Method for determining length of strap of battery module

Abstract

The present application provides a method for determining the length of a strap of a battery module. The method comprises: calculating a theoretical geometric length of a strap on the basis of a geometric size of a battery module; calculating a theoretical pre-tightening force of the strap on the basis of a pre-tightening force requirement of the battery module; performing a tensile test on the strap to obtain a linear coefficient between the amount of deformation and a tensile force of the strap; and determining whether the linear coefficient falls within a predetermined interval, and if yes, correcting the theoretical geometric length on the basis of the product of the theoretical pre-tightening force and the linear coefficient to obtain a corrected length of the strap.

Description

A method for determining the length of battery module strapping.

[0001] This application claims priority to Chinese Patent Application No. 202410945768.X, filed on July 15, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery module technology, and in particular to a method for determining the length of battery module strapping. Background Technology

[0003] Battery modules are typically composed of multiple stacked cells. To ensure the integrity and rigidity of the battery module, strapping is used around it. The strapping generates a pre-tightening force along the length of the battery module, thereby pressing the cells, end plates, and insulating sheets together. It is evident that the magnitude of the pre-tightening force generated by the strapping directly affects the integrity and rigidity of the battery module. The pre-tightening force of the strapping is strongly correlated with the length of the strapping, making the length of the strapping one of the key design considerations for battery modules. Technical issues

[0004] The preload generated by a strapping band is related not only to its length but also to many other parameters, such as the cross-sectional shape and size of the strapping band and its material. Current research on preload in this field is insufficient, and therefore, there is no explicit method for calculating strapping band length in relevant technical specifications. Those skilled in the art often use a method of initially determining the strapping band length, testing to determine the preload, adjusting the strapping band length based on the test results, and repeating the test and adjustment until the preload meets the requirements. However, the strapping band length tested using this method can only be adapted to the battery module used during testing. Whenever the size and specifications of the battery module change, repeated testing and adjustments are required for the new battery module, which is cumbersome, time-consuming, and labor-intensive, slowing down the entire battery module production process. Technical solutions

[0005] This application provides a method for determining the length of battery module strapping, comprising the following steps:

[0006] Calculate the theoretical geometric length of the strapping based on the geometric dimensions of the battery module; calculate the theoretical preload of the strapping based on the preload requirements of the battery module;

[0007] Tensile tests were conducted on the strapping to obtain the linear coefficient between the strapping deformation and the tensile force.

[0008] Determine whether the linear coefficient is within the predetermined range. If so, correct the theoretical geometric length based on the product of the theoretical preload and the linear coefficient to obtain the corrected length of the strapping. If not, change the material of the strapping, re-obtain the linear coefficient, and determine whether the linear coefficient is within the predetermined range. Beneficial effects

[0009] The beneficial effects of the method for determining the length of battery module strapping provided in this application are as follows: A linear coefficient reflecting the linear relationship between strapping deformation and tensile force is obtained through tensile testing. The theoretical geometric length is corrected by using the product of the linear coefficient and the theoretical preload, ensuring that the strapping can generate the theoretical preload, thereby guaranteeing that the integrity and rigidity of the battery module meet the requirements. Furthermore, when the size or required preload of the battery module changes, the linear coefficient is used, and the new battery module size or preload is substituted to recalculate the length of the strapping, eliminating the need for repeated tensile tests and adjustments as in related technologies. This saves tedious testing and adjustment work, reduces manpower and material resources, and improves the production efficiency of battery modules. Attached Figure Description

[0010] Figure 1 is a flowchart illustrating a method for determining the length of a battery module strapping strap according to this application. Embodiments of the present invention

[0011] The theoretical geometric length of the strapping is calculated based on the geometric dimensions of the battery module. This is the length of the strapping without considering the preload, assuming that the strapping is tightly attached to the corresponding installation area on the outer surface of the battery module along its length. The calculation of the theoretical geometric length and theoretical preload can be performed either before or after the tensile test.

[0012] The linearity coefficient reflects the deformation capacity of the strapping. Its predetermined range can be given based on test results or experience. The strapping should be neither too tight, which would lead to installation difficulties and poor compatibility, nor too loose, which would cause insufficient rigidity of the battery module, expansion of the battery module, displacement exceeding the design range, and affect the actual lifespan.

[0013] The theoretical geometric length can be corrected by multiplying the theoretical preload and the linear coefficient. For example, the theoretical geometric length can be directly subtracted from the product of the theoretical preload and the linear coefficient. Alternatively, a correction coefficient can be given based on practical experience. After amplifying or reducing the product of the theoretical preload and the linear coefficient using the correction coefficient, the product can be added or subtracted from the theoretical geometric length. Or, the difference between the theoretical geometric length and the product of the theoretical preload and the linear coefficient can be directly amplified or reduced using the correction coefficient.

[0014] For cable ties made of the same material, even if their length, thickness, width, and other dimensional parameters change, the linear coefficient between their deformation and tensile force remains almost unchanged. For example, for cable ties with widths of 19mm, 23mm, and 30mm, the difference in their linear coefficients is less than 0.002, which is acceptable for the length design of the cable ties. Therefore, the method for determining the length of the battery module cable ties in this solution involves obtaining the linear coefficient through a tensile test before determining the length of the cable ties. Then, the theoretical geometric length is corrected based on the product of the linear coefficient and the theoretical preload to obtain the corrected length. Since the linear coefficient reflects the relationship between the deformation of the cable ties and the tensile force, the product of the theoretical preload and the linear coefficient reflects the theoretical deformation required for the cable ties to generate the theoretical preload. By using this theoretical deformation to correct the theoretical geometric length, it can be ensured that the cable ties can generate the theoretical preload, thereby ensuring that the integrity and rigidity of the battery module meet the requirements.

[0015] As mentioned above, the linear coefficient mainly depends on the material of the strapping, and is minimally affected by other factors such as the strapping width and battery module size. Therefore, when the battery module size or required preload changes, this solution simply uses the linear coefficient and recalculates the strapping length by substituting the new battery module size or preload, without needing to repeat tensile tests and adjustments as required by related technologies. This eliminates tedious testing and adjustment work, saves significant manpower and resources, and improves battery module production efficiency.

[0016] Meanwhile, this solution also judges the linear coefficient through a preset range, which can ensure that the tightness of the strapping is moderate. It is neither too tight, which would make the strapping difficult to install and have poor compatibility, nor too loose, which would cause insufficient rigidity of the battery module, expansion of the battery module, displacement exceeding the design range, and affect the actual lifespan.

[0017] When determining whether the linear coefficient is within the predetermined range, if not, change the material of the strapping, re-obtain the linear coefficient, and determine whether the linear coefficient is within the predetermined range.

[0018] This solution outlines the actions to be taken when the linear coefficient is outside a predetermined range. Since the linear coefficient in this solution mainly depends on the material of the strapping, and is minimally affected by other factors such as the strapping width and battery module size, directly replacing the strapping material has a higher correction efficiency if the linear coefficient is outside the predetermined range.

[0019] [Referencing (Detailed Rule 20.6) 13.02.2025] The corrected length of the strapping is calculated according to the following formula: L = L1 - KF2

[0020] [Cited from (Detailed Rules 20.6) 13.02.2025]

[0021] In the formula, L represents the corrected length of the strapping; L1 represents the theoretical geometric length of the strapping; F2 represents the theoretical preload of the strapping; and K represents the linearity coefficient of the strapping.

[0022] This solution provides a formula for calculating the corrected length of the strapping.

[0023] The linearity coefficient of the strapping tape is calculated using the following formula:

[0024]

[0025] In the formula, K represents the linearity coefficient of the strapping; ΔL represents the deformation of the strapping when stretched; and F represents the tensile force on the strapping.

[0026] This solution provides a formula for calculating the linearity coefficient of the strapping.

[0027] The predetermined interval is defined as a linear coefficient greater than or equal to 0.001 and less than or equal to 0.004.

[0028] Based on extensive experimental data from the inventors, this solution provides a recommended range for the predetermined interval, ensuring that the tightness of the strapping is moderate. It is neither too tight, which would make installation difficult and cause poor compatibility, nor too loose, which would result in insufficient rigidity of the battery module, expansion of the battery module causing displacement beyond the design range, and affecting the actual lifespan.

[0029] When conducting a tensile test on the cable ties, at least two sets of cable ties with different widths should be selected for the tensile test.

[0030] Since different widths of strapping are often used in actual production, this solution recommends using at least two sets of strapping with different widths in the tensile test to ensure that the tensile test data can cover actual usage conditions.

[0031] When conducting a tensile test on the strapping, the tensile force applied to the strapping should be less than or equal to 1000 kgf.

[0032] This solution recommends a range of tensile forces applied to the strapping during the tensile test. This range matches the range of tensile forces applied to the strapping during the actual assembly of the battery module, ensuring that the data obtained from the tensile test matches the actual situation.

[0033] The theoretical preload of the strapping is calculated using the following formula:

[0034] F2=F1 / m

[0035] In the formula, F2 represents the theoretical preload of the strapping, m represents the number of strappings, and F1 represents the preload required by the battery module.

[0036] This solution provides a formula for calculating the theoretical preload of the strapping.

[0037] [Referencing (Detailed Rule 20.6) 13.02.2025] The theoretical geometric length of the strapping is calculated according to the following formula: L1=D1*n+D2*(n-1)+(D3+D4)*2

[0038] [Cited from (Detailed Rules 20.6) 13.02.2025]

[0039] In the formula, L1 represents the theoretical geometric length of the strapping; D1 represents the thickness of the battery cell in the battery module; D2 represents the gap between the battery cells; n represents the number of battery cells; D3 represents the thickness of the end plate in the battery module; and D4 represents the thickness of the insulating sheet of the end plate.

[0040] This solution provides a formula for calculating the theoretical geometric length of the strapping.

[0041] After obtaining the linear coefficient, the linear coefficient and the predetermined interval are amplified using the amplification factor; when calculating the correction length, the product of the theoretical preload, the linear coefficient, and the reciprocal of the amplification factor is subtracted from the theoretical geometric length; the amplification factor is divisible by 50.

[0042] The magnification factor is divisible by 50, meaning it is an integer multiple of 50, such as 50, 100, or 150.

[0043] In actual production, the preload is often a multiple of 50, while the linear coefficient often has too many decimal places, which is inconvenient for recording and calculation. Therefore, this solution extracts the amplification factor from the preload and uses the amplification factor to amplify the linear coefficient to facilitate the recording and calculation of the linear coefficient. Correspondingly, the predetermined interval also needs to be amplified using the linear coefficient (that is, the upper and lower limits of the predetermined interval need to be multiplied by the amplification factor). When calculating the correction length, the linear coefficient needs to be multiplied by the reciprocal of the amplification factor to remove the amplification factor.

[0044] As shown in Figure 1, a method for determining the length of a battery module bundling strap includes the following steps:

[0045] S1. Calculate the theoretical geometric length of the strapping based on the geometric dimensions of the battery module; calculate the theoretical preload of the strapping based on the preload requirements of the battery module.

[0046] S2. Conduct a tensile test on the strapping to obtain the linearity coefficient between the strapping deformation and the tensile force.

[0047] S3. Determine whether the linear coefficient is within the predetermined range. If not, change the material of the strapping, obtain the linear coefficient again, and determine whether the linear coefficient is within the predetermined range. That is, repeat steps S2 to S3. If yes, proceed to step S4.

[0048] S4. Correct the theoretical geometric length by multiplying the theoretical preload and the linear coefficient to obtain the corrected length of the strapping.

[0049] [Cited in Article (20.6) 13.02.2025] In the embodiments provided in this application, the theoretical geometric length of the strapping can be calculated in step S1 according to the following formula: L1=D1*n+D2*(n-1)+(D3+D4)*2

[0050] [Cited from (Detailed Rules 20.6) 13.02.2025]

[0051] In the formula, L1 represents the theoretical geometric length of the strapping; D1 represents the thickness of the battery cell in the battery module; D2 represents the gap between the battery cells; n represents the number of battery cells; D3 represents the thickness of the end plate in the battery module; and D4 represents the thickness of the insulating sheet of the end plate.

[0052] In the embodiments provided in this application, the theoretical preload of the strapping can be calculated in step S1 according to the following formula:

[0053] F2=F1 / m

[0054] In the formula, F2 represents the theoretical preload of the strapping, m represents the number of strappings, and F1 represents the preload required by the battery module.

[0055] In the embodiments provided in this application, when conducting tensile tests on the strapping, at least two sets of strapping with different widths are selected for the tensile tests. When selecting the width of the strapping, widths that are actually used in the production process can be selected, such as strapping with a width of 19mm, 23mm, or 30mm, so that the tensile test can better represent the actual situation.

[0056] In the embodiments provided in this application, the length of the strapping is less than or equal to 1m when performing a tensile test on the strapping. This range matches the actual range of strapping lengths used, ensuring that the data obtained from the tensile test matches the actual situation.

[0057] In the embodiments provided in this application, when performing a tensile test on the strapping, the tensile force applied to the strapping is less than or equal to 1000 kgf.

[0058] In the embodiments provided in this application, the linearity coefficient of the strapping is calculated according to the following formula:

[0059]

[0060] In the formula, K represents the linearity coefficient of the strapping; ΔL represents the deformation of the strapping when stretched; and F represents the tensile force on the strapping.

[0061] In the embodiments provided in this application, the range of the predetermined interval is that the linear coefficient is greater than or equal to 0.001 and less than or equal to 0.004, that is, 0.001≤K≤0.004.

[0062] [Cited in Article (20.6) 13.02.2025] In the embodiments provided in this application, the corrected length of the strapping is calculated in step S4 according to the following formula: L = L1 - KF2

[0063] [Cited from (Detailed Rules 20.6) 13.02.2025]

[0064] In the formula, L represents the corrected length of the strapping.

[0065] In the embodiments provided in this application, after obtaining the linear coefficient, an amplification factor is used to amplify the linear coefficient and the predetermined interval; when calculating the correction length, the theoretical preload, the product of the linear coefficient and the reciprocal of the amplification factor, is subtracted from the theoretical geometric length; the amplification factor is divisible by 50. That is, in step S2, the linear coefficient of the strapping is calculated using the following formula:

[0066]

[0067] In the formula, V represents the magnification factor, V=50, 100, 150...

[0068] Correspondingly, the range of the predetermined interval should be expanded to include linear coefficients greater than or equal to 0.05 and less than or equal to 0.2, i.e., 0.05≤K≤0.2.

[0069] [Referencing (Details 20.6) 13.02.2025] Correspondingly, in step S4, the corrected length of the strapping is calculated according to the following formula: L=L1-KF2 / V

[0070] [Cited from (Detailed Rules 20.6) 13.02.2025]

[0071] In the embodiments provided in this application, if the size or required preload of the battery module changes, step S1 is repeated to calculate the new theoretical geometric length and theoretical preload, and then the process jumps to step S4 to recalculate the length of the strapping. There is no need to repeat steps S2 to S3.

Claims

1.A method for determining the length of a battery module bundling belt, comprising the following steps: calculating a theoretical geometric length of the bundling belt according to the geometric size of a battery module; calculating a theoretical pre-tightening force of the bundling belt according to the pre-tightening force requirement of the battery module; performing a tensile test on the bundling belt to obtain a linear coefficient between the deformation and the tension of the bundling belt; determining whether the linear coefficient is within a predetermined range, and if so, correcting the theoretical geometric length according to the product of the theoretical pre-tightening force and the linear coefficient to obtain a corrected length of the bundling belt; if not, changing the material of the bundling belt, re-obtaining the linear coefficient and determining whether the linear coefficient is within the predetermined range; calculating the corrected length of the bundling belt according to the following formula: L = L1 - KF2, wherein L represents the corrected length of the bundling belt, L1 represents the theoretical geometric length of the bundling belt, F2 represents the theoretical pre-tightening force of the bundling belt, and K represents the linear coefficient of the bundling belt; calculating the linear coefficient of the bundling belt according to the following formula: K = ΔL / F, wherein K represents the linear coefficient of the bundling belt, ΔL represents the deformation of the bundling belt when stretched, and F represents the tension applied to the bundling belt; the range of the predetermined range is that the linear coefficient is greater than or equal to 0.001 and less than or equal to 0.004; when performing the tensile test on the bundling belt, at least two groups of the bundling belts with different widths are selected to perform the tensile test; when performing the tensile test on the bundling belt, the tension applied to the bundling belt is less than or equal to 1000 kgf; calculating the theoretical pre-tightening force of the bundling belt according to the following formula: F2 = F1 / m, wherein F2 represents the theoretical pre-tightening force of the bundling belt, m represents the number of the bundling belts, and F1 represents the pre-tightening force required by the battery module; calculating the theoretical geometric length of the bundling belt according to the following formula: L1 = D1*n + D2*(n-1) + (D3+D4)*2, wherein L1 represents the theoretical geometric length of the bundling belt, D1 represents the thickness of a battery cell in the battery module, D2 represents the gap of the battery cell, n represents the number of the battery cells, D3 represents the thickness of an end plate in the battery module, and D4 represents the thickness of an insulating sheet of the end plate; after obtaining the linear coefficient, the linear coefficient and the predetermined range are amplified using an amplification coefficient; when calculating the corrected length, the theoretical geometric length is reduced by the product of the theoretical pre-tightening force, the linear coefficient and the inverse of the amplification coefficient; the amplification coefficient can be divided by 50. ​ ​ 2. The method of claim 1, wherein, ​ 3. The method of claim 1, wherein, ​ ​ ​ 4. The method of claim 1, wherein, ​ ​ ​ 5. The method of claim 1, wherein, ​ 6. The method of claim 1 to 5, wherein, ​ 7. The method of claim 1 to 5, wherein, ​ 8. The method of claim 1 to 5, wherein, ​ ​ ​ 9. [Entry into the record (Rule 20.6) 13.02.2025] A method of determining the length of a battery module strapping band according to any one of claims 1 to 5, wherein, ​ ​ 10. The method of claim 1 to 5, wherein, ​

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