039] Figure 2 A schematic diagram of the state of the battery cells in the battery pack before cycling in the battery cell cycle test tooling design method provided in an embodiment of the present application;

[0040] Figure 3 A schematic diagram of the state of the battery cells in the battery pack after cycling in the battery cell cycle test tooling design method provided in an embodiment of the present application;

[0041] Figure 4 A schematic diagram of the structure of the battery cell cycle test tooling provided in an embodiment of the present application.

[0042] Reference numerals:

[0043] 100, thin film pressure sensor; 210, first displacement sensor; 220, second displacement sensor; 310, left end plate; 320, right end plate; 410, pressure plate; 420, spring; 430, support seat; 440, guide rod; 450, substrate; 500, battery cell to be tested. DETAILED DESCRIPTION

[0044] The technical solution of the present application will be described clearly and completely below in conjunction with the embodiments. Obviously, the described embodiments are 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 ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0045] Figure 1 A flowchart of a method for designing a battery cell cycle test tooling provided in one embodiment of the present application.

[0046] Reference Figure 1 As shown, the battery cell cycle test fixture design method provided in the embodiment of the present application includes the following steps:

[0047] Step S100, performing a cycle test on the battery pack to obtain the constraint stiffness of the battery cells in the battery pack during the cycle;

[0048] Step S200, determining the equivalent stiffness of the cycle test fixture of the battery cell according to the constraint stiffness;

[0049] Step S300: design a cyclic test tool according to the equivalent stiffness.

[0050] Specifically, in step S200, the constraint stiffness of the battery cell in the battery pack is equal to the equivalent stiffness of the cycle test fixture.

[0051] By utilizing the technical solution provided in the above-mentioned embodiments of the present application, by obtaining the constraint stiffness of the battery cells in the battery pack during the cycle process, the equivalent stiffness of the cycle test fixture of the battery cells is determined according to the constraint stiffness, and then the cycle test fixture is designed according to the equivalent stiffness. In this way, the designed cycle test fixture can provide the battery cells to be tested with the same varying extrusion force as in the battery pack during the cycle test, simulating the state of the battery cells undergoing cycle testing in the battery pack, thereby keeping the stress state of the single battery cell during the cycle test consistent with its stress state in the battery pack, which is conducive to making the test results of the single battery cell more accurately characterize its cycle performance in the battery pack.

[0052] In some specific embodiments of the present application, step S100 specifically includes the following steps:

[0053] Step S110, performing a cycle test on the battery pack for a preset time;

[0054] Step S120, determining a pressure change value of a single cell in the battery pack before and after the cycle;

[0055] Step S130, determining a thickness change value of a single cell in the battery pack before and after the cycle;

[0056] Step S140: determining the constraint stiffness according to the pressure change value and the thickness change value.

[0057] Specifically, in step S110, the battery pack is subjected to a cycle test for a preset time, wherein the cycle test refers to a certain number of charge and discharge cycles of the battery pack. The preset time can be understood as the number of charge and discharge cycles, and specifically, the preset time is the period from the start of the charge and discharge cycle of the battery pack to the time when the thickness of the battery cell changes significantly and can be accurately measured.

[0058] Specifically, in step S140, the specific formula for determining the constraint stiffness according to the pressure change value and the thickness change value is:

[0059] k′=ΔF / Δt; (1)

[0060] In formula (1), k′ is the constraint stiffness; ΔF is the pressure change value; Δt is the thickness change value;

[0061] In this way, by measuring the pressure change value of a single battery cell in the battery pack before and after the cycle, and the thickness change value of a single battery cell in the battery pack before and after the cycle, the external constraint stiffness of the single battery cell in the battery pack during the cycle process can be obtained. Therefore, by reasonably increasing the equivalent stiffness equivalent to the external constraint stiffness in the single battery cell cycle test, it is possible to ensure that the stress state of the single battery cell in the cycle test is consistent with its stress state in the battery pack, which is conducive to making the test results of the single battery cell more accurately characterize its cycle performance in the battery pack.

[0062] In some specific embodiments of the present application, step S120 specifically includes the following steps:

[0063] Step S121, measuring the initial pressure of the battery cell at the center of the battery pack before cycling;

[0064] Step S122, measuring the current pressure of the battery cell located at the center of the battery pack after the cycle;

[0065] Step S123: determine the pressure change value according to the initial pressure and the current pressure.

[0066] Specifically, in step S121, the film pressure sensor 100 is used to measure the initial pressure of the battery cell at the center of the battery pack before the cycle. Since the thickness of the film pressure sensor 100 is very small, the thickness of the film pressure sensor 100 itself is basically ignored, thereby ensuring the accuracy of the measurement data. Figure 2 As shown, the thin film pressure sensor 100 is arranged on one side of the battery cell located at the center of the battery pack (if the total number of battery cells in the battery pack is an even number, the thin film pressure sensor 100 is arranged between the two middle battery cells for pressure testing). Before the battery pack is cycled, the initial pressure F0 on the thin film pressure sensor 100 is read;

[0067] In step S122, the thin film pressure sensor 100 is also used to measure the current pressure of the battery cell located at the center of the battery pack after the cycle. Figure 3 As shown, after the battery pack is cycle tested, the current pressure F1 on the thin film pressure sensor 100 is read;

[0068] In step S123, the specific formula for determining the pressure change value according to the initial pressure and the current pressure is:

[0069] ΔF=F1-F0 (2)

[0070] In formula (2), ΔF is the pressure change value; F0 is the initial pressure; F1 is the current pressure;

[0071] In this way, by setting a thin film pressure sensor 100 at the battery cell at the center of the battery pack, and using the thin film pressure sensor 100 to measure the initial pressure of the battery cell at the center of the battery pack before the cycle and the current pressure after the cycle, the pressure difference from the battery pack shell to the battery cell at the center before and after the cycle test can be obtained. At the same time, by measuring the pressure of the battery cell at the center of the battery pack, since the battery cell at the center is subjected to more uniform force, it is helpful to make the measured pressure data closer to the real pressure data.

[0072] In some specific embodiments of the present application, step S130 specifically includes the following steps:

[0073] Step S131, measuring the initial average thickness of the battery cells in the battery pack before cycling;

[0074] Step S132, measuring the current average thickness of the battery cells in the battery pack after cycling;

[0075] Step S133, determining the thickness change value according to the initial average thickness and the current average thickness.

[0076] Specifically, in step S131, a displacement sensor is used to measure the initial average thickness of the battery cells in the battery pack before cycling. Figure 2 As shown, in some specific embodiments, the displacement sensor includes two, namely a first displacement sensor 210 and a second displacement sensor 220, wherein the first displacement sensor 210 is arranged between the leftmost battery cell and the left end plate 310 of the battery pack, and the second displacement sensor 220 is arranged between the rightmost battery cell and the right end plate 320 of the battery pack. Before the battery pack is cycle tested, the initial distance a0 between the left end plate 310 and the right end plate 320 is obtained by readings of the first displacement sensor 210 and the second displacement sensor 220;

[0077] The initial average thickness of a single cell is t0, which is calculated by the following formula:

[0078] t0=a0 / n (3)

[0079] In formula (3), t0 is the initial average thickness of a single battery cell; a0 is the initial distance between the left end plate 310 and the right end plate 320; n is the number of battery cells in the battery pack;

[0080] In step S132, the displacement sensor is also used to measure the current average thickness of the battery cells in the battery pack after the cycle. Figure 3 As shown, after the battery pack is cycle tested, the current distance a1 between the left end plate 310 and the right end plate 320 is obtained through the readings of the first displacement sensor 210 and the second displacement sensor 220;

[0081] The current average thickness of a single cell is t1, which is calculated by the following formula:

[0082] t1=a1 / n (4)

[0083] In formula (4), t1 is the current average thickness of a single battery cell; a1 is the current distance between the left end plate 310 and the right end plate 320; n is the number of battery cells in the battery pack;

[0084] In step S133, the specific formula for determining the thickness change value according to the initial average thickness and the current average thickness is:

[0085] Δt=t1-t0 (5)

[0086] In formula (5), Δt is the thickness change value; t0 is the initial average thickness of a single battery cell; t1 is the current average thickness of a single battery cell;

[0087] According to formula (1), formula (2), formula (3), formula (4) and formula (5), the formula for constraint stiffness can be obtained as follows:

[0088] k′=(F1-F0)n / (a1-a0) (6)

[0089] In formula (6), k′ is the constraint stiffness; F0 is the initial pressure; F1 is the current pressure; n is the number of cells in the battery pack; a0 is the initial distance between the left end plate 310 and the right end plate 320; a1 is the current distance between the left end plate 310 and the right end plate 320;

[0090] In this way, by measuring the initial pressure and current pressure of the battery cell at the center position in the battery pack, and measuring the initial distance and current distance between the left end plate 310 and the right end plate 320, the value of the constraint stiffness k′ can be calculated using formula (6); since the constraint stiffness k′ of the battery cell in the battery pack is equal to the equivalent stiffness k of the cycle test fixture, that is, k=k″, the value of the equivalent stiffness k is obtained. By reasonably increasing the equivalent stiffness equivalent to the external constraint stiffness in the cycle test of a single battery cell, it is beneficial to keep the stress state of the cycle test of the single battery cell consistent with its stress state in the battery pack.

[0091] In some specific embodiments of the present application, step S300 includes: determining the elastic coefficient of the cyclic test fixture according to the equivalent stiffness. For example, the cyclic test fixture includes a spring, and the elastic coefficient of the spring can be made equal to the equivalent stiffness k calculated by step 200, so that the stress state of the cyclic test of the single cell is consistent with the stress state in the battery pack. Specifically, the elastic coefficient of the spring can be calculated by the following formula:

[0092]

[0093] In formula (7), G is the shear modulus of the material (MPa); d is the material diameter (mm); n is the effective number of coils of the spring; D is the mean diameter of the spring (mm);

[0094] Thus, after the material of the spring is determined, the elastic coefficient of the spring is adjusted to a value equal to the equivalent stiffness by adjusting the diameter of the spring wire, the effective number of coils of the spring and the center diameter of the spring.

[0095] In some specific embodiments of the present application, step S300 also includes: determining the initial position of the cycle test fixture according to the initial pressure. For example, the cycle test fixture includes a spring, and the elastic coefficient of the spring is equal to the equivalent stiffness, both of which are k. Then, according to the initial pressure F0 and the equivalent stiffness k calculated in step 200, the compression amount X0 of the spring of the cycle test fixture at the initial position can be determined, X0 = F0 / k, and the position of the battery cell to be tested is adjusted so that the compression amount of the spring corresponding to the initial position of the battery cell to be tested on the cycle test fixture is X0, which can ensure that the pressure corresponding to the initial position of the battery cell to be tested on the cycle test fixture is equal to the pressure in the battery pack.

[0096] In some specific embodiments of the present application, step S300 also includes: determining the elastic limit of the cycle test fixture according to the current pressure. For example, the cycle test fixture includes a spring, and the elastic coefficient of the spring is equal to the equivalent stiffness, both of which are k. Then, according to the current pressure F1 and the equivalent stiffness k calculated in step 200, the compression amount X1 of the spring of the cycle test fixture at the current position can be determined, X1 = F1 / k, and by making the retractable length of the spring greater than X1, it is ensured that the extrusion of the battery cell on the test fixture during the cycle test is always within the elastic limit of the spring, preventing the over-extrusion of the spring from causing the battery cell to be over-extruded, affecting the cycle test results of the battery cell.

[0097] Reference Figure 4 As shown, the embodiment of the present application also provides a battery cell cycle test fixture, which is made by the battery cell cycle test fixture design method in the above embodiment of the present application, and the fixture includes a pressing plate 410 and a spring 420, wherein the pressing plate 410 is used to abut against the surface of the battery cell 500 to be tested; one end of the spring 420 is connected to the pressing plate 410, and the extrusion force between the pressing plate 410 and the battery cell 500 to be tested can be changed by telescopic deformation, and the elastic coefficient of the spring 420 is the equivalent stiffness of the fixture. The parameters of the spring 420 are selected according to the variables in the above formula (7), so that the elastic coefficient of the spring 420 is equal to the equivalent stiffness of the fixture.

[0098] In this way, by performing a cycle test on the battery cell 500 to be tested through the cycle test fixture in the present application, the squeezing spring 420 can provide the battery cell 500 to be tested with the same changing squeezing force as in the battery pack during the cycle test, thereby simulating the state of the battery cell undergoing a cycle test in the battery pack, thereby keeping the stress state of the single battery cell during the cycle test consistent with its stress state in the battery pack, which is beneficial for the test results of the single battery cell to more accurately characterize its cycle performance in the battery pack.

[0099] Reference Figure 4As shown, in some specific embodiments, the tooling also includes a support seat 430, a guide rod 440 and a base plate 450. The support seat 430 is used to place the battery cell 500 to be tested; the guide rod 440 is arranged on the support seat 430, and a guide hole is opened on the pressure plate 410. The guide rod 440 is arranged in the guide hole of the pressure plate 410 so as to be slidably connected with the pressure plate 410; the base plate 450 is detachably mounted on the guide rod 440 through a fixing member, and the base plate 450 is connected to the other end of the spring 420. In this way, the battery pack is simulated by the base plate 450 and the support seat 430. During the test, the base plate 450 is driven by the compression of the spring 420 to squeeze the battery cell, thereby simulating the dynamic squeezing force of the battery pack on the battery cell, which is conducive to keeping the stress state of the cycle test of the single battery cell consistent with its stress state in the battery pack, so that the test results of the single battery cell more accurately represent its cycle performance in the battery pack.

[0100] In some specific embodiments, the fixing member may be a nut, and the guide rod 440 is provided with an external thread, and the position of the nut on the guide rod 440 can be adjusted by screwing the nut, thereby adjusting the position of the substrate 450 on the guide rod 440. Before the cycle test, the position of the substrate 450 is adjusted by screwing the nut, so that the compression amount of the spring 420 corresponding to the initial position of the test cell 500 in the cycle test fixture is X0, which can ensure that the pressure corresponding to the initial position of the test cell 500 in the cycle test fixture is equal to the pressure in the battery pack.

[0101] In some specific embodiments, the pressure plate 410 and the spring 420 are symmetrically arranged. For example, the pressure plate 410 includes two symmetrical pieces, and the spring 420 includes two symmetrical groups. This can more realistically simulate the state and shape of uniform force on the battery cells in the battery pack.

[0102] In some specific embodiments, a scale is provided on the guide rod 440 along the length direction of the guide rod 440, so that the position of the substrate 450 can be adjusted by screwing the nut, and then the position of the pressure plate 410 is adjusted. The pressure corresponding to the initial position of the battery cell 500 to be tested in the cycle test fixture is equal to the pressure in the battery pack.

[0103] The following examples illustrate the design method of the battery cell cycle test fixture and the battery cell cycle test fixture of the present application:

[0104] Take the battery pack with five cells as an example:

[0105] The initial pressure F0 of the battery cell at the center of the battery pack before the cycle is measured to be 0N, and the distance a0 between the first displacement sensor 210 and the second displacement sensor 220 is 260mm;

[0106] Charge and discharge the battery pack 1000 times;

[0107] After the cycle charge and discharge is completed, the current pressure F1 of the battery cell located at the center of the battery pack after the cycle is measured to be 13000N, and the distance a1 between the first displacement sensor 210 and the second displacement sensor 220 is 265mm;

[0108] According to k′=(F1-F0)n / (a1-a0), it can be obtained that the constraint stiffness k′=(13000-0)5 / (265-260)=13000N / mm;

[0109] The equivalent stiffness of the cyclic test fixture is k = k′ = 13000 N / mm;

[0110] Therefore, it is necessary to select a spring 420 with an elastic coefficient of 13000 N / mm as the spring 420 in the cycle test fixture.

[0111] A battery cell cycle test method is also provided in an embodiment of the present application, and a battery cell cycle test tooling in the above embodiment of the present application is used to perform cycle testing on the battery cell.

[0112] The cell cycle test method in the present application is used to perform cycle tests on the cell to be tested, simulating the pressure state of the cell during the cycle test in the battery pack, thereby keeping the stress state of the single cell during the cycle test consistent with its stress state in the battery pack, which is conducive to making the test results of the single cell more accurately characterize its cycle performance in the battery pack.

[0113] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0114] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0115] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0116] In the present application, the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0117] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A battery cell cycle test fixture design method, characterized in that: include: Performing a cycle test on the battery pack to obtain the constraint stiffness of the battery cells in the battery pack during the cycle; Determining the equivalent stiffness of the cycle test fixture of the battery cell according to the constraint stiffness; The cyclic test fixture is designed according to the equivalent stiffness.

2. The battery cell cycle test fixture design method according to claim 1, characterized in that: The performing cycle test on the battery pack to obtain the restraint stiffness of the battery cells in the battery pack during the cycle process includes: Performing a cycle test on the battery pack for a preset time; Determine the pressure change value of a single battery cell in the battery pack before and after the cycle; Determining the thickness change value of a single cell in the battery pack before and after the cycle; The constraint stiffness is determined according to the pressure change value and the thickness change value.

3. The battery cell cycle test fixture design method according to claim 2, characterized in that: The determining of the pressure change value of a single battery cell in the battery pack before and after the cycle includes: Measuring the initial pressure of the battery cell at the center of the battery pack before cycling; measuring the current pressure of the battery cell located at the center of the battery pack after cycling; The pressure change value is determined according to the initial pressure and the current pressure.

4. The battery cell cycle test fixture design method according to claim 3, characterized in that: The determining of the thickness change value of a single battery cell in the battery pack before and after the cycle includes: Measuring the initial average thickness of the battery cells in the battery pack before cycling; Measuring the current average thickness of the battery cells in the battery pack after cycling; The thickness change value is determined according to the initial average thickness and the current average thickness.

5. The battery cell cycle test tool design method according to claim 3 or 4, characterized in that: The designing of the cyclic test fixture according to the equivalent stiffness includes: determining the elastic coefficient of the cyclic test fixture according to the equivalent stiffness.

6. The battery cell cycle test fixture design method according to claim 5, characterized in that: The designing of the cyclic test fixture according to the equivalent stiffness further includes: determining an initial position of the cyclic test fixture according to the initial pressure.

7. The battery cell cycle test fixture design method according to claim 6, characterized in that: The designing of the cyclic test fixture according to the equivalent stiffness further includes: determining the elastic limit of the cyclic test fixture according to the current pressure.

8. A battery cell cycle test tool, characterized in that: The tool is made by the battery cell cycle test tool design method according to any one of claims 1 to 7, and the tool comprises: A pressing plate, used to abut against the surface of the battery cell to be tested; A spring, one end of which is connected to the pressing plate, can change the extrusion force between the pressing plate and the battery cell to be tested through telescopic deformation, and the elastic coefficient of the spring is the equivalent stiffness of the tooling.

9. The battery cell cycle test fixture according to claim 8, characterized in that: The tooling also includes: Support seat, used to place the battery cell to be tested; A guide rod, disposed on the support seat, wherein the guide rod is slidably connected to the pressure plate; A base plate is detachably mounted on the guide rod and is connected to the other end of the spring.

10. A battery cell cycle test method, characterized in that: The battery cell cycle test tool described in claim 8 or 9 is used to perform a cycle test on the battery cell.

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