Battery cell capacity test method and device, computer readable storage medium and processor

Abstract

The invention provides a battery cell capacity testing method and device, a computer readable storage medium and a processor, and relates to the technical field of lithium ion power batteries. The method comprises the following steps: according to a first capacity grading process step, controlling to-be-tested cells of a current batch to carry out preliminary discharging; and after the initial discharge is finished, obtaining a preset characteristic parameter value of the to-be-tested cell. And screening out a target battery cell from the to-be-detected battery cells according to the preset characteristic parameter value. And controlling the target battery cell to perform subsequent discharge according to the second capacity grading step until the target characteristic parameter value corresponding to the subsequent discharge is smaller than or equal to the target parameter threshold value, and ending the subsequent discharge. And determining the capacity of the to-be-tested cell according to the first discharge capacity corresponding to the initial discharge, or according to the first discharge capacity corresponding to the initial discharge and the second discharge capacity corresponding to the subsequent discharge. The battery cell capacity test method provided by the invention can simplify battery cell capacity test steps, reduce energy consumption and save cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium-ion power batteries, and particularly relates to a battery cell capacity testing method and device, a computer readable storage medium and a processor. BACKGROUND

[0002] With the decreasing of fossil resources, new energy vehicles are rising in the world. As the core component of new energy vehicles, power batteries have the advantages of high specific energy, large specific power and long service life, and are therefore widely used in battery electric vehicles (BEV) and hybrid electric vehicles (HEV). Among them, lithium-ion batteries (hereinafter referred to as batteries) of ternary materials have rapidly occupied the main market of power batteries due to their outstanding advantages in capacity and performance. However, the voltage and capacity of a single battery cell that constitutes a battery cannot meet the requirements of general new energy vehicles, which requires a certain number of battery cells to be connected in series or parallel to meet customer demand, i.e. so-called battery cell grouping. Battery cell grouping has high consistency requirements for battery cells, including internal resistance, voltage and capacity, etc. The capacity and voltage of battery cells are decisively affected by the capacity grading process, which requires us to strictly control the battery cells in the capacity grading process.

[0003] The existing capacity grading process is to first charge the formed battery cell at room temperature and atmospheric pressure with a rate current of ≤1C to full state of charge (SOC) of 100% SOC, and then discharge the battery cell with a rate current of ≤1C to the cut-off voltage to obtain the capacity of the battery cell.

[0004] However, the existing technology for obtaining the capacity of the battery cell has complex test steps, long test time, high energy consumption and high production cost. SUMMARY

[0005] The present application provides a battery cell capacity testing method and device, a computer readable storage medium and a processor, which can simplify the battery cell capacity testing steps, reduce energy consumption and save costs.

[0006] In a first aspect, the present application provides a battery cell capacity testing method, which comprises: controlling the preliminary discharge of the battery cells to be tested in the current batch according to the first capacity grading step. After the preliminary discharge is completed, the preset characteristic parameter value of the battery cell to be tested is obtained. The target battery cell is selected from the battery cell to be tested according to the preset characteristic parameter value. The target battery cell is controlled to be discharged according to the second capacity grading step until the target characteristic parameter value corresponding to the subsequent discharge is less than or equal to the target parameter threshold, and the subsequent discharge is ended. The capacity of the battery cell to be tested is determined according to the first discharge capacity corresponding to the preliminary discharge, or according to the first discharge capacity corresponding to the preliminary discharge and the second discharge capacity corresponding to the subsequent discharge.

[0007] The above scheme involves controlling all cells under test in the current batch to undergo preliminary discharge in the first capacity assessment step, and then obtaining preset characteristic parameter values ​​for all cells under test. Target cells are then selected from the cells under test based on these preset characteristic parameter values. This allows for the classification of the cells under test in the current batch, identifying the target cells that require subsequent discharge. This eliminates the need for subsequent discharge of all cells under test after the preliminary discharge, simplifying the cell capacity testing process, reducing energy consumption, and saving costs.

[0008] Furthermore, the target cell is controlled to undergo subsequent discharge according to the second capacity grading step until the target characteristic parameter value corresponding to the subsequent discharge is less than or equal to the target parameter threshold, at which point the subsequent discharge ends. It is evident that the initial and subsequent discharges of the target cell are equivalent to multi-step discharge, which can eliminate the influence of external factors such as temperature and contact resistance on the cell capacity test results, thus improving the authenticity and accuracy of the cell capacity test results.

[0009] Finally, based on the first discharge capacity corresponding to the initial discharge process, or based on the first discharge capacity corresponding to the initial discharge process and the second discharge capacity corresponding to the subsequent discharge process, this application can accurately determine the true capacity of the cell under test. This facilitates optimization of capacity consistency and reduces the coefficient of variation (COV).

[0010] In one possible design, preset characteristic parameter values ​​include rebound voltage values. Target cells are selected from the cells under test based on these preset characteristic parameter values, including: Cells under test whose rebound voltage value is greater than the preset rebound voltage threshold are identified as target cells.

[0011] The above scheme utilizes the rebound voltage to reflect the degree of elimination of internal polarization effects and the recovery state of internal electrochemical balance within the tested cell. An excessively high rebound voltage may indicate severe polarization at the end of discharge, meaning the cell has not actually reached a true cutoff state, and continued discharge will lead to over-discharge. Therefore, using the rebound voltage as a preset characteristic parameter to screen target cells requiring further discharge improves the accuracy of target cell screening, facilitating accurate classification of the tested cells. This simplifies the cell capacity testing process, reduces energy consumption, and saves costs.

[0012] In one possible design, preset characteristic parameter values ​​include DC internal resistance values. Target cells are selected from the cells under test based on these preset characteristic parameter values, including: Cells with a DC internal resistance value greater than a preset DC internal resistance threshold are identified as target cells.

[0013] Through the above scheme, the tested cells with high DC internal resistance have greater polarization, and their capacity will be fully discharged. After subsequent discharge, some polarization can be eliminated in these cells with high DC internal resistance, and their true capacity will be released. Therefore, using DC internal resistance as a preset characteristic parameter to screen target cells for subsequent discharge improves the accuracy of target cell screening, facilitating accurate classification of the tested cells. This simplifies the cell capacity testing process, reduces energy consumption, and saves costs.

[0014] In one possible design, the target characteristic parameter value includes the rebound voltage value. The target cell is controlled to undergo subsequent discharge according to the second capacity grading step until the target characteristic parameter value corresponding to the subsequent discharge is less than or equal to the target parameter threshold, at which point the subsequent discharge ends, including: The target cell is then controlled to undergo subsequent discharge according to the second capacity grading step. After the subsequent discharge is completed, the rebound voltage value of the target cell is obtained. When the rebound voltage value is less than or equal to the preset rebound voltage threshold, the subsequent discharge ends.

[0015] In one possible design, the capacity of the cell under test is determined based on the first discharge capacity corresponding to the initial discharge, or based on the first discharge capacity corresponding to the initial discharge and the second discharge capacity corresponding to subsequent discharges, including: For a battery cell under test whose preset characteristic parameter value is less than or equal to the corresponding preset parameter threshold after the initial discharge, the capacity of the battery cell under test is equal to the first discharge capacity. For a battery cell under test whose preset characteristic parameter value is greater than the corresponding preset parameter threshold after the initial discharge, and whose target characteristic parameter value is less than or equal to the corresponding target parameter threshold after subsequent discharge, the capacity of the battery cell under test is equal to the sum of the first discharge capacity and the second discharge capacity.

[0016] The above scheme uses different capacity determination methods to determine the final capacity of the test cell that has only undergone preliminary discharge and the test cell that has undergone preliminary discharge and subsequent discharge. This method is objective and accurate, and helps to improve the authenticity and accuracy of the cell capacity.

[0017] In one possible design, the first filling step differs from the second filling step.

[0018] Through the above scheme, the discharge current in the second capacity grading step can be smaller than the discharge current in the first capacity grading step, and / or the discharge cutoff voltage in the second capacity grading step can be lower than the discharge cutoff voltage in the first capacity grading step. This eliminates the polarization effect and ensures the accuracy of cell capacity measurement.

[0019] In one possible design, the number of subsequent discharges is greater than or equal to 1.

[0020] Secondly, this application provides a cell capacity testing device, which includes a first control unit, an acquisition unit, a screening unit, a second control unit, and a determination unit.

[0021] The system comprises the following components: a first control unit controls the initial discharge of the current batch of cells under test according to the first capacity grading step; an acquisition unit acquires preset characteristic parameter values ​​of the cells under test after the initial discharge; a screening unit selects target cells from the cells under test based on the preset characteristic parameter values; a second control unit controls the target cells to undergo subsequent discharge according to the second capacity grading step until the target characteristic parameter value corresponding to the subsequent discharge is less than or equal to a target parameter threshold, at which point the subsequent discharge ends; and a determination unit determines the capacity of the cells under test based on the first discharge capacity corresponding to the initial discharge, or based on the first discharge capacity corresponding to the initial discharge and the second discharge capacity corresponding to the subsequent discharge.

[0022] Thirdly, this application provides a computer-readable storage medium including a stored program, wherein, when the program is running, it controls the device where the computer-readable storage medium is located to execute any of the cell capacity testing methods in the first aspect.

[0023] Fourthly, this application provides a processor for running a program, wherein the program executes any of the cell capacity testing methods in the first aspect.

[0024] The cell capacity testing apparatus provided in the second aspect, the computer-readable storage medium provided in the third aspect, and the processor provided in the fourth aspect can execute the cell capacity testing method provided in the first aspect and its various possible implementations. The beneficial effects can be found in the beneficial effects brought about by the first aspect and its various possible implementations, and will not be repeated here. Attached Figure Description

[0025] Figure 1 This is a schematic flowchart of a cell capacity testing method provided in an embodiment of this application.

[0026] Figure 2 This is a schematic diagram showing the distribution of rebound voltage after the initial discharge of the current batch of battery cells under test.

[0027] Figure 3 This is a schematic diagram showing the distribution of rebound voltage after the current batch of test cells has been fully discharged.

[0028] Figure 4 This is a schematic diagram showing the distribution of DC internal resistance of the current batch of battery cells after initial discharge.

[0029] Figure 5This is a schematic diagram showing the capacity distribution of the battery cell under test at different rebound voltage differences.

[0030] Figure 6 This is a schematic flowchart of a cell capacity testing method provided in an embodiment of this application.

[0031] Figure 7 This is a schematic flowchart of a cell capacity testing method provided in an embodiment of this application.

[0032] Figure 8 This is a schematic diagram of the structure of a battery cell capacity testing device provided in an embodiment of this application. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims and drawings of this application are intended to cover non-exclusive inclusion.

[0035] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of the phrase "embodiment" in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0036] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists, A and B exist simultaneously, or B exists. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0037] Furthermore, the terms "first," "second," etc., in the specification and claims of this application or in the aforementioned drawings are used to distinguish different objects rather than to describe a specific order, and may explicitly or implicitly include one or more of the features.

[0038] In the description of this application, unless otherwise stated, "multiple" means two or more (including two), and similarly, "multiple groups" means two or more (including two groups).

[0039] In the description of this application, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linkage" should be interpreted broadly. For example, "connection" or "linkage" in mechanical structures can refer to a physical connection. Similarly, "connection" or "linkage" in circuit structures can refer not only to a physical connection but also to an electrical or signal connection. This could be a direct connection (physical connection) or an indirect connection via at least one intermediate component, as long as the circuit is connected. It could also refer to the internal connection between two components. Signal connections can refer to connections via circuits or via media, such as radio waves. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0040] In the manufacturing process of lithium-ion batteries, capacity testing is a crucial step. It is not only used to calibrate the capacity of the cells, but also serves as an important basis for eliminating defective cells and ensuring cell consistency.

[0041] Cell capacity testing is significantly affected by cell temperature, contact resistance, and cell polarization. When cell temperature, contact resistance, or cell polarization fluctuates greatly during cell capacity testing, the cell capacity will deviate significantly, and the measured capacity will not be the true capacity of the cell, resulting in a large capacity deviation. This can lead to problems such as excessive system voltage drop and shortened lifespan during subsequent cell assembly.

[0042] To address the issue of capacity consistency, some existing technologies employ fitting methods to estimate the actual capacity of the battery cells. For example, patent CN119758109A (2025-04-05) dynamically compensates for capacity deviations caused by temperature differences in the capacity testing cabinet by fitting a functional relationship between temperature and capacity coefficient. Patent CN119846360A (2025-04-21) uses reference capacity values ​​to correct measured data from the capacity testing cabinet, improving testing accuracy without hardware upgrades. Patent CN119881690A (2025-04-29) combines the calibration capacity of the constant temperature chamber with the temperature-capacity relationship curve of the production line to construct a calibration equation, making the testing results closer to actual needs.

[0043] In other existing technologies, a multi-step discharge test is performed on all cells under test in the current batch at the same time, in order to eliminate the influence of external factors such as temperature and contact internal resistance through multi-step discharge, so as to test the true capacity of the cell.

[0044] However, the existing cell capacity testing methods are complex, time-consuming, energy-intensive, and costly to produce.

[0045] Based on the above-mentioned problems in the existing technology, this application provides a cell capacity testing method to simplify the cell capacity testing process, save testing time, reduce testing energy consumption, and lower testing costs.

[0046] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.

[0047] This application provides a method for testing the capacity of battery cells, wherein the main body executing this method is a battery cell capacity testing device. This device can be a capacity grading cabinet. The capacity grading cabinet includes a control system, a data acquisition module, channels and fixtures, a safety protection system, and a heat dissipation system. The control system acts as the brain of the capacity grading cabinet, responsible for commanding, monitoring, and managing data throughout the entire charging and discharging process. This control system can be an industrial computer, PLC, embedded controller, etc. The control system can pre-set the capacity grading steps before executing the battery cell capacity testing method, and can also execute each step of the battery cell capacity testing method according to the pre-set steps. Alternatively, the device can be a separate controller that can communicate with the capacity grading cabinet used to discharge the battery cell under test, and can control the capacity grading cabinet to perform corresponding operations. This application does not limit the specific implementation of this method.

[0048] Figure 1 This is a flowchart illustrating a cell capacity testing method provided in an embodiment of this application. This method is for cell capacity testing during the capacity grading process. The capacity grading process is a core technological step in lithium-ion battery production, primarily referring to the continuous and purposeful operational stages during cell capacity grading. Examples include constant current charging, constant voltage charging, resting (storage), and constant current discharging. By strictly controlling the parameters of charging, discharging, and resting stages, the core performance indicators of each cell can be accurately measured, such as cell capacity and internal resistance. Based on these core performance indicators, cells can be screened and graded to ensure consistent, safe, and reliable performance of battery modules composed of multiple cells. Figure 1 As shown, the method includes the following steps.

[0049] S101. Control the current batch of cells to be tested to perform preliminary discharge according to the first capacity grading step.

[0050] The current batch of cells under test consists of multiple cells from the same production batch, all intended for capacity testing. Before testing, all cells in the batch are correctly installed onto the respective channels of the capacity testing cabinet, ensuring secure connections and correct polarity. After setting the first capacity testing step and ensuring the current batch of cells under test is correctly installed onto the respective channels of the capacity testing cabinet, preliminary discharge can be initiated, allowing each channel to begin constant current discharge.

[0051] The first step of the capacitance measurement process is used to control the battery cell under test to perform an initial discharge.

[0052] In some examples, the first step of the capacitance reduction process may be to discharge to 2.5V with a constant DC current a (Amperes, A).

[0053] In some examples, the first step of the capacitance reduction process may be to discharge to 2.0V with a constant DC current a (Amperes, A).

[0054] In some examples, the first capacitance-grading step may be to discharge to 2.5V with a constant DC current a (Amperes, A), let it stand for x hours, and then discharge to 2.0V with a constant DC current b (Amperes, A). Here, x can be 50 minutes or 1 hour, etc., and b ≤ a.

[0055] In some examples, the first step of the discharge process may be to discharge to 2.5V with a constant DC current a (Amperes, A), and then discharge at a constant voltage of 2.5V, with the discharge current reduced to 0.05C to cut off the discharge.

[0056] The above only illustrates four simple first capacity-dividing steps. In actual testing, the first capacity-dividing steps can be adjusted appropriately, and the first capacity-dividing steps may also include those described in the embodiments of this application. The first capacity-dividing steps are not specifically limited.

[0057] For cells produced in the same batch, the capacity grading steps are the same during the discharge process in the same step. For example, the first capacity grading step used when the cells under test in the current batch are initially discharged in S101 can be the same, and can be any of the first capacity grading steps shown in the example above, or any other capacity grading step not shown.

[0058] S101 can control the current batch of cells under test to undergo preliminary discharge, so as to obtain the preset characteristic parameter values ​​of the cells under test after the preliminary discharge.

[0059] S102. After the initial discharge is completed, obtain the preset characteristic parameter values ​​of the cell under test.

[0060] The initial discharge in S101 is generally a constant current discharge. After the constant current discharge ends, polarization effects will exist on the electrode surface of the cell under test, including concentration polarization and electrochemical polarization. If the preset characteristic parameter values ​​of the cell under test are measured directly immediately after the initial discharge, the accuracy of the measurement will be affected because the polarization inside the cell has not yet stabilized and the cell has not returned to an equilibrium state. Therefore, after S101 or before S102, the method also includes a static treatment of the cell under test to eliminate the influence of polarization effects.

[0061] The required settling time may vary slightly depending on the material system and capacity of the battery cells. The settling time can follow the capacity testing cabinet operating procedures or the technical specifications provided by the battery cell manufacturer. For example, the settling time could be 30 minutes, 1 hour, 2 hours, etc.

[0062] Furthermore, since temperature fluctuations can affect the voltage stability and internal chemical reaction rate of the battery cell under test, thereby affecting the settling effect and the accuracy of the preset characteristic parameter measurements, the settling process should be carried out in a constant temperature environment. For example, it can be settling at a constant temperature of 25±2℃.

[0063] After the cell under test has been allowed to stand for a while, the preset characteristic parameter values ​​of the cell under test can be obtained through S102.

[0064] The preset characteristic parameter values ​​are the preset characteristic parameters of the cell under test. These preset characteristic parameters can be parameters that reveal the internal state of the cell, such as rebound voltage or DC internal resistance (DCR). They are also important parameters used to determine whether the initial discharge has truly stopped, ensuring the accuracy of capacity testing and the health of the cell.

[0065] Taking the capacity testing method using a capacity grading cabinet as an example, the preset characteristic parameter values ​​can be acquired by the data acquisition module of the capacity grading cabinet. After acquiring the preset characteristic parameter values, the data acquisition module can send these values ​​to the display module, allowing the display module to show the preset characteristic parameter values ​​and thus enabling the testing personnel to understand the specific discharge situation. After acquiring the preset characteristic parameter values, the data acquisition module can also send these values ​​to the control system, so that the control system can perform the following operation S103 based on the preset characteristic parameter values.

[0066] S103. Select the target cell from the cells to be tested according to the preset characteristic parameter values.

[0067] Each preset characteristic parameter value corresponds to a preset parameter threshold, and different preset characteristic parameter values ​​correspond to different preset parameter thresholds. For example, when the preset characteristic parameter is rebound voltage, the rebound voltage value corresponds to a preset rebound voltage threshold. When the preset characteristic parameter is DC internal resistance, the DC internal resistance value corresponds to a preset DC internal resistance threshold.

[0068] The specific implementation process of S103 can be as follows: compare the preset characteristic parameter value with the corresponding preset parameter threshold; filter the battery cells to be tested whose preset characteristic parameter value is greater than the corresponding preset parameter threshold; and determine the selected battery cells to be tested as target battery cells.

[0069] Therefore, the target cell is selected from the current batch of cells under test whose preset characteristic parameter values ​​are greater than the corresponding preset parameter thresholds. Thus, the cells under test in the current batch are classified into two categories: the first category consists of cells whose preset characteristic parameter values ​​are less than or equal to the corresponding preset parameter thresholds after initial discharge; these cells only require initial discharge and do not need further discharge. The second category consists of cells whose preset characteristic parameter values ​​are greater than the corresponding preset parameter thresholds after initial discharge; these are the target cells. These cells require not only initial discharge but also further discharge after the initial discharge, as shown in S104. This classification saves the subsequent discharge process for the first category of cells under test, simplifies the cell capacity testing process, reduces energy consumption, and saves costs.

[0070] As can be seen, the S103 can be used to classify the cells under test in the current batch to determine which cells under test only need to be initially discharged and which cells under test need to be subsequently discharged after the initial discharge. This avoids performing subsequent discharge on all cells under test in the current batch after the initial discharge, thereby simplifying the cell capacity testing process, reducing energy consumption and saving costs.

[0071] It should be noted that for the first type of battery cell under test, when the obtained preset characteristic parameter value is less than or equal to the corresponding preset parameter threshold, the channel where the battery cell under test is located will automatically stop the initial discharge.

[0072] S104. Control the target cell to perform subsequent discharge according to the second capacity grading step.

[0073] The timing of the second capacity testing step can be either before executing the cell capacity testing method or at any time before executing S104, as long as it does not affect the execution of S104. This application embodiment does not limit this.

[0074] The second capacity grading step is used to control the target cell to perform subsequent discharge. The second capacity grading step can be the same as the first capacity grading step, or it can be different from the first capacity grading step.

[0075] To eliminate polarization effects and ensure the accuracy of cell capacity measurement, the discharge current in the second capacity grading step can be smaller than the discharge current in the first capacity grading step, and / or the discharge cutoff voltage in the second capacity grading step can be lower than the discharge cutoff voltage in the first capacity grading step. For example, if the first capacity grading step discharges to 2.5V with a constant current of 0.2C, the second capacity grading step can discharge to 2.0V with a constant current of 0.1C. The above are merely examples of the first and second capacity grading steps and do not constitute a limitation on the technical solution of this application.

[0076] It should be noted that after performing a subsequent discharge on the target cell in S104, some target cells will meet the trigger condition for the end of the subsequent discharge (i.e., the target characteristic parameter value corresponding to the subsequent discharge is less than or equal to the target parameter threshold), while others will not. For target cells that still do not meet the trigger condition for the end of the subsequent discharge, a second or even more subsequent discharges are required. Therefore, after S104, S105 is needed to determine whether the target characteristic parameter value corresponding to the subsequent discharge is less than or equal to the target parameter threshold. If yes, then S106 is executed; otherwise, the process returns to S104 and subsequent steps.

[0077] For a target cell requiring multiple subsequent discharges, the second capacity grading steps corresponding to each subsequent discharge can be the same or different. When the second capacity grading steps for multiple subsequent discharges are different, to eliminate polarization effects and ensure the accuracy of cell capacity measurement, the discharge current in the second capacity grading step of each subsequent discharge can be smaller than that of each previous discharge, and / or the discharge cutoff voltage in the corresponding second capacity grading step can be lower. For example, if the second capacity grading step corresponding to the first subsequent discharge is a constant current discharge of 0.1C to 2.0V, the second capacity grading step corresponding to the second subsequent discharge can be a constant current discharge of 0.05C to 2.0V. The above is merely an example of the second capacity grading steps for multiple subsequent discharges and does not constitute a limitation on the technical solution of this application.

[0078] S105. Determine whether the target characteristic parameter value corresponding to the subsequent discharge is less than or equal to the target parameter threshold.

[0079] The target characteristic parameter value is the value of the target characteristic parameter of the target battery cell. The target characteristic parameter can be a parameter that reveals the internal state of the battery cell, and it is also an important parameter used to determine whether the subsequent discharge has truly stopped, which can ensure the accuracy of capacity testing and the health of the battery cell.

[0080] The target characteristic parameter value can be acquired by the data acquisition module of the discharge control cabinet. After acquiring the target characteristic parameter value, the data acquisition module can send it to the display module so that the display module can display the target characteristic parameter value, thereby facilitating the inspection personnel to understand the specific discharge situation. After acquiring the target characteristic parameter value, the data acquisition module can also send the target characteristic parameter value to the control system so that the control system can execute the operation of S105 based on the target characteristic parameter value.

[0081] S106, End subsequent discharge.

[0082] For target cells whose target characteristic parameter values ​​are less than or equal to the target parameter threshold, the channel containing the target cell will automatically stop discharging.

[0083] S107. Determine the capacity of the cell under test based on the first discharge capacity corresponding to the initial discharge, or based on the first discharge capacity corresponding to the initial discharge and the second discharge capacity corresponding to the subsequent discharge.

[0084] The first discharge capacity is equal to the product of the discharge current and the discharge duration during the initial discharge process.

[0085] For a target cell requiring only one subsequent discharge, the second discharge capacity is equal to the product of the discharge current and the discharge duration during that subsequent discharge. For a target cell requiring multiple subsequent discharges, the second discharge capacity is equal to the sum of the discharge capacities corresponding to all subsequent discharges. Specifically, the discharge capacity corresponding to each subsequent discharge is equal to the product of the discharge current and the discharge duration during that subsequent discharge.

[0086] In this embodiment, after controlling all cells under test in the current batch to undergo preliminary discharge according to the first capacity grading step, preset characteristic parameter values ​​of all cells under test are obtained. Then, target cells are selected from the cells under test based on the preset characteristic parameter values. In this way, the cells under test in the current batch can be classified, and target cells that need to be subsequently discharged can be determined. This eliminates the need to perform subsequent discharge on all cells under test after the preliminary discharge, thereby simplifying the cell capacity testing process, reducing energy consumption, and saving costs.

[0087] Furthermore, the target cell is controlled to undergo subsequent discharge according to the second capacity grading step until the target characteristic parameter value corresponding to the subsequent discharge is less than or equal to the target parameter threshold, at which point the subsequent discharge ends. It is evident that the initial and subsequent discharges of the target cell are equivalent to multi-step discharge, which can eliminate the influence of external factors such as temperature and contact resistance on the cell capacity test results, thus improving the authenticity and accuracy of the cell capacity test results.

[0088] Finally, based on the first discharge capacity corresponding to the initial discharge process, or based on the first discharge capacity corresponding to the initial discharge process and the second discharge capacity corresponding to the subsequent discharge process, this application can accurately determine the true capacity of the cell under test. This facilitates optimization of capacity consistency and reduces the capacity variation coefficient.

[0089] In summary, the cell capacity testing method provided in this application not only eliminates the influence of external factors such as temperature and contact resistance on the cell capacity test results, but also simplifies the cell capacity testing process, reducing energy consumption and saving costs. Therefore, this application can simplify the cell capacity testing process while ensuring the authenticity and accuracy of the cell capacity test results, thus achieving the effects of reducing energy consumption and saving costs.

[0090] Based on the cell capacity testing method provided in the above embodiments, in a first possible implementation, the preset characteristic parameter can be the rebound voltage, the preset characteristic parameter value corresponds to the rebound voltage value, and the rebound voltage value corresponds to a preset rebound voltage threshold. In this case, the process of selecting target cells from the cells under test according to the preset characteristic parameter value can be: determining the cells under test with rebound voltage values ​​greater than the preset rebound voltage threshold as target cells.

[0091] Specifically, after the initial discharge, the rebound voltage values ​​of all cells under test can be obtained. Then, the obtained rebound voltage values ​​are compared with a preset rebound voltage threshold, and cells with rebound voltage values ​​greater than the preset threshold are selected as target cells. Finally, the selected cells with rebound voltage values ​​greater than the preset threshold are determined as target cells.

[0092] The rebound voltage reflects the degree of elimination of internal polarization effects and the recovery state of internal electrochemical balance in the tested battery cell. An excessively high rebound voltage may indicate that the tested cell was severely polarized at the end of discharge and had not actually reached a true cutoff state; continued discharge would lead to over-discharge. Alternatively, the rebound voltage can reflect the true state of charge (SOC) of the tested cell to a certain extent, especially in the low SOC range below 10%. Every 1% SOC difference in rebound voltage indicates a significant difference. A high rebound voltage suggests that due to temperature, contact resistance, or polarization, the tested cell has not discharged to 0% SOC and requires further discharge to completely deplete its capacity. Therefore, the rebound voltage can be used as a preset characteristic parameter to screen target cells that require further discharge.

[0093] Figure 2 This is a schematic diagram showing the distribution of rebound voltage after the initial discharge of the current batch of battery cells under test. Figure 2 The horizontal axis represents the cell serial number, and the vertical axis represents the rebound voltage value, in mV (millivolts). Additionally, Figure 2The rebound voltage of the cell under test was measured after the initial discharge was completed and the cell under test was left to stand for 10 minutes.

[0094] like Figure 2 As shown, after the initial discharge, the rebound voltage of the tested cells mainly ranges from 2000mV to 2300mV, although some cells exhibit rebound voltages exceeding 2300mV. Therefore, the preset rebound voltage threshold can be set to 2300mV. Consequently, when selecting target cells from the tested cells based on their rebound voltage values, cells with rebound voltages greater than 2300mV can be identified as target cells for subsequent discharge.

[0095] Figure 3 This is a schematic diagram showing the rebound voltage distribution of the test cells in the current batch after full discharge. Some test cells only underwent initial discharge, while others underwent one or more subsequent discharges after the initial discharge. All test cells were fully discharged. Full discharge means that the preset characteristic parameter value of the test cell is less than or equal to a preset parameter threshold at the end of the initial discharge, or that the target characteristic parameter value is less than or equal to a target parameter threshold at the end of the subsequent discharge. Figure 3 The horizontal axis represents the cell number, and the vertical axis represents the rebound voltage value, in mV. Figure 3 The rebound voltage of the cell under test is measured after all discharges have ended and the cell under test has been left to stand still.

[0096] like Figure 3 As shown, after being fully discharged, the rebound voltage of the tested cells is less than 2300mV.

[0097] In the second possible implementation, the preset characteristic parameter can be the DC internal resistance, and the preset characteristic parameter value corresponds to the DC internal resistance value, which in turn corresponds to a preset DC internal resistance threshold. In this case, the process of selecting the target cell from the cells under test based on the preset characteristic parameter value can be as follows: the cells under test with a DC internal resistance value greater than the preset DC internal resistance threshold are identified as the target cells.

[0098] Specifically, after the initial discharge, the DC internal resistance values ​​of all cells under test can be obtained. Then, the obtained DC internal resistance values ​​are compared with a preset DC internal resistance threshold, and cells with DC internal resistance values ​​greater than the preset threshold are selected as target cells. Finally, the selected cells with DC internal resistance values ​​greater than the preset threshold are identified as target cells.

[0099] Because the tested cells with high DC internal resistance have greater polarization, their capacity will be fully discharged. After subsequent discharge, some polarization of these tested cells with high DC internal resistance can be eliminated, and their true capacity can be discharged. Therefore, DC internal resistance can be used as a preset characteristic parameter to screen target cells that need to be subsequently discharged.

[0100] Figure 4 This is a schematic diagram showing the DC internal resistance distribution of the current batch of battery cells after initial discharge. Figure 4 The horizontal axis represents the cell serial number, and the vertical axis represents the DC internal resistance value, in mΩ (milliohms). Additionally, Figure 4 The DC internal resistance of the battery cell under test is measured after the initial discharge is completed and the battery cell is left to stand still.

[0101] like Figure 4 As shown, after the initial discharge of the battery cell under test, the DC internal resistance of the rebound voltage is mainly concentrated below 0.6mΩ, although some battery cells under test have a DC internal resistance exceeding 0.6mΩ. Therefore, the preset DC internal resistance threshold can be set to 0.6mΩ. Thus, when selecting target battery cells from the battery cells under test based on their DC internal resistance, battery cells with a DC internal resistance greater than 0.6mΩ can be identified as target battery cells for subsequent discharge.

[0102] It should be noted that this application only illustrates the selection of target cells from the cells under test based on the values ​​of two preset characteristic parameters, namely rebound voltage and DC internal resistance, and does not constitute a limitation on the technical solution of this application. In practice, other characteristic parameters of the cell can also be used as preset characteristic parameters, and target cells can also be selected from the cells under test based on the values ​​of these preset characteristic parameters. This application does not limit this.

[0103] Based on the above example, regardless of whether the target cell is selected from the cells under test based on the rebound voltage value, DC internal resistance value, or other preset characteristic parameter values, the decision to end the subsequent discharge process can be determined based on the rebound voltage value. Therefore, in some possible designs, the target characteristic parameter can be the rebound voltage, and the target characteristic parameter value corresponds to the rebound voltage value.

[0104] In this case, the target cell is controlled to perform subsequent discharge according to the second capacity grading step until the target characteristic parameter value corresponding to the subsequent discharge is less than or equal to the target parameter threshold, and the subsequent discharge ends. The implementation process can be as follows: the target cell is controlled to perform subsequent discharge according to the second capacity grading step; after the subsequent discharge ends, the rebound voltage value of the target cell is obtained; when the rebound voltage value is less than or equal to the preset rebound voltage threshold, the subsequent discharge ends.

[0105] The reasons for using rebound voltage as the target characteristic parameter are similar to those for using rebound voltage as the preset characteristic parameter, and will not be repeated here.

[0106] Based on the cell capacity testing method provided in the above embodiments, for a cell under test that only needs to undergo preliminary discharge, the process of determining the capacity of the cell under test according to the first discharge capacity corresponding to the preliminary discharge, or according to the first discharge capacity corresponding to the preliminary discharge and the second discharge capacity corresponding to the subsequent discharge, can be as follows: for a cell under test whose preset characteristic parameter value is less than or equal to the corresponding preset parameter threshold after the preliminary discharge, the capacity of the cell under test is equal to the first discharge capacity.

[0107] Because the tested cells with preset characteristic parameter values ​​less than or equal to the corresponding preset parameter thresholds only underwent preliminary discharge and not subsequent discharge, these tested cells only have discharge parameters corresponding to the preliminary discharge process, and not discharge parameters corresponding to the subsequent discharge process. These discharge parameters include parameters such as discharge current value and discharge duration.

[0108] The initial discharge capacity corresponding to the initial discharge is equal to the product of the discharge current and the discharge duration during the initial discharge process.

[0109] For cells under test whose preset characteristic parameter values ​​are less than or equal to the corresponding preset parameter thresholds after the initial discharge, these cells only need to undergo initial discharge to achieve a full discharge effect. Therefore, after the initial discharge, the first discharge capacity can be determined based on the discharge parameters corresponding to the initial discharge, and the first discharge capacity can be determined as the true capacity of these cells under test. This improves the efficiency of capacity testing of these cells under test and avoids over-discharge caused by subsequent discharge of these cells under test, or unnecessary energy consumption and cost losses.

[0110] It should be noted that, for test cells that only require preliminary discharge, the timing for determining the capacity of these test cells can be either after the preliminary discharge is completed or after all test cells in the current batch have completed all discharge processes. This application does not limit this to either of these methods.

[0111] Based on the cell capacity testing method provided in the above embodiments, for a target cell that needs to undergo subsequent discharge, the process of determining the capacity of the cell under test according to the first discharge capacity corresponding to the initial discharge, or according to the first discharge capacity corresponding to the initial discharge and the second discharge capacity corresponding to the subsequent discharge, can be as follows: for a cell under test whose preset characteristic parameter value is greater than the corresponding preset parameter threshold after the initial discharge, and whose target characteristic parameter value is less than or equal to the corresponding target parameter threshold after the subsequent discharge, the capacity of the cell under test is equal to the sum of the first discharge capacity and the second discharge capacity.

[0112] Because the target cells with preset characteristic parameter values ​​greater than the corresponding preset parameter thresholds underwent not only initial discharge but also subsequent discharge, these target cells possess discharge parameters corresponding to the initial discharge process and the subsequent discharge process. These discharge parameters include parameters such as discharge current value and discharge duration.

[0113] As described above, the first discharge capacity corresponding to the initial discharge is equal to the product of the discharge current and the discharge duration during the initial discharge process.

[0114] As explained in S104, the target cell undergoes a subsequent discharge more than or equal to 1 time. For target cells that have undergone different subsequent discharges, the method for determining the corresponding second discharge capacity can be found in the explanation in S107, which will not be repeated here.

[0115] For test cells whose preset characteristic parameter values ​​are greater than the corresponding preset parameter thresholds after the initial discharge, and whose target characteristic parameter values ​​are less than or equal to the corresponding target parameter thresholds after subsequent discharges, one or more subsequent discharges are required after the initial discharge to achieve a full discharge effect. Furthermore, both the initial and subsequent discharges have corresponding discharge capacities. Therefore, the final capacity of these test cells is determined by summing the first discharge capacity corresponding to the initial discharge and the second discharge capacity corresponding to the subsequent discharge, ensuring a true and accurate cell capacity.

[0116] Figure 5 This is a schematic diagram showing the capacity distribution of the battery cell under test at different rebound voltage differences. Figure 5 The horizontal axis represents the cell number, and the vertical axis represents the cell capacity, in Ah (ampere-hours). Figure 5 The orange dots represent the capacity of the cell under test when the rebound voltage difference is small, and the blue dots represent the capacity of the cell under test when the rebound voltage difference is large.

[0117] like Figure 5 As shown, when the rebound voltage difference is large, the capacity difference of the tested cells is large, and the capacity distribution is relatively dispersed. When the rebound voltage difference is small, the capacity difference of the tested cells is small, and the capacity distribution is relatively concentrated. Therefore, it is necessary to perform one or more discharge steps on the tested cells to make their rebound voltage values ​​less than or equal to a preset rebound voltage threshold. This results in a more concentrated rebound voltage value and a smaller rebound voltage difference among the tested cells, ensuring a more concentrated capacity distribution and facilitating cell pairing.

[0118] Figure 6 This is a flowchart illustrating a cell capacity testing method provided in an embodiment of this application. According to a specific embodiment of this application, as follows... Figure 6 As shown, the cell capacity testing method includes the following steps.

[0119] S601. Control the current batch of cells under test to perform preliminary discharge according to the first capacity grading step.

[0120] The specific implementation of S601 is similar to that of S101 mentioned above, and this application will not elaborate on S601 here.

[0121] S602. After the initial discharge is completed, obtain the rebound voltage value of the cell under test.

[0122] The specific implementation of S602 is similar to that of S102 mentioned above, and this application will not elaborate on S602 here.

[0123] S603. The test cell whose rebound voltage value is greater than the preset rebound voltage threshold is identified as the target cell.

[0124] S604. Control the target cell to perform subsequent discharge according to the second capacity grading step.

[0125] The specific implementation of S604 is similar to that of S104 mentioned above, and this application will not elaborate on S604 here.

[0126] S605. Determine whether the rebound voltage value corresponding to the subsequent discharge is less than or equal to the preset rebound voltage threshold.

[0127] If yes, then execute S606; otherwise, return to execute S604 and subsequent steps.

[0128] S606, End subsequent discharge.

[0129] For the cell under test whose rebound voltage value is less than or equal to the corresponding preset rebound voltage threshold after the initial discharge, the capacity of the cell under test shall be determined according to S607. For the cell under test whose rebound voltage value is greater than the corresponding preset rebound voltage threshold after the initial discharge, and whose rebound voltage value is less than or equal to the corresponding preset rebound voltage threshold after subsequent discharge, the capacity of the cell under test shall be determined according to S608.

[0130] S607. The first discharge capacity corresponding to the initial discharge is determined as the capacity of the cell to be tested.

[0131] S608. The capacity of the cell under test is determined by summing the first discharge capacity corresponding to the initial discharge and the second discharge capacity corresponding to the subsequent discharge.

[0132] Figure 7 This is a flowchart illustrating a cell capacity testing method provided in an embodiment of this application. According to a specific embodiment of this application, as follows... Figure 7As shown, the cell capacity testing method includes the following steps.

[0133] S701. Control the current batch of cells under test to perform preliminary discharge according to the first capacity grading step.

[0134] The specific implementation of S701 is similar to that of S101 mentioned above, and this application will not elaborate on S701 here.

[0135] S702. After the initial discharge is completed, obtain the DC internal resistance value of the cell under test.

[0136] The specific implementation of S702 is similar to that of S102 mentioned above, and this application will not elaborate on S702 here.

[0137] S703. The cell under test with a DC internal resistance value greater than the preset DC internal resistance threshold is identified as the target cell.

[0138] S704. Control the target cell to perform subsequent discharge according to the second capacity grading step.

[0139] The specific implementation of S704 is similar to that of S104 mentioned above, and this application will not elaborate on S704 here.

[0140] S705. Determine whether the rebound voltage value corresponding to the subsequent discharge is less than or equal to the preset rebound voltage threshold.

[0141] If yes, proceed to step S706; otherwise, return to step S704 and the subsequent steps.

[0142] S706, End subsequent discharge.

[0143] For the cell under test whose DC internal resistance is less than or equal to the corresponding preset DC internal resistance threshold after the initial discharge, the capacity of the cell under test shall be determined according to S707. For the cell under test whose DC internal resistance is greater than the corresponding preset DC internal resistance threshold after the initial discharge, and whose rebound voltage is less than or equal to the corresponding preset rebound voltage threshold after subsequent discharge, the capacity of the cell under test shall be determined according to S708.

[0144] S707. The first discharge capacity corresponding to the initial discharge is determined as the capacity of the cell to be tested.

[0145] S708. The capacity of the cell under test is determined by summing the first discharge capacity corresponding to the initial discharge and the second discharge capacity corresponding to the subsequent discharge.

[0146] It should be noted that in the foregoing embodiments, the preset characteristic parameter value can be either the rebound voltage value or the rebound voltage range value. The rebound voltage range value is the difference between the rebound voltage value and the discharge cutoff voltage. When the preset rebound voltage threshold is 2300mV, the preset rebound voltage range threshold can be 300mV. Assuming the preset characteristic parameter value is the rebound voltage range value, then the rebound voltage value in the above embodiments can be replaced with the rebound voltage range value, and the preset rebound voltage threshold in the above embodiments can be replaced with the preset rebound voltage range threshold.

[0147] Figure 8 This is a schematic diagram of the structure of a cell capacity testing device provided in an embodiment of this application, as shown below. Figure 8 As shown, the battery cell capacity testing device provided in this application embodiment includes a first control unit 801, an acquisition unit 802, a screening unit 803, a second control unit 804, and a determination unit 805.

[0148] The first control unit 801 is used to control the current batch of cells under test to perform preliminary discharge according to the first capacity grading step.

[0149] The acquisition unit 802 is used to acquire the preset characteristic parameter values ​​of the battery cell under test after the initial discharge is completed.

[0150] The screening unit 803 is used to screen out target cells from the cells to be tested according to preset characteristic parameter values.

[0151] The second control unit 804 is used to control the target cell to perform subsequent discharge according to the second capacity grading step until the target characteristic parameter value corresponding to the subsequent discharge is less than or equal to the target parameter threshold, and then the subsequent discharge ends.

[0152] The determining unit 805 is used to determine the capacity of the cell under test based on the first discharge capacity corresponding to the initial discharge, or based on the first discharge capacity corresponding to the initial discharge and the second discharge capacity corresponding to the subsequent discharge.

[0153] In some possible designs, the screening unit 803 is specifically used to identify the battery cell under test whose rebound voltage value is greater than a preset rebound voltage threshold as the target battery cell.

[0154] In some possible designs, the screening unit 803 is also specifically used to identify the test cell whose DC internal resistance value is greater than a preset DC internal resistance threshold as the target cell.

[0155] In some possible designs, the target characteristic parameter values ​​include the bounce voltage value.

[0156] The second control unit 804 is specifically used to control the target cell to perform subsequent discharge according to the second capacity grading step. After the subsequent discharge ends, the rebound voltage value of the target cell is acquired. When the rebound voltage value is less than or equal to a preset rebound voltage threshold, the subsequent discharge ends.

[0157] In some possible designs, the determining unit 805 is specifically used to determine that, for a cell under test whose preset characteristic parameter value is less than or equal to the corresponding preset parameter threshold after the initial discharge, the capacity of the cell under test is equal to the first discharge capacity.

[0158] For a cell under test whose preset characteristic parameter value is greater than the corresponding preset parameter threshold after the initial discharge, and whose target characteristic parameter value is less than or equal to the corresponding target parameter threshold after subsequent discharge, the capacity of the cell under test is equal to the sum of the first discharge capacity and the second discharge capacity.

[0159] In some possible designs, the first filling step differs from the second filling step.

[0160] In some possible designs, the number of subsequent discharges is greater than or equal to 1.

Claims

1. A method for testing the capacity of a battery cell, characterized in that, include: The first capacity grading step controls the initial discharge of the current batch of cells to be tested; After the initial discharge is completed, the preset characteristic parameter values ​​of the battery cell under test are obtained; Target cells are selected from the cells to be tested based on the preset characteristic parameter values; According to the second capacity grading step, the target cell is controlled to perform subsequent discharge until the target characteristic parameter value corresponding to the subsequent discharge is less than or equal to the target parameter threshold, and then the subsequent discharge ends. The capacity of the cell under test is determined based on the first discharge capacity corresponding to the initial discharge, or based on the first discharge capacity corresponding to the initial discharge and the second discharge capacity corresponding to the subsequent discharge.

2. The method according to claim 1, characterized in that, The preset characteristic parameter value includes a rebound voltage value, and the step of selecting target cells from the cells under test based on the preset characteristic parameter value includes: The cell under test whose rebound voltage value is greater than the preset rebound voltage threshold is identified as the target cell.

3. The method according to claim 1, characterized in that, The preset characteristic parameter value includes a DC internal resistance value. The step of selecting target cells from the cells under test based on the preset characteristic parameter value includes: The cell under test whose DC internal resistance value is greater than the preset DC internal resistance threshold is identified as the target cell.

4. The method according to claim 2 or 3, characterized in that, The target characteristic parameter value includes the rebound voltage value; The step of controlling the target cell to perform subsequent discharge according to the second capacity grading step, until the target characteristic parameter value corresponding to the subsequent discharge is less than or equal to the target parameter threshold, and then ending the subsequent discharge, includes: The target battery cell is subsequently discharged according to the second capacity grading step; After the subsequent discharge ends, the rebound voltage value of the target cell is obtained; When the rebound voltage value is less than or equal to the preset rebound voltage threshold, the subsequent discharge ends.

5. The method according to claim 4, characterized in that, Determining the capacity of the cell under test based on the first discharge capacity corresponding to the initial discharge, or based on the first discharge capacity corresponding to the initial discharge and the second discharge capacity corresponding to the subsequent discharge, includes: For a cell under test whose preset characteristic parameter value is less than or equal to the corresponding preset parameter threshold after the initial discharge is completed, the capacity of the cell under test is equal to the first discharge capacity. For a cell under test whose preset characteristic parameter value is greater than the corresponding preset parameter threshold after the initial discharge, and whose target characteristic parameter value is less than or equal to the corresponding target parameter threshold after the subsequent discharge, the capacity of the cell under test is equal to the sum of the first discharge capacity and the second discharge capacity.

6. The method according to claim 1, characterized in that, The first capacity division step is different from the second capacity division step.

7. The method according to claim 1, characterized in that, The number of subsequent discharges is greater than or equal to 1.

8. A cell capacity testing device, characterized in that, include: The first control unit is used to control the current batch of cells under test to perform preliminary discharge according to the first capacity grading step; The acquisition unit is used to acquire preset characteristic parameter values ​​of the battery cell under test after the initial discharge is completed; A screening unit is used to screen out target cells from the cells to be tested according to the preset characteristic parameter values; The second control unit is used to control the target cell to perform subsequent discharge according to the second capacity grading step, until the target characteristic parameter value corresponding to the subsequent discharge is less than or equal to the target parameter threshold, and then the subsequent discharge ends. The determining unit is used to determine the capacity of the cell under test based on the first discharge capacity corresponding to the initial discharge, or based on the first discharge capacity corresponding to the initial discharge and the second discharge capacity corresponding to the subsequent discharge.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes a stored program, wherein, when the program is executed, it controls the device containing the computer-readable storage medium to perform the cell capacity testing method according to any one of claims 1 to 7.

10. A processor, characterized in that, The processor is used to run a program, wherein the program executes the cell capacity testing method according to any one of claims 1 to 7.

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