Sodium ion battery pack equalization method and system based on battery cell monomer capacity correction

Abstract

The invention provides a sodium ion battery pack equalization method and system based on battery cell monomer capacity correction, and relates to the field of sodium ion battery packs, the method comprises the following steps: carrying out constant current charging on a sodium ion battery pack, then carrying out constant current discharging, and obtaining dynamic voltages of each battery cell at multiple charging time points and dynamic voltages of each battery cell at multiple charging time points; calculating the residual chargeable capacity and the residual dischargeable capacity of the battery cell, and judging whether the battery cell is replaced or not; if it is judged that the battery cells are replaced, the replaced battery cells are determined based on the residual chargeable capacity and the residual dischargeable capacity of each battery cell; if it is judged that the battery cells are not replaced, for each battery cell, the equalization mode of the sodium-ion battery pack is determined according to the residual chargeable capacity and the residual dischargeable capacity of the battery cell, capacity equalization is carried out, and the method has the advantage that the load adjusting efficiency of the sodium-ion battery pack is improved.

Description

Technical Field

[0001] The present invention relates to the field of sodium ion battery packs, and in particular to a sodium ion battery pack balancing method and system based on cell single-unit capacity correction. Background Art

[0002] Energy storage batteries and power batteries have high capacity and voltage requirements, so the cells need to be grouped in series and parallel. The key to grouping is to ensure the consistency of the cell's state of charge (SOC), internal resistance, capacity and other indicators. As a rising star, sodium-ion batteries have a less mature manufacturing process than lithium-ion batteries. During the grouping process, it is more likely that the battery pack capacity will not meet the shipping standards due to cell consistency issues. This problem will increase accordingly after the cells have been shelved for a long time.

[0003] Usually, the capacity test process of the battery pack is full charge → static → full discharge → static → charge to the shipping state. When the battery pack capacity is unqualified, the existing method usually uses the static SOC-OCV (Open Circuit Voltage) curve measured experimentally to find the SOC value by comparing the OCV value, so as to estimate the capacity that needs to be adjusted. However, if the shipping state of the battery pack falls to the plateau period, that is, the relationship between its state of charge (SOC) and open circuit voltage (OCV) enters a relatively stable stage, the effect of SOC changes on OCV is small, and the error of the estimation method will increase, resulting in repeated load adjustments to achieve the target capacity. In addition, in the prior art, the charge and discharge curve of the characteristic battery cell is used to estimate the load adjustment capacity of the abnormal battery cell. When the actual capacity of the abnormal battery cell is significantly different from that of the characteristic battery cell, the error of the estimation result will increase, which will also result in the need for repeated load adjustments.

[0004] Therefore, it is necessary to provide a sodium ion battery pack balancing method and system based on cell single capacity correction to solve the problem of inaccurate load adjustment estimation and the need for repeated load adjustment in the prior art. Summary of the invention

[0005] The present invention provides a sodium ion battery pack balancing method based on cell single capacity correction, comprising: performing constant current charging on the sodium ion battery pack to obtain the dynamic voltage of each cell of the sodium ion battery pack at multiple charging time points during the charging process; performing constant current discharge on the charged sodium ion battery pack to obtain the dynamic voltage of each cell of the sodium ion battery pack at multiple discharge time points during the discharge process; for each cell of the sodium ion battery pack, based on the dynamic voltage of the cell at multiple charging time points during the charging process, calculating the remaining chargeable capacity of the cell, and based on the dynamic voltage of the cell at multiple discharge time points during the discharge process, calculating the remaining dischargeable capacity of the cell; judging whether to replace the cell based on the remaining chargeable capacity and the remaining dischargeable capacity of each cell; if it is determined that the cell is to be replaced, determining the replaced cell based on the remaining chargeable capacity and the remaining dischargeable capacity of each cell; if it is determined that the cell is not to be replaced, determining the balancing method of the sodium ion battery pack according to the remaining chargeable capacity and the remaining dischargeable capacity of each cell, and performing capacity balancing.

[0006] Furthermore, the remaining rechargeable capacity of the battery cell is calculated based on the dynamic voltage of the battery cell at multiple charging time points during the charging process, including: taking the battery cell with charging priority cutoff as the charging reference battery cell; when the charging of the sodium ion battery pack is cut off, recording the charging cutoff voltage of each battery cell and the charging cutoff voltage of the charging reference battery cell, and interpolating the remaining charging time difference of each battery cell based on the corresponding relationship between the dynamic voltage of the charging reference battery cell and the charging time; and calculating the remaining rechargeable capacity of the battery cell based on the remaining charging time difference, the actual capacity of the battery cell, the actual capacity of the charging reference battery cell and the charging current.

[0007] Furthermore, the remaining chargeable capacity of the battery cell is calculated according to the following formula: ,in, is the remaining chargeable capacity of the ith battery cell, is the constant charging current, is the remaining charging time difference corresponding to the i-th battery cell, is the actual capacity of the ith battery cell, It is the actual capacity of the charging reference battery.

[0008] Furthermore, the remaining dischargeable capacity of the battery cell is calculated based on the dynamic voltage of the battery cell at multiple discharge time points during the discharge process, including: taking the battery cell with discharge priority cutoff as the discharge reference battery cell; when the discharge of the sodium ion battery pack is cut off, recording the discharge cutoff voltage of each battery cell and the discharge cutoff voltage of the discharge reference battery cell, and interpolating the remaining discharge time difference of each battery cell based on the corresponding relationship between the dynamic voltage of the discharge reference battery cell and the discharge time; and calculating the remaining dischargeable capacity of the battery cell based on the remaining discharge time difference, the actual capacity of the battery cell, the actual capacity of the discharge reference battery cell and the discharge current.

[0009] Furthermore, the remaining discharge capacity of the battery cell is calculated according to the following formula: ,in, is the remaining discharge capacity of the ith battery cell, is the constant discharge current, is the remaining discharge time difference corresponding to the i-th battery cell, is the actual capacity of the ith battery cell, It is the actual capacity of the discharge reference battery.

[0010] Furthermore, based on the remaining chargeable capacity and the remaining dischargeable capacity of each battery cell, it is determined whether to replace the battery cell, including: determining the maximum balancing capacity according to the remaining chargeable capacity, the remaining dischargeable capacity of each battery cell and the actual discharge capacity of the battery pack; if the maximum balancing capacity is less than the target capacity of the battery pack, replacing the battery cell; if the maximum balancing capacity is greater than or equal to the target capacity of the battery pack, capacity balancing is performed.

[0011] Furthermore, according to the remaining chargeable capacity and the remaining dischargeable capacity of each battery cell, the balancing mode of the sodium ion battery pack is determined, including: for each battery cell, according to the remaining chargeable capacity and the remaining dischargeable capacity of the battery cell, determining the balanced discharge capacity and the balanced charge capacity corresponding to the battery cell; according to the balanced discharge capacity and the balanced charge capacity corresponding to each battery cell, determining the balancing mode of the sodium ion battery pack.

[0012] Further, according to the remaining chargeable capacity and the remaining dischargeable capacity of the battery cell, the balanced discharge capacity and the balanced charge capacity corresponding to the battery cell are determined, including: if the remaining chargeable capacity of the battery cell is less than or equal to the target boost capacity, then based on the target boost capacity and the remaining chargeable capacity of the battery cell, the balanced discharge capacity corresponding to the battery cell is calculated; if the remaining dischargeable capacity of the battery cell is less than or equal to the target boost capacity, then based on the target boost capacity and the remaining chargeable capacity of the battery cell, the balanced charge capacity corresponding to the battery cell is calculated.

[0013] Furthermore, according to the balanced discharge capacity and balanced charge capacity corresponding to each battery cell, the balanced mode of the sodium ion battery pack is determined, including: calculating the balanced discharge capacity of the sodium ion battery pack according to the balanced discharge capacity of each battery cell; calculating the balanced charge capacity of the sodium ion battery pack according to the balanced discharge capacity of each battery cell; determining the balanced mode corresponding to the sodium ion battery pack according to the smaller value of the balanced discharge capacity of the sodium ion battery pack and the balanced charge capacity of the sodium ion battery pack.

[0014] The present invention provides a sodium ion battery pack balancing system based on cell single capacity correction, and applies the above-mentioned sodium ion battery pack balancing method based on cell single capacity correction, including: a data acquisition module, used to perform constant current charging on the sodium ion battery pack, and obtain the dynamic voltage of each cell of the sodium ion battery pack at multiple charging time points during the charging process; and also used to perform constant current discharge on the charged sodium ion battery pack, and obtain the dynamic voltage of each cell of the sodium ion battery pack at multiple discharge time points during the discharge process; a data analysis module, used to analyze the dynamic voltage of each cell of the sodium ion battery pack based on the cell during the charging process. The remaining chargeable capacity of the battery cell is calculated based on the dynamic voltage at multiple charging time points, and the remaining dischargeable capacity of the battery cell is calculated based on the dynamic voltage at multiple discharge time points during the discharge process; a capacity balancing module is used to determine whether to replace the battery cell based on the remaining chargeable capacity and the remaining dischargeable capacity of each battery cell; if it is determined that the battery cell is to be replaced, the replacement battery cell is determined based on the remaining chargeable capacity and the remaining dischargeable capacity of each battery cell; if it is determined that the battery cell is not to be replaced, the balancing method of the sodium ion battery pack is determined according to the remaining chargeable capacity and the remaining dischargeable capacity of each battery cell, and capacity balancing is performed.

[0015] Compared with the prior art, the sodium ion battery pack balancing method and system based on cell single capacity correction provided by the present invention has at least the following beneficial effects: By real-time monitoring and recording the dynamic voltage of the battery cell during the charging and discharging process, the remaining chargeable capacity and remaining dischargeable capacity of each battery cell can be more accurately evaluated. This helps to promptly identify batteries with degraded or abnormal performance, so that corresponding measures can be taken to avoid the decline of the overall performance of the battery pack.

[0016] Based on the remaining capacity information of the battery cells, the balancing method of the battery pack can be determined and capacity balancing can be performed. This helps ensure that each battery cell in the battery pack is maintained at a similar capacity level, thereby improving the overall consistency and stability of the battery pack.

[0017] Through accurate cell capacity assessment, some cells can be prevented from premature damage due to overcharge and discharge. This helps to extend the service life of the entire battery pack and reduce the replacement and repair costs caused by cell damage.

[0018] When a serious degradation of cell performance is detected, the method can determine the cell that needs to be replaced based on the remaining capacity information. This helps to replace the poorly performing cell in a timely manner to prevent it from affecting the performance and life of the entire battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] This specification will be further described in the form of exemplary embodiments, which will be described in detail by the accompanying drawings. These embodiments are not restrictive, and in these embodiments, the same number represents the same structure, wherein: Figure 1 It is a flow chart of a sodium ion battery pack balancing method based on cell single capacity correction according to some embodiments of this specification; Figure 2 It is a schematic diagram of the charging end, the discharging end, and the state of charge of the sodium ion battery pack when charged to the shipping state according to some embodiments of this specification; Figure 3 It is a schematic diagram of the calculation result of the remaining charging capacity of each battery cell at the charging end without correction based on the actual capacity of the battery cell as shown in some embodiments of this specification; Figure 4 It is a schematic diagram of the calculation result of the remaining discharge capacity of each battery cell at the end of discharge without correction based on the actual capacity of the battery cell as shown in some embodiments of this specification; Figure 5 It is a schematic diagram of the charge state of each battery cell after selecting the charging end, the discharging end, and the charging back to the shipping state after discharge equalization as shown in some embodiments of this specification; Figure 6 It is a schematic diagram of the charge state of each battery cell at the charging end, the discharging end, and the charging state to the shipping state after discharge equalization as shown in other embodiments of this specification; Figure 7 It is a module schematic diagram of a sodium ion battery pack equalization system based on cell single capacity correction according to some embodiments of this specification. DETAILED DESCRIPTION

[0020] In order to more clearly illustrate the technical solutions of the embodiments of this specification, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some examples or embodiments of this specification. For ordinary technicians in this field, this specification can also be applied to other similar scenarios based on these drawings without creative work. Unless it is obvious from the language environment or otherwise explained, the same reference numerals in the figures represent the same structure or operation.

[0021] Figure 1 is a flow chart of a sodium ion battery pack balancing method based on cell single capacity correction according to some embodiments of this specification, such as Figure 1 As shown, the sodium ion battery pack balancing method based on cell single unit capacity correction may include the following steps.

[0022] Step 110 , performing constant current charging on the sodium ion battery pack, and obtaining the dynamic voltage of each cell of the sodium ion battery pack at multiple charging time points during the charging process.

[0023] Specifically, the sodium ion battery pack is charged with constant current to a preset charging cut-off voltage through the total positive and total negative interfaces, and the dynamic voltage of each battery cell of the sodium ion battery pack at multiple charging time points during the charging process is recorded. It can be understood that when the dynamic voltage of a battery cell of the sodium ion battery pack reaches the preset charging cut-off voltage, the charging of the sodium ion battery pack is terminated.

[0024] Step 120 , performing constant current discharge on the charged sodium ion battery pack, and obtaining the dynamic voltage of each cell of the sodium ion battery pack at multiple discharge time points during the discharge process.

[0025] Specifically, the charged sodium ion battery pack is discharged at a constant current to a preset discharge cut-off voltage through the total positive and total negative interfaces, and the dynamic voltage of each cell of the sodium ion battery pack at multiple discharge time points during the discharge process is recorded. It can be understood that when the dynamic voltage of a cell of the sodium ion battery pack is the preset discharge cut-off voltage, the discharge of the sodium ion battery pack is cut off.

[0026] Step 130, for each battery cell of the sodium ion battery pack, the remaining chargeable capacity of the battery cell is calculated based on the dynamic voltage of the battery cell at multiple charging time points during the charging process, and the remaining dischargeable capacity of the battery cell is calculated based on the dynamic voltage of the battery cell at multiple discharge time points during the discharging process.

[0027] In some embodiments, the remaining chargeable capacity of the battery cell is calculated based on the dynamic voltage of the battery cell at multiple charging time points during the charging process, including: The cell with priority charging cutoff is used as the charging reference cell. For example, the sodium ion battery pack includes cell 1, cell 2, cell 3, and cell 4, wherein cell 4 is the cell whose dynamic voltage first reaches the preset charging cutoff voltage after constant current charging, and cell 4 is used as the charging reference cell; When the sodium ion battery pack is charged, the charging cut-off voltage of each battery cell and the charging cut-off voltage of the charging reference battery cell are recorded, and the remaining charging time difference of each battery cell is obtained by interpolation based on the corresponding relationship between the dynamic voltage of the charging reference battery cell and the charging time. Specifically, a charging voltage change curve characterizing the corresponding relationship between the dynamic voltage and the charging time of the charging reference battery cell can be generated according to the dynamic voltage of the charging reference battery cell at multiple charging time points. For each battery cell, a time point consistent with the charging cut-off voltage of the battery cell can be found on the charging voltage change curve of the charging reference battery cell according to the charging cut-off voltage of the battery cell. The remaining charging time difference of the battery cell is the difference between the time point consistent with the charging cut-off voltage of the battery cell and the time point when the charging of the charging reference battery cell is terminated. The remaining chargeable capacity of the battery cell is calculated based on the charging time difference, the actual capacity of the battery cell, the actual capacity of the charging reference battery cell, and the charging current.

[0028] Specifically, the remaining chargeable capacity of the battery cell is calculated according to the following formula: , in, is the remaining chargeable capacity of the ith battery cell, is the constant charging current, is the remaining charging time difference corresponding to the i-th battery cell, is the actual capacity of the ith battery cell, is the actual capacity of the charging reference cell. The actual capacity of the ith cell and the actual capacity of the charging reference cell can be obtained through the incoming material data, and both are known parameters.

[0029] In some embodiments, the remaining dischargeable capacity of the battery cell is calculated based on the dynamic voltage of the battery cell at multiple discharge time points during the discharge process, including: The cell with the priority discharge cutoff is used as the discharge reference cell. For example, the sodium ion battery pack includes cell 1, cell 2, cell 3, and cell 4, wherein cell 3 is the cell whose dynamic voltage first reaches the preset discharge cutoff voltage after constant current discharge, and cell 3 is used as the charging reference cell; When the sodium ion battery pack is discharged, the discharge cut-off voltage of each battery cell and the discharge cut-off voltage of the discharge reference battery cell are recorded, and the remaining discharge time difference of each battery cell is obtained by interpolation based on the correspondence between the dynamic voltage and the discharge time of the discharge reference battery cell. Specifically, a discharge voltage change curve characterizing the correspondence between the dynamic voltage and the discharge time of the discharge reference battery cell can be generated according to the dynamic voltage of the discharge reference battery cell at multiple discharge time points. For each battery cell, a time point consistent with the discharge cut-off voltage of the battery cell can be found on the discharge voltage change curve of the discharge reference battery cell according to the discharge cut-off voltage of the battery cell. The remaining discharge time difference of the battery cell is the difference between the time point consistent with the discharge cut-off voltage of the battery cell and the time point when the discharge of the discharge reference battery cell is discharged; The remaining dischargeable capacity of the battery cell is calculated based on the discharge time difference, the actual capacity of the battery cell, the actual capacity of the discharge reference battery cell, and the discharge current.

[0030] Specifically, the remaining discharge capacity of the battery cell is calculated according to the following formula: , in, is the remaining discharge capacity of the ith battery cell, is the constant discharge current, is the remaining discharge time difference corresponding to the i-th battery cell, is the actual capacity of the ith battery cell, is the actual capacity of the discharge reference cell. The actual capacity of the ith cell and the actual capacity of the discharge reference cell can be obtained through the incoming material data, and both are known parameters.

[0031] Step 140: Determine whether to replace the battery cell based on the remaining chargeable capacity and the remaining dischargeable capacity of each battery cell.

[0032] In some embodiments, step 140 specifically includes: Determine the maximum balancing capacity based on the remaining chargeable capacity, remaining dischargeable capacity and actual discharge capacity of each battery cell; If the maximum equalization capacity is less than the target capacity of the battery pack, the battery cell should be replaced; If the maximum balancing capacity is greater than or equal to the target capacity of the battery pack, capacity balancing is performed.

[0033] Specifically, the maximum balancing capacity can be calculated according to the following formula: , in, is the maximum balanced capacity, It is the actual discharge capacity of the battery pack, that is, the capacity discharged when the discharge is terminated after the first charge of the battery pack is terminated. The actual discharge capacity of the battery pack can be measured by measuring equipment during the discharge process.

[0034] Step 150: If it is determined that a battery cell is to be replaced, the battery cell to be replaced is determined based on the remaining chargeable capacity and the remaining dischargeable capacity of each battery cell.

[0035] Specifically, for each battery cell, if , it is determined that the battery cell needs to be replaced, among which, is the target capacity of the battery pack.

[0036] Step 160: If it is determined that the battery cell is not to be replaced, a balancing method for the sodium ion battery pack is determined according to the remaining chargeable capacity and the remaining dischargeable capacity of each battery cell, and capacity balancing is performed.

[0037] In some embodiments, determining a balancing method of a sodium ion battery pack according to the remaining chargeable capacity and the remaining dischargeable capacity of each battery cell includes: For each battery cell, determining a balanced discharge capacity and a balanced charge capacity corresponding to the battery cell according to the remaining chargeable capacity and the remaining dischargeable capacity of the battery cell; The balancing method of the sodium ion battery pack is determined based on the balanced discharge capacity and balanced charge capacity corresponding to each battery cell.

[0038] In some embodiments, determining the balanced discharge capacity and the balanced charge capacity corresponding to the battery cell according to the remaining chargeable capacity and the remaining dischargeable capacity of the battery cell includes: If the remaining chargeable capacity of the battery cell is less than or equal to the target increased capacity, the balanced discharge capacity corresponding to the battery cell is calculated based on the target increased capacity and the remaining chargeable capacity of the battery cell; If the remaining dischargeable capacity of the battery cell is less than or equal to the target increased capacity, the equalized charging capacity corresponding to the battery cell is calculated based on the target increased capacity and the remaining chargeable capacity of the battery cell.

[0039] In some embodiments, determining a balancing method of a sodium ion battery pack according to a balanced discharge capacity and a balanced charge capacity corresponding to each battery cell includes: According to the balanced discharge capacity of each battery cell, the balanced discharge capacity of the sodium ion battery pack is calculated; according to the balanced discharge capacity of each battery cell, the balanced charge capacity of the sodium ion battery pack is calculated; The equalization mode corresponding to the sodium ion battery group is determined according to the smaller value of the equalization discharge capacity of the sodium ion battery group and the equalization charge capacity of the sodium ion battery group.

[0040] Specifically: If the remaining chargeable capacity of the battery cell is less than or equal to the target capacity, that is ,in, , then the battery cell needs to be discharged evenly.

[0041] The balanced discharge capacity of the battery cell can be determined according to the following formula: , in, is the equilibrium discharge capacity corresponding to the ith cell, Increase capacity for your goals.

[0042] The total equalization capacity of the sodium-ion battery pack is: , in, is the total balanced capacity of the sodium-ion battery pack.

[0043] If the remaining discharge capacity of the battery cell is less than or equal to the target capacity increase, that is, , then the battery cell needs to adopt charge balancing.

[0044] The equalization charging capacity corresponding to the battery cell can be determined according to the following formula: , in, is the balanced charging capacity corresponding to the i-th battery cell.

[0045] The total equalization capacity of the sodium-ion battery pack is: , in, is the total balanced capacity of the sodium-ion battery pack.

[0046] Both discharge equalization and charge equalization can achieve the target capacity, which can be specifically compared and For example, a balancing method with a smaller total balancing capacity is selected as the balancing method corresponding to the sodium ion battery pack.

[0047] The beneficial effects of the sodium-ion battery pack balancing method based on cell single capacity correction are explained below in combination with experimental data.

[0048] Taking a sodium-ion battery pack consisting of four cells as an example, the actual capacity of each cell can be obtained through the incoming material data, C 1 :22Ah, C2:26Ah, C3:25Ah, C4:23Ah.

[0049] Figure 2 The charge end, discharge end, and charge state of the sodium ion battery pack are shown. It can be seen that the actual measured capacity of the battery pack is Ca: 20Ah, C3 is the battery cell that is preferentially cut off at the charge end, and C1 is the battery cell that is preferentially cut off at the discharge end.

[0050] The goal is to achieve a sodium-ion battery pack capacity of 22Ah.

[0051] Ignoring the difference in internal resistance, the dynamic voltage of the battery cell corresponds to the SOC one by one. The battery cell charging end uses C3, which is cut off first, as a reference to obtain the remaining chargeable capacity of each battery cell. For example, the dynamic voltage of C1 at the charging end is V c1 , find the dynamic voltage equal to V in the end-of-charge curve of C3 c1 point (the SOC at this point is different from C 1 The SOC at the charging end is consistent with C 3 Charging terminal dynamic voltage V c3 The time difference between them is recorded as △Tci, corresponding to C 3 The charging capacity is , according to the actual capacity of the battery cell, we can get C 1 The remaining charge capacity at the end of charging is .

[0052] Figure 3 The calculation results of the remaining charge capacity of each battery cell at the end of charging are shown without correction based on the actual capacity of the battery cell. , represented by red numbers), calculated based on the remaining charge capacity of each battery cell at the end of charging after correction with the actual capacity of the battery cell ( , represented by black numbers), as shown in the following table.

[0053]

[0054] Figure 4 The calculation results of the remaining discharge capacity of each battery cell at the end of discharge without correction based on the actual capacity of the battery cell are shown ( ), represented by red numbers), calculated based on the residual discharge capacity of each battery cell at the end of discharge after correction of the actual capacity of the battery cell ( , represented by black numbers), as shown in the following table.

[0055]

[0056] Maximum capacity achievable through balancing , Not less than the target capacity C of the sodium-ion battery pack, so the target capacity can be achieved through balancing. Target capacity increase .

[0057] After the actual capacity correction of the battery cells, the battery cells with the remaining charge capacity less than 2Ah at the end of charging are 3# and 4#, and the balanced discharge capacity is 2Ah and 1Ah respectively, totaling 3Ah. The battery cells with the remaining discharge capacity less than 2Ah at the end of discharging are 1# and 2#, and the balanced charge capacity is 2Ah and 1Ah respectively, totaling 3Ah. The workload of charging and discharging balance is selected to be the same. Figure 5 The state of charge of each cell at the end of charge, the end of discharge, and the state of charge to the shipping state after discharge balancing is selected. It can be seen that the capacity of the battery pack is increased to 22Ah.

[0058] When the actual capacity correction of the battery cells is not used, the battery cells with remaining charge capacity less than 2Ah at the charging end are 3# and 4#, and the balanced discharge capacity is 2Ah and 0.9Ah respectively. Figure 6 The charge state of each battery cell at the end of charge, the end of discharge, and the state of return to shipment after discharge balancing is selected. It can be seen that the capacity of the battery pack is increased to 21.9Ah, which has not reached the target capacity and needs to be balanced again.

[0059] Figure 7 is a schematic diagram of a module of a sodium ion battery pack balancing system based on cell single capacity correction according to some embodiments of this specification, such as Figure 7 As shown, the sodium ion battery pack balancing system based on cell single capacity correction may include a data acquisition module, a data analysis module and a capacity balancing module.

[0060] A data acquisition module is used to perform constant current charging on the sodium ion battery pack based on the charging cut-off voltage, and obtain the dynamic voltage of each battery cell of the sodium ion battery pack at multiple charging time points during the charging process; and is also used to perform constant current discharge on the charged sodium ion battery pack based on the discharge cut-off voltage, and obtain the dynamic voltage of each battery cell of the sodium ion battery pack at multiple discharge time points during the discharge process; A data analysis module is used to calculate the remaining chargeable capacity of each cell of the sodium ion battery pack based on the dynamic voltage of the cell at multiple charging time points during the charging process, and to calculate the remaining dischargeable capacity of the cell based on the dynamic voltage of the cell at multiple discharge time points during the discharge process; The capacity balancing module is used to determine whether to replace the battery cell based on the remaining chargeable capacity and the remaining dischargeable capacity of each battery cell; if it is determined to replace the battery cell, the replacement battery cell is determined based on the remaining chargeable capacity and the remaining dischargeable capacity of each battery cell; if it is determined not to replace the battery cell, the balancing method of the sodium ion battery pack is determined according to the remaining chargeable capacity and the remaining dischargeable capacity of each battery cell to perform capacity balancing.

[0061] The sodium-ion battery pack balancing system based on cell single capacity correction can be used to execute the sodium-ion battery pack balancing method based on cell single capacity correction, which will not be described in detail here.

[0062] Finally, it should be understood that the embodiments described in this specification are only used to illustrate the principles of the embodiments of this specification. Other variations may also fall within the scope of this specification. Therefore, as an example and not a limitation, alternative configurations of the embodiments of this specification may be considered consistent with the teachings of this specification. Accordingly, the embodiments of this specification are not limited to the embodiments explicitly introduced and described in this specification.

Claims

1. A sodium ion battery pack balancing method based on cell single capacity correction, characterized in that: include: The sodium ion battery pack is charged with a constant current to obtain the dynamic voltage of each cell of the sodium ion battery pack at multiple charging time points during the charging process; The charged sodium ion battery pack is discharged at a constant current to obtain the dynamic voltage of each cell of the sodium ion battery pack at multiple discharge time points during the discharge process; For each cell of the sodium ion battery pack, the remaining chargeable capacity of the cell is calculated based on the dynamic voltage of the cell at multiple charging time points during the charging process, and the remaining dischargeable capacity of the cell is calculated based on the dynamic voltage of the cell at multiple discharge time points during the discharging process; Based on the remaining chargeable capacity and the remaining dischargeable capacity of each battery cell, determine whether to replace the battery cell; If it is determined that the battery cell is to be replaced, the battery cell to be replaced is determined based on the remaining chargeable capacity and the remaining dischargeable capacity of each battery cell; If it is determined that the battery cells will not be replaced, the balancing method of the sodium-ion battery pack is determined based on the remaining chargeable capacity and the remaining dischargeable capacity of each battery cell, and capacity balancing is performed.

2. The sodium ion battery pack balancing method based on cell single capacity correction according to claim 1, characterized in that: Based on the dynamic voltage of the battery cell at multiple charging time points during the charging process, the remaining chargeable capacity of the battery cell is calculated, including: The cell with priority charging cutoff is used as the charging reference cell; When the sodium ion battery pack is charged, the charging cut-off voltage of each battery cell and the charging cut-off voltage of the charging reference battery cell are recorded, and the remaining charging time difference of each battery cell is interpolated based on the corresponding relationship between the dynamic voltage of the charging reference battery cell and the charging time; The remaining chargeable capacity of the battery cell is calculated based on the remaining charging time difference, the actual capacity of the battery cell, the actual capacity of the charging reference battery cell, and the charging current.

3. The sodium ion battery pack balancing method based on cell single capacity correction according to claim 2, characterized in that: Calculate the remaining chargeable capacity of the battery cell according to the following formula: ， in, is the remaining chargeable capacity of the ith battery cell, is the constant charging current, is the remaining charging time difference corresponding to the i-th battery cell, is the actual capacity of the ith battery cell, It is the actual capacity of the charging reference battery.

4. The sodium ion battery pack balancing method based on cell single capacity correction according to claim 2, characterized in that: Based on the dynamic voltage of the battery cell at multiple discharge time points during the discharge process, the remaining dischargeable capacity of the battery cell is calculated, including: The cell with discharge priority cutoff is used as the discharge reference cell; When the sodium ion battery pack is discharged, the discharge cut-off voltage of each battery cell and the discharge cut-off voltage of the discharge reference battery cell are recorded, and the remaining discharge time difference of each battery cell is interpolated based on the corresponding relationship between the dynamic voltage of the discharge reference battery cell and the discharge time; The remaining discharge capacity of the battery cell is calculated based on the remaining discharge time difference, the actual capacity of the battery cell, the actual capacity of the discharge reference battery cell, and the discharge current.

5. The sodium ion battery pack balancing method based on cell single capacity correction according to claim 2, characterized in that: Calculate the remaining discharge capacity of the battery cell according to the following formula: ， in, is the remaining discharge capacity of the ith battery cell, is the constant discharge current, is the remaining discharge time difference corresponding to the i-th battery cell, is the actual capacity of the ith battery cell, It is the actual capacity of the discharge reference battery.

6. The sodium ion battery pack balancing method based on cell single capacity correction according to claim 2, characterized in that: Based on the remaining chargeable capacity and the remaining dischargeable capacity of each battery cell, determine whether to replace the battery cell, including: Determine the maximum balancing capacity based on the remaining chargeable capacity, remaining dischargeable capacity and actual discharge capacity of each battery cell; If the maximum equalization capacity is less than the target capacity of the battery pack, the battery cell should be replaced; If the maximum balancing capacity is greater than or equal to the target capacity of the battery pack, capacity balancing is performed.

7. The sodium ion battery pack balancing method based on cell single capacity correction according to any one of claims 1 to 6, characterized in that: According to the remaining chargeable capacity and the remaining dischargeable capacity of each battery cell, the balancing method of the sodium ion battery pack is determined, including: For each battery cell, determining a balanced discharge capacity and a balanced charge capacity corresponding to the battery cell according to the remaining chargeable capacity and the remaining dischargeable capacity of the battery cell; The balancing method of the sodium ion battery pack is determined based on the balanced discharge capacity and balanced charge capacity corresponding to each battery cell.

8. The sodium ion battery pack balancing method based on cell single capacity correction according to claim 7, characterized in that: According to the remaining chargeable capacity and the remaining dischargeable capacity of the battery cell, the corresponding balanced discharge capacity and balanced charge capacity of the battery cell are determined, including: If the remaining chargeable capacity of the battery cell is less than or equal to the target increased capacity, the balanced discharge capacity corresponding to the battery cell is calculated based on the target increased capacity and the remaining chargeable capacity of the battery cell; If the remaining dischargeable capacity of the battery cell is less than or equal to the target increased capacity, the equalized charging capacity corresponding to the battery cell is calculated based on the target increased capacity and the remaining chargeable capacity of the battery cell.

9. The sodium ion battery pack balancing method based on cell single capacity correction according to claim 7, characterized in that: According to the balanced discharge capacity and balanced charge capacity corresponding to each battery cell, the balanced method of the sodium ion battery pack is determined, including: Calculate the balanced discharge capacity of the sodium ion battery pack based on the balanced discharge capacity of each battery cell; Calculate the balanced charging capacity of the sodium-ion battery pack based on the balanced discharge capacity of each battery cell; The equalization mode corresponding to the sodium ion battery group is determined according to the smaller value of the equalization discharge capacity of the sodium ion battery group and the equalization charge capacity of the sodium ion battery group.

10. A sodium ion battery pack equalization system based on cell single capacity correction, characterized in that: The sodium ion battery pack balancing method based on cell single capacity correction according to any one of claims 1 to 9 comprises: The data acquisition module is used to perform constant current charging on the sodium ion battery pack and obtain the dynamic voltage of each battery cell of the sodium ion battery pack at multiple charging time points during the charging process; and is also used to perform constant current discharge on the charged sodium ion battery pack and obtain the dynamic voltage of each battery cell of the sodium ion battery pack at multiple discharge time points during the discharge process; A data analysis module is used to calculate the remaining chargeable capacity of each cell of the sodium ion battery pack based on the dynamic voltage of the cell at multiple charging time points during the charging process, and to calculate the remaining dischargeable capacity of the cell based on the dynamic voltage of the cell at multiple discharge time points during the discharge process; The capacity balancing module is used to determine whether to replace the battery cell based on the remaining chargeable capacity and the remaining dischargeable capacity of each battery cell; if it is determined to replace the battery cell, the replacement battery cell is determined based on the remaining chargeable capacity and the remaining dischargeable capacity of each battery cell; if it is determined not to replace the battery cell, the balancing method of the sodium ion battery pack is determined according to the remaining chargeable capacity and the remaining dischargeable capacity of each battery cell to perform capacity balancing.

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