Battery cell testing method

Abstract

The application provides a battery cell testing method, which comprises the following steps: obtaining a reference battery cell from a plurality of battery cells to be tested; discharging the reference battery cell at a constant current value; determining whether the difference between the power of the reference battery cell and a preset power is within a preset range; if the difference between the power of the reference battery cell and the preset power is within the preset range, taking the constant current value as a reference current value; discharging non-reference battery cells in the plurality of battery cells to be tested at the reference current value; and determining whether the non-reference battery cells meet the requirements. The technical scheme provided by the application can solve the problem that the method of testing battery cells by using a fixed current value in the related art has a high risk.

Description

Technical Field

[0001] The present invention relates to the technical field of power batteries, and in particular to a battery cell testing method. Background Art

[0002] With the development of the new energy vehicle industry, the demand for new energy power batteries is increasing, and car companies are also placing higher and higher demands on the power density and endurance of battery cells. The overall power density and life of a car battery pack are usually closely related to the consistency of the grouped battery cells. If the consistency of the grouped battery cells is relatively poor, using the same current for charging and discharging will cause some batteries to be overcharged or over-discharged, thereby shortening the overall cycle life of the module. In order to improve the consistency of shipped batteries, battery suppliers usually formulate corresponding shipping specifications. Before the battery cells are shipped to the customer, necessary sorting processes are added to remove batteries with relatively large DCR (Directive Current Resistance) deviations, so that qualified battery cells meet the customer's power requirements.

[0003] In related technologies, due to the limitations of the test equipment range, for power-type cells, battery suppliers generally use simple online discharge DCR test results (for example, fixed current value, discharge for 10s) to determine whether they are within the preset specification range as the basis for cell shipment.

[0004] However, under the same conditions, the power value and DCR value of the same battery cell do not show a strict negative correlation. That is, a battery cell with a small DCR value does not necessarily have a large power value, and a battery cell with a DCR value outside the preset specification range may also meet the power requirements. Therefore, there is a great risk in using the online DCR value obtained by simply discharging the battery cell at a fixed current value as the standard for mass-produced battery cell shipments. Summary of the Invention

[0005] The present invention provides a battery cell testing method to solve the problem in the related art that a method of testing a battery cell using a fixed current value has a great risk.

[0006] The present invention provides a battery cell testing method, which includes: obtaining a reference battery cell from multiple battery cells to be tested; discharging the reference battery cell at a constant current value, judging whether the difference between the power value of the reference battery cell and a preset power is within a preset range, and if the difference between the power value of the reference battery cell and the preset power is within the preset range, using the constant current value as a reference current value; discharging a non-reference battery cell from the multiple battery cells to be tested at the reference current value, and determining whether the power value of the non-reference battery cell meets the requirements.

[0007] Further, the reference cell is discharged at a constant current value, and it is determined whether the difference between the power value of the reference cell and the preset power is within a preset range. If the difference between the power value of the reference cell and the preset power is within the preset range, the constant current value is used as the reference current value. The steps include: discharging the reference cell at a constant current value within a preset time, obtaining the cut-off voltage of the reference cell, and determining whether the difference between the cut-off voltage of the reference cell and the preset cut-off voltage is within a preset range; if the difference between the cut-off voltage of the reference cell and the preset cut-off voltage is within a preset range, the constant current value is used as the discharge current value of the reference cell; obtaining multiple voltage values ​​corresponding to multiple time points of the reference cell within the preset time; obtaining the power value of the reference cell according to the preset time, the discharge current value of the reference cell, the multiple time points, and the multiple voltage values ​​corresponding to the multiple time points; determining whether the difference between the power value of the reference cell and the preset power is within the preset range. If the difference between the power value of the reference cell and the preset power is within the preset range, the discharge current value of the reference cell is used as the reference current value.

[0008] Furthermore, the reference battery cell is discharged at a constant current value to determine whether the difference between the power value of the reference battery cell and the preset power is within a preset range. If the difference between the power value of the reference battery cell and the preset power is within the preset range, the step of using the constant current value as the reference current value also includes: if the difference between the cut-off voltage of the reference battery cell and the preset cut-off voltage is not within the preset range, the constant current value is changed.

[0009] Furthermore, a non-reference battery cell among multiple battery cells to be tested is discharged at a reference current value, and the step of determining whether the non-reference battery cell meets the requirements includes: discharging the non-reference battery cell at a constant current at the reference current value within a preset time to obtain a cut-off voltage of the non-reference battery cell, and judging whether the difference between the cut-off voltage of the non-reference battery cell and the preset cut-off voltage is within a preset range; when the difference between the cut-off voltage of the non-reference battery cell and the preset cut-off voltage is within the preset range, it is determined that the non-reference battery cell meets the requirements.

[0010] Furthermore, after the step of discharging a non-reference cell among the multiple cells to be tested at a reference current value to determine whether the non-reference cell meets the requirements, the cell testing method further includes: obtaining an initial voltage value of the non-reference cell, and obtaining a DCR specification of the non-reference cell according to the cut-off voltage, initial voltage value and reference current value of the non-reference cell.

[0011] Furthermore, the non-reference battery cell among the multiple battery cells to be tested is discharged at a reference current value, and the step of determining whether the non-reference battery cell meets the requirements includes: discharging the non-reference battery cell at the reference current value to a preset cut-off voltage, obtaining the discharge time of the non-reference battery cell, and judging whether the difference between the discharge time and the preset time is within a preset range; when the difference between the discharge time and the preset time is within the preset range, it is determined that the non-reference battery cell meets the requirements.

[0012] Furthermore, after the step of discharging a non-reference cell among the multiple cells to be tested at a reference current value to determine whether the non-reference cell meets the requirements, the cell testing method further includes: obtaining an initial voltage value of the non-reference cell, and obtaining a DCR specification of the non-reference cell according to a preset cut-off voltage, the initial voltage value, and the reference current value.

[0013] Furthermore, there are multiple reference battery cells, and it is determined whether the difference between the power value of the reference battery cell and the preset power is within a preset range. If the difference between the power value of the reference battery cell and the preset power is within the preset range, the step of using the discharge current value of the reference battery cell as the reference current value includes: obtaining the absolute value of the difference between the power value of multiple reference battery cells and the preset power, and selecting the discharge current value of the reference battery cell with the smallest absolute value of the difference as the reference current value.

[0014] Furthermore, the step of obtaining the power value of the reference cell according to the preset time, the discharge current value of the reference cell, multiple time points, and multiple voltage values ​​corresponding to the multiple time points includes: using the formula Obtain the power value of the reference cell; wherein P is the power value of the reference cell, I is the reference current value, t is the preset time, and U(t) is a plurality of voltage values ​​corresponding to a plurality of time points.

[0015] Furthermore, before the step of obtaining a reference cell from the plurality of cells to be tested, the cell testing method further includes: setting the cell to be tested to a preset SOC.

[0016] By applying the technical solution of the present invention, when the cell to be tested needs to be tested, a reference cell is obtained from the cell to be tested, and then the reference cell is tested. During the test, the reference cell is discharged at a constant current value to determine whether the difference between the power value of the reference cell and the preset power is within a preset range. If the difference between the power value of the reference cell and the preset power is within a preset range, the constant current value is used as a reference current value, and the reference current value is used to discharge the non-reference cell in the cell to be tested, and determine whether the power value of the non-reference cell meets the requirements. Since the non-reference cell is tested by using the constant current value of the reference cell that meets the conditions as the reference current value, the test method of the cell is improved and optimized, so that there is no need to use a single fixed current value to discharge the cell to calculate the online DCR value as the standard for mass production cell shipment, thereby improving the accuracy of the cell test and improving the quality rate of the cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0018] Figure 1 A flow chart of a battery cell testing method according to an embodiment of the present invention is shown;

[0019] Figure 2 shows another step diagram of a battery cell testing method provided in accordance with an embodiment of the present invention;

[0020] Figure 3 shows a voltage-time curve diagram of a reference battery cell provided according to a specific embodiment of the present invention;

[0021] Figure 4 shows a voltage-time curve diagram of a non-reference cell provided according to a specific embodiment of the present invention;

[0022] Figure 5 Another voltage-time curve diagram of a non-reference battery cell provided according to a specific embodiment of the present invention is shown. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the preset scope of protection of the present invention.

[0024] like Figures 1 to 5 As shown, an embodiment of the present invention provides a battery cell testing method, which includes:

[0025] S200, obtaining a reference cell from a plurality of cells to be tested;

[0026] S300, discharging the reference cell at a constant current value, determining whether a difference between a power value of the reference cell and a preset power value is within a preset range; if the difference between the power value of the reference cell and the preset power value is within the preset range, using the constant current value as a reference current value;

[0027] S400 : Discharging a non-reference cell among the plurality of cells to be tested at a reference current value to determine whether the power value of the non-reference cell meets the requirement.

[0028] According to the technical solution of the present invention, when the cell to be tested needs to be tested, a reference cell is obtained from the cell to be tested, and then the reference cell is tested. During the test, the reference cell is discharged at a constant current value to determine whether the difference between the power value of the reference cell and the preset power is within a preset range. If the difference between the power value of the reference cell and the preset power is within a preset range, the constant current value is used as the reference current value, and the reference current value is used to discharge the non-reference cell in the cell to be tested, and determine whether the power value of the non-reference cell meets the requirements. Since the constant current value of the qualified reference cell is used as the reference current value to test the non-reference cell, the cell testing method is improved and optimized, so that there is no need to use a single fixed current value to discharge the cell to calculate the online DCR value as the standard for mass production cell shipment, thereby improving the accuracy of the cell test and improving the quality rate of the cell. Moreover, since the quality rate of the cell is improved, the consistency of the cells in the same batch is improved, thereby improving the performance and life of the power battery composed of grouped cells.

[0029] It should be noted that, in step S200, a reference cell is obtained from a plurality of cells to be tested, and a reference current value can be obtained by using the reference cell. The number of the reference cells can be one or more.

[0030] In step S300, the reference cell is discharged at a constant current value to determine whether the reference cell meets the requirements. Discharging the reference cell at a constant current value has the advantage of being easy to operate. During the test, the same test equipment is used, and the temperature setting during the test is maintained within the range of ±2°C of the preset temperature. For example, if the preset test temperature is 25°C, the temperature is maintained between 23°C and 27°C during the test. Different reference cells can be discharged at different current values.

[0031] Specifically, in step S400, since the reference cell meets the requirements when discharged at the reference current value, the non-reference cell can be discharged using the reference current value to determine whether the non-reference cell meets the requirements. During the test process, the test conditions of the non-reference cell must be consistent with the test conditions of the reference cell. For example, the non-reference cell and the reference cell use the same test equipment, and the temperature during the test is kept within the range of ±2°C of the preset temperature.

[0032] It should be noted that the preset range of the difference between the power value of the reference cell and the preset power is within the range of ±2% of the preset power of the cell to be tested.

[0033] like Figure 2As shown, the reference cell is discharged at a constant current value, and it is determined whether the difference between the power value of the reference cell and the preset power is within a preset range. If the difference between the power value of the reference cell and the preset power is within the preset range, the step S300 of using the constant current value as the reference current value includes:

[0034] S310, discharging the reference cell at a constant current value within a preset time, obtaining a cutoff voltage of the reference cell, and determining whether a difference between the cutoff voltage of the reference cell and a preset cutoff voltage is within a preset range;

[0035] S320: If the difference between the cut-off voltage of the reference cell and the preset cut-off voltage is within a preset range, use the constant current value as the discharge current value of the reference cell;

[0036] S340, obtaining multiple voltage values ​​corresponding to multiple time points of the reference cell within a preset time;

[0037] S350, obtaining a power value of the reference cell according to a preset time, a discharge current value of the reference cell, a plurality of time points, and a plurality of voltage values ​​corresponding to the plurality of time points;

[0038] S360: Determine whether the difference between the power value and the preset power is within a preset range. If the difference between the power value and the preset power is within the preset range, use the discharge current value of the reference cell as the reference current value.

[0039] In this embodiment, when testing the reference battery cell, the reference battery cell is discharged at a constant current value within a preset time, and the cutoff voltage of the reference battery cell can be obtained. The cutoff voltage of the reference battery cell is compared with the preset cutoff voltage to determine whether the difference between the cutoff voltage of the reference battery cell and the preset cutoff voltage is within a preset range. If the difference between the cutoff voltage of the reference battery cell and the preset cutoff voltage is within the preset range, it indicates that the cutoff voltage of the reference battery cell meets the requirements, and the constant current value can be used as the discharge current value of the reference battery cell. The test equipment is used to obtain multiple voltage values ​​corresponding to multiple time points within a preset time for the reference battery cell. The power value of the reference battery cell is calculated using a formula based on the preset time, the discharge current value of the reference battery cell, multiple time points, and the multiple voltage values ​​corresponding to the multiple time points. The calculated power value of the reference battery cell is compared with the preset power value to determine whether the difference between the power value and the preset power is within a preset range. If the difference between the power value of the reference battery cell and the preset power is within the preset range, it indicates that the power value of the reference battery cell meets the requirements, and the reference battery cell can be used as a standard for shipment judgment, and the discharge current value of the reference battery cell can be used as a reference current value.

[0040] Specifically, in step S310, the cutoff voltage of the reference cell is obtained by discharging the reference cell at a constant current value within a preset time. The cutoff voltage of the reference cell can then be compared with the preset cutoff voltage to determine whether the difference between the cutoff voltage of the reference cell and the preset cutoff voltage is within a preset range. If the difference between the cutoff voltage of the reference cell and the preset cutoff voltage is within the preset range, it indicates that the cutoff voltage of the reference cell meets the requirements, and the constant current value can be used as the discharge current value of the reference cell. If the difference between the cutoff voltage of the reference cell and the preset cutoff voltage is not within the preset range, it indicates that the cutoff voltage of the reference cell does not meet the requirements, and the reference cell cannot be used as a standard for shipment judgment and cannot be shipped to the client.

[0041] The discharge current value refers to the discharge current value when the difference between the discharge cut-off voltage of the reference cell and the preset cut-off voltage is within a preset range. The reference current value refers to the current value applied when discharging a non-reference cell among the multiple cells to be tested.

[0042] It should be noted that, in step S340, a test device may be used to obtain a plurality of voltage values ​​corresponding to a plurality of time points within a preset time.

[0043] In this embodiment, in step S360, the calculated power value of the reference cell is compared with the preset power value to determine whether the difference between the power value and the preset power is within a preset range. If the difference between the power value of the reference cell and the preset power is within the preset range, it indicates that the power value of the reference cell meets the requirements, and the reference cell can be used as a standard for shipment judgment, and the discharge current value of the reference cell is used as the reference current value. If the difference between the power value of the reference cell and the preset power is not within the preset range, it indicates that the power value of the reference cell does not meet the requirements, and the reference cell cannot be used as a standard for shipment judgment and cannot be shipped to the client.

[0044] Specifically, when the absolute value of the difference between the cutoff voltage of the reference cell and the preset cutoff voltage is less than or equal to 0.5 V, the constant current value can be used as the discharge current value of the reference cell. When the absolute value of the difference between the power value of the reference cell and the preset power is less than or equal to 8 W, the discharge current value of the reference cell can be used as the reference current value.

[0045] like Figure 2 As shown, the reference cell is discharged at a constant current value, and it is determined whether the difference between the power value of the reference cell and the preset power is within a preset range. If the difference between the power value of the reference cell and the preset power is within the preset range, the step S300 of using the constant current value as the reference current value further includes:

[0046] S330, if the difference between the cutoff voltage of the reference battery cell and the preset cutoff voltage is not within the preset range, the constant current value is changed. By changing the constant current value, the reference battery cell is tested, and the discharge current value of the reference battery cell can be obtained.

[0047] Specifically, the reference battery cell is discharged at the changed plurality of constant current values within a preset time, the corresponding plurality of cutoff voltages of the reference battery cell obtained by discharging at the changed plurality of constant current values are obtained, the plurality of obtained cutoff voltages are compared with the preset cutoff voltage respectively, until the difference between the cutoff voltage of the reference battery cell and the preset cutoff voltage is within the preset range, the constant current value corresponding to the cutoff voltage of the reference battery cell is taken as the discharge current value, and the discharge current value of the reference battery cell is obtained.

[0048] In the embodiment, the non-reference battery cell in the plurality of to-be-tested battery cells is discharged at the reference current value, and the step S400 of determining whether the non-reference battery cell meets the requirements comprises:

[0049] S410, the non-reference battery cell is discharged at the reference current value within a preset time, the cutoff voltage of the non-reference battery cell is obtained, and it is judged whether the difference between the cutoff voltage of the non-reference battery cell and the preset cutoff voltage is within the preset range. When the difference between the cutoff voltage of the non-reference battery cell and the preset cutoff voltage is within the preset range, it is determined that the non-reference battery cell meets the requirements. The above-mentioned test method of the non-reference battery cell has the advantage of being convenient to operate.

[0050] In the embodiment, for the same batch of to-be-tested battery cells, the same reference current value is used for constant current discharge within a preset time, and the cutoff voltage of the to-be-tested battery cell is obtained. For the reference battery cell and the non-reference battery cell, the obtained cutoff voltage can be compared with the preset cutoff voltage. Thus, the power value of the to-be-tested battery cell is determined whether it meets the requirements.

[0051] It should be noted that under the same test conditions, since the reference battery cell is discharged at the reference current value within a preset time, the difference between the cutoff voltage of the reference battery cell and the preset cutoff voltage is within the preset range, it can be determined that the power value of the reference battery cell meets the requirements. Therefore, the non-reference battery cell can be discharged at the reference current value within a preset time, the cutoff voltage of the non-reference battery cell is obtained, and it is judged whether the difference between the cutoff voltage of the non-reference battery cell and the preset cutoff voltage is within the preset range. The method is used to test the non-reference battery cell.

[0052] Specifically, if the difference between the cutoff voltage of the non-reference battery cell and the preset cutoff voltage is not within the preset range, the non-reference battery cell does not meet the requirements.

[0053] In this embodiment, after step S400 of discharging a non-reference cell among the plurality of cells to be tested at a reference current value to determine whether the non-reference cell meets the requirements, the cell testing method further includes:

[0054] S510 , obtaining an initial voltage value of the non-reference cell, and obtaining a DCR specification of the non-reference cell according to the cut-off voltage, the initial voltage value, and the reference current value of the non-reference cell.

[0055] Specifically, by the formula DCR=(V 初 -V 止 ) / I to calculate the DCR specification of the battery cell, where V 初 Represents the initial voltage of the battery cell, V 止 Represents the cut-off voltage of the battery cell, and I represents the reference current value.

[0056] It should be noted that for reference cells that meet the requirements, the DCR specifications of the reference cells can also be calculated using the above formula and shipped to the client.

[0057] In this embodiment, the step S400 of discharging a non-reference cell among the plurality of cells to be tested at a reference current value and determining whether the non-reference cell meets the requirements includes:

[0058] S420: Discharge the non-reference cell at a reference current value to a preset cutoff voltage, obtain the discharge time of the non-reference cell, and determine whether the difference between the discharge time and the preset time is within a preset range. If the difference between the discharge time and the preset time is within the preset range, the non-reference cell is determined to meet the requirements. The above non-reference cell testing method has the advantage of being easy to operate.

[0059] In this embodiment, for the same batch of cells to be tested, the same reference current value is used to discharge to a preset cutoff voltage, thereby obtaining the cutoff voltage of the cells to be tested. For both reference cells and non-reference cells, the obtained discharge time can be compared with the preset time, thereby serving as an indicator to determine whether the power value of the cells to be tested meets the requirements.

[0060] It should be noted that if the difference between the discharge time of the non-reference cell and the preset time is not within the preset range, the non-reference cell does not meet the requirements.

[0061] The discharge time refers to the time it takes for the battery cell to be tested to discharge at a reference current value to a preset cut-off voltage.

[0062] In this embodiment, after step S400 of discharging a non-reference cell among the plurality of cells to be tested at a reference current value to determine whether the non-reference cell meets the requirements, the cell testing method further includes:

[0063] S520 , obtaining an initial voltage value of the non-reference cell, and obtaining a DCR specification of the non-reference cell according to a preset cut-off voltage, the initial voltage value, and a reference current value.

[0064] Specifically, by the formula DCR=(V 初 -V) / I to calculate the DCR specification of the non-reference cell, where V represents the preset cut-off voltage.

[0065] The cut-off voltage refers to the lowest operating voltage at which the battery cannot continue to discharge. The initial voltage refers to the voltage of the battery before it begins to discharge.

[0066] In this embodiment, there are multiple reference cells, and step S360 of determining whether the difference between the power value and the preset power is within a preset range, and if the difference between the power value and the preset power is within the preset range, using the discharge current value of the reference cell as the reference current value includes:

[0067] S361. Obtain the absolute value of the difference between the power values ​​of multiple reference cells and the preset power, and select the discharge current value of the reference cell with the smallest absolute value of the difference as the reference current value. Using the above scheme, the discharge current value of the reference cell with the smallest absolute value of the difference can be used as the reference current value. The reference current value can be used to test non-reference cells, and the error between the power value of the non-reference cells and the preset power can be minimized.

[0068] In step S350, the power value of the reference cell can be calculated using a formula according to the preset time, the discharge current value of the reference cell, multiple time points, and multiple voltage values ​​corresponding to the multiple time points.

[0069] Specifically, step S350 of obtaining the power value of the reference cell according to the preset time, the discharge current value of the reference cell, multiple time points, and multiple voltage values ​​corresponding to the multiple time points includes:

[0070] S351, through the formula Obtain the power value of the reference cell; where P is the power value of the reference cell, I is the reference current value, t is the preset time, and U(t) is the multiple voltage values ​​corresponding to multiple time points. Calculating the power value of the reference cell using an integral method can make the calculated power value of the reference cell closer to the actual power value.

[0071] In this embodiment, the multiple time points are time points selected at equal intervals within a preset time.

[0072] Specifically, before step S200 of obtaining a reference cell from a plurality of cells to be tested, the cell testing method further includes:

[0073] S100: Setting the battery cell to be tested to a preset SOC (State of Charge). By adopting the above steps, the initial state of the battery cells can be made consistent, thereby making the test results more accurate.

[0074] It should be noted that in step S320, if the difference between the cutoff voltage of the reference cell and the preset cutoff voltage is not within the preset range, the constant current value is changed. That is, when multiple tests are performed on the same reference cell, the SOC of the reference cell needs to be adjusted to the preset SOC before each test. Before the test begins, the cell to be tested needs to be left to rest for a period of time to allow the cell to reach a stable state.

[0075] In this embodiment, the preset time is less than or equal to 60 seconds, and the preset cut-off voltage is less than or equal to 4V, which can avoid over-discharging of the battery cell and thus prevent damage to the battery cell.

[0076] It should be noted that under the same test conditions, for example, the same test temperature, the same test equipment, and the same SOC state of the battery cell, the reference battery cell is discharged at a constant power value within a preset time to obtain the cut-off voltage of the reference battery cell, and the cut-off voltage is compared with the preset cut-off voltage, and it is determined whether the difference between the cut-off voltage of the reference battery cell and the preset cut-off voltage is within a preset range. If the difference between the cut-off voltage of the reference battery cell and the preset cut-off voltage is within the preset range, the constant power value is used as the power value of the reference battery cell. If the difference between the cut-off voltage of the reference battery cell and the preset cut-off voltage is not within the preset range, the constant power value is changed, and under the same test conditions, the reference battery cell is discharged at multiple different constant power values ​​after the change within a preset time until the difference between the cut-off voltage of the reference battery cell and the preset cut-off voltage is within the preset range. The changed constant power value corresponding to the cut-off voltage of the reference battery cell is used as the power value of the reference battery cell.

[0077] In addition, due to the limited range of the DCR test equipment for battery cells currently shipped on mass production lines, the method of directly testing the battery cell power by discharging the reference battery cell at a constant power value within a preset time to obtain the power value of the reference battery cell is far from sufficient (overrange). Therefore, the battery cell can be tested by discharging the reference battery cell at a constant current value within a preset time.

[0078] The following describes the process in conjunction with specific embodiments:

[0079] In a specific embodiment, the number of reference cells is 18, and the power values ​​obtained by testing the reference cells using the above two test methods are as follows:

[0080]

[0081]

[0082] Among them, the Pmax method is to perform a discharge test on the reference battery cell at a constant power value within a preset time to obtain the power value of the reference battery cell. The Imax method is to perform a discharge test on the reference battery cell at a constant current value within a preset time and calculate the power value of the reference battery cell. ΔP is the difference between the power values ​​obtained by the Imax method and the Pmax method.

[0083] In this embodiment, the test temperature (25°C), SOC adjustment method (discharge mode), battery cell SOC state (34.5% SOC), preset time (10s), preset cut-off voltage (3.01V), test equipment, and data collection interval (10ms) of the two test methods are all consistent.

[0084] In the above table, the power value of the reference cell obtained by discharging the reference cell at a constant power value within a preset time is compared with the calculated power value of the reference cell. The difference between the two is less than 8W. This verifies that the method of discharging the reference cell at a constant current value within a preset time to determine whether the power value of the reference cell meets the requirements is feasible.

[0085] It should be noted that for this specific embodiment, the difference between the calculated power value of the reference cell and the power value of the reference cell obtained by discharging the cell at a constant power value within a preset time is within the range of 8W. For cells of other power, this difference will vary with the power of the cell and is not limited to 8W. The power value of the cell obtained by the Pmax method is the preset power.

[0086] like Figure 3 As shown, in step S300, the reference cell is discharged at a constant current value to determine whether the reference cell meets the requirements. If the reference cell meets the requirements, the constant current value is used as the reference current value, and the five reference cells are discharged at a constant current to a preset cut-off voltage within a preset time, thereby obtaining different discharge current values ​​of the five reference cells, wherein I1 represents the discharge current value of the first reference cell, I2 represents the discharge current value of the second reference cell, I3 represents the discharge current value of the third reference cell, I4 represents the discharge current value of the fourth reference cell, I5 represents the discharge current value of the fifth reference cell, T represents the preset time, and Vcut represents the preset cut-off voltage.

[0087] like Figure 4As shown, in step S410, the non-reference battery cell is discharged at a constant current with a reference current value within a preset time to obtain a cutoff voltage of the non-reference battery cell, and it is determined whether the difference between the cutoff voltage of the non-reference battery cell and the preset cutoff voltage is within a preset range. When the difference between the cutoff voltage of the non-reference battery cell and the preset cutoff voltage is within the preset range, it is determined that the non-reference battery cell meets the requirements, and the three non-reference battery cells are discharged at the reference current value within the preset time to obtain different cutoff voltages of the three non-reference battery cells, wherein V1 represents the cutoff voltage of the first non-reference battery cell, V2 represents the cutoff voltage of the second non-reference battery cell, V3 represents the cutoff voltage of the third non-reference battery cell, I represents the reference current value, and T represents the preset time.

[0088] like Figure 5 As shown, in step S420, the non-reference battery cell is discharged at a reference current value to a preset cut-off voltage, the discharge time of the non-reference battery cell is obtained, and it is determined whether the difference between the discharge time and the preset time is within a preset range. When the difference between the discharge time and the preset time is within the preset range, it is determined that the non-reference battery cell meets the requirements, and the three non-reference battery cells are discharged at a reference current value to a preset cut-off voltage, thereby obtaining different discharge times for the three non-reference battery cells, wherein T1 represents the discharge time of the first non-reference battery cell, T2 represents the discharge time of the second non-reference battery cell, T3 represents the discharge time of the third non-reference battery cell, I represents the reference current value, and Vcut represents the preset cut-off voltage.

[0089] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0090] Unless otherwise specifically stated, the relative arrangement of the parts and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the preset scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to actual proportional relationships. The technology, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be considered as part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following figures, and therefore, once an item is defined in one figure, it does not need to be further discussed in subsequent figures.

[0091] In the description of the application, it should be understood that the orientation words such as "front, back, up, down, left, right", "transverse, vertical, perpendicular, horizontal" and "top, bottom" and the like indicated orientation or positional relationship are generally based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the application and simplifying the description, without the opposite description, these orientation words do not indicate and imply that the device or element referred to must have a particular orientation or be constructed and operated in a particular orientation, therefore it cannot be understood as a limitation on the preset scope of protection of the application; the orientation words "inner, outer" refer to the inner and outer relative to the contour of each component.

[0092] For the convenience of description, spatial relative terms such as "over", "above", "upper surface", "upper" and the like can be used herein to describe the spatial positional relationship of one device or feature with other devices or features as shown in the drawings. It should be understood that the spatial relative terms are intended to include different orientations in use or operation in addition to the orientation of the device described in the drawings. For example, if the device in the drawings is inverted, the device described as "above" or "over" other devices or structures will be positioned "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below" orientations. The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein are interpreted accordingly.

[0093] In addition, it should be noted that the use of "first", "second" and the like to define parts is only for the convenience of distinguishing the corresponding parts, and the above words have no special meaning unless otherwise stated, therefore it cannot be understood as a limitation on the preset scope of protection of the application.

[0094] The above description is only the preferred embodiment of the application and is not intended to limit the application. For those skilled in the art, the application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application shall be included in the preset scope of protection of the application.

Claims

1. A battery cell testing method, characterized in that: The battery cell testing method includes: Obtain a reference cell from multiple cells to be tested; Discharging the reference cell at a constant current value, determining whether a difference between a power value of the reference cell and a preset power value is within a preset range, and using the constant current value as a reference current value if the difference between the power value of the reference cell and the preset power value is within the preset range; wherein, the reference cell is discharged at the constant current value within a preset time, the cut-off voltage of the reference cell is obtained, and it is determined whether the difference between the cut-off voltage of the reference cell and the preset cut-off voltage is within a preset range; if the difference between the cut-off voltage of the reference cell and the preset cut-off voltage is within the preset range, the constant current value is used as the discharge current value of the reference cell; a plurality of voltage values ​​corresponding to a plurality of time points within the preset time of the reference cell are obtained; and a power value of the reference cell is obtained according to the preset time, the discharge current value of the reference cell, the plurality of time points, and the plurality of voltage values ​​corresponding to the plurality of time points; Determining whether a difference between the power value of the reference cell and a preset power is within a preset range, and if the difference between the power value of the reference cell and the preset power is within the preset range, using the discharge current value of the reference cell as a reference current value; There are multiple reference cells, and the absolute values ​​of the differences between the power values ​​of the multiple reference cells and the preset power are obtained, and the discharge current value of the reference cell with the smallest absolute value of the difference is selected as the reference current value; The non-reference cells among the plurality of cells to be tested are discharged at the reference current value to determine whether the power values ​​of the non-reference cells meet the requirements.

2. The battery cell testing method according to claim 1, wherein: The step of discharging the reference cell at the constant current value, determining whether a difference between a power value of the reference cell and a preset power is within a preset range, and if the difference between the power value of the reference cell and the preset power is within the preset range, using the constant current value as a reference current value further includes: If the difference between the cut-off voltage of the reference cell and the preset cut-off voltage is not within a preset range, the constant current value is changed.

3. The battery cell testing method according to claim 1, wherein: The step of discharging the non-reference battery cell among the plurality of battery cells to be tested at the reference current value and determining whether the non-reference battery cell meets the requirements includes: The non-reference battery cell is discharged with a constant current at the reference current value within a preset time to obtain a cutoff voltage of the non-reference battery cell, and it is determined whether the difference between the cutoff voltage of the non-reference battery cell and the preset cutoff voltage is within a preset range. When the difference between the cutoff voltage of the non-reference battery cell and the preset cutoff voltage is within the preset range, it is determined that the non-reference battery cell meets the requirements.

4. The battery cell testing method according to claim 3, characterized in that: After the step of discharging the non-reference battery cells among the plurality of battery cells to be tested at the reference current value to determine whether the non-reference battery cells meet the requirements, the battery cell testing method further includes: An initial voltage value of the non-reference cell is obtained, and a DCR specification of the non-reference cell is obtained according to the cut-off voltage of the non-reference cell, the initial voltage value, and the reference current value.

5. The battery cell testing method according to claim 1, wherein: The step of discharging the non-reference battery cell among the plurality of battery cells to be tested at the reference current value and determining whether the non-reference battery cell meets the requirements includes: Discharge the non-reference battery cell at the reference current value to a preset cut-off voltage, obtain the discharge time of the non-reference battery cell, and determine whether the difference between the discharge time and the preset time is within a preset range. When the difference between the discharge time and the preset time is within the preset range, determine that the non-reference battery cell meets the requirements.

6. The battery cell testing method according to claim 5, characterized in that: After the step of discharging the non-reference battery cells among the plurality of battery cells to be tested at the reference current value to determine whether the non-reference battery cells meet the requirements, the battery cell testing method further includes: An initial voltage value of the non-reference cell is obtained, and a DCR specification of the non-reference cell is obtained according to the preset cut-off voltage, the initial voltage value, and the reference current value.

7. The battery cell testing method according to claim 1, characterized in that: The step of obtaining the power value of the reference cell according to the preset time, the discharge current value of the reference cell, the multiple time points, and the multiple voltage values ​​corresponding to the multiple time points includes: By formula Obtaining a power value of the reference cell; Where P is the power value of the reference cell, I is the reference current value, t is the preset time, U （t） are multiple voltage values ​​corresponding to multiple time points.

8. The battery cell testing method according to claim 1, wherein: Before the step of obtaining the reference battery cell from a plurality of battery cells to be tested, the battery cell testing method further includes: The battery cell to be tested is set to a preset SOC.

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