Compensation method for monomer cell capacity and compensation device thereof

Abstract

The application provides a compensation method and device for single cell capacity, and the specific steps are as follows: pretreating a battery pack to be maintained; automatically matching discharging and charging of the battery pack to be maintained; establishing an optimized OCV table; respectively calculating the power difference of the highest average voltage of the battery and the lowest average voltage of the battery, the power difference of the highest voltage of the fault cell and the lowest voltage of the fault cell; establishing a classification table of the fault cell; calculating the ratio of the power difference of the battery and the fault cell, and formulating a corresponding compensation strategy. The compensation device comprises a connection control module, a battery management system and a compensation control module, and the control ends of relays, a charging and discharging module and a voltage detection module are connected with the compensation control module. Through hierarchical compensation, the compensation control module is integrated with the corresponding capacity following the attenuation degree, and the charging and discharging module performs more accurate voltage regulation, so that the compensation cell is close to the average voltage.

Description

Technical Field

[0001] This invention relates to the field of new energy batteries, and in particular to a method and device for compensating the capacity of a single battery cell. Background Technology

[0002] The new energy industry is currently experiencing an unprecedented boom. To improve battery energy density and reduce costs, the capacity of individual battery cells is increasing. Many new energy vehicles, such as light trucks, buses, and heavy trucks, as well as energy storage systems, are using a large number of cells exceeding 300Ah. Moreover, the production of large-capacity cells is constantly expanding, and the cycle life of cells is getting higher and higher. Many lithium iron phosphate cells have exceeded 4,000 cycles, and some manufacturers can reach 6,000 to 8,000 cycles. Battery maintenance over a long lifespan has become an urgent problem to be solved. The most prominent issue is that some cells will inevitably experience capacity decay over a long lifespan. General balancing methods alone are no longer sufficient to meet the battery maintenance needs. When the imbalance of individual cells reaches a certain limit, the cells must be replaced. Because of the large cell capacity, there are many series in a single module, and the modules are basically welded together, requiring the replacement of the entire module. The replacement operation is complex and costly.

[0003] Currently, battery balancing systems are divided into active balancing and passive balancing. Active balancing can only solve the problem of uneven self-discharge rate to a limited extent, while passive balancing is even less effective, as both are basically helpless against capacity degradation. When the imbalance of individual cells exceeds about 5% of the cell capacity, it will seriously affect its performance. Commonly used balancing systems are powerless to address this, especially when the battery pack's state of charge (SOC) is around 30% during use. In this case, in addition to power limitation, the vehicle's range will also be severely reduced, and it may even experience a power outage and shutdown failure. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a method and device for compensating the capacity of a single battery cell. By using several single battery cells with the same chemical properties but different capacities as the battery pack cells in parallel, and incorporating appropriate capacities according to a pre-designed strategy, and connecting them in parallel to the battery pack cells with declining capacity, it can effectively compensate for the excessive voltage difference caused by battery capacity decline. Moreover, it is low in cost, and the capacity is actively compensated according to the amount of battery decline, making it very intelligent and suitable for various vehicles and energy storage power supply systems.

[0005] This invention provides a method for compensating the capacity of a single battery cell, specifically including the following steps:

[0006] S1. Pre-treatment of the battery pack to be repaired:

[0007] S11. Discharge the battery pack to be repaired to below 30% and define the rated standard capacity of the battery pack as Y*Q. At the same time, set the voltage of the first cell B1, the second cell B2 and the third cell B3 to Vj±10mV respectively, where Vj is the voltage value when the capacity of the faulty cell is 30%-40%.

[0008] S12. Activate the battery management system. The battery management system sends the average voltage Vp of the battery pack and the voltage Va of the faulty cell to the CAN network in real time.

[0009] S13. Close the seventh relay K7 and charge the faulty cell in the battery pack with a current I of 4Q through the first charging and discharging module. At the same time, the compensation control module judges the voltage range of the voltage difference between the average voltage Vp of the battery pack and the voltage Va of the faulty cell. When |Va-Vp|≥20mV or Va≥Vj, stop charging the faulty cell.

[0010] S14. Based on step S13, close the relays corresponding to different compensation level strategies, implement the compensation level strategy for the faulty cells in the battery pack until the battery pack stops charging. At this time, the compensation control module records the compensation level of this charging and uses it as the default compensation level to be started when the next charging or discharging event occurs for the first time.

[0011] S2. Following the preprocessing in step S1, automatically match and discharge the battery pack to be repaired:

[0012] S21. If the average voltage Vp of the battery pack is greater than or equal to the preset voltage value G of the battery pack when the battery pack is at 90-80% charge, the compensation control module records the highest average voltage HVp of the battery pack and the highest voltage HVa of the faulty cell respectively.

[0013] S22. If the average voltage Vp of the battery pack is less than the preset voltage value G of the battery pack when the battery pack is at 90-80% charge, the compensation control module will not record the voltage value.

[0014] S3. Following the preprocessing in S1, the battery pack to be repaired is automatically matched and charged. If the compensation control module stores the compensation level, charging is performed as follows; otherwise, charging is performed directly:

[0015] S31. Create an optimized OCV form:

[0016] S311. Based on the SOC and voltage values ​​of each row in the basic OCV form, set 5*M% and V respectively. 5*M The value of M is a natural number from 0 to 20, that is, 0%, 5%, ... 100% correspond to V0, V5, ... V 100 ;

[0017] S312. Sequentially set each voltage value in the optimized OCV form to correspond one-to-one with the SOC in each row of the basic OCV form, i.e., V N There is a one-to-one correspondence between N% and N%, where N is a natural number from 0 to 100. The calculation expression is as follows:

[0018] N = 5 * M

[0019] V N+i =V 5*M +(V 5*(M+1) -V 5*M )÷5*i, where i takes the value 1, 2, 3, or 4;

[0020] S32. Based on the optimized OCV form, establish a classification table for faulty cells to obtain a table model for single cell capacity compensation. The table model for single cell capacity compensation includes C, D, E and F4 types of cells.

[0021] S33. Calculate the difference in charge between the highest average voltage HVp and the lowest average voltage LVp of the battery pack, Δθ_standard, i.e., Δθ_standard = θHP - θLP, where θHP and θLP are the SOC values ​​corresponding to the highest average voltage HVp and the lowest average voltage LVp of the battery pack, respectively.

[0022] S34. Calculate the charge difference Δθa between the highest voltage HVa and the lowest voltage LVA of the faulty cell, i.e., Δθa = θHa - θLa, where θHa and θLa are the SOC values ​​corresponding to the highest voltage HVa and the lowest voltage LVA of the faulty cell, respectively.

[0023] S35. Based on steps S33 and S34, calculate the ratio of the difference in charge between the battery pack and the faulty cell, and formulate a corresponding compensation strategy, i.e. W = Δθ_standard ÷ Δθ_a, where W is the proportion of the faulty cell's SOC to the battery pack's SOC, which is converted to the faulty cell's capacity percentage as 100 * W%.

[0024] Let the preset change level be S, and the specific expression is as follows:

[0025] S=(100%-100*W%)÷[Q÷(Y*Q)]

[0026] In the formula, 100% - 100*W% is the actual difference between the standard cell capacity and the faulty cell capacity, and Q ÷ (Y*Q) is the percentage of the compensated cell capacity in the total battery pack capacity.

[0027] S351. If the preset change level |S|≥1, the capacity of the faulty cell is not equal to the standard capacity of the standard cell. If the capacity of the faulty cell is greater than the standard capacity of the standard cell, the compensation level is reduced. If the capacity of the faulty cell is less than the standard capacity of the standard cell, the compensation level is increased. If the adjusted compensation level is outside the range of 0 to 6, the nearest principle is adopted to adjust the compensation level to 0 or 6 and record it.

[0028] S352. If the preset variation level |S| < 1, the capacity of the faulty cell is equal to the standard capacity of the standard cell. Calculations are performed based on the recorded voltage value of the faulty cell, and the first charge / discharge module is activated to compensate for the faulty cell. The specific steps are as follows:

[0029] S3521. If |θHP-θHa|≥1%, that is, when the capacity of the faulty cell shifts upward by more than 1%, the voltage value of the faulty cell shifts downward as a whole to discharge; if the capacity of the faulty cell shifts downward by more than 1%, the voltage value of the faulty cell shifts upward as a whole to charge.

[0030] S3522. If |θHP-θHa| < 1%, that is, the capacity of the faulty cell shifts upward or downward by less than 1%, then the voltage value of the faulty cell will not be adjusted.

[0031] Preferably, in step S21, if the battery charge is less than 30% and the current in the battery satisfies -10A≤I≤10A, the compensation control module updates the average voltages Vp and Va, and obtains the lowest average battery voltage LVp and the lowest voltage LFa of the faulty cell.

[0032] Preferably, the C-type battery cell has a rated standard capacity of 50% Y*Q, the E-type battery cell has a rated standard capacity of 200% Y*Q, and the D-type and F-type battery cells have a rated capacity of Y*Q equal to that of the standard battery cell.

[0033] Preferably, the SOC difference between the voltage values ​​of the Class C cells and the Class E cells is inversely proportional to the standard SOC difference.

[0034] Preferably, the voltage of the D-type battery cell is higher than that of the standard battery cell at the same time, and the voltage value of the D-type battery cell is the voltage value corresponding to the rated standard battery cell capacity Y*Q increased by 5% SOC; the voltage of the F-type battery cell is lower than that of the standard battery cell at the same time, and the voltage value of the F-type battery cell is the voltage value corresponding to the rated standard battery cell capacity Y*Q reduced by 5% SOC.

[0035] In another aspect, the present invention provides a compensation device for a method of compensating the capacity of a single battery cell, characterized in that it includes a connection control module, a battery management system (BMS), and a compensation control module. The connection control module includes leads, a relay, a battery cell, a voltage detection module, and a charge / discharge module. The control terminals of the relay, the charge / discharge module, and the voltage detection module are respectively connected to a first terminal, a second terminal, and a third terminal of the compensation control module. The first and second ends of the first cell B1, the second cell B2, and the third cell B3 are respectively connected to the first mounting ends of the first lead and the second lead via the first relay K1, the third relay K3, and the fifth relay K5. The two ends of the first charge / discharge module are respectively connected to the fourth mounting ends of the first lead and the second lead. The fifth mounting ends of the first lead and the second lead are connected to the two ends of the faulty cell via the seventh relay K7. The third and fourth ends of the first cell B1, the second cell B2, and the third cell B3 are respectively connected to the first mounting ends of the third lead and the fourth lead via the second relay K2, the fourth relay K4, and the sixth relay K6. The fourth and fifth mounting ends of the third lead and the fourth lead are respectively connected to the two ends of the voltage detection module and the second charge / discharge module.

[0036] Preferably, the capacities of the first battery cell B1, the second battery cell B2, and the third battery cell B3 are Q, 2Q, and 3Q, respectively. If the first relay K1, the third relay K3, and the fifth relay K5 are individually activated, or any two relays are activated, or the first relay K1, the third relay K3, and the fifth relay K5 are activated simultaneously, then there are 6 different capacity combinations, corresponding to 6 different compensation levels.

[0037] Compared with the prior art, the present invention has the following advantages:

[0038] 1. This invention overcomes the shortcomings of existing battery balancing systems by providing large-capacity compensation for faulty cells, and its integration into the capacity of individual cells can achieve a capacity compensation of 20% or even more.

[0039] 2. This invention can perform graded compensation by selecting different cells to divide the battery into different grades. The capacity of each cell can be defined by the user. The larger the capacity of the selected cell, the larger the maximum compensation capacity. As the number of battery pack cycles increases, the capacity decay gradually increases. The compensation control module will incorporate the corresponding capacity according to the degree of decay.

[0040] 3. In addition to graded control of cell capacity compensation, the present invention allows for more specific and precise voltage regulation of the charging and discharging module, making the compensated cell closer to the average voltage and solving the voltage difference problem.

[0041] 4. This invention replaces battery module replacement with cell capacity compensation, which extends battery life, reduces operational complexity, and saves maintenance costs. Attached Figure Description

[0042] Figure 1 This is a diagram showing the composition of the control module in the device for single-cell capacity compensation according to the present invention.

[0043] Figure 2 This is a diagram showing the communication and control relationships in the device for single-cell capacity compensation according to the present invention;

[0044] Figure 3 This is a graph of the optimized OCV table used in the compensation method for the capacity of a single battery cell in this invention.

[0045] Figure 4 This is a classification diagram of faulty cells in the compensation method for the capacity of a single battery cell according to the present invention;

[0046] Figure 5 This is a flowchart of the method for compensating the capacity of a single battery cell according to the present invention. Detailed Implementation

[0047] To fully describe the technical content, structural features, objectives, and effects of this invention, a detailed description will be provided below in conjunction with the accompanying drawings.

[0048] The specific process of the compensation method for the capacity of a single battery cell is implemented as follows: Figure 5 As shown:

[0049] S1. Pre-process the battery pack to be repaired.

[0050] S2. Through the preprocessing in step S1, the battery pack to be repaired is automatically matched and discharged.

[0051] S3. Based on the preprocessing in S1, the battery pack to be repaired is automatically matched and charged. If the compensation control module stores the compensation level, it will be charged in the following manner; otherwise, it will be charged directly.

[0052] Furthermore, the pretreatment process for the battery pack to be repaired described in step S1 includes,

[0053] S11. Discharge the battery pack to be repaired to below 30% and define the rated standard capacity of the battery as Y*Q. At the same time, set the voltages of the first cell B1, the second cell B2 and the third cell B3 to Vj±10mV respectively.

[0054] S12. Activate the battery management system. The battery management system sends the average voltage Vp of the battery pack and the voltage Va of the faulty cell to the CAN network in real time.

[0055] S13. Close the seventh relay K7 and charge the faulty cell in the battery pack with a current I of 4Q through the first charging and discharging module. At the same time, the compensation control module judges the voltage range of the voltage difference between the average voltage Vp and the faulty cell voltage Va. When |Va-Vp|≥20mV or Va≥Vj, Vj is the voltage value when the faulty cell capacity is 30%-40%, stop charging the faulty cell.

[0056] S14. Based on step S13, close the relays corresponding to different compensation level strategies, implement the compensation level strategy for the faulty cells in the battery pack until the battery pack stops charging. At this time, the compensation control module records the compensation level of this charging and uses it as the default compensation level to be started when the next charging or discharging event occurs for the first time.

[0057] Furthermore, the method for automatically matching and discharging the battery pack to be repaired described in step S2 includes,

[0058] S21. If the average voltage Vp of the battery pack is greater than or equal to the preset voltage value G of the battery pack when the battery pack is at 90-80% charge, preferably, the preset voltage value G corresponds to the voltage values ​​of ternary lithium battery cells and lithium iron phosphate battery cells of 3.9V and 3.5V respectively, then the compensation control module records the highest average voltage HVp of the battery pack and the highest voltage HVa of the faulty battery cell respectively.

[0059] Specifically, if the battery pack's charge is less than 30% and the current in the battery pack satisfies -10A≤I≤10A, the compensation control module updates the average voltages Vp and Va, and obtains the minimum average voltage LVp of the battery pack and the minimum voltage LFa of the faulty cell.

[0060] S22. If the average voltage Vp is less than the preset voltage value G of the battery pack when the battery charge is 90-80%, the compensation control module will not record the voltage value.

[0061] Furthermore, the method for automatically matching and charging the battery pack to be repaired described in step S3 includes, S31, establishing an optimized OCV form:

[0062] S311. Based on the SOC and voltage values ​​of each row in the basic OCV form, set 5*M% and V respectively. 5*M The value of M is a natural number from 0 to 20, that is, 0%, 5%, ... 100% correspond to V0, V5, ... V 100 .

[0063] S312. Sequentially set the 101 voltage values ​​in the optimized OCV form to correspond one-to-one with the SOC of each row in the basic OCV form, i.e., V N There is a one-to-one correspondence between N% and N%, where N is a natural number from 0 to 100. The calculation expression is as follows:

[0064] N = 5 * M

[0065] V N+i =V M +(V 5*(M+1) -V M )÷5*i, where i takes the value 1, 2, 3, or 4.

[0066] Preferably, when the standard cell's SOC is 96%, the corresponding voltage V 96 At this point, N = 95, M = 19, and i = 1. According to the calculation expression, we can obtain: V 96 =V 95 +(V 100 -V 95 )÷5*1=4.125+(4.182-4.125)÷5*1=4.136V;

[0067] When the standard cell's SOC is 19%, its corresponding voltage V 19 At this point, N = 15, M = 3, i = 4. According to the calculation expression, we can obtain: V 19 =V 15 +(V 20 -V 15 )÷5*4=3.314+(3.406-3.314)÷5*4=3.388V.

[0068] S32. Based on the optimized OCV form, establish a classification table for faulty cells to obtain a table model for single cell capacity compensation. The table model for single cell capacity compensation includes four types of cells: C, D, E, and F. These four types of cells reflect the characteristics of faulty cells.

[0069] according to Figure 4 As shown, specifically, to clearly illustrate the experimental design, a battery discharge system consisting of multiple cells connected in series was used. Class C cells were pre-set to have 50% of their rated standard capacity of 300Ah (150Ah), Class E cells to have 200% of their rated standard capacity of 300Ah (600Ah), and Class D and Class F cells to have the same rated standard capacity of 300Ah. The SOC difference between the voltage values ​​of Class C and Class E cells was inversely proportional to the standard SOC difference. At any given moment, the voltage of a Class D cell was higher than that of a standard cell; the voltage value of a Class D cell was the voltage value corresponding to a 5% increase in SOC from the rated standard capacity of 300Ah. Conversely, the voltage of a Class F cell was lower than that of a standard cell; the voltage value of a Class F cell was the voltage value corresponding to a 5% decrease in SOC from the rated standard capacity of 300Ah.

[0070] S33. Calculate the difference in charge between the highest average voltage HVp and the lowest average voltage LVp of the battery pack, Δθ_standard, i.e., Δθ_standard = θHP - θLP, where θHP and θLP are the SOC values ​​corresponding to the highest average voltage HVp and the lowest average voltage LVp of the battery pack, respectively.

[0071] S34. Calculate the charge difference Δθa between the highest voltage HVa and the lowest voltage LVA of the faulty cell. Δθa = θHa - θLa, where θHa and θLa are the SOC values ​​corresponding to the highest voltage HVa and the lowest voltage LVA of the faulty cell, respectively.

[0072] S35. Based on steps S33 and S34, calculate the ratio of the difference in charge between the battery pack and the faulty cell, and formulate a corresponding compensation strategy, i.e. W = Δθ_standard ÷ Δθ_a, where W is the proportion of the faulty cell's SOC to the battery pack's SOC, which is converted to the faulty cell's capacity percentage as 100 * W%.

[0073] Let the preset change level be S, and the specific expression is as follows:

[0074] S=(100%-100*W%)÷[Q÷(Y*Q)]

[0075] In the formula, 100% - 100*W% is the actual difference between the standard cell capacity and the faulty cell capacity, and Q ÷ (Y*Q) is the percentage of the compensated cell capacity in the total battery pack capacity.

[0076] Preferably, the SOC of the faulty cell Δθa and the SOC of the battery pack Δθ are inversely proportional, that is, the larger the value, the smaller the capacity.

[0077] S351. If the preset change level |S|≥1, the capacity of the faulty cell is not equal to the capacity of the standard cell. If the capacity of the faulty cell is less than the capacity of the standard cell, the compensation level is reduced. If the capacity of the faulty cell is greater than the capacity of the standard cell, the compensation level is increased. If the adjusted compensation level is outside the range of 0 to 6, the nearest principle is adopted to adjust the compensation level to 0 or 6 and record it.

[0078] S352. If the preset variation level |S| < 1, the capacity of the faulty cell is equal to the standard telecommunications capacity. Calculations are performed based on the recorded voltage value of the faulty cell, and the first charge / discharge module is activated to compensate for the faulty cell. The specific steps are as follows:

[0079] S3521. If |θHP-θHa|≥1%, that is, when the capacity of the faulty cell shifts upward by more than 1%, the voltage value of the faulty cell shifts downward as a whole for charging; if the capacity of the faulty cell shifts downward by more than 1%, the voltage value of the faulty cell shifts upward as a whole for discharging.

[0080] S3522. If |θHP-θHa| < 1%, that is, the capacity of the faulty cell shifts upward or downward by less than 1%, then the voltage value of the faulty cell will not be adjusted.

[0081] Preferably, during the automatic matching process in steps S2 and S3, the compensation level is updated during the charging process. During the discharging process, the corresponding relay is activated according to the capacity compensation level set during the charging process, and the battery cell can be used normally until the next charging event occurs.

[0082] Furthermore, to better illustrate the automatic matching and charging of the battery pack under repair using this method, the specific performance of the four types of cells (C, D, E, and F) obtained in step S32 is analyzed. The specific analysis process is as follows:

[0083] When the four types of battery cells are connected separately in the same series-connected discharge battery system, they will all follow the following rules. Figure 3 and Figure 4 The corresponding voltage characteristics are shown in the table. Each row represents the voltage value of various types of faulty batteries at the same time. For ease of explanation, the standard cell battery voltage sequence number column (i.e., column 4) is used, with rows 0 to 20. The voltage step corresponding to each row is set from bottom to top as T0 to T20. 20， This column serves as a reference column, showing the voltage steps of Class C and Class E cells and the standard battery voltage step T when the standard battery SOC is 50%. 10 Similarly, the voltage of Class D cells is one step lower, T. 09 The voltage of the F-class battery cell is one step higher than T. 11 .

[0084] like Figure 4 As shown, for Class C cells, when the battery system is charged to 75% of the standard battery's SOC (State of Charge), i.e., the standard cell capacity is 75%, the voltage of the Class C cell at this time is T. 20 ,correspond Figure 4 The value in the table is 4.182V, which has reached the battery's maximum protection voltage, meaning that for Class C cells, it has reached the charging limit voltage T. 20 At this point, the C-class cell can be considered to have 100% of its actual capacity. When the same battery system discharges to 25% of the standard battery's SOC, the voltage of the C-class cell is T0, which has reached the minimum protection voltage of the battery. That is, the C-class battery has reached its discharge limit, and the faulty cell has 0% capacity at this point.

[0085] According to step S33, calculate the difference in charge between the battery's highest average voltage HVp and lowest average voltage LVp, Δθ_standard, i.e., Δθ_standard = θHP - θLP, Δθ_standard = 75% - 25% = 50%.

[0086] According to step S34, the difference in charge Δθa between the highest voltage HVa and the lowest voltage LVA of the faulty cell is calculated, i.e., Δθa = θHa - θLa, Δθa = 100% - 0% = 100%.

[0087] Calculate the ratio of the difference in charge between the battery and the faulty cell according to step S35, and formulate a corresponding compensation strategy, i.e., W = Δθstandard ÷ Δθa, W = 50% ÷ 100% = 0.5.

[0088] As shown by the mathematical expression, a Class C cell has 0.5 times the capacity of a standard battery. In a series-connected battery system, within the same time period, the capacity difference ratio is inversely proportional to the actual measured capacity value. Class C cells can only operate at the T5 and T6 voltage values ​​corresponding to the standard cell voltage. 15 Therefore, when HVa > HVP and LVA < LVP, the capacity of Class C cells degrades, and an increase in capacity is needed to improve battery performance.

[0089] like Figure 4 As shown, for Class D cells, when the battery system is charged to 100% of the standard battery's SOC, the voltage of the Class D cell is T. 19 The battery's maximum protection voltage has not been reached, which corresponds to 95% of the SOC of a Class D cell. It is still 5% short of reaching the charging limit voltage. Similarly, when the battery system discharges to 5% of the standard battery's SOC, the voltage of the Class D cell, T0, has reached the battery's minimum protection voltage, meaning it has reached the discharge limit voltage for Class D batteries. This can be expressed mathematically as:

[0090] θHP+5%=θHa

[0091] θLP+5%=θLa

[0092] As can be seen from the mathematical expression, the voltage of Class D cells tends to be higher than that of standard cells. Therefore, when HVa > HVP and LVA > LVP, the voltage of Class D cells is higher than that of other cells.

[0093] like Figure 4 As shown, for Class E cells, when the battery system is charged to 100% of the standard battery's SOC, the voltage of the Class E cell is T. 15 The voltage of the E-class cell only reaches 75% of its SOC, which is far from the charging limit voltage for the E-class cell. Similarly, when the battery system discharges to 0% of the standard battery SOC, the voltage of the E-class cell is T5, which only reaches 25% of the E-class cell SOC, meaning that the discharge limit voltage for the E-class cell is far from the discharge limit voltage.

[0094] According to step S33, calculate the difference in charge between the battery's highest average voltage HVp and lowest average voltage LVp, Δθ_standard, that is, Δθ_standard = θHP - θLP, Δθ_standard = 100% - 0% = 100%.

[0095] According to step S34, the difference in charge Δθa between the highest voltage HVa and the lowest voltage LVA of the faulty cell is calculated, i.e., Δθa = θHa - θLa, Δθa = 75% - 25% = 50%.

[0096] Calculate the ratio of the difference in charge between the battery and the faulty cell according to step S35, and formulate a corresponding compensation strategy, i.e., W = Δθstandard ÷ Δθa, W = 100% ÷ 50% = 2.

[0097] Mathematical expressions show that Class E cells have twice the capacity of standard batteries. In a series-discharge battery system, within the same time period, the capacity difference ratio is inversely proportional to the actual measured capacity value. Class E cells can achieve the same capacity at T0 and T1 corresponding to the voltage values ​​of standard cells. 20 When used between cells, and their own voltage is far from reaching the discharge limit voltage, the E-class cells are basically caused by too many compensation levels when HVa < HVP and LVA > LVP.

[0098] like Figure 4 As shown, for Class F cells, when the battery system is charged to 95% of the standard battery's SOC, the voltage of the Class F cell is T. 20 The battery has reached its maximum protection voltage, which is the charging limit voltage for Class F batteries. Similarly, when the battery system discharges to 0% of the standard battery's SOC, the voltage of the Class F cell, T1, has not yet reached the battery's minimum protection voltage. This can be expressed mathematically as:

[0099] θHP-5% = θHa

[0100] θLP-5% = θLa

[0101] The mathematical expression shows that the voltage of Class F cells tends to decrease compared to standard cells. Therefore, when HVa < HVP and LVA < LVP, the voltage of Class F cells is lower than that of other cells.

[0102] In a preferred embodiment of the present invention, the compensation device for the compensation method of single cell capacity, such as... Figure 1 and Figure 2As shown, it includes a connection control module, a battery management system (BMS), and a compensation control module. The connection control module includes leads, relays, battery cells, a voltage detection module, and a charge / discharge module. The control terminals of the relays, the charge / discharge module, and the voltage detection module are respectively connected to the first, second, and third terminals of the compensation control module. The first charge / discharge module can charge the capacity-degrading battery cells by closing the seventh relay K7.

[0103] The first charge / discharge module can adjust the voltage of the faulty battery cell. It can charge to increase the voltage, with the charging voltage not exceeding Vj. Preferably, Vj corresponds to 3.5V for ternary lithium battery cells and 3.1V for lithium iron phosphate battery cells. It can also discharge to decrease the voltage, with the discharging voltage not lower than 2.5V. Moreover, the capacity of discharging and charging can be precisely controlled. The compensation control module controls the first relay K1, the third relay K3, and the fifth relay K5 to adjust the amount of compensation capacity. During the normal charging and use of the battery pack, the decrease or increase of the new compensation cell level will occur when the Va value is close to Vj, but it will not occur during the discharge event.

[0104] The Battery Management System (BMS) has conventional battery parameter detection functions and control strategy execution functions. It can send battery parameters such as the average voltage Vp, highest single-cell voltage Vh, lowest single-cell voltage VL, all cell voltage values, and SOC to the CAN network according to the communication protocol.

[0105] The compensation control module receives battery information from the battery management system (BMS) on the CAN network, analyzes it, and implements different relay on / off combinations according to the control strategy requirements. It also performs standby cell voltage detection and charge / discharge voltage adjustment to achieve different capacity level combinations of the first cell B1, the second cell B2, and the third cell B3. These combinations are then connected in parallel to the two ends of the individual cells experiencing capacity degradation, achieving reasonable capacity compensation for the degraded individual cells. Simultaneously, the compensation control module has a fault detection function. If it detects that the first cell B1, the second cell B2, and the third cell B3 cannot charge or discharge to the appropriate voltage value as required by the strategy, it sends a fault alarm to the CAN network, reminding the user to promptly repair or replace the device.

[0106] The first and second ends of the first battery cell B1, the second battery cell B2, and the third battery cell B3 are respectively connected to the first mounting end, the second mounting end, and the third mounting end of the first lead and the second lead through the first relay K1, the third relay K3, and the fifth relay K5. The two ends of the first charging and discharging module are respectively connected to the fourth mounting end of the first lead and the second lead. The fifth mounting end of the first lead and the second lead is connected to the two ends of the faulty battery cell through the seventh relay K7.

[0107] The third and fourth terminals of the first battery cell B1, the second battery cell B2, and the third battery cell B3 are respectively connected to the first, second, and third mounting terminals of the third and fourth leads via the second relay K2, the fourth relay K4, and the sixth relay K6. The fourth and fifth mounting terminals of the third and fourth leads are respectively connected to the two ends of the voltage detection module and the second charge / discharge module. When one or two, or all three of the second relay K2, the fourth relay K4, and the sixth relay K6 are activated, the second charge / discharge module can charge or discharge the battery, or the voltage detection module can detect the voltage at both ends of the battery.

[0108] The capacities of the first cell B1, the second cell B2, and the third cell B3 are Q, 2Q, and 3Q, respectively. If the first relay K1, the third relay K3, and the fifth relay K5 are activated individually, or any two relays are activated, or the first relay K1, the third relay K3, and the fifth relay K5 are activated simultaneously, six different capacity combinations can be achieved, enabling step-by-step compensation of the battery pack capacity attenuation.

[0109] The following describes in further detail a method and apparatus for compensating the capacity of a single battery cell according to the present invention, with reference to specific embodiments:

[0110] In this embodiment, taking a ternary lithium battery cell as an example, the capacities of the first cell B1, the second cell B2, and the third cell B3 in the compensation device of the present invention are 10Ah, 20Ah, and 30Ah, respectively. If the first relay K1, the third relay K3, and the fifth relay K5 are individually activated, or any two relays are activated, or K1, K3, and K5 are activated simultaneously, then six different capacity combinations will occur, namely 10Ah, 20Ah, 30Ah, 40Ah, 50Ah, and 60Ah, which can realize the step-by-step compensation of battery pack capacity decay cells.

[0111] During battery system discharge, if the second relay K2, the fourth relay K4, and the sixth relay K6 are individually activated, the voltage detection module and the second charge / discharge module will determine whether to charge or discharge the first cell B1, the second cell B2, and the third cell B3 based on the detected voltage values, maintaining their voltage values ​​at Vj. When there is an idle cell among the first cell B1, the second cell B2, and the third cell B3 (not participating in the compensation level operation), that cell is activated sequentially, and the voltage detection module detects its voltage. If the cell voltage V is less than 3.5V, the cell is charged through the second charge / discharge module at a current of 40A. Charging stops when V ≥ 3.5V. If the voltage V is greater than 3.5V, the cell is discharged through the second charge / discharge module at a current of 40A. Discharging stops when V ≤ 3.5V, ultimately maintaining the idle cell at approximately 3.5V. If the voltage of the idle cell is not within this range, the N+1 level capacity compensation strategy is not allowed, but the N-1 level capacity compensation strategy (where N is a natural number from 0 to 6) can be executed.

[0112] The specific process of the compensation method of the present invention is implemented as follows: Figure 5 As shown:

[0113] S1. Pre-process the ternary lithium battery pack to be repaired.

[0114] S11. Discharge the ternary lithium battery pack to be repaired to below 30%, and define the rated standard capacity of the ternary lithium battery pack as 30*10=300Ah. At the same time, set the voltage of the first cell B1, the second cell B2 and the third cell B3 to 3.5±10mV respectively.

[0115] S12. Activate the battery management system. The battery management system sends the average voltage Vp of the ternary lithium battery pack and the voltage Va of the faulty cell to the CAN network in real time.

[0116] S13. Close the seventh relay K7 and charge the faulty cell in the ternary battery pack with a current of 40A through the first charging and discharging module. At the same time, the compensation control module judges the voltage range of the voltage difference between the average voltage Vp and the faulty cell voltage Va. When |Va-Vp|≥20mV or Va≥3.5V, the charging of the faulty cell is stopped.

[0117] S14. Based on step S13, close the relays corresponding to different compensation level strategies to implement the compensation level strategy for the faulty cells in the ternary lithium battery pack until the ternary lithium battery pack stops charging. At this time, the compensation control module records the compensation level of this charging. Level 1 compensation can be executed in the preprocessing stage and used as the default compensation level to be started when the next charging or discharging event occurs for the first time.

[0118] S2. Through the preprocessing in step S1, the ternary lithium battery pack to be repaired is automatically matched and discharged.

[0119] S21. If the average voltage Vp of the ternary lithium battery pack is greater than or equal to the preset voltage value G of the battery when the charge is 90-80%, the compensation control module records the highest average voltage of the ternary lithium battery pack (4.093V) and the highest voltage of the faulty cell (4.136V).

[0120] If the battery pack's charge is less than 30%, and the current in the battery pack satisfies -10A≤I≤10A, then the compensation control module updates the average voltages Vp and Va, and obtains the minimum average voltage of the battery pack LVp = 3.471V and the minimum voltage of the faulty cell LFa = 3.388V.

[0121] S22. If the average voltage Vp < 3.9V, the compensation control module will not record the voltage value.

[0122] S3. Based on the preprocessing in S1, the ternary lithium battery pack to be repaired is automatically matched and charged. If the compensation control module stores the compensation level, it is charged in the following manner; otherwise, it is charged directly.

[0123] S31. Create an optimized OCV form:

[0124] S311. Based on the SOC and voltage values ​​of each row in the basic OCV form, set 5*M% and V respectively. 5*M The value of M is a natural number from 0 to 20, that is, 0%, 5%, ... 100% correspond to V0, V5, ... V 100 .

[0125] S312. Sequentially set the 101 voltage values ​​in the optimized OCV form to correspond one-to-one with the SOC of each row in the basic OCV form, i.e., V N There is a one-to-one correspondence between N% and N%, where N is a natural number from 0 to 100. The calculation expression is as follows:

[0126] N = 5 * M

[0127] V N+i =V 5*M +(V 5*(M+1) -V 5*M )÷5*i, where i takes the value 1, 2, 3, or 4.

[0128] S32. Based on the optimized OCV form, establish a classification table for faulty cells to obtain a table model for individual cell capacity compensation. In this embodiment, class C cells are selected for the table model for individual cell capacity compensation.

[0129] S33. Calculate the difference in charge Δθ_standard between the highest average voltage of the ternary lithium battery pack (4.093V) and the lowest average voltage of the ternary lithium battery pack (3.471V), i.e., Δθ_standard = 90% - 25% = 65%, where 90% and 25% are the SOC values ​​corresponding to the highest average voltage of the battery pack (4.093V) and the lowest average voltage of the battery pack (3.471V), respectively.

[0130] S34. Calculate the charge difference Δθa between the highest voltage of the faulty cell (4.136V) and the lowest voltage of the faulty cell (3.388V). Δθa = 96% - 19% = 77%, 96%, and 19% are the SOC values ​​corresponding to the highest voltage of the faulty cell (4.136V) and the lowest voltage of the faulty cell (3.388V), respectively.

[0131] S35. Based on steps S33 and S34, calculate the ratio of the difference in charge between the ternary lithium battery pack and the faulty cell, and formulate a corresponding compensation strategy, i.e. W = Δθ_standard ÷ Δθ_a = 65% ÷ 77% ≈ 0.84, where 0.84 is the proportion of the faulty cell's SOC to the battery pack's SOC, which is converted to a faulty cell capacity percentage of 84%.

[0132] Let the preset change level be S, then S = (100% - 84%) ÷ [10 ÷ (300)] = 4.8.

[0133] S351. If the preset variation level |S|≥1, the capacity of the faulty cell is not equal to the standard capacity of the standard cell. If the capacity of the faulty cell is less than the standard capacity of the standard cell, the compensation level is reduced. If the capacity of the faulty cell is greater than the standard capacity of the standard cell, the compensation level is increased. At this time, the value of S is 4.8. After removing the decimal part, the variation level needs to be increased by 4 levels. Adding the original fault level of 1, the final compensation level that should be adjusted now is 5 levels. The compensation control module records this level value.

[0134] S352. If the preset variation level |S| < 1, the capacity of the faulty cell is equal to the standard capacity of the standard cell. Calculations are performed based on the recorded voltage value of the faulty cell, and the first charge / discharge module is activated to compensate for the faulty cell. The specific steps are as follows:

[0135] S3521. If |θHP-θHa|≥1%, that is, when the capacity of the faulty cell shifts upward by more than 1%, the voltage value of the faulty cell shifts downward as a whole to discharge; if the capacity of the faulty cell shifts downward by more than 1%, the voltage value of the faulty cell shifts upward as a whole to charge.

[0136] The specific operating steps are as follows: Close the seventh relay K7, and charge or discharge the faulty cell in the battery pack with a current of 40A through the first charging and discharging module. At the same time, the compensation control module judges the voltage range of the voltage difference between the average voltage Vp and the faulty cell voltage Va. When |Va-Vp|≥20mV or Va≥3.5V, stop charging the faulty cell. When |Va-Vp|≥20mV or Va≤3.5V, stop discharging the faulty cell.

[0137] S3522. If |θHP-θHa| < 1%, that is, the capacity of the faulty cell shifts upward or downward by less than 1%, then the voltage value of the faulty cell will not be adjusted.

[0138] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for compensating the capacity of a single battery cell, characterized in that, Specifically, the following steps are included: S1. Pre-treatment of the battery pack to be repaired: S11. Discharge the battery pack to be repaired to below 30% and define the rated standard capacity of the battery pack as Y*Q. At the same time, set the voltage of the first cell B1, the second cell B2 and the third cell B3 to Vj±10mV respectively, where Vj is the voltage value when the capacity of the faulty cell is 30%-40%. S12. Activate the battery management system. The battery management system sends the average voltage Vp of the battery pack and the voltage Va of the faulty cell to the CAN network in real time. S13. The first charging and discharging module charges the faulty cell in the battery pack with a current I of 4Q. At the same time, the compensation control module judges the voltage range of the voltage difference between the average voltage Vp of the battery pack and the voltage Va of the faulty cell. When |Va-Vp|≥20mV or Va≥Vj, the charging of the faulty cell is stopped. S14. Based on step S13, close the relays corresponding to different compensation level strategies, implement the compensation level strategy for the faulty cells in the battery pack until the battery pack stops charging. At this time, the compensation control module records the compensation level of this charging and uses it as the default compensation level to be started when the next charging or discharging event occurs for the first time. S2. Following the preprocessing in step S1, automatically match and discharge the battery pack to be repaired: S21. If the average voltage Vp of the battery pack is greater than or equal to the preset voltage value G of the battery pack when the battery pack is at 90-80% charge, the compensation control module records the highest average voltage HVp of the battery pack and the highest voltage HVa of the faulty cell respectively. S22. If the average voltage Vp of the battery pack is less than the preset voltage value G of the battery pack when the battery pack is at 90-80% charge, the compensation control module will not record the voltage value. S3. Following the preprocessing in S1, the battery pack to be repaired is automatically matched and charged. If the compensation control module stores the compensation level, charging is performed as follows; otherwise, charging is performed directly: S31. Create an optimized OCV form: S311. Based on the SOC and voltage values ​​of each row in the basic OCV form, set 5*M% and V respectively. 5*M The value of M is a natural number from 0 to 20, that is, 0%, 5%, and 100% correspond to V0, V5, and V6, respectively. 100 ; S312. Sequentially set each voltage value in the optimized OCV form to correspond one-to-one with the SOC in each row of the basic OCV form, i.e., V N This corresponds one-to-one with N%, where N is a natural number from 0 to 100. The calculation expression is as follows: N=5*M; V N +i=V5* M + (V5*(M+1)-V5*) M ) ÷ 5*i, where i can take the values ​​1, 2, 3, and 4; S32. Based on the optimized OCV form, establish a classification table for faulty cells to obtain a table model for single cell capacity compensation. The table model for single cell capacity compensation includes four types of cells: C, D, E, and F. The C-class cells are 50% of the rated standard capacity Y*Q, the E-class cells are 200% of the rated standard capacity Y*Q, and the D-class cells and F-class cells are each equal to the rated capacity Y*Q of the standard cells. S33. Calculate the difference in charge between the highest average voltage HVp and the lowest average voltage LVp of the battery pack, Δθ, i.e., Δθ = θHP - θLP, where θHP and θLP are the SOC values ​​corresponding to the highest average voltage HVp and the lowest average voltage LVp of the battery pack, respectively. S34. Calculate the charge difference Δθa between the highest voltage HVa and the lowest voltage LVA of the faulty cell, i.e., Δθa = θHa - θLa, where θHa and θLa are the SOC values ​​corresponding to the highest voltage HVa and the lowest voltage LVA of the faulty cell, respectively. S35. Based on steps S33 and S34, calculate the ratio of the difference in charge capacity between the battery pack and the faulty cell, and formulate a corresponding compensation strategy, i.e., W = Δθstandard ÷ Δθa, where W is the proportion of the faulty cell's SOC to the battery pack's SOC, converted to a faulty cell capacity percentage of 100*W%. Let the preset change level be S, and the specific expression is as follows: S=(100%-100*W%)÷[Q÷(Y*Q)]; In the formula, 100%-100*W% is the actual difference between the standard cell capacity and the faulty cell capacity, and Q÷(Y*Q) is the percentage of the compensated cell capacity in the total battery pack capacity. S351. If the preset change level |S|≥1, the capacity of the faulty cell is not equal to the standard capacity of the standard cell. If the capacity of the faulty cell is greater than the standard capacity of the standard cell, the compensation level is reduced. If the capacity of the faulty cell is less than the standard capacity of the standard cell, the compensation level is increased. If the adjusted compensation level exceeds the range of 0 to 6, the nearest compensation level will be used to adjust the compensation level to 0 or 6, and this will be recorded. S352. If the preset variation level |S| < 1, the capacity of the faulty cell is equal to the standard capacity of the standard cell. Calculations are performed based on the recorded voltage value of the faulty cell, and the first charge / discharge module is activated to compensate for the faulty cell. The specific steps are as follows: S3521. If |θHP-θHa|≥1%, that is, when the capacity of the faulty cell shifts upward by more than 1%, the voltage value of the faulty cell shifts downward as a whole to discharge; if the capacity of the faulty cell shifts downward by more than 1%, the voltage value of the faulty cell shifts upward as a whole to charge. S3522. If |θHP-θHa|<1%, that is, when the capacity of the faulty cell shifts upward or downward by less than 1%, then the voltage value of the faulty cell will not be adjusted.

2. The method for compensating the capacity of a single battery cell according to claim 1, characterized in that, In step S21, if the battery charge is less than 30% and the current in the battery satisfies -10A≤I≤10A, the compensation control module updates the average voltages Vp and Va, and obtains the lowest average battery voltage LVp and the lowest voltage LFa of the faulty cell.

3. The method for compensating the capacity of a single battery cell according to claim 1, characterized in that, The SOC difference between the voltage values ​​of the Class C cells and the Class E cells is inversely proportional to the standard SOC difference.

4. The method for compensating the capacity of a single battery cell according to claim 1, characterized in that, The voltage of the D-type battery cell is higher than that of the standard battery cell at the same time. The voltage value of the D-type battery cell is the voltage value corresponding to the rated standard battery cell capacity Y*Q increased by 5% SOC. The voltage of the F-type battery cell is lower than that of the standard battery cell at the same time. The voltage value of the F-type battery cell is the voltage value corresponding to the rated standard battery cell capacity Y*Q decreased by 5% SOC.

5. A compensation device for a method of compensating the capacity of a single battery cell according to any one of claims 1-4, characterized in that, It includes a connection control module, a battery management system (BMS), and a compensation control module. The connection control module includes leads, relays, battery cells, a voltage detection module, and a charge / discharge module. The control terminals of the relays, the charge / discharge module, and the voltage detection module are respectively connected to the first terminal, the second terminal, and the third terminal of the compensation control module. The first and second ends of the first cell B1, the second cell B2, and the third cell B3 are respectively connected to the first mounting ends of the first lead and the second lead via the first relay K1, the third relay K3, and the fifth relay K5. The two ends of the first charge / discharge module are respectively connected to the fourth mounting ends of the first lead and the second lead. The fifth mounting ends of the first lead and the second lead are connected to the two ends of the faulty cell via the seventh relay K7. The third and fourth ends of the first cell B1, the second cell B2, and the third cell B3 are respectively connected to the first mounting ends of the third lead and the fourth lead via the second relay K2, the fourth relay K4, and the sixth relay K6. The fourth and fifth mounting ends of the third lead and the fourth lead are respectively connected to the two ends of the voltage detection module and the second charge / discharge module.

6. The compensation device according to claim 5, characterized in that, The capacities of the first battery cell B1, the second battery cell B2, and the third battery cell B3 are Q, 2Q, and 3Q, respectively. If the first relay K1, the third relay K3, and the fifth relay K5 are individually activated, or any two relays are activated, or the first relay K1, the third relay K3, and the fifth relay K5 are activated simultaneously, then there are 6 different capacity combinations, corresponding to 6 different compensation levels.

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