Method for determining pre-tightening force of battery module and method for manufacturing battery module

Abstract

The present invention relates to the technical field of battery modules, and provides a method for determining the pre-tightening force of a battery module and a method for manufacturing a battery module. The method for determining the pre-tightening force of the battery module includes the following steps: S1. Install a bundling strap on the battery module; S2. Measure the length of the battery module after installing the bundling strap as the first length; S3. Remove the bundling strap, squeeze the battery module until the length of the battery module is equal to the first length, and use the squeezing force at this time as the pre-tightening force. The present invention can overcome the deficiencies in the prior art that directly use the squeezing force of the battery module as the pre-tightening force, resulting in inaccurate pre-tightening force values and the inability to guarantee the integrity and stiffness of the battery module.

Description

Technical Field

[0001] The present invention relates to the technical field of battery modules, and particularly to a method for determining the pre-tightening force of a battery module and a method for manufacturing a battery module. Background Art

[0002] In order to meet the target energy and voltage requirements, existing battery modules are generally formed by stacking multiple battery cells, with buffer pads provided between adjacent battery cells, and end plates provided on the outer sides of the outermost battery cells; in order to ensure the integrity and stiffness of the battery module, a binding band is also provided around the battery module, and its installation method is that after the battery cells, buffer pads, and end plates in the battery module are stacked, an extrusion tooling is used to squeeze the battery module along the arrangement direction of the battery cells to shorten the length of the battery module, and at this time, the binding band is sleeved; then the extrusion tooling is released, and the battery module will rebound along the length direction of the battery module and stretch the binding band, thereby generating a pre-tightening force along the length direction of the battery module.

[0003] The magnitude of the pre-tightening force generated by the binding band directly affects the integrity and stiffness of the battery module. Therefore, the judgment of the magnitude of the pre-tightening force of the binding band is one of the key points in the design of the battery module. Existing technologies often directly use the maximum extrusion force during the process of squeezing the battery module by the extrusion tooling as the pre-tightening force of the binding band; however, according to the generation principle of the pre-tightening force of the binding band, the pre-tightening force and the extrusion force cannot actually be directly equivalent. Directly equating the extrusion force and the pre-tightening force will result in an inaccurate judgment of the pre-tightening force, and further lead to an inaccurate judgment of the tightness of the battery module, and the integrity and stiffness of the battery module cannot be guaranteed. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art that directly use the extrusion force of the battery module as the pre-tightening force, resulting in inaccurate pre-tightening force values and the inability to guarantee the integrity and stiffness of the battery module, and provide a method for determining the pre-tightening force of a battery module and a method for manufacturing a battery module.

[0005] In a first aspect, the present invention provides a method for determining the pre-tightening force of a battery module, comprising the following steps:

[0006] S1. Install the binding band on the battery module;

[0007] S2. Measure the length of the battery module after installing the binding band as the first length;

[0008] S3. Remove the binding band, squeeze the battery module until the length of the battery module is equal to the first length, and use the extrusion force at this time as the pre-tightening force.

[0009] The length of the battery module refers to the dimension of the battery module along the arrangement direction of the battery cells.

[0010] In step S3, the specific ways of squeezing the battery module include but are not limited to: starting from a relatively small initial squeezing force and gradually increasing the squeezing force until the length of the battery module is equal to the first length; starting from a relatively large initial squeezing force and gradually decreasing the squeezing force until the length of the battery module is equal to the first length.

[0011] In this solution, the battery module is first squeezed and the bundling strap is installed. Subsequently, the battery module is released, and the length of the battery module in the state with the bundling strap installed is measured. At this time, the length of the battery module is negatively correlated with the magnitude of the pre-tightening force. Subsequently, the bundling strap is removed and the battery module is squeezed again. At this time, the length of the battery module is also negatively correlated with the magnitude of the squeezing force. Therefore, if the battery module is squeezed until its length is equal to the first length, it can be considered that the squeezing force at this time is equal to the pre-tightening force that the bundling strap can provide.

[0012] Compared with directly taking the maximum squeezing force during the process of squeezing the battery module by the squeezing tooling as the pre-tightening force of the bundling strap in the prior art, this solution adds the first length determined by the magnitude of the pre-tightening force as a judgment basis, and selects the squeezing force when the length of the battery module is equal to the first length as the pre-tightening force, which can more accurately estimate the magnitude of the pre-tightening force that the bundling strap can provide, thereby more accurately judging the tightness of the battery module and ensuring the integrity and stiffness of the battery module.

[0013] Preferably, step S3 includes:

[0014] S31. Squeeze the battery module until the length of the battery module is less than the first length, and remove the bundling strap;

[0015] S32. Decrease the squeezing force until the length of the battery module returns to the first length, and take the squeezing force at this time as the pre-tightening force.

[0016] In step S32, the specific ways of decreasing the squeezing force include but are not limited to continuous decrease and stepped decrease.

[0017] In this solution, in step S3, a method of first squeezing the battery module again to reduce its length and then decreasing the squeezing force to make the battery module return to the first length is adopted, which can facilitate the removal of the bundling strap and prevent the situation that the bundling strap cannot be removed due to too tight a fit between the bundling strap and the battery module, or the bundling strap and the battery module scratching each other.

[0018] Preferably, in step S32, the squeezing force decreases linearly with time.

[0019] This solution gradually relaxes the battery module by means of linearly decreasing the extrusion force over time until it returns to the first length. On the one hand, it can avoid sudden changes in the extrusion force, which may lead to sudden stress changes inside the battery module, resulting in inaccurate pre-tightening force readings of the battery module or even damage to the battery module. On the other hand, the continuous linear change of the extrusion force in this solution can also facilitate the control of the length of the battery module, so that the length of the battery module can be restored to the first length as accurately as possible, and thus a more accurate pre-tightening force value can be obtained.

[0020] Preferably, the rate of linearly decreasing the extrusion force over time is less than or equal to 40 N / s.

[0021] Based on the applicant's actual engineering experience, this solution obtains the specific value range of the rate of decreasing the extrusion force, that is, less than or equal to 40 Newtons per second.

[0022] Preferably, step S32 includes:

[0023] S321. Set a limiting member on the battery module. The limiting member is arranged along the length direction of the battery module, and a first limiting portion and a second limiting portion are respectively arranged at both ends of the limiting member. The distance between the first limiting portion and the second limiting portion is equal to the first length.

[0024] S322. Decrease the extrusion force until both ends of the battery module in its length direction respectively abut against the first limiting portion and the second limiting portion, and use the extrusion force at this time as the pre-tightening force.

[0025] The specific setting method of the limiting member includes but is not limited to directly connecting to the battery module, placing on the battery module, or being held by an operator; the specific structures of the first limiting portion and the second limiting portion include but are not limited to limiting blocks, limiting columns, and limiting plates.

[0026] This solution sets a limiting member on the battery module. When neither end of the battery module abuts against the first limiting portion and the second limiting portion, or only one side can abut against the first limiting portion or the second limiting portion, it means that the current length of the battery module is less than the first length; and when both ends of the battery module respectively abut against the first limiting portion and the second limiting portion, it means that the length of the battery module has returned to the first length. It can be seen that this solution can very intuitively show whether the battery module has returned to the first length without the operator repeatedly measuring the length of the battery module, thus improving the measurement efficiency of the pre-tightening force.

[0027] Preferably, in steps S1 and S3, the battery module is extruded by applying an extrusion force to the end plate of the battery module.

[0028] This solution extrudes the battery module through the end plate, which can avoid damage to the battery module during the extrusion process.

[0029] Preferably, the bundling strap includes a steel strap.

[0030] This solution makes the strapping band include a steel strip, which is beneficial to using the strength of the steel to provide the required pre-tightening force for the battery module.

[0031] In a second aspect, the present invention provides a method for manufacturing a battery module, including the following steps:

[0032] Step A: Measure the pre-tightening force generated by the strapping band according to a method for determining the pre-tightening force of a battery module in the present invention;

[0033] Step B: Determine whether the pre-tightening force is within the design range. If so, use the strapping band to strap the battery module to complete the manufacture of the battery module; if not, adjust the size of the buffer pad or the size of the strapping band, and repeat Steps A to B.

[0034] The specific value range of the design range can be obtained through actual engineering experience, theoretical analysis, simulation calculation, etc., so as to avoid insufficient stiffness of the battery module due to too small pre-tightening force and avoid damage to the battery module due to too large pre-tightening force.

[0035] After obtaining the accurate pre-tightening force value through the method for determining the pre-tightening force of the battery module of the present invention, this solution further judges the magnitude of the pre-tightening force value; if the pre-tightening force is within the design range, the pre-tightening force of this type of strapping band meets the design requirements, and this type of strapping band can be used to strap the battery module and perform subsequent operations on the battery module until the manufacture of the battery module is completed; if not, the pre-tightening force can be adjusted by adjusting the size of the buffer pad or the strapping band; among them, the method of adjusting the buffer pad is applicable to on-site temporary adjustment or occasions where the pre-tightening force deviates little from the design range; the method of adjusting the strapping band is applicable to long-term adjustment by the design party or occasions where the pre-tightening force deviates too much from the design range.

[0036] Preferably, in Step S1, the extrusion force for extruding the battery module is greater than the upper limit of the design range and less than the expansion force of the battery cell stack.

[0037] According to the actual test data of the applicant, the pre-tightening force that the strapping band can provide is actually less than the extrusion force for extruding the battery module in Step S1; therefore, this solution gives the value range of the extrusion force in Step S1, which can not only ensure that the battery module can generate a pre-tightening force that meets the requirements of the design range after installing the strapping band, but also avoid damage to the battery module during the extrusion process.

[0038] Preferably, if the pre-tightening force is greater than the upper limit of the design range, increase the size of the strapping band along the length direction of the battery module; if the pre-tightening force is less than the lower limit of the design range, decrease the size of the strapping band along the length direction of the battery module.

[0039] This solution provides a specific adjustment method for the bundling strap when the pre-tightening force does not meet the requirements of the design range.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] 1. The present invention provides a method for determining the pre-tightening force of a battery module. By adding the first length determined by the magnitude of the pre-tightening force as a judgment basis and selecting the extrusion force when the length of the battery module is equal to the first length as the pre-tightening force, it is possible to more accurately estimate the magnitude of the pre-tightening force that the bundling strap can provide, thereby more accurately judging the tightness of the battery module and ensuring the integrity and stiffness of the battery module.

[0042] 2. The present invention provides a method for manufacturing a battery module. After obtaining an accurate pre-tightening force value through the method for determining the pre-tightening force of a battery module of the present invention, the magnitude of the pre-tightening force value is further judged to ensure that the pre-tightening force of the bundling strap is within the design range, thereby avoiding the situation where the stiffness of the battery module is insufficient due to too small pre-tightening force of the bundling strap or the battery module is damaged due to too large pre-tightening force of the bundling strap. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is a schematic flow chart of a method for determining the pre-tightening force of a battery module of the present invention;

[0044] Figure 2 is a schematic diagram of the extrusion method of the battery module in a method for determining the pre-tightening force of a battery module of the present invention;

[0045] Figure 3 is a schematic diagram of the usage method of the limiting member in a method for determining the pre-tightening force of a battery module of the present invention;

[0046] Figure 4 is a schematic flow chart of a method for manufacturing a battery module of the present invention;

[0047] Reference numerals: 1 - battery module; 2 - bundling strap; 3 - limiting member; 31 - first limiting portion; 32 - second limiting portion. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0048] The present invention will be further described in detail below in conjunction with test examples and specific embodiments. However, it should not be understood that the scope of the above-mentioned subject matter of the present invention is limited to the following embodiments, and all technologies implemented based on the content of the present invention belong to the scope of the present invention.

[0049] Unless otherwise specified, in the description of the specific embodiments of the present invention, the expression terms indicating the orientation or positional relationship such as "upper", "lower", "left", "right", "center", "inner", "outer", etc. are all based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship when the invention product / device / installation is in its usual use. These terms of orientation or positional relationship are only for the convenience of describing the solution of the present invention or simplifying the description in the specific embodiments, so as to facilitate technicians to quickly understand the solution, rather than indicating or implying that a specific device / component / element must have a specific orientation, or be constructed and operated in a specific positional relationship. Therefore, it should not be construed as a limitation to the present invention.

[0050] In addition, when terms such as "horizontal", "vertical", "hanging", "parallel" appear, it does not mean that the corresponding device / component / element is required to be absolutely horizontal or vertical or hanging or parallel, but can be slightly inclined or have a deviation. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined. Or, it can be simply understood that the corresponding device / component / element is arranged in the directions of "horizontal", "vertical", "hanging", "parallel", etc., and can have an error / deviation of ±10% relative to the corresponding direction setting, more preferably within ±8%, more preferably within ±6%, more preferably within ±5%, more preferably within ±4%. As long as the corresponding device / component / element is within the error / deviation range, it can still play its role in the solution of the present invention.

[0051] In addition, when expressions such as "first", "second", "third", etc. appear in the terms, they are only used to distinguish the description of the same or similar components, and should not be construed as emphasizing or implying the relative importance of a specific component.

[0052] In addition, in the description of the embodiments of the present invention, "several", "multiple", "a number of" represent at least 2. It can be any situation such as 2, 3, 4, 5, 6, 7, 8, 9, etc., or even more than 9.

[0053] In addition, in the description of the technical solution of the present invention, unless otherwise clearly specified / defined / limited, where terms such as "set", "installed", "connected", "linked", "provided with", "laid", "arranged" appear, they 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 connection means commonly used in the art such as welding, riveting, bolting, threaded connection, etc. This connection can be a mechanical connection, an electrical connection or a communication connection; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two elements.

[0054] Example 1

[0055] As Figure 1 shown, a method for determining the pre-tightening force of a battery module includes the following steps:

[0056] S1. Install the bundling strap 2 on the battery module 1;

[0057] S2. Measure the length of the battery module 1 after installing the bundling strap 2 as the first length;

[0058] S3. Remove the bundling strap 2, squeeze the battery module 1 until the length of the battery module 1 is equal to the first length, and use the squeezing force at this time as the pre-tightening force.

[0059] In an optional implementation manner, the specific method of step S1 is to squeeze the battery module 1 to a length less than the dimension of the bundling strap 2 along the length direction of the battery module 1, and then put the bundling strap 2 on the battery module 1, so as to avoid mutual scratching between the bundling strap 2 and the battery module 1 during the installation process, or the situation that it is too difficult to install the bundling strap 2.

[0060] It should be noted that if the battery module 1 is squeezed in step S1 for the convenience of installing the bundling strap 2, then the battery module 1 needs to be loosened in step S2 to avoid the simultaneous action of the squeezing force and the pre-tightening force of the bundling strap 2, resulting in the situation that the first length cannot accurately match the magnitude of the pre-tightening force.

[0061] In an optional implementation manner, in steps S1 and S3, as Figure 2 and Figure 3 shown, the battery module 1 is squeezed by applying a squeezing force to the end plate of the battery module 1; F in the figure represents the squeezing force. Specifically, when squeezing the battery module 1 in step S1, step S3, and the subsequent steps S31, S32, and S322 described below, the battery module 1 can be squeezed from both side end plates of the battery module 1; a squeezing tool can be used during squeezing.

[0062] In an optional implementation manner, a steel belt is selected as the bundling strap 2.

[0063] In an optional implementation manner, step S3 includes:

[0064] S31. Squeeze the battery module 1 until the length of the battery module 1 is less than the first length, and then remove the bundling strap 2;

[0065] S32. Reduce the squeezing force until the length of the battery module 1 returns to the first length, and use the squeezing force at this time as the pre-tightening force.

[0066] In an alternative embodiment, the extrusion force decreases linearly with time. For example, the extrusion force decreases by 10 N per second, or the extrusion force decreases by 20 N per second. Further, in this embodiment, it is preferred that the rate at which the extrusion force decreases linearly with time is less than or equal to 40 N / s.

[0067] In an alternative embodiment, step S32 includes:

[0068] S321. A limiting member 3 is provided on the battery module 1. The limiting member 3 is arranged along the length direction of the battery module 1. A first limiting portion 31 and a second limiting portion 32 are respectively provided at both ends of the limiting member 3. The distance between the first limiting portion 31 and the second limiting portion 32 is equal to the first length;

[0069] S322. Reduce the extrusion force until both ends of the battery module 1 along its length direction respectively abut against the first limiting portion 31 and the second limiting portion 32, and use the extrusion force at this time as the pre-tightening force.

[0070] The usage mode of the limiting member 3 is as Figure 3 shown. X in the figure represents the first length; more specifically, in this embodiment, a caliper is selected as the limiting member 3. The distance between the first limiting portion 31 and the second limiting portion 32 can be quantitatively adjusted through the scale and the self-adjusting function of the caliper, so as to adapt to different sizes of the first length; and the caliper, as an existing technology, can be directly purchased; it can also be used for other tests when idle.

[0071] Embodiment 2

[0072] As Figure 4 shown, a method for manufacturing a battery module includes the following steps:

[0073] Step A. Measure the pre-tightening force generated by the bundling strap 2 according to the method for determining the pre-tightening force of a battery module in Embodiment 1;

[0074] Step B. Determine whether the pre-tightening force is within the designed range. If so, use the bundling strap 2 to bundle the battery module to complete the manufacturing of the battery module; if not, adjust the size of the buffer pad or the size of the bundling strap 2, and repeat Step A to Step B.

[0075] In an alternative embodiment, in step S1, the extrusion force for extruding the battery module 1 is greater than the upper limit of the designed range and less than the expansion force of the battery cell stack.

[0076] In an alternative embodiment, if the pre-tightening force is greater than the upper limit of the designed range, increase the size of the bundling strap 2 along the length direction of the battery module 1; if the pre-tightening force is less than the lower limit of the designed range, reduce the size of the bundling strap 2 along the length direction of the battery module 1.

[0077] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for determining the preload force of a battery module, characterized in that: The following steps are included: S1, installing the strapping belt (2) on the battery module (1); S2, measuring the length of the battery module (1) after the strapping belt (2) is installed as a first length; S3, removing the strapping belt (2), squeezing the battery module (1) until the length of the battery module (1) is equal to the first length, and the squeezing force at this time is regarded as the pre-tightening force; Step S3 comprises: S31, squeezing the battery module (1) until the length of the battery module (1) is less than a first length, and removing the strapping belt (2); S32, reducing the squeezing force until the length of the battery module (1) is restored to the first length, and the squeezing force at this time is used as the pre-tightening force.

2. A method for determining the preload force of a battery module according to claim 1, characterized in that: In step S32, the squeezing force decreases linearly with time.

3. A method for determining the preload force of a battery module according to claim 2, characterized in that: The rate at which the extrusion pressure decreases linearly with time is less than or equal to 40N / S.

4. A method for determining the preload force of a battery module according to claim 1, characterized in that: Step S32 comprises: S321, arranging a limiter (3) on the battery module (1), wherein the limiter (3) is arranged along the length direction of the battery module (1), and a first limiter (31) and a second limiter (32) are respectively arranged at two ends of the limiter (3), and the distance between the first limiter (31) and the second limiter (32) is equal to a first length; S322, reducing the extrusion force until the two ends of the battery module (1) along its length direction respectively abut against the first limiting portion (31) and the second limiting portion (32), and the extrusion force at this time is used as the pre-tightening force.

5. A method for determining the preload force of a battery module according to any one of claims 1 to 4, characterized in that: In step S1 and step S3, the battery module (1) is squeezed by applying a squeezing force to the end plate of the battery module (1).

6. A method for determining the preload force of a battery module according to any one of claims 1 to 4, characterized in that: The strapping belt (2) comprises a steel belt.

7. A method for manufacturing a battery module, characterized in that: The following steps are included: Step A, measuring the preload force generated by the strapping belt (2) according to the method for determining the preload force of a battery module according to any one of claims 1 to 6; Step B, determining whether the preload force is within the design range; if so, using the strapping tape (2) to strap the battery module to complete the manufacture of the battery module; if not, adjusting the size of the buffer pad or adjusting the size of the strapping tape (2), and repeating steps A to B.

8. A method for manufacturing a battery module according to claim 7, characterized in that: In step S1, the squeezing force of squeezing the battery module (1) is greater than the upper limit of the design range and less than the expansion force of the battery cell stack.

9. A method for manufacturing a battery module according to claim 7, characterized in that: In step B, if the pre-tightening force is greater than the upper limit of the design range, the dimension of the strapping belt (2) along the length direction of the battery module (1) is increased; if the pre-tightening force is less than the lower limit of the design range, the dimension of the strapping belt (2) along the length direction of the battery module (1) is reduced.

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