A multi-point pre-load application battery test fixture and method

Abstract

The application discloses a kind of multi-point pre-tightening force applied battery test fixture and method, the battery test fixture includes base, first clamping plate, top plate, second clamping plate and multiple groups of height adjusting assembly;First clamping plate is supported above base by spoke sensor, and form the accommodation space of placing battery test piece between with second clamping plate, second clamping plate is driven by height adjusting assembly to be close to or far from first clamping plate to apply pre-tightening force.The annular pressure film sensor of the application is placed between nut seat and second clamping plate, to avoid direct contact with battery test piece, reduce the interference of temperature rise and surface deformation, improve the measurement accuracy of multi-point local pre-tightening force;By controlling host computer to target pre-tightening force as given value, measured pre-tightening force as feedback value carries out negative feedback closed-loop regulation, drives servo motor to drive screw micro-feeding or back-off, so that global pre-tightening force is uniform or according to preset gradient distribution, eliminate the uneven stress caused by single point fulcrum, accurately simulate the real compression environment of battery.

Description

Technical Field

[0001] This invention relates to the field of battery testing fixture technology, and in particular to a battery testing fixture and method for applying preload at multiple points. Background Technology

[0002] Currently, experiments testing the expansion force of lithium-ion batteries often utilize a bolt-constant-clearance fixture combined with a spoke sensor. The spoke sensor's high accuracy and stability make this combination widely used. However, this method has limitations: the spoke sensor can only measure the force at a single point, namely the resultant force of the preload applied by the fixture. During the application of the preload, the spoke sensor provides a fulcrum, leading to a significant force application to the bolts near the fulcrum and uneven force application to the bolts at the ends farther from the fulcrum.

[0003] In a plane, uneven preload can cause excessive stress in some areas and insufficient stress in others, and only a suitable preload is crucial for battery performance. To address this issue, methods such as multi-point pressure film sensors or array-type pressure film sensors have been used. However, pressure film sensors, attached to the battery surface and clamped between the battery and the fixture, are susceptible to several problems: first, they are affected by battery temperature rise; second, the presence of cushioning components such as foam introduces a hysteresis effect, preventing the simultaneous measurement of the preload applied by the battery clamping system; and finally, in most cases, the battery and fixture dimensions are not perfectly matched, with the fixture often larger than the battery, making it difficult to directly control the preload provided by the bolts at the battery's suspended end.

[0004] The aforementioned defects prevent existing fixtures from stably measuring the actual preload force at various points on the clamping plate, and also make it difficult to achieve precise application of uniform or gradient preload, which seriously affects the testing accuracy of lithium-ion batteries and the realism of environmental simulation. Summary of the Invention

[0005] This invention provides a battery testing fixture and method for applying preload at multiple points, which solves the technical problems of existing fixtures being unable to achieve stable multi-point measurement of preload at various points on the clamping plate, and being difficult to combine with the spoke sensor to calibrate the reference expansion force to achieve uniform or gradient preload application, thus failing to simulate the diverse external pressure environment of the battery.

[0006] In view of the above technical problems, embodiments of the present invention provide a battery testing fixture with multi-point pre-tightening force application, including a base, a first clamping plate, a top plate, a second clamping plate, and multiple sets of height adjustment components; the top wall of the base and the bottom wall of the top plate are fixedly connected by side plates, forming a receiving space for accommodating the second clamping plate and the first clamping plate; the first clamping plate is supported above the base by a spoke sensor, and forms a receiving space for placing a battery specimen between itself and the second clamping plate; the battery specimen is placed on the first clamping plate; the multiple sets of height adjustment components pass through the second clamping plate and the first clamping plate and are installed in the receiving space, and are used to adjust the second clamping plate to move closer to or further away from the first clamping plate, so that the second clamping plate applies a pre-tightening force to the battery specimen; a compensating support column is installed on the bottom surface of the first clamping plate;

[0007] Each set of height adjustment components includes a servo motor mounted on the top wall of the top plate, a drive gear mounted on the bottom wall of the top plate and connected to the output shaft of the servo motor, a driven gear meshing with the drive gear, a lead screw passing through the driven gear and the second clamping plate and rotatably connected between the top plate and the base, and a nut seat threadedly connected to the lead screw.

[0008] The nut seat is fixedly installed on the top surface of the second clamping plate. The nut seat is connected to the second clamping plate through a guide limiting member. An upper hard pressure equalizing pad, an annular pressure film sensor, and a lower hard pressure equalizing pad are sequentially arranged between the lower end surface of the nut seat and the top surface of the second clamping plate. The annular pressure film sensor, the upper hard pressure equalizing pad, and the lower hard pressure equalizing pad are all arranged around the lead screw. Gyroscopes are installed on the top surface of the second clamping plate and the bottom surface of the first clamping plate. The spoke sensor is used to measure the reference value of the preload force of the battery specimen.

[0009] Optionally, the number of height adjustment components is set to 6, divided into 2 groups, with 3 height adjustment components in each group, and each group is arranged symmetrically about the red axis about the first clamping plate.

[0010] Optionally, the upper and lower surfaces of the battery specimen are provided with cushioning elements, which are foam.

[0011] Optionally, the battery test fixture with multi-point pre-tightening force application further includes a multi-channel data acquisition module and a control host. The multi-channel data acquisition module is used to synchronously acquire the output signals of each of the annular pressure film sensors, the reference signals of the wheel spoke sensors, and the attitude signals of the gyroscope. The control host is used to receive the output signals of the annular pressure film sensors, the reference signals of the wheel spoke sensors, and the attitude signals of the gyroscope, and output control commands to each servo motor.

[0012] This invention also provides a battery testing method for applying preload at multiple points, implemented using the aforementioned battery testing fixture for applying preload at multiple points, comprising:

[0013] S1. Upon power-on, perform a self-check of the communication status of each annular pressure diaphragm sensor, spoke sensor, gyroscope, servo motor, and control host. If any abnormality is detected, an alarm will be triggered and loading will be prohibited.

[0014] S2, the input target pressure distribution, allowable error range, loading speed, single fine-tuning step size, stabilization holding time, and safety upper limit; the target pressure distribution is the same uniform pressure or gradient pressure at the test points of each annular pressure film sensor;

[0015] S3. Collect the initial values ​​of each unloaded annular pressure diaphragm sensor as the zero point, and perform reference calibration through the wheel spoke sensor to establish the conversion relationship between the electrical signal and the actual preload.

[0016] S4. Control each servo motor to drive the second clamping plate closer to the first clamping plate. When the annular pressure film sensor detects that the pressure starts to rise or the second clamping plate contacts the battery specimen and the compensation support column, the closed-loop fine-tuning stage is entered.

[0017] S5. Periodically collect pressure data at each test point. The attitude angle between the second clamping plate and the first clamping plate will and corresponding target value The pressure error was obtained by comparison. It also determines whether there is an exceedance of the safety limit, a sudden change in pressure, or an abnormal attitude. If an abnormality is found, loading is stopped or a minor rollback is performed.

[0018] S6. Based on the pressure error at each test point, control the corresponding servo motor to feed forward or retract backward, so that the pressure at each test point tends to the target range.

[0019] S7. By controlling the host computer, the pressure at each test point and the attitude of the second clamping plate and the first clamping plate are collected again. Steps S5 to S6 are executed iteratively until the pressure at each test point is reached. All are within the allowable error range and the relative tilt of the second clamping plate to the first clamping plate is less than the set threshold.

[0020] S8. When no significant drift occurs at any test point within the stable holding time, the preload is deemed to have been applied and the test holding state is entered. During the charge and discharge cycle of the battery specimen, if the pressure at a certain test point deviates from the target range, the closed-loop fine-tuning process is automatically re-entered.

[0021] In this invention, by placing the annular pressure film sensor between the nut seat and the second clamping plate, the sensor does not directly contact the battery specimen, completely avoiding interference from battery temperature rise, foam hysteresis, and local deformation of the battery surface on the measurement results, thus achieving stable and accurate measurement of local preload at each force application point. Simultaneously, by controlling the host computer to perform negative feedback closed-loop adjustment with the target preload as the given value and the measured preload from the annular pressure film sensor as the feedback value, and cooperating with the servo motor driving the lead screw for micro-feeding or retraction, the preload of the fixture is made uniform or distributed according to a preset gradient across the entire area, eliminating the problem of uneven force distribution caused by single-point fulcrums. Furthermore, it can automatically correct preload drift during the charge-discharge cycle of the battery specimen, significantly improving test stability and data accuracy.

[0022] Furthermore, this invention, by setting a height-adjustable compensating support column between the base and the first clamping plate, ensures that the upper end face of the compensating support column is at the same height as the pressure-bearing upper surface of the battery specimen and its surface buffer, effectively supporting the suspended area of ​​the second clamping plate. This prevents local bending at the end due to lack of support and ensures that the preload applied by the end height adjustment component can be effectively transmitted to the pressure area of ​​the battery specimen. This solves the problem of uncontrolled end preload when the clamp and battery size do not match, significantly improving the adaptability of the clamp. At the same time, the control host collects and displays pressure data at each point in real time, forming a visualization of the pressure distribution across the entire clamping plate area. This facilitates the testing personnel to monitor and record the expansion behavior of the battery specimen, providing a reliable basis for judging the health status of the battery. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a cross-sectional view of the overall structure of a battery test fixture with multi-point pre-tightening force applied in one embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of the overall structure of a battery test fixture with multi-point pre-tightening force applied in one embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram of the overall structure of a battery test fixture with multi-point pre-tightening force applied in another embodiment of the present invention.

[0027] The reference numerals in the accompanying drawings are as follows:

[0028] 1-Base, 2-First clamping plate, 3-Top plate, 4-Second clamping plate, 5-Height adjustment component, 51-Servo motor, 52-Driving gear, 53-Driven gear, 54-Lead screw, 55-Nut seat, 6-Side plate, 7-Spoke sensor, 8-Battery specimen, 9-Annular pressure film sensor, 10-Gyroscope, 11-Compensation support column. Detailed Implementation

[0029] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0030] In the description of this invention, it should be understood that the terms "longitudinal," "radial," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0031] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0032] like Figures 1 to 3As shown, an embodiment of the present invention provides a battery testing fixture with multi-point pre-tightening force application, including a base 1, a first clamping plate 2, a top plate 3, a second clamping plate 4, and multiple sets of height adjustment components 5; the top wall of the base 1 and the bottom wall of the top plate 3 are fixedly connected by a side plate 6, forming a receiving space for accommodating the second clamping plate 4 and the first clamping plate 2; the first clamping plate 2 is supported above the base 1 by a spoke sensor 7, and forms a receiving space for placing a battery specimen 8 between itself and the second clamping plate 4; the battery specimen 8 is placed on the first clamping plate 2; the multiple sets of height adjustment components 5 pass through the second clamping plate 4 and the first clamping plate 2 and are installed in the receiving space, and are used to adjust the second clamping plate 4 to move closer to or further away from the first clamping plate 2, so that the second clamping plate 4 applies a pre-tightening force to the battery specimen 8.

[0033] Each set of height adjustment components 5 includes a servo motor 51 mounted on the top wall of the top plate 3, a drive gear 52 mounted on the bottom wall of the top plate 3 and connected to the output shaft of the servo motor 51, a driven gear 53 meshing with the drive gear 52, a lead screw 54 passing through the driven gear 53 and the second clamping plate 4 and rotatably connected between the top plate 3 and the base 1, and a nut seat 55 threadedly connected to the lead screw 54.

[0034] The nut seat 55 is fixedly installed on the top surface of the second clamping plate 4. The nut seat 55 is connected to the second clamping plate 4 through a guide limiting member. An upper hard pressure equalizing pad, an annular pressure film sensor 9, and a lower hard pressure equalizing pad are sequentially arranged between the lower end face of the nut seat 55 and the top surface of the second clamping plate 4. The annular pressure film sensor 9, the upper hard pressure equalizing pad, and the lower hard pressure equalizing pad are all arranged around the lead screw 54. A gyroscope 10 is installed on the top surface of the second clamping plate 4 and the bottom surface of the first clamping plate 2. The spoke sensor 7 is used to measure the reference value of the preload force of the battery specimen 8.

[0035] In one embodiment, such as Figures 1 to 3As shown, a compensating support column 11 is installed on the bottom surface of the first clamping plate 2. Understandably, the compensating support column 11 is installed between the base 1 and the first clamping plate 2, and its height can be adjusted by a wrench to accommodate battery specimens 8 of different sizes. When the length or width of the clamp is greater than the battery size, there is a suspended area of ​​the second clamping plate 4 on the outer side of the battery end. By adjusting the compensating support column 11 so that its upper end face is aligned with the height of the pressure-bearing upper surface of the battery specimen 8 and its surface buffer, effective support is provided to the suspended area when the upper clamping plate presses down. This prevents the end of the second clamping plate 4 from undergoing local bending deformation due to lack of support, ensuring that the pre-tightening force applied by the end height adjustment component 5 can be effectively transmitted to the pressure area of ​​the battery, avoiding loss of control of the pre-tightening force at that location, and thus ensuring the uniformity and controllability of the pre-tightening force throughout the clamp. This solves the technical problem of difficulty in effectively transmitting the end pre-tightening force when the clamp and battery size do not match.

[0036] In one embodiment, such as Figures 1 to 3 As shown, the number of height adjustment components 5 is set to 6, divided into 2 groups, with 3 height adjustment components 5 in each group, and each group is arranged symmetrically about the first clamping plate 2 on the red axis.

[0037] In one embodiment, such as Figures 1 to 3 As shown, the upper and lower surfaces of the battery specimen 8 are provided with cushioning elements, which are foam.

[0038] In one embodiment, such as Figures 1 to 3 As shown, the battery test fixture with multi-point pre-tightening force application also includes a multi-channel data acquisition module and a control host. The multi-channel data acquisition module is used to synchronously acquire the output signals of each of the annular pressure film sensors 9, the reference signal of the wheel spoke sensor 7, and the attitude signal of the gyroscope 10. The control host is used to receive the output signals of the annular pressure film sensors 9, the reference signal of the wheel spoke sensor 7, and the attitude signal of the gyroscope 10, and output control commands to each servo motor 51.

[0039] This invention also provides a battery testing method for applying preload at multiple points, implemented using the aforementioned battery testing fixture for applying preload at multiple points, comprising:

[0040] S1. After the battery test fixture is powered on, check the communication status of each annular pressure film sensor 9, spoke sensor 7, gyroscope 10, each servo motor 51 and the control host. If any channel has no signal or the driver is abnormal, the control host will prohibit loading and output an alarm.

[0041] S2. The host computer reads the target pressure distribution, allowable error range, loading speed, single fine-tuning step size, stable holding time and safety upper limit input by the tester. The target pressure distribution is the same uniform pressure at the test points of each annular pressure film sensor 9, or a gradient pressure with high pressure at the center and low pressure at the edges, and high pressure on one side and low pressure on the other side.

[0042] S3. Acquire the initial values ​​of each annular pressure film sensor 9 as zero points in the unloaded state, and perform benchmark calibration through the spoke sensor 7 to establish the conversion relationship between the electrical signals of each channel and the actual preload.

[0043] S4. The host controller outputs a low-speed loading command to each servo motor 51. The servo motor 51 drives the drive gear 52 to rotate the driven gear 53. The driven gear 53 drives the lead screw 54 to rotate. The lead screw 54 cooperates with the nut seat 55 to make the second clamping plate 4 approach the first clamping plate 2 along the axial direction of the lead screw 54. When the annular pressure film sensor 9 detects that the pressure starts to rise or the second clamping plate 4 contacts the battery test piece 8 and the compensation support column 11, the closed-loop fine-tuning stage begins.

[0044] S5. The host computer periodically collects pressure data at each test point. The attitude angle between the second clamping plate and the first clamping plate will and corresponding target value The pressure error was obtained by comparison. It also determines whether there are situations such as exceeding the safety limit, sudden pressure changes, or abnormal posture. If a safety abnormality occurs, it immediately stops loading or performs a minor rollback.

[0045] S6. If a certain test point If the value is below the target range, the host computer outputs a positive feed command to the servo motor 51 corresponding to the test point, causing the lead screw 54 to drive the second clamping plate to press down slightly in a localized manner; if a certain test point If the position is above the target range, a reverse retraction command is output to slightly loosen the leadscrew; if the position is within the target range, the current position is maintained.

[0046] S7. By controlling the host, the pressure at each test point and the posture of the second clamping plate 4 and the first clamping plate 2 are collected again. Steps S5 to S6 are repeated until all S6 are within the allowable error range and the relative tilt of the second clamping plate 4 and the first clamping plate 2 is less than the set threshold.

[0047] S8. When no significant drift occurs at any point within the stable holding time, the host control determines that the pre-tightening force has been applied and enters the test holding state. During the charge and discharge cycle of the battery test piece 8, if the pressure at a certain test point deviates from the target range, the closed-loop fine-tuning process is automatically re-entered.

[0048] In one specific embodiment, such as Figure 2and Figure 3 As shown, the specific process of the test method for the battery test fixture with multi-point preload application is as follows:

[0049] The first method is to apply uniform preload in a plane. This embodiment is used to ensure that the preload at each point of force application in the pressure plane of the battery specimen 8 is basically the same, thereby simulating the stress state of the battery under uniform constraint conditions.

[0050] Step 1: Initial Fixture Inspection

[0051] Check that the base 1, first clamping plate 2, second clamping plate 4, lead screw 54, nut seat 55, servo motor 51, drive gear 52, and driven gear 53 are securely installed. Confirm that the second clamping plate 4 can move smoothly up and down along the lead screw 54, avoiding jamming, skewness, or localized wobbling during the downward pressing process. Install annular pressure diaphragm sensors 9 between each nut seat 55 and the second clamping plate 4. Pass the lead screw 54 through the center hole of the annular pressure diaphragm sensor 9, so that the preload applied downward by the lead screw 54 is loaded onto the annular pressure diaphragm sensor 9 through the nut seat 55 and then transmitted to the second clamping plate 4. With this setup, each annular pressure diaphragm sensor 9 corresponds to a force application point, allowing real-time detection of the localized preload input to the second clamping plate 4 at that point. Since the annular pressure diaphragm sensor 9 is not directly attached to the surface of the battery specimen 8, nor is it clamped between the battery specimen 8 and the foam, the influence of battery temperature rise, foam hysteresis, and localized deformation of the battery surface on the measurement results can be reduced.

[0052] Step 2: Place the battery to be tested:

[0053] Place the battery test piece 8 to be tested at the designated position on the first clamping plate 2. If foam, insulating pads or buffer layers need to be installed on the surface of the battery test piece 8, place the foam or insulating pads together with the battery test piece 8 to make the test state close to the actual module assembly state.

[0054] Step 3: Adjust compensation support column 11:

[0055] When the length or width of the clamp is greater than the size of the battery specimen 8, there will be a suspended area of ​​the second clamping plate 4 on the outer side of the end of the battery specimen 8. At this time, the height of the compensating support column 11 is adjusted by wrench so that the upper end face of the compensating support column 11 is at the same height as the pressure-bearing upper surface of the battery specimen 8 and its surface buffer. That is, the effective height of the compensating support column 11 from the upper surface of the first clamping plate 2 to its upper end face is adjusted so that it can provide support for the suspended area when the second clamping plate 4 is pressed down. The purpose of this step is to prevent the end of the second clamping plate 4 from bending locally due to lack of support, and to avoid the force applied by the end screw 54 not being effectively transmitted to the pressure area of ​​the battery specimen 8.

[0056] Step 4: Connect the sensor to the control unit:

[0057] Each annular pressure diaphragm sensor 9 is connected to the multi-channel signal acquisition module. The voltage or resistance signal acquired by each channel is input to the control host. The control host converts the output value of each sensor into the actual preload force at each force application point according to the pre-calibrated sensor pressure-electrical signal correspondence. For example, the six force application points are denoted as P1, P2, P3, P4, P5, and P6, and the corresponding measured preload forces are denoted as F1, F2, F3, F4, F5, and F6, respectively.

[0058] Step 5: Wheel spoke sensor reference calibration:

[0059] Before applying the preload, the overall force on the fixture is calibrated using the spoke sensor 7. The nut seat 55 is fixed to the second clamping plate 4 with screws, and the annular pressure diaphragm sensor 9 is placed between the nut seat 55 and the surface of the second clamping plate 4, providing an initial value.

[0060] The specific operation method is as follows: Record the initial values ​​of each annular pressure diaphragm sensor 9 as the zero point before startup. Control the lead screw 54 to gradually apply known pressures, such as 100N, 200N, 300N, 400N, and 500N. Simultaneously record the reference force value measured by the spoke sensor 7 and the output value of each annular pressure diaphragm sensor 9. The control host corrects each annular pressure diaphragm sensor 9 based on the reference data from the spoke sensor 7, eliminating sensitivity differences and installation errors between different sensors.

[0061] Step 6: Set a uniform target preload:

[0062] Input the target preload force into the control unit. For example, set the target preload force for all six application points to 500N. Simultaneously set the allowable error range, for example, ±5%. Then the allowable pressure range for each point is 475N to 525N.

[0063] Step 7: Start the servo motor 51 for initial downward pressure:

[0064] The servo motor 51 is started, and the servo motor 51 drives the driven gear 53 to rotate through the driving gear 52, which in turn drives the lead screw 54 to rotate. The lead screw 54 drives the second clamping plate 4 to move slowly downward. When the second clamping plate 4 contacts the battery test piece 8 and the compensation support column 11, it enters a low-speed pressurization state to avoid damage to the battery test piece 8, the annular pressure film sensor 9, or the clamping structure caused by instantaneous impact.

[0065] Step 8: Collect the preload force at each point:

[0066] The control host reads the output values ​​of each annular pressure diaphragm sensor 9 in real time and converts them into F1, F2, F3, F4, F5, and F6. The control host then compares the measured pressure at each point with the target pressure of 500N.

[0067] Step 9: Perform negative feedback adjustment:

[0068] When the pressure at a certain point is lower than the target range, for example, F2 = 460N, which is less than 475N, the control host determines that the pressure at point P2 is insufficient and controls the servo motor 51 corresponding to P2 to continue to press down slightly. When the pressure at a certain point is higher than the target range, for example, F4 = 540N, which is higher than 525N, the control host determines that the pressure at point P4 is too high and controls the servo motor 51 corresponding to P4 to retract slightly. When the pressure at a certain point is between 475N and 525N, that point maintains its current position. The control host repeatedly executes the process of "acquiring pressure - calculating error - adjusting lead screw 54 - acquiring pressure again" until the pressure at all points falls within the set error range.

[0069] Step 10: Check the parallelism of each clamping plate.

[0070] Gyroscopes 10 are installed on the second clamping plate 4 and the first clamping plate 2 respectively. The control host reads the attitude angles of the second clamping plate 4 and the first clamping plate 2 in real time and calculates the relative tilt between them. If the second clamping plate 4 is detected to be tilted relative to the first clamping plate 2, for example, tilting downward to the left, it indicates that the left area may be too tightly compressed, while the right area may be insufficiently compressed. At this time, the control host, based on the pressure values ​​at each point, makes fine adjustments to the corresponding servo motors 51 on the left or right side, so that the second clamping plate 4 gradually returns to a parallel state.

[0071] Step 11: Determine if uniform pre-tightening is complete.

[0072] The uniform preload is considered to have been applied successfully when the following conditions are met:

[0073] The measured pressures at all six points were within the allowable error range of the target pressure.

[0074] The relative tilt between the second clamping plate 4 and the first clamping plate 2 is less than the set threshold.

[0075] The pressure at each point remained relatively stable for a certain period of time.

[0076] For example, if the pressure at all six points remains stable between 475N and 525N and shows no significant change after 30 seconds, the system determines that the uniform pre-tightening of the plane is complete.

[0077] Step 12, Maintaining stability during the cyclic testing process:

[0078] During the charge-discharge cycle of battery specimen 8, the pressure at various points may change due to expansion, contraction, temperature rise, or structural relaxation. The control host continues to collect the pressure at each point in real time and matches it with data such as voltage, current, temperature, SOC, and cycle count of battery specimen 8 for subsequent analysis of the battery expansion force variation pattern. If the pressure at a certain point deviates from the target range, the system restarts negative feedback fine-tuning to restore that point to the target pressure range.

[0079] The second method is to apply a gradient preload. This embodiment is used to ensure that the preload at each point of force application in the pressure plane of the battery specimen 8 is distributed according to a preset gradient, thereby simulating the stress state of the battery under non-uniform constraint conditions in the module or battery pack.

[0080] Step 1: Complete the installation of the fixture and battery specimen 8.

[0081] Following steps one through five of the first planar uniform preload application method, complete the initial fixture inspection, battery specimen 8 placement, compensation support column 11 adjustment, annular pressure film sensor 9 installation, signal acquisition module connection, and spoke sensor 7 reference calibration.

[0082] Step 2: Divide the force application area:

[0083] Based on the positions of the lead screws 54 on the second clamping plate 4, multiple force application points are divided into different regions. For example, the six force application points are arranged in two rows and three columns: the top row is P1, P2, and P3; the bottom row is P4, P5, and P6. Among them, P2 and P5 can be defined as the central region, and P1, P3, P4, and P6 can be defined as the edge region.

[0084] Step 3: Determine the object to be simulated for gradient pressure:

[0085] Based on actual testing requirements, determine the pressure distribution pattern to be simulated. For example, if it is necessary to simulate the situation where the central region of the prismatic battery expands significantly and the edge region is less constrained, a high preload can be set in the central region and a low preload in the edge region. If it is necessary to simulate the situation where the battery specimen 8 experiences greater pressure on the side closer to the module end plate and less pressure on the side farther from the end plate, a high preload can be set on one side and a low preload on the other side.

[0086] Step 4: Set the target preload at different points:

[0087] Set the target preload for each point in the control unit. For example, when using a gradient pressure mode with a high center and low edge, you can set: P2 and P5 as the center area with a target preload of 600N; P1, P3, P4, and P6 as the edge areas with a target preload of 400N. The allowable error can still be set to ±5%, so the allowable range for the center area points is 570N to 630N; and the allowable range for the edge area points is 380N to 420N.

[0088] Step 5: Start the servo motor 51 for initial downward pressure:

[0089] The servo motor 51 is started, and the servo motor 51 drives the driven gear 53 to rotate through the driving gear 52, which in turn drives the lead screw 54 to rotate, causing the second clamping plate 4 to move slowly downward. When the second clamping plate 4 contacts the battery specimen 8 and the compensation support column 11, the system enters the low-speed loading stage. At this time, each point no longer pursues the same pressure, but is independently controlled according to its own set target pressure.

[0090] Step 6: Collect pressure data at each location:

[0091] The control host reads the output signals of each annular pressure diaphragm sensor 9 in real time and converts them into actual preload forces F1, F2, F3, F4, F5, and F6 at each point. Then, the control host compares the actual pressure at each point with the target pressure corresponding to that point. For example, F2 is compared with 600N; F5 is compared with 600N; and F1, F3, F4, and F6 are compared with 400N respectively.

[0092] Step 7: Adjust the pressure at each point independently:

[0093] The control host controls the corresponding servo motor 51 to drive the lead screw 54 for fine-tuning based on the pressure deviation at each point. For example, when the measured pressure F2 at point P2 is 550N, which is less than the target range of 570N to 630N in the central area, the control host controls the servo motor 51 corresponding to P2 to continue pressing down. When the measured pressure F5 at point P5 is 640N, which is greater than the target range of 570N to 630N in the central area, the control host controls the servo motor 51 corresponding to P5 to slightly retract. When the measured pressure F1 at point P1 is 430N, which is greater than the target range of 380N to 420N in the edge area, the control host controls the servo motor 51 corresponding to P1 to slightly retract. When the measured pressure F3 at point P3 is 390N, which is within the target range of the edge area, point P3 maintains its current position. In this way, each point is independently adjusted according to different target values, ultimately forming a preset gradient pressure distribution.

[0094] Step 8: Determine the stability of the pressure gradient.

[0095] When the pressure at points P2 and P5 in the central region stabilizes within the range of 570N to 630N, and the pressure at points P1, P3, P4, and P6 in the edge region stabilizes within the range of 380N to 420N, the control unit initially determines that the gradient pressure loading is complete. It then maintains this pressure for a period of time, such as 30 seconds. If there is no significant pressure drift at any point, the gradient preload is then determined to be applied successfully.

[0096] Step 9: Determine the clamping plate's attitude using the gyroscope 10:

[0097] Because gradient pressure itself causes different areas to experience different forces, the second clamping plate 4 may exhibit a certain tendency to tilt. The control host collects attitude angles using gyroscopes 10 on the second clamping plate 4 and the first clamping plate 2 to determine whether the clamping plate tilt exceeds the allowable range. If the tilt exceeds a set threshold, the control host corrects the tilt based on the pressure distribution target. For example, while ensuring that the pressure in the central area is higher than that in the edge area, the pressure at the points on the left and right sides within the same area is appropriately adjusted to prevent the second clamping plate 4 from tilting excessively.

[0098] Step 10: Maintain gradient pressure and conduct the test:

[0099] After applying the gradient pressure, the system can optionally enter recording mode, where the host continuously records the pressure data at each point without adjusting the preload. Alternatively, it can remain in control mode. During the charge-discharge cycle of battery specimen 8, if the pressure at a certain point deviates from its target range due to battery expansion, relaxation, or temperature changes, the system automatically performs local fine-tuning. For example, if the pressure at point P2 in the central region rises from 600N to 660N due to battery expansion, exceeding the allowable range, the host will control the corresponding servo motor 51 at P2 to slightly retract, restoring it to the target range.

[0100] Step 11: Generate gradient pressure distribution data:

[0101] The control unit generates pressure distribution data based on the pressure values ​​at each point and their corresponding spatial locations. This data can be used to analyze the 8-cycle performance, expansion behavior, capacity decay, and abnormal stress changes of battery specimens under different preload conditions. When a pressure change in a certain area deviates significantly from the normal cycle trend, it indicates a risk of abnormal expansion in that area. This data, combined with voltage, temperature, capacity, and internal resistance data, can further determine the battery's health status.

[0102] The above-described embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A battery testing fixture with multi-point preload application, characterized in that, The system includes a base (1), a first clamping plate (2), a top plate (3), a second clamping plate (4), and multiple sets of height adjustment components (5). The top wall of the base (1) and the bottom wall of the top plate (3) are fixedly connected by a side plate (6), forming a receiving space for accommodating the second clamping plate (4) and the first clamping plate (2). The first clamping plate (2) is supported above the base (1) by a spoke sensor (7), and forms a receiving space for placing a battery specimen (8) between itself and the second clamping plate (4). The battery specimen (8) is placed on the first clamping plate (2). The multiple sets of height adjustment components (5) pass through the second clamping plate (4) and the first clamping plate (2) and are installed in the receiving space, and are used to adjust the second clamping plate (4) to move closer to or further away from the first clamping plate (2) so that the second clamping plate (4) applies a pre-tightening force to the battery specimen (8). A compensating support column (11) is installed on the bottom surface of the first clamping plate (2). Each set of height adjustment components (5) includes a servo motor (51) mounted on the top wall of the top plate (3), a drive gear (52) mounted on the bottom wall of the top plate (3) and connected to the output shaft of the servo motor (51), a driven gear (53) meshing with the drive gear (52), a lead screw (54) passing through the driven gear (53) and the second clamping plate (4) and rotatably connected between the top plate (3) and the base (1), and a nut seat (55) threadedly connected to the lead screw (54). The nut seat (55) is fixedly installed on the top surface of the second clamping plate (4). The nut seat (55) is connected to the second clamping plate (4) through a guide limiting member. An upper hard pressure equalizing pad, an annular pressure film sensor (9) and a lower hard pressure equalizing pad are arranged sequentially between the lower end face of the nut seat (55) and the top surface of the second clamping plate (4). The annular pressure film sensor (9), the upper hard pressure equalizing pad and the lower hard pressure equalizing pad are all arranged around the lead screw. A gyroscope (10) is installed on the top surface of the second clamping plate (4) and the bottom surface of the first clamping plate (2). The spoke sensor (7) is used to measure the reference value of the preload of the battery specimen (8).

2. The battery test fixture with multi-point preload application according to claim 1, characterized in that, The number of height adjustment components (5) is set to 6, divided into 2 groups, each group having 3 height adjustment components (5), and each group is arranged symmetrically about the first clamping plate (2) on the red axis.

3. The battery test fixture with multi-point preload application according to claim 2, characterized in that, The upper and lower surfaces of the battery specimen (8) are provided with cushioning elements, which are foam.

4. The battery test fixture with multi-point preload application according to claim 3, characterized in that, It also includes a multi-channel data acquisition module and a control host. The multi-channel data acquisition module is used to synchronously acquire the output signals of each of the annular pressure film sensors (9), the reference signal of the spoke sensor (7), and the attitude signal of the gyroscope (10). The control host is used to receive the output signals of the annular pressure film sensors (9), the reference signal of the spoke sensor (7), and the attitude signal of the gyroscope (10), and output control commands to each servo motor (51).

5. A battery testing method for applying preload at multiple points, characterized in that, The implementation is carried out using the multi-point preload application battery test fixture as described in any one of claims 1-4, comprising: S1. Power on and check the communication status of each annular pressure film sensor (9), wheel spoke sensor (7), gyroscope (10), each servo motor (51) and control host. If any abnormality is found, an alarm will be triggered and loading will be prohibited. S2, the input target pressure distribution, allowable error range, loading speed, single fine-tuning step size, stable holding time and safety upper limit; the target pressure distribution is the same uniform pressure or gradient pressure at the test points of each annular pressure film sensor (9); S3. Collect the initial values ​​of each unloaded annular pressure film sensor (9) as the zero point, and perform benchmark calibration through the wheel spoke sensor (7) to establish the conversion relationship between the electrical signal and the actual preload. S4. Control each servo motor (51) to drive the second clamping plate (4) to approach the first clamping plate (2). When the annular pressure film sensor (9) detects that the pressure starts to rise or the second clamping plate (4) contacts the battery test piece (8) and the compensation support column (11), the closed-loop fine-tuning stage is entered. S5. Periodically collect pressure data at each test point. The attitude angle between the second clamping plate (4) and the first clamping plate (2) will and corresponding target value The pressure error was obtained by comparison. It also determines whether there is an exceedance of the safety limit, a sudden change in pressure, or an abnormal attitude. If an abnormality is found, loading is stopped or a minor rollback is performed. S6. Based on the pressure error at each test point, control the corresponding servo motor (51) to feed forward or retreat in reverse so that the pressure at each test point tends to the target range. S7. By controlling the host computer, the pressure at each test point and the attitude of the second clamping plate (4) and the first clamping plate (2) are collected again. Steps S5 to S6 are executed iteratively until the pressure at each test point is reached. All are within the allowable error range and the relative tilt of the second clamping plate (4) and the first clamping plate (2) is less than the set threshold; S8. When no significant drift occurs at any of the test points within the stable holding time, the pre-tightening force is determined to be applied and the test holding state is entered. During the charge and discharge cycle of the battery test piece (8), if the pressure at a certain test point deviates from the target range, the closed-loop fine-tuning process is automatically re-entered.

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