Sodium-ion battery pack balancing method and system based on correction of single cell capacity

Abstract

The present invention provides a method and system for balancing a sodium-ion battery pack based on correction of the capacity of each single battery cell, which relates to the field of sodium-ion battery packs. The method includes: after constant-current charging of the sodium-ion battery pack, followed by constant-current discharging, obtaining the dynamic voltage of each battery cell at multiple charging time points and the dynamic voltage at multiple charging time points, calculating the remaining rechargeable capacity and the remaining dischargeable capacity of the battery cell, and determining whether to replace the battery cell; if it is determined to replace the battery cell, based on the remaining rechargeable capacity and the remaining dischargeable capacity of each battery cell, determining the battery cell to be replaced; if it is determined not to replace the battery cell, for each battery cell, according to the remaining rechargeable capacity and the remaining dischargeable capacity of the battery cell, determining the balancing method of the sodium-ion battery pack and performing capacity balancing, which has the advantage of improving the load regulation efficiency of the sodium-ion battery pack.

Description

Technical Field

[0001] The present invention relates to the field of sodium-ion battery packs, and particularly to a balancing method and system for sodium-ion battery packs based on the correction of the capacity of single battery cells. Background Art

[0002] Energy storage batteries and power batteries require a relatively high capacity and voltage, so battery cells need to be grouped in series and parallel. The key to grouping is to ensure the consistency of indicators such as the state of charge (SOC), internal resistance, and capacity of the battery cells. As a rising star, sodium-ion batteries have less mature manufacturing processes than lithium-ion batteries. During the grouping process, it is easier to have problems where the capacity of the battery pack cannot meet the shipping standards due to the consistency issues of the battery cells, and this problem will be correspondingly exacerbated after the battery cells are stored for a long time.

[0003] Generally, the capacity test process of a battery pack is full charge → static state → full discharge → static state → charge to the shipping state. When the capacity of the battery pack is unqualified, the existing method usually measures the static SOC-OCV (Open Circuit Voltage) curve through experiments, looks up the SOC value by comparing the OCV value, and thus estimates the capacity that needs to be charge-adjusted. However, if the shipping state of the battery pack falls into the plateau period, that is, the relationship between its state of charge (SOC) and open circuit voltage (OCV) enters a relatively stable stage, and the influence of SOC change on OCV is small, the error of this estimation method will increase, resulting in the need to repeat the charge adjustment multiple times to achieve the target capacity. In addition, in the prior art, the charge adjustment capacity of abnormal battery cells is estimated through the charge and discharge curves of characteristic battery cells. When the actual capacity difference between the abnormal battery cells and the characteristic battery cells is large, the error of the estimation result will increase, and it will also lead to the need to repeat the charge adjustment multiple times.

[0004] Therefore, it is necessary to provide a balancing method and system for sodium-ion battery packs based on the correction of the capacity of single battery cells to solve the problem in the prior art that the charge adjustment estimation is inaccurate and the charge adjustment needs to be repeated multiple times. Summary of the Invention

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

[0006] Further, calculating the remaining rechargeable capacity of the battery cell based on the dynamic voltages of the battery cell at multiple charging time points during the charging process includes: using the battery cell with the earliest charging cut-off as the charging reference battery cell; when the sodium-ion battery pack reaches the charging cut-off, recording the charging cut-off voltage of each battery cell and the charging cut-off voltage of the charging reference battery cell, and interpolating to obtain 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; 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] Further, the remaining rechargeable capacity of the battery cell is calculated according to the following formula: , where is the remaining rechargeable capacity of the i-th battery cell, is the constant-current charging current, is the remaining charging time difference corresponding to the i-th battery cell, is the actual capacity of the i-th battery cell, is the actual capacity of the charging reference battery cell.

[0008] Further, calculating the remaining dischargeable capacity of the battery cell based on the dynamic voltages of the battery cell at multiple discharging time points during the discharging process includes: using the battery cell with the earliest discharging cut-off as the discharging reference battery cell; when the sodium-ion battery pack reaches the discharging cut-off, recording the discharging cut-off voltage of each battery cell and the discharging cut-off voltage of the discharging reference battery cell, and interpolating to obtain the remaining discharging time difference of each battery cell based on the corresponding relationship between the dynamic voltage of the discharging reference battery cell and the discharging time; calculating the remaining dischargeable capacity of the battery cell based on the remaining discharging time difference, the actual capacity of the battery cell, the actual capacity of the discharging reference battery cell, and the discharging current.

[0009] Further, calculate the remaining discharge capacity of the battery cell according to the following formula: , where is the remaining discharge capacity of the i-th battery cell, is the constant current discharge current, is the remaining discharge time difference corresponding to the i-th battery cell, is the actual capacity of the i-th battery cell, is the actual capacity of the reference discharge battery cell.

[0010] Further, based on the remaining charge capacity and remaining discharge capacity of each battery cell, determine whether to replace the battery cell, including: determine the maximum equalization capacity according to the remaining charge capacity, remaining discharge capacity and actual discharge capacity of the battery pack of each battery cell; if the maximum equalization capacity is less than the target capacity of the battery pack, replace the battery cell; if the maximum equalization capacity is greater than or equal to the target capacity of the battery pack, perform capacity equalization.

[0011] Further, determine the equalization method of the sodium-ion battery pack according to the remaining charge capacity and remaining discharge capacity of each battery cell, including: for each battery cell, determine the equalization discharge capacity and equalization charge capacity corresponding to the battery cell according to the remaining charge capacity and remaining discharge capacity of the battery cell; determine the equalization method of the sodium-ion battery pack according to the equalization discharge capacity and equalization charge capacity corresponding to each battery cell.

[0012] Further, determine the equalization discharge capacity and equalization charge capacity corresponding to the battery cell according to the remaining charge capacity and remaining discharge capacity of the battery cell, including: if the remaining charge capacity of the battery cell is less than or equal to the target boost capacity, calculate the equalization discharge capacity corresponding to the battery cell based on the target boost capacity and the remaining charge capacity of the battery cell; if the remaining discharge capacity of the battery cell is less than or equal to the target boost capacity, calculate the equalization charge capacity corresponding to the battery cell based on the target boost capacity and the remaining charge capacity of the battery cell.

[0013] Further, determine the equalization method of the sodium-ion battery pack according to the equalization discharge capacity and equalization charge capacity corresponding to each battery cell, including: calculate the equalization discharge capacity of the sodium-ion battery pack according to the equalization discharge capacity of each battery cell; calculate the equalization charge capacity of the sodium-ion battery pack according to the equalization discharge capacity of each battery cell; determine the equalization method corresponding to the sodium-ion battery pack according to the smaller value of the equalization discharge capacity and equalization charge capacity of the sodium-ion battery pack.

[0014] The present invention provides a sodium-ion battery pack equalization system based on the correction of the single-cell capacity of the battery cells, and applies the above-mentioned sodium-ion battery pack equalization method based on the correction of the single-cell capacity of the battery cells, including: a data acquisition module, which is used to perform constant-current charging on the sodium-ion battery pack to obtain the dynamic voltages of each battery cell in the sodium-ion battery pack at multiple charging time points during the charging process; and is also used to perform constant-current discharging on the charged sodium-ion battery pack to obtain the dynamic voltages of each battery cell in the sodium-ion battery pack at multiple discharging time points during the discharging process; a data analysis module, which is used to calculate the remaining rechargeable capacity of each battery cell in the sodium-ion battery pack based on the dynamic voltages of the battery cell at multiple charging time points during the charging process, and calculate the remaining dischargeable capacity of the battery cell based on the dynamic voltages of the battery cell at multiple discharging time points during the discharging process; a capacity equalization module, which is used to determine whether to replace the battery cells based on the remaining rechargeable capacity and the remaining dischargeable capacity of each battery cell; if it is determined to replace the battery cells, determine the battery cells to be replaced based on the remaining rechargeable capacity and the remaining dischargeable capacity of each battery cell; if it is determined not to replace the battery cells, determine the equalization method of the sodium-ion battery pack according to the remaining rechargeable capacity and the remaining dischargeable capacity of each battery cell, and perform capacity equalization.

[0015] Compared with the prior art, the sodium-ion battery pack equalization method and system based on the correction of the single-cell capacity of the battery cells provided by the present invention at least have the following beneficial effects:

[0016] By real-time monitoring and recording the dynamic voltages of the battery cells during the charging and discharging processes, the remaining rechargeable capacity and the remaining dischargeable capacity of each battery cell can be more accurately evaluated. This helps to timely detect battery cells with degraded performance or abnormalities, so as to take corresponding measures to avoid the decline of the overall performance of the battery pack.

[0017] According to the remaining capacity information of the battery cells, the equalization method of the battery pack can be determined, and capacity equalization can be performed. This helps to ensure that each battery cell in the battery pack maintains a similar capacity level, thereby improving the overall consistency and stability of the battery pack.

[0018] Through accurate evaluation of the battery cell capacity, some battery cells can be prevented from being prematurely damaged due to overcharging and over-discharging. This helps to extend the service life of the entire battery pack and reduce the replacement and maintenance costs caused by battery cell damage.

[0019] When it is detected that the performance of the battery cell has seriously deteriorated, the method can determine the battery cell to be replaced based on the remaining capacity information. This helps to timely replace the battery cell with poor performance to prevent it from affecting the performance and life of the entire battery pack. Description of the Drawings

[0020] This specification will be further described by way of exemplary embodiments, which will be described in detail with reference to the accompanying drawings. These embodiments are not restrictive. In these embodiments, the same reference numerals represent the same structures, where:

[0021] Figure 1 is a schematic flow chart of a sodium-ion battery pack equalization method based on correction of the single-cell capacity according to some embodiments of this specification;

[0022] Figure 2 is a schematic diagram of the state of charge at the end of charging, the end of discharging, and the state of charge when charging to the shipping state of a sodium-ion battery pack according to some embodiments of this specification;

[0023] Figure 3 is a schematic diagram of the calculation results of the remaining charging capacity at the end of charging of each battery cell without correcting according to the actual capacity of the battery cell according to some embodiments of this specification;

[0024] Figure 4 is a schematic diagram of the calculation results of the remaining discharging capacity at the end of discharging of each battery cell without correcting according to the actual capacity of the battery cell according to some embodiments of this specification;

[0025] Figure 5 is a schematic diagram of the state of charge of each battery cell at the end of charging, the end of discharging, and when returning to charge to the shipping state after selecting discharge equalization according to some embodiments of this specification;

[0026] Figure 6 is a schematic diagram of the state of charge of each battery cell at the end of charging, the end of discharging, and when returning to charge to the shipping state after selecting discharge equalization according to some other embodiments of this specification;

[0027] Figure 7 is a schematic block diagram of a sodium-ion battery pack equalization system based on correction of the single-cell capacity according to some embodiments of this specification. Detailed implementation manners

[0028] To more clearly illustrate the technical solutions of the embodiments of this specification, the accompanying drawings required for the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some examples or embodiments of this specification. For those of ordinary skill in the art, without creative efforts, this specification can also be applied to other similar scenarios based on these drawings. Unless obvious from the language context or otherwise stated, the same reference numerals in the figures represent the same structures or operations.

[0029] Figure 1 is a schematic flow chart of a sodium-ion battery pack equalization method based on correction of the single-cell capacity according to some embodiments of this specification, as Figure 1As shown, the method for balancing a sodium-ion battery pack based on the correction of the single-cell capacity of the battery cells may include the following steps.

[0030] Step 110: Constant-current charge the sodium-ion battery pack to obtain the dynamic voltages of each battery cell in the sodium-ion battery pack at multiple charging time points during the charging process.

[0031] Specifically, constant-current charge the sodium-ion battery pack through the total positive and total negative interfaces to a preset charging cut-off voltage, and record the dynamic voltages of each battery cell in the sodium-ion battery pack at multiple charging time points during the charging process. It can be understood that when the dynamic voltage of a certain battery cell in the sodium-ion battery pack reaches the preset charging cut-off voltage, the sodium-ion battery pack stops charging.

[0032] Step 120: Constant-current discharge the charged sodium-ion battery pack to obtain the dynamic voltages of each battery cell in the sodium-ion battery pack at multiple discharge time points during the discharging process.

[0033] Specifically, constant-current discharge the charged sodium-ion battery pack through the total positive and total negative interfaces to a preset discharge cut-off voltage, and record the dynamic voltages of each battery cell in the sodium-ion battery pack at multiple discharge time points during the discharging process. It can be understood that when the dynamic voltage of a certain battery cell in the sodium-ion battery pack is the preset discharge cut-off voltage, the sodium-ion battery pack stops discharging.

[0034] Step 130: For each battery cell in the sodium-ion battery pack, calculate the remaining rechargeable capacity of the battery cell based on the dynamic voltages of the battery cell at multiple charging time points during the charging process, and calculate the remaining dischargeable capacity of the battery cell based on the dynamic voltages of the battery cell at multiple discharge time points during the discharging process.

[0035] In some embodiments, calculating the remaining rechargeable capacity of the battery cell based on the dynamic voltages of the battery cell at multiple charging time points during the charging process includes:

[0036] Taking the battery cell with the earliest charging cut-off as the charging reference battery cell. For example, the sodium-ion battery pack includes battery cells 1, 2, 3, and 4. Among them, battery cell 4 is the battery cell whose dynamic voltage first reaches the preset charging cut-off voltage after constant-current charging, then battery cell 4 is used as the charging reference battery cell;

[0037] When the sodium-ion battery pack is charged to cut-off, record the charging cut-off voltage of each cell and the charging cut-off voltage of the charging reference cell. Based on the corresponding relationship between the dynamic voltage and charging time of the charging reference cell, interpolate to obtain the remaining charging time difference of each cell. Specifically, according to the dynamic voltages of the charging reference cell at multiple charging time points, generate a charging voltage change curve representing the corresponding relationship between the dynamic voltage and charging time of the charging reference cell. For each cell, according to the charging cut-off voltage of the cell, find the time point on the charging voltage change curve of the charging reference cell that is consistent with the charging cut-off voltage of the cell. The remaining charging time difference of the cell is the difference between the time point consistent with the charging cut-off voltage of the cell and the time point when the charging of the charging reference cell is cut off;

[0038] Based on the charging time difference, the actual capacity of the cell, the actual capacity of the charging reference cell, and the charging current, calculate the remaining chargeable capacity of the cell.

[0039] Specifically, calculate the remaining chargeable capacity of the cell according to the following formula:

[0040] ,

[0041] Wherein, is the remaining chargeable capacity of the i-th cell, is the constant current charging current, is the remaining charging time difference corresponding to the i-th cell, is the actual capacity of the i-th cell, is the actual capacity of the charging reference cell. The actual capacity of the i-th cell and the actual capacity of the charging reference cell can be obtained from the incoming material data and are both known parameters.

[0042] In some embodiments, based on the dynamic voltages of the cell at multiple discharge time points during the discharge process, calculate the remaining dischargeable capacity of the cell, including:

[0043] Take the cell with the earliest discharge cut-off as the discharge reference cell. For example, the sodium-ion battery pack includes cell 1, cell 2, cell 3, and cell 4. Among them, cell 3 is the cell whose dynamic voltage first reaches the preset discharge cut-off voltage after constant current discharge, then cell 3 is used as the charging reference cell;

[0044] When the sodium-ion battery pack reaches the discharge cut-off, record the discharge cut-off voltage of each cell and the discharge cut-off voltage of the reference cell for discharge. Based on the corresponding relationship between the dynamic voltage and discharge time of the reference cell for discharge, interpolate to obtain the remaining discharge time difference of each cell. Specifically, according to the dynamic voltages of the reference cell for discharge at multiple discharge time points, generate a discharge voltage change curve representing the corresponding relationship between the dynamic voltage and discharge time of the reference cell for discharge. For each cell, according to the discharge cut-off voltage of the cell, find the time point on the discharge voltage change curve of the reference cell for discharge that is the same as the discharge cut-off voltage of the cell. The remaining discharge time difference of the cell is the difference between the time point that is the same as the discharge cut-off voltage of the cell and the time point when the reference cell for discharge reaches the discharge cut-off;

[0045] Based on the discharge time difference, the actual capacity of the cell, the actual capacity of the reference cell for discharge, and the discharge current, calculate the remaining dischargeable capacity of the cell.

[0046] Specifically, calculate the remaining dischargeable capacity of the cell according to the following formula:

[0047] ,

[0048] where, is the remaining dischargeable capacity of the i-th cell, is the constant current discharge current, is the remaining discharge time difference corresponding to the i-th cell, is the actual capacity of the i-th cell, is the actual capacity of the reference cell for discharge. The actual capacity of the i-th cell and the actual capacity of the reference cell for discharge can be obtained from the incoming material data and are both known parameters.

[0049] Step 140, based on the remaining rechargeable capacity and the remaining dischargeable capacity of each cell, determine whether to replace the cell.

[0050] In some embodiments, step 140 specifically includes:

[0051] According to the remaining rechargeable capacity, the remaining dischargeable capacity of each cell, and the actual discharge capacity of the battery pack, determine the maximum equalization capacity;

[0052] If the maximum equalization capacity is less than the target capacity of the battery pack, replace the cell;

[0053] If the maximum equalization capacity is greater than or equal to the target capacity of the battery pack, perform capacity equalization.

[0054] Specifically, the maximum equalization capacity can be calculated according to the following formula:

[0055] ,

[0056] Among them, is the maximum equalization capacity, is the actual discharge capacity of the battery pack, that is, the capacity discharged when the battery pack reaches the discharge cut-off after the first charge cut-off. The actual discharge capacity of the battery pack can be measured by a measuring device during the discharge process.

[0057] Step 150, if it is determined to replace the battery cells, based on the remaining rechargeable capacity and remaining dischargeable capacity of each battery cell, determine the battery cells to be replaced.

[0058] Specifically, for each battery cell, if , it is determined that the battery cell needs to be replaced, where is the target capacity of the battery pack.

[0059] Step 160, if it is determined not to replace the battery cells, based on the remaining rechargeable capacity and remaining dischargeable capacity of each battery cell, determine the equalization method of the sodium-ion battery pack and perform capacity equalization.

[0060] In some embodiments, determining the equalization method of the sodium-ion battery pack according to the remaining rechargeable capacity and remaining dischargeable capacity of each battery cell includes:

[0061] For each battery cell, based on the remaining rechargeable capacity and remaining dischargeable capacity of the battery cell, determine the corresponding equalization discharge capacity and equalization recharge capacity of the battery cell;

[0062] Based on the corresponding equalization discharge capacity and equalization recharge capacity of each battery cell, determine the equalization method of the sodium-ion battery pack.

[0063] In some embodiments, determining the corresponding equalization discharge capacity and equalization recharge capacity of the battery cell according to the remaining rechargeable capacity and remaining dischargeable capacity of the battery cell includes:

[0064] If the remaining rechargeable capacity of the battery cell is less than or equal to the target boost capacity, based on the target boost capacity and the remaining rechargeable capacity of the battery cell, calculate the corresponding equalization discharge capacity of the battery cell;

[0065] If the remaining dischargeable capacity of the battery cell is less than or equal to the target boost capacity, based on the target boost capacity and the remaining rechargeable capacity of the battery cell, calculate the corresponding equalization recharge capacity of the battery cell.

[0066] In some embodiments, determining the equalization method of the sodium-ion battery pack according to the corresponding equalization discharge capacity and equalization recharge capacity of each battery cell includes:

[0067] Based on the equalization discharge capacity of each battery cell, calculate the equalization discharge capacity of the sodium-ion battery pack; based on the equalization discharge capacity of each battery cell, calculate the equalization recharge capacity of the sodium-ion battery pack;

[0068] Determine the corresponding balancing method of the sodium-ion battery pack according to the smaller value of the balanced discharge capacity and the balanced charge capacity of the sodium-ion battery pack.

[0069] Specifically: If the remaining rechargeable capacity of the battery cell is less than or equal to the target boosting capacity, that is , where , then the battery cell needs to adopt discharge balancing.

[0070] The corresponding balanced discharge capacity of the battery cell can be determined according to the following formula:

[0071] ,

[0072] where is the corresponding balanced discharge capacity of the i-th battery cell, is the target boosting capacity.

[0073] Total balanced capacity of the sodium-ion battery pack:

[0074] ,

[0075] where is the total balanced capacity of the sodium-ion battery pack.

[0076] If the remaining dischargeable capacity of the battery cell is less than or equal to the target boosting capacity, that is , then the battery cell needs to adopt charge balancing.

[0077] The corresponding balanced charge capacity of the battery cell can be determined according to the following formula:

[0078] ,

[0079] where is the corresponding balanced charge capacity of the i-th battery cell.

[0080] Total balanced capacity of the sodium-ion battery pack:

[0081] ,

[0082] where is the total balanced capacity of the sodium-ion battery pack.

[0083] Both discharge balancing and charge balancing can achieve the target capacity. Specifically, a more appropriate scheme can be selected by comparing and . For example, select the balancing method with a smaller total balanced capacity as the corresponding balancing method of the sodium-ion battery pack.

[0084] The beneficial effects of the sodium-ion battery pack equalization method based on the correction of the single-cell capacity will be described below in conjunction with experimental data.

[0085] Taking a sodium-ion battery pack composed of four cells as an example, the actual capacity of each cell can be obtained from the incoming material data, C 1 : 22 Ah, C2: 26 Ah, C3: 25 Ah, C4: 23 Ah.

[0086] Figure 2 The charging end, discharging end, and state of charge at the time of charging to the shipping state of the sodium-ion battery pack are shown. It can be seen that the measured capacity of the battery pack Ca: 20 Ah, C3 is the cell that is preferentially cut off at the charging end, and C1 is the cell that is preferentially cut off at the discharging end.

[0087] Taking the sodium-ion battery pack capacity reaching 22 Ah as the target.

[0088] Under the condition of ignoring the internal resistance difference, the dynamic voltage of the cell corresponds one-to-one with the SOC. Taking the preferentially cut-off C3 at the charging end of the cell as the reference benchmark, the remaining chargeable capacity of each cell is obtained. For example, the dynamic voltage at the charging end of C1 is V c1 , and find the point on the charging end curve of C3 where the dynamic voltage is equal to V c1 (the SOC of this point is the same as the SOC at the charging end of C 1 ), and the time difference between it and the dynamic voltage V 3 at the charging end of C c3 is denoted as △Tci, and the charging capacity corresponding to C 3 is , and the remaining charging capacity at the charging end of C 1 is obtained by correcting according to the actual capacity of the cell as .

[0089] Figure 3 shows the calculation results of the remaining charging capacity at the charging end of each cell without correcting according to the actual capacity of the cell (represented by red numbers), and the calculation results of the remaining charging capacity at the charging end of each cell after correcting according to the actual capacity of the cell ( , represented by black numbers), as shown in the following table.

[0090]

[0091] Figure 4 shows the calculation results of the remaining discharging capacity at the discharging end of each cell without correcting according to the actual capacity of the cell ( ), represented by red numbers), and the calculation results of the remaining discharging capacity at the discharging end of each cell after correcting according to the actual capacity of the cell ( , represented by black numbers), as shown in the following table.

[0092]

[0093] The maximum capacity achievable through balancing , is not less than the target capacity C of the sodium-ion battery pack, so the target capacity can be achieved through balancing. The target increased capacity .

[0094] After correcting with the actual capacity of the battery cells, the battery cells with remaining charging capacity less than 2 Ah at the end of charging are No. 3 and No. 4, and the balancing discharge capacities are 2 Ah and 1 Ah respectively, with a total of 3 Ah. The battery cells with remaining discharge capacity less than 2 Ah at the end of discharge are No. 1 and No. 2, and the balancing charge capacities are 2 Ah and 1 Ah respectively, with a total of 3 Ah. The workloads of charging balancing and discharging balancing are selected to be the same. Figure 5 It is the state of charge of each battery cell at the end of charging, at the end of discharge, and when recharged to the shipping state after selecting discharging balancing, and it can be known that the capacity of the battery pack is increased to 22 Ah.

[0095] When not correcting with the actual capacity of the battery cells, the battery cells with remaining charging capacity less than 2 Ah at the end of charging are No. 3 and No. 4, and the balancing discharge capacities are 2 Ah and 0.9 Ah respectively. Figure 6 It is the state of charge of each battery cell at the end of charging, at the end of discharge, and when recharged to the shipping state after selecting discharging balancing, and it can be known that the capacity of the battery pack is increased to 21.9 Ah, which does not reach the target capacity and needs to be balanced again.

[0096] Figure 7 It is a schematic diagram of the modules of a sodium-ion battery pack balancing system based on the correction of the capacity of individual battery cells as shown in some embodiments of this specification, such as Figure 7 shown, the sodium-ion battery pack balancing system based on the correction of the capacity of individual battery cells may include a data acquisition module, a data analysis module, and a capacity balancing module.

[0097] The 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 voltages of each battery cell of the sodium-ion battery pack at multiple charging time points during the charging process; it is also used to perform constant current discharging on the charged sodium-ion battery pack based on the discharging cut-off voltage, and obtain the dynamic voltages of each battery cell of the sodium-ion battery pack at multiple discharging time points during the discharging process;

[0098] The data analysis module is used to, for each battery cell of the sodium-ion battery pack, calculate the remaining rechargeable capacity of the battery cell based on the dynamic voltages of the battery cell at multiple charging time points during the charging process, and calculate the remaining dischargeable capacity of the battery cell based on the dynamic voltages of the battery cell at multiple discharging time points during the discharging process;

[0099] A capacity balancing module is used to determine whether to replace a battery cell based on the remaining rechargeable capacity and the remaining dischargeable capacity of each battery cell; if it is determined to replace a battery cell, the battery cell to be replaced is determined based on the remaining rechargeable capacity and the remaining dischargeable capacity of each battery cell; if it is determined not to replace a battery cell, the balancing method of the sodium-ion battery pack is determined according to the remaining rechargeable capacity and the remaining dischargeable capacity of each battery cell, and capacity balancing is performed.

[0100] The sodium-ion battery pack balancing system based on the correction of the single-cell capacity can be used to execute the sodium-ion battery pack balancing method based on the correction of the single-cell capacity, which will not be elaborated here.

[0101] 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 deformations may also fall within the scope of this specification. Therefore, by way of example rather than limitation, alternative configurations of the embodiments of this specification can be regarded as 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 cell will not 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 the capacity is balanced; 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 obtained by interpolation based on the corresponding relationship between the dynamic voltage and the discharge time of the discharge reference battery cell. Specifically, according to the dynamic voltage of the discharge reference battery cell at multiple discharge time points, a discharge voltage change curve characterizing the corresponding relationship between the dynamic voltage and the discharge time of the discharge reference battery cell is generated. For each battery cell, according to the discharge cut-off voltage of the battery cell, the time point consistent with the discharge cut-off voltage of the battery cell is searched on the discharge voltage change curve of the discharge reference 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; Calculate 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; 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; The maximum balancing capacity is calculated according to the following formula: ， in, is the maximum balanced capacity, The actual discharge capacity of the battery pack, that is, the capacity released when the discharge is terminated after the first charge of the battery pack is terminated. is the remaining chargeable capacity of the ith battery cell, is the remaining discharge capacity of the ith battery cell.

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 1, 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.

5. The sodium ion battery pack balancing method based on cell single capacity correction according to any one of claims 1 to 4, 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.

6. The sodium ion battery pack balancing method based on cell single capacity correction according to claim 5, 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 dischargeable capacity of the battery cell.

7. The sodium ion battery pack balancing method based on cell single capacity correction according to claim 5, 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 equalization charge capacity of the sodium ion battery pack based on the equalization charge 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.

8. 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 7 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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