Battery pack conformity testing methods, testing components, and battery systems

Abstract

This application discloses a battery pack consistency detection method, detection components, and a battery system. The method includes: determining a first time point and a second time point; wherein the first time point is the migration time when a battery cell migrates from a first non-voltage plateau interval corresponding to the battery cell to a first voltage plateau interval corresponding to the battery cell during a single charge; the second time point is the migration time when another battery cell migrates from a second non-voltage plateau interval corresponding to the battery cell to a second voltage plateau interval corresponding to the battery cell during a single charge, or the second time point is the average of the migration times corresponding to at least two battery cells; and obtaining a battery pack consistency detection result based on the first and second time points. Through the above method, this application can efficiently detect the consistency of a battery pack.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a battery pack consistency testing method, testing components, and battery system. Background Technology

[0002] Since 2021, the installed capacity of lithium iron phosphate (LFP) batteries in China's new energy vehicles has surpassed that of ternary lithium batteries, completely reversing the trend since 2018 where the annual production of LFP batteries lagged behind that of ternary lithium batteries. Furthermore, the proportion of LFP batteries continues to increase. For vehicles, the safe use of LFP batteries has always been a key concern. The consistency testing of LFP battery packs is more difficult than that of ternary lithium battery packs, which has become a crucial challenge that must be overcome in the development of LFP batteries.

[0003] Currently, the commonly used consistency testing method for lithium iron phosphate battery packs mainly involves testing the battery after it has been left to stand for a long time at the charging and discharging ends, allowing the battery voltage to stabilize. This testing method is time-consuming and labor-intensive. Summary of the Invention

[0004] The main technical problem addressed by this application is to provide a battery pack consistency testing method, testing equipment, and battery system that can efficiently test the consistency of battery packs.

[0005] To address the aforementioned technical problems, this application provides a battery pack consistency detection method. The battery pack includes at least two individual battery cells. The charging process of each battery cell includes a voltage plateau interval and a non-voltage plateau interval, with the voltage plateau interval following the non-voltage plateau interval. During the charging process of the battery cell, the voltage plateau migrates from the non-voltage plateau interval to the voltage plateau interval. The battery pack consistency detection method includes: determining a first time point and a second time point; wherein the first time point is the migration time when one battery cell migrates from the first non-voltage plateau interval corresponding to that battery cell to the first voltage plateau interval corresponding to that battery cell during a single charging process; the second time point is the migration time when another battery cell migrates from the second non-voltage plateau interval corresponding to that battery cell to the second voltage plateau interval corresponding to that battery cell during a single charging process, or the second time point is the average of the migration times corresponding to at least two battery cells; and based on the first and second times points, a battery pack consistency detection result is obtained.

[0006] The determination of the first time point and the second time point includes: acquiring first charging data and second charging data; wherein the first charging data includes the first voltage of a single battery cell at each time point, and the second charging data includes the second voltage of another single battery cell at each time point; obtaining the voltage difference at each time point based on the difference between the first voltage at each time point and the second voltage at each time point; and obtaining the first time point and the second time point based on the voltage difference at each time point.

[0007] Wherein, the first voltage at each moment is the first voltage at each moment within a preset interval, and the second voltage at each moment is the second voltage at each moment within a preset interval, and the preset interval is a non-voltage plateau interval; based on the first voltage at each moment and the second voltage at each moment, the voltage difference at each moment is obtained, including: based on the difference between the first voltage at each moment within the preset interval and the second voltage at each moment within the preset interval, the voltage difference at each moment is obtained; based on the voltage difference at each moment, the first moment and the second moment are obtained, including: based on the voltage difference at each moment within the preset interval, the first moment and the second moment are obtained.

[0008] The method of obtaining the first time and the second time based on the pressure difference at each time within a preset interval includes: in response to the first voltage being greater than the second voltage, the time corresponding to the maximum pressure difference is taken as the first time corresponding to a single battery cell, and the time corresponding to the minimum pressure difference is taken as the second time corresponding to another battery cell; in response to the first voltage being less than the second voltage, the time corresponding to the maximum pressure difference is taken as the second time corresponding to another battery cell, and the time corresponding to the minimum pressure difference is taken as the first time corresponding to a single battery cell.

[0009] Specifically, the capacity deviation between the first charging capacity and the second charging capacity is determined, and the rated capacity is obtained; wherein, the first charging capacity is the capacity charged by a single battery cell during a first charging duration, the first charging duration is the charging duration of a single battery cell from the start of charging to a first moment, the second charging capacity is the capacity charged by another single battery cell during a second charging duration, or, the second charging capacity is the average capacity charged by at least two single battery cells during a second charging duration, the second charging duration is the charging duration from the start of charging to a second moment, and the rated capacity is the rated capacity of at least two initial single battery cells; the ratio between the capacity deviation and the rated capacity is used as the SOC deviation within the battery pack.

[0010] The process involves charging with a constant current; determining the capacity deviation between the first charging capacity and the second charging capacity, including: obtaining a first charging duration based on a first moment and the start of charging; obtaining a second charging duration based on a second moment and the start of charging; obtaining the first charging capacity based on the first charging duration and the current value of the constant current; obtaining the second charging capacity based on the second charging duration and the current value of the constant current; and obtaining the capacity deviation using the difference between the first charging capacity and the second charging capacity.

[0011] Specifically, the capacity deviation is obtained for any two charging processes that meet the charging requirements within a preset time period; wherein the capacity deviation is the difference between the first charging capacity and the second charging capacity corresponding to the charging process, and the charging requirements include the charging temperature corresponding to the charging process meeting a temperature threshold; in response to the capacity deviation corresponding to the latter charging process that meets the charging requirements being greater than the capacity deviation corresponding to the other charging process that meets the charging requirements, it is determined that there is cell self-discharge in the battery pack within the preset time period.

[0012] Specifically, based on the first time point and the second time point, the battery pack consistency detection result is obtained, including: in response to the inconsistency between the first time point and the second time point, determining that the battery pack is inconsistent; and / or, the battery pack is a lithium iron phosphate battery pack.

[0013] To solve the above-mentioned technical problems, another technical solution adopted in this application is: to provide a detection component, which includes at least two acquisition elements and a processing element; the at least two acquisition elements correspond one-to-one with at least two battery cells of the battery pack, and the acquisition elements are used to connect to the corresponding battery cells to acquire the voltage of the battery cells; the processing element is communicatively connected to the at least two acquisition elements respectively, and is used to receive the voltage acquired by each acquisition element, and to perform the above-mentioned method based on the voltage acquired by each acquisition element.

[0014] To solve the above-mentioned technical problems, another technical solution adopted in this application is to provide a battery system, which includes a battery pack and a detection component connected in communication, and the detection device is the detection component mentioned above.

[0015] The above technical solution obtains the battery pack consistency detection result based on the first and second time points. The first and second time points represent the migration time of the voltage plateau of different battery cells from the non-voltage plateau range to the voltage plateau range. Therefore, this application determines whether the battery pack is consistent by determining whether the migration time of the voltage plateau from the non-voltage plateau range to the voltage plateau range is consistent. That is, this application determines whether the battery pack is consistent by the order in which the voltage plateaus migrate.

[0016] In addition, this application only requires one charging process and does not require the battery pack to be fully charged and discharged to complete the battery pack consistency test. That is, this application can efficiently perform battery pack consistency test without damaging the battery pack. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating an embodiment of the battery pack consistency detection method provided in this application;

[0018] Figure 2 This is a schematic diagram of an embodiment of the charging voltage curve provided in this application;

[0019] Figure 3 This is a schematic diagram of another embodiment of the charging voltage curve provided in this application;

[0020] Figure 4 This is a flowchart illustrating one embodiment of step S11;

[0021] Figure 5 This is a schematic diagram of an embodiment of the filling capacity change curve provided in this application;

[0022] Figure 6 This is a schematic diagram of an embodiment of the differential pressure change curve provided in this application;

[0023] Figure 7 This is a schematic diagram of the structure of an embodiment of the detection component provided in this application;

[0024] Figure 8 This is a schematic diagram of an embodiment of the battery system provided in this application. Detailed Implementation

[0025] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0026] In the following description, specific details such as particular system architectures, interfaces, and technologies are presented for illustrative purposes rather than for limiting purposes, in order to provide a thorough understanding of this application.

[0027] In this document, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " generally indicates that the preceding and following related objects have an "or" relationship. Furthermore, "many" in this document means two or more. Moreover, the term "at least one" in this document means any combination of at least two of any one or more of a plurality of objects. For example, including at least one of A, B, and C can mean including any one or more elements selected from the set consisting of A, B, and C.

[0028] Please see Figure 1 , Figure 1 This is a flowchart illustrating an embodiment of the battery pack consistency detection method provided in this application. It should be noted that if substantially the same result is obtained, the embodiment of this application is not necessarily identical. Figure 1 The illustrated process sequence is limited. For example... Figure 1 As shown, this embodiment includes:

[0029] For example, a lithium iron phosphate (LFP) battery pack consists of 10 individual LFP cells. Suppose that the lowest capacity LFP cell has a capacity of 2000mAh, while the other nine cells each have a capacity of 2500mAh. When the LFP battery pack discharges, all 10 cells discharge simultaneously, and the voltage of each cell decreases as its capacity decreases. When the lowest capacity LFP cell (2000mAh) finishes discharging, its voltage will reach 2.8V. The other nine cells (2500mAh each) still have remaining capacity and a voltage above 3.0V. However, the Battery Management System (BMS) has already detected that one LFP cell has reached 2.8V and will activate the over-discharge protection, stopping the entire LFP battery pack from discharging. This results in the entire LFP battery pack having a discharge capacity of only 2000mAh.

[0030] For example, a fully charged lithium iron phosphate battery cell has a voltage of 4.2V. The lithium iron phosphate battery pack BMS is set to overcharge protection for individual cells at 4.25V. The voltage of a lithium iron phosphate battery cell increases with its capacity. When a low-capacity lithium iron phosphate battery cell with a capacity of 2000mAh is fully charged, its voltage reaches 4.25V, while the other nine lithium iron phosphate battery cells are not yet fully charged and their voltages are below 4.1V. However, the BMS has already detected that the voltage of one lithium iron phosphate battery cell is higher than 4.25V, so it activates the overcharge protection, and the entire lithium iron phosphate battery pack stops charging, resulting in the entire lithium iron phosphate battery pack only being charged to 2000mAh.

[0031] The lowest capacity lithium iron phosphate battery cell determines the charging and discharging capacity of the lithium iron phosphate battery pack. The lithium iron phosphate battery cell with the worst cycle life and charge / discharge characteristics determines the overall performance of the lithium iron phosphate battery pack.

[0032] Please see Figure 2 and Figure 3 , Figure 2 This is a schematic diagram of an embodiment of the charging voltage curve provided in this application. Figure 3This is a schematic diagram of another embodiment of the charging voltage curve provided in this application. When the consistency deviation of the battery cells in the lithium iron phosphate battery pack occurs, the charging voltage curve of the deviated lithium iron phosphate battery cell will shift from that of other lithium iron phosphate battery cells during the charging process, forming a significant offset window. Furthermore, as the usage time of the lithium iron phosphate battery pack increases, the consistency deviation of the lithium iron phosphate battery pack will increase.

[0033] It should be noted that the battery pack includes at least two battery cells. The charging process of a battery cell includes a voltage plateau interval and a non-voltage plateau interval. The voltage plateau interval is located after the non-voltage plateau interval. During the charging process of a battery cell, the voltage plateau of the battery cell migrates from its corresponding non-voltage plateau interval to its corresponding voltage plateau interval.

[0034] Step S11: Determine the first time point and the second time point.

[0035] The method in this embodiment is used to perform consistency testing on lithium iron phosphate battery packs to determine whether there is a consistency deviation problem in the lithium iron phosphate cells, that is, to determine whether there is a consistency deviation within the lithium iron phosphate battery pack.

[0036] During battery pack charging, when the battery is in the voltage plateau range, the voltage of a single cell remains relatively constant while the charging capacity continuously increases. When the battery is outside the voltage plateau range, the voltage of a single cell increases with the charging capacity. When the charging capacity reaches a certain value, or when the voltage of a single cell reaches a certain value, the cell enters the voltage plateau range. Since a single cell initially has zero stored capacity when charging, it can be understood that as the battery pack charges, the stored capacity of each cell continuously increases, and the voltage of each cell increases accordingly. When the voltage of a single cell reaches a certain value, or in other words, when the stored capacity of a single cell reaches a certain value, the cell enters the voltage plateau range, at which point the voltage of the single cell remains relatively constant while the stored capacity continues to increase.

[0037] Because the individual cells within a battery pack are initially configured identically during assembly, during each charge cycle, if all cells in the pack have zero or the same stored capacity at the start of charging (i.e., if the voltages of all cells are the same at the start of charging), then the stored capacity of each cell remains essentially consistent with the charging time. In other words, the timing of the voltage plateau transitioning from its corresponding non-voltage plateau range to its corresponding voltage plateau range is essentially the same for each cell. However, if the individual cells have different voltages at the start of charging, creating a voltage difference or a capacity difference (e.g., cell A is not fully discharged while cell B is fully discharged, so cell A still has some charge and its voltage is higher than cell B), then the cell with the higher voltage reaches its voltage plateau range earlier. In other words, the cell with stored capacity reaches its voltage plateau range earlier. Therefore, if the voltage plateaus of two individual cells in a battery pack migrate from their respective non-voltage plateau ranges to the voltage plateau range at different times during the charging process, then the two individual cells are not identical.

[0038] For example, such as Figure 2 As shown, the voltage of cell A in the battery pack is 3.23V at the beginning of charging, while the voltage of cell B is 3.26V. The voltages of cells A and B are different, indicating a voltage difference between them, or in other words, a capacity difference. The time when cell B's voltage plateau transitions from its corresponding non-plateau range to its corresponding plateau range—that is, when cell B reaches 3.36V and transitions to its corresponding plateau range—is 24:00. Similarly, the time when cell A's voltage plateau transitions from its corresponding non-plateau range to its corresponding plateau range—that is, when cell A reaches 3.36V and transitions to its corresponding plateau range—is 30:00. Therefore, the higher-voltage cell B reaches its plateau range earlier, resulting in a discrepancy between the voltage of cells B and A within the battery pack.

[0039] In this embodiment, a first time point and a second time point are determined. The first time point is the migration time of a battery cell during a charging process, where the cell migrates from a first non-voltage plateau region to a first voltage plateau region. The second time point is the migration time of another battery cell during the same charging process, where the cell migrates from a second non-voltage plateau region to a second voltage plateau region. Alternatively, the second time point can be the average of the migration times for at least two battery cells.

[0040] In one embodiment, the first moment is the migration time when a battery cell migrates from a first non-voltage plateau region corresponding to a battery cell to a first voltage plateau region corresponding to a battery cell during a single charge. The second moment is the migration time when another battery cell migrates from a second non-voltage plateau region corresponding to another battery cell to a second voltage plateau region corresponding to another battery cell during the same single charge. In one specific embodiment, one battery cell is the highest-voltage battery cell in the battery pack, and the other battery cell is the lowest-voltage battery cell in the battery pack, which facilitates subsequent determination of whether the highest-voltage and lowest-voltage battery cells in the battery pack are consistent. In other specific embodiments, one battery cell is any battery cell in the battery pack, and the other battery cell is any other battery cell in the battery pack besides the aforementioned one battery cell, which facilitates subsequent determination of whether any two battery cells in the battery pack are consistent.

[0041] In one embodiment, the first moment is the migration time of a single battery cell during a single charge cycle, from a first non-voltage plateau region corresponding to the battery cell to a first voltage plateau region corresponding to the battery cell. The second moment is the average of the migration times corresponding to at least two battery cells. In one specific embodiment, the single battery cell is the highest-voltage battery cell in the battery pack, which facilitates subsequent determination of whether the migration time of the highest-voltage battery cell is consistent with the average migration time (mean migration time) corresponding to at least two battery cells in the battery pack. In other specific embodiments, the single battery cell is the lowest-voltage battery cell in the battery pack, which facilitates subsequent determination of whether the migration time of the lowest-voltage battery cell is consistent with the average migration time (mean migration time) corresponding to at least two battery cells in the battery pack. In other specific embodiments, the single battery cell is any single battery cell in the battery pack, which facilitates subsequent determination of whether the migration time of any single battery cell is consistent with the average migration time (mean migration time) corresponding to at least two battery cells in the battery pack.

[0042] In one embodiment, the first and second moments can be obtained from local storage or cloud storage. Of course, in other embodiments, the first and second moments can also be obtained by charging the battery pack in real time, and no specific limitation is made here.

[0043] To improve the accuracy of the first and second time points obtained, and thus improve the accuracy of subsequent consistency detection results based on the first and second time points, in one embodiment, the battery pack is charged using a constant current and the temperature inside the battery pack is maintained within a preset temperature range. The magnitude of the constant current and the preset temperature range are not limited and can be set according to actual usage needs.

[0044] Step S12: Based on the first time point and the second time point, obtain the battery pack consistency detection result.

[0045] In this embodiment, the battery pack consistency detection result is obtained based on a first time point and a second time point. The first and second time points represent the migration times of the voltage plateau from the non-voltage plateau range to the voltage plateau range. Therefore, based on the first and second time points, it is possible to determine whether the migration times of the voltage plateau from the non-voltage plateau range to the voltage plateau range are consistent, thereby determining whether the battery pack is internally consistent. That is, this application determines whether the battery pack is internally consistent by the order in which the voltage plateau migrates. Since this application does not need to determine the consistency problem within the battery pack based on the relationship between the battery pack's OCV and SOC, it does not need to calculate the SOC value, avoiding the problem of decreased accuracy of the consistency detection result due to errors in the calculated SOC value. Furthermore, this application only requires one charging process and does not require the battery pack to be fully charged and discharged to complete the battery pack consistency detection. That is, this application can efficiently perform battery pack consistency detection without damaging the battery pack. In addition, the battery pack consistency detection method provided by this application has low requirements for charging current and battery pack temperature; a constant current is sufficient, and it can be performed at low, high, and normal temperatures.

[0046] In one embodiment, inconsistency within the battery pack is determined in response to the discrepancy between the first and second time points. For example, consider a battery cell as the highest voltage battery cell in the battery pack and another battery cell as the lowest voltage battery cell in the battery pack: During a single charge, the highest voltage battery cell migrates from the first non-voltage plateau region corresponding to it to the corresponding first voltage plateau region at 18:00, i.e., the first time point is 18:00; During the same single charge, the lowest voltage battery cell migrates from the second non-voltage plateau region corresponding to it to the corresponding second voltage plateau region at 18:45, i.e., the second time point is 18:45; Therefore, the highest voltage battery cell and the lowest voltage battery cell in the battery pack enter their respective voltage plateau regions at different times, i.e., the voltage plateau migration times of the highest voltage battery cell and the lowest voltage battery cell in the battery pack are different, thus indicating inconsistency within the battery pack.

[0047] It should be noted that when the second moment is the migration time of another battery cell during a single charge cycle, from the second non-voltage plateau interval corresponding to that battery cell to the second voltage plateau interval corresponding to that battery cell, if the first moment and the second moment are the same, it only indicates that the two battery cells within the battery pack are consistent, not that all battery cells within the battery pack are consistent. Therefore, it is necessary to perform pairwise consistency checks on the battery cells within the battery pack.

[0048] In one embodiment, the present application further includes: determining the capacity deviation between the first charging capacity and the second charging capacity, and obtaining the rated capacity; wherein, the first charging capacity is the capacity charged by a battery cell in the first charging duration, the first charging duration is the charging duration of a battery cell from the start of charging to the first moment, the second charging capacity is the capacity charged by another battery cell in the second charging duration, or, the second charging capacity is the average of the capacities charged by at least two battery cells in the second charging duration, and the second charging duration is the charging duration from the start of charging to the second moment.

[0049] For example, a battery pack includes battery cell A, battery cell B, and battery cell C. The first charge capacity is the capacity charged by battery cell A during the first charging period, and the second charge capacity is the capacity charged by battery cell B during the second charging period. Since the first charge capacity corresponding to battery cell A is AH0, the second charge capacity corresponding to battery cell B is AH1, and the rated capacity is Cap, the capacity deviation between the first charge capacity and the second charge capacity is dAH = |AH0 - AH1|, and the SOC deviation within the battery pack is dAH / Cap.

[0050] For example, consider a battery pack comprising battery cells A, B, and C, with a first charging capacity equal to the capacity charged by battery cell C during the first charging period, and a second charging capacity equal to the average capacity charged by battery cells A, B, and C during the second charging period. Since the first charging capacity corresponding to battery cell C is AH0, the second charging capacity, which is the average capacity charged by battery cells A, B, and C during the second charging period, is AH1, and the rated capacity is Cap, the capacity deviation between the first and second charging capacities is dAH = |AH0 - AH1|, and the SOC deviation within the battery pack is dAH / Cap.

[0051] For example, consider a battery pack consisting of battery cell A and battery cell C. Battery cell A is the highest voltage battery cell in the battery pack, and battery cell C is the lowest voltage battery cell in the battery pack. The first charge capacity is the capacity charged by battery cell A during the first charging period, and the second charge capacity is the capacity charged by battery cell C during the second charging period. Since the first charge capacity corresponding to battery cell A is AH0, and the second charge capacity corresponding to battery cell C is AH1 and the rated capacity is Cap, the capacity deviation between the first charge capacity and the second charge capacity is dAH = |AH1 - AH0|. The maximum SOC deviation within the battery pack is dAH / Cap.

[0052] In one specific embodiment, charging is performed using a constant current, and the capacity deviation between the first charging capacity and the second charging capacity is determined. Specifically, a first charging duration is obtained based on a first moment and the start time of charging, and a second charging duration is obtained based on a second moment and the start time of charging; the first charging capacity is obtained based on the first charging duration and the current value of the constant current, and the second charging capacity is obtained based on the second charging duration and the current value of the constant current; the capacity deviation is obtained using the difference between the first charging capacity and the second charging capacity. Specifically, the first charging capacity is calculated using the ampere-hour integration method with the first charging duration and the current value of the constant current, and the second charging capacity is calculated using the ampere-hour integration method with the second charging duration and the current value of the constant current. The difference between the first charging capacity and the second charging capacity is the capacity deviation.

[0053] In one embodiment, the application further includes: obtaining the capacity deviation corresponding to any two charging processes that meet the charging requirements within a preset time period, wherein the capacity deviation is the difference between the first charging capacity and the second charging capacity corresponding to the charging process; in response to the capacity deviation corresponding to the later charging process that meets the charging requirements being greater than the capacity deviation corresponding to the other charging process that meets the charging requirements, determining that there is cell self-discharge in the battery pack within the preset time period. That is, by comparing the capacity deviation corresponding to any two charging processes that meet the charging requirements within the preset time period, if the capacity deviation corresponding to the later charging process that meets the charging requirements is greater than the capacity deviation corresponding to the earlier charging process that meets the charging requirements, it is determined that there is cell self-discharge in the battery pack within the preset time period.

[0054] The charging requirements include that the charging temperature during the charging process meets a temperature threshold; however, the size of the temperature threshold is not limited and can be set according to actual usage needs.

[0055] For example, the capacity deviation and time corresponding to each charging process within a preset time period are obtained, specifically (dAH) k ,T k ), (dAH k+1 ,T k+1 ), ……、(dAH k+n ,T k+n Compare the capacity deviations of any two charging processes that meet the charging requirements. If the capacity deviation of the later charging process that meets the charging requirements is greater than the capacity deviation of the earlier charging process that meets the charging requirements, then a single battery cell self-discharge has occurred within the preset time period. For example, if dAH k+1 >dAH k If a single battery cell self-discharges within the preset time period, the self-discharge rate is α = (dAH) k+1 -dAH k ) / (T k+1 -T k Based on the comparison between the measured self-discharge rate α and the safe self-discharge rate of individual battery cells, the safety risks of the battery pack are warned.

[0056] In the above embodiments, the battery pack consistency detection result is obtained based on the first time and the second time. The first time and the second time represent the migration time of the voltage plateau of different battery cells from the non-voltage plateau range to the voltage plateau range. Therefore, this application determines whether the battery pack is consistent by determining whether the migration time of the voltage plateau from the non-voltage plateau range to the voltage plateau range is consistent. That is, this application determines whether the battery pack is consistent by the order in which the voltage plateaus migrate.

[0057] In addition, this application only requires one charging process and does not require the battery pack to be fully charged and discharged to complete the battery pack consistency test. That is, this application can efficiently perform battery pack consistency test without damaging the battery pack.

[0058] Please see Figure 4 , Figure 4 This is a flowchart illustrating one embodiment of step S11. It should be noted that if substantially the same result is achieved, the embodiments of this application do not necessarily differ. Figure 4 The illustrated process sequence is limited. For example... Figure 4 As shown, this embodiment includes:

[0059] Step S41: Determine the first charging data and the second charging data.

[0060] In this embodiment, first charging data and second charging data are acquired; wherein, the first charging data includes the first voltage of a battery cell at each time, and the second charging data includes the second voltage at each time, wherein the second voltage is the voltage of another battery cell, or the second voltage is the average of the voltages corresponding to at least two battery cells.

[0061] For example, consider a battery pack consisting of cell A, cell B, and cell C: One cell is cell A, and the first charging data includes the first voltage of cell A at various times. Another cell is cell B, and the second charging data includes the second voltage of cell B at various times. As another example, if one cell is cell C, the first charging data includes the first voltage of cell C at various times, and the average voltage of cells A, B, and C is the second voltage, then the second charging data includes the average voltage of cells A, B, and C at various times.

[0062] In one embodiment, the first and second charging data can be obtained from local storage or cloud storage. Of course, in other embodiments, the battery pack can be charged in real time to obtain the first and second charging data; this is not limited to these embodiments.

[0063] Step S42: Based on the difference between the first voltage and the second voltage at each time, obtain the voltage difference at each time.

[0064] In this embodiment, the voltage difference at each time step is obtained based on the difference between the first voltage and the second voltage at each time step. The absolute value of the difference between the first voltage and the second voltage at each time step is taken as the voltage difference at each time step.

[0065] Since the first and second moments characterize the moments when the voltage plateau transitions from a non-voltage plateau region to a voltage plateau region during charging, in order to improve the efficiency of subsequently determining the first and second moments, in one embodiment, the first voltage at each moment is the first voltage at each moment within a preset interval, and the second voltage at each moment is the second voltage at each moment within a preset interval, where the preset interval is the non-voltage plateau region. In this case, the voltage difference at each moment is obtained based on the first and second voltages. Specifically, the voltage difference at each moment within the preset interval is obtained based on the difference between the first voltage at each moment within the preset interval and the second voltage at each moment within the preset interval. That is, only the voltage difference at each moment within the preset interval needs to be calculated, without needing to calculate the voltage difference at each moment from the start of charging to the voltage plateau region, thus improving the efficiency of obtaining the voltage difference at each moment. This, in turn, improves the efficiency of subsequently determining the first and second moments based on the voltage difference at each moment, and further improves the efficiency of battery pack consistency detection.

[0066] In one specific embodiment, the preset interval is a combination of a non-voltage plateau interval and a partial voltage plateau interval. Specifically, during the charging process, there are two voltage plateau intervals and one non-voltage plateau interval, with the non-voltage plateau interval located between the two voltage plateau intervals; the preset interval includes the non-voltage plateau interval and the partial voltage plateau interval connected to the non-voltage plateau interval. For example, the SOC interval is [SOC... n SOC m SOC n The range is [30%, 60%), SOC m The range is (65%, 90%).

[0067] Step S43: Based on the pressure difference at each time point, obtain the first time point and the second time point.

[0068] In this embodiment, the first time point and the second time point are obtained based on the pressure difference at each time point.

[0069] like Figure 5 , Figure 6 As shown, Figure 5 This is a schematic diagram of an embodiment of the filling capacity change curve provided in this application. Figure 6This is a schematic diagram of an embodiment of the differential pressure change curve provided in this application. During charging, the voltage of a single cell in the battery pack increases with the increase of the charging capacity. After the voltage plateau of a single cell migrates from the non-voltage plateau range to the voltage plateau range, the voltage of the single cell remains basically unchanged while the charging capacity continues to increase. Therefore, it can be understood that the voltage of a single cell reaches its maximum when its voltage plateau migrates to the voltage plateau range. Since the voltage of a single cell reaches its maximum when its voltage plateau migrates to the voltage plateau range first, while the voltage of another single cell continues to increase with the increase of the charging capacity because its voltage plateau has not yet migrated to the voltage plateau range, the voltage difference between the two cells reaches its maximum after the voltage plateau of one cell migrates to the voltage plateau range first, and then gradually decreases. Therefore, the moment corresponding to the maximum voltage difference can be taken as the moment when the voltage plateau of one cell migrates to the voltage plateau range. Since the voltage plateau of one battery cell first migrates to the corresponding voltage plateau range, the voltage of the battery cell that migrates to the corresponding voltage plateau range remains unchanged, while the voltage of the other battery cell that has not migrated to the corresponding voltage plateau range continues to increase until its voltage plateau range is reached, at which point its voltage reaches its maximum. Therefore, after the voltage plateau of the other battery cell migrates to the corresponding voltage plateau range, since both battery cells have migrated to the voltage plateau range, their voltages no longer change, and the voltage difference between them is minimal and essentially constant. Thus, the moment corresponding to the minimum voltage difference can be taken as the moment when the voltage plateau of the other battery cell migrates to the corresponding voltage plateau range.

[0070] Therefore, in one embodiment, in response to the first voltage being greater than the second voltage, the time corresponding to the maximum voltage difference is taken as the first time corresponding to a single battery cell, and the time corresponding to the minimum voltage difference is taken as the second time corresponding to another battery cell; in response to the first voltage being less than the second voltage, the time corresponding to the maximum voltage difference is taken as the second time corresponding to another battery cell, and the time corresponding to the minimum voltage difference is taken as the first time corresponding to a single battery cell.

[0071] In one embodiment, the voltage difference at each moment is obtained based on the first voltage and the second voltage. Specifically, the voltage difference at each moment within the preset interval is obtained based on the difference between the first voltage at each moment within the preset interval and the second voltage at each moment within the preset interval. Then, the first moment and the second moment are obtained based on the voltage difference at each moment. Specifically, the first moment and the second moment are obtained based on the voltage difference at each moment within the preset interval.

[0072] Please see Figure 7 , Figure 7This is a schematic diagram of an embodiment of the detection component provided in this application. The detection component 70 includes at least two acquisition elements 71 and a processing element 72; the at least two acquisition elements 71 correspond one-to-one with at least two battery cells in the battery pack, and the acquisition elements 71 are used to connect to the corresponding battery cells to acquire the voltage of the battery cells; the processing element 72 is communicatively connected to the at least two acquisition elements 71 respectively, and is used to receive the voltage acquired by each acquisition element 71, and perform the steps of any of the battery pack consistency detection method embodiments described above based on the voltage acquired by each acquisition element 71.

[0073] The detection component 70 obtains the battery pack consistency detection result based on the first and second time points. The first and second time points represent the migration times of the voltage plateaus of different battery cells from non-voltage plateau ranges to voltage plateau ranges. Therefore, in this application, the detection component 70 determines whether the battery pack is internally consistent by determining whether the migration times of the voltage plateaus from the non-voltage plateau range to the voltage plateau range are consistent. That is, the detection component 70 provided in this application determines whether the battery pack is internally consistent by the order in which the voltage plateaus migrate. Furthermore, this application only requires one charging process and does not require the battery pack to be fully charged and then fully discharged to complete the battery pack consistency detection by the detection component 70. In other words, this application can efficiently perform battery pack consistency detection without damaging the battery pack.

[0074] Please see Figure 8 , Figure 8 This is a schematic diagram of a battery system embodiment provided in this application. The battery system 80 includes a battery pack 81 and a detection component 70 that are communicatively connected to each other. Since the detection component 70 obtains the battery pack consistency detection result based on a first time and a second time, the first and second times represent the migration times of voltage plateaus of different battery cells from non-voltage plateau intervals to voltage plateau intervals. Therefore, in this application, the detection component 70 determines whether the battery pack is consistent by determining whether the migration times of the voltage plateaus from the non-voltage plateau interval to the voltage plateau interval are consistent. That is, the detection component 70 provided in this application determines whether the battery pack is consistent by the order in which the voltage plateaus migrate. Furthermore, this application only requires one charging process and does not require the battery pack to be fully charged and discharged to complete the battery pack consistency detection by the detection component 70. That is, this application can efficiently perform battery pack consistency detection without damaging the battery pack. Therefore, the battery system 80 provided in this application also possesses the above-mentioned effects.

[0075] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A method for detecting battery pack consistency, characterized in that, The battery pack includes at least two battery cells. The charging process of each battery cell includes a voltage plateau interval and a non-voltage plateau interval. The voltage plateau interval is located after the non-voltage plateau interval. During the charging process of the battery cell, the voltage plateau of the battery cell migrates from the non-voltage plateau interval to the voltage plateau interval. The method includes: Determine a first time point and a second time point; wherein, the first time point is the migration time when a battery cell migrates from a first non-voltage plateau interval corresponding to the battery cell to a first voltage plateau interval corresponding to the battery cell during a single charge; the second time point is the migration time when another battery cell migrates from a second non-voltage plateau interval corresponding to the other battery cell to a second voltage plateau interval corresponding to the other battery cell during a single charge. Based on the first time point and the second time point, the consistency detection result of the battery pack is obtained; The determination of the first time point and the second time point includes: Acquire first charging data and second charging data; wherein, the first charging data includes the first voltage of the battery cell at each moment, and the second charging data includes the second voltage of the other battery cell at each moment; The voltage difference at each time point is obtained based on the difference between the first voltage at each time point and the second voltage at each time point; Based on the pressure difference at each time point, the first time point and the second time point are obtained.

2. The method according to claim 1, characterized in that, The first voltage at each moment is the first voltage at each moment within a preset interval, and the second voltage at each moment is the second voltage at each moment within the preset interval, wherein the preset interval is a non-voltage plateau interval; The method of obtaining the voltage difference at each time point based on the first voltage and the second voltage at each time point includes: Based on the difference between the first voltage at each time point within the preset interval and the second voltage at each time point within the preset interval, the voltage difference at each time point within the preset interval is obtained; The process of obtaining the first time and the second time based on the pressure difference at each time includes: The first time and the second time are obtained based on the pressure difference at each time within the preset interval.

3. The method according to claim 2, characterized in that, The process of obtaining the first time and the second time based on the pressure difference at each time point within the preset interval includes: In response to the first voltage being greater than the second voltage, the time corresponding to the maximum voltage difference is taken as the first time corresponding to the one battery cell, and the time corresponding to the minimum voltage difference is taken as the second time corresponding to the other battery cell. In response to the first voltage being less than the second voltage, the time corresponding to the maximum voltage difference is taken as the second time corresponding to the other battery cell, and the time corresponding to the minimum voltage difference is taken as the first time corresponding to the first battery cell.

4. The method according to claim 1, characterized in that, The method further includes: Determine the capacity deviation between the first charging capacity and the second charging capacity, and obtain the rated capacity; wherein, the first charging capacity is the capacity charged by the battery cell in the first charging duration, the first charging duration is the charging duration of the battery cell from the start of charging to the first time, the second charging capacity is the capacity charged by the other battery cell in the second charging duration, or, the second charging capacity is the average of the capacity charged by the at least two battery cells in the second charging duration, the second charging duration is the charging duration from the start of charging to the second time, and the rated capacity is the rated capacity of the at least two initial battery cells; The ratio between the capacity deviation and the rated capacity is taken as the SOC deviation within the battery pack.

5. The method according to claim 4, characterized in that, Charging is performed using a constant current; determining the capacity deviation between the first charging capacity and the second charging capacity includes: Based on the first time point and the charging start time, the first charging duration is obtained; and based on the second time point and the charging start time, the second charging duration is obtained. The first charging capacity is obtained based on the first charging time and the current value of the constant current; and the second charging capacity is obtained based on the second charging time and the current value of the constant current. The capacity deviation is obtained by using the difference between the first filling capacity and the second filling capacity.

6. The method according to claim 1, characterized in that, The method further includes: Obtain the capacity deviation corresponding to any two charging processes that meet the charging requirements within a preset time period; wherein, the capacity deviation is the difference between the first charging capacity and the second charging capacity corresponding to the charging process, and the charging requirements include the charging temperature corresponding to the charging process meeting a temperature threshold. If the capacity deviation of a subsequent charging process that meets the charging requirements is greater than the capacity deviation of another charging process that meets the charging requirements, it is determined that there is cell self-discharge in the battery pack within the preset time period.

7. The method according to claim 1, characterized in that, The process of obtaining the battery pack consistency detection result based on the first time point and the second time point includes: In response to the inconsistency between the first time and the second time, it is determined that the battery pack is inconsistent; And / or, the battery pack is a lithium iron phosphate battery pack.

8. A detection component, characterized in that, The detection component includes: At least two acquisition elements are provided, each corresponding to at least two individual cells in the battery pack. The acquisition elements are connected to the corresponding individual cells to acquire the voltage of the individual cells. A processing element is communicatively connected to each of the at least two acquisition elements, for receiving voltages acquired by each acquisition element, and for performing the method according to any one of claims 1-7 based on the voltages acquired by each acquisition element.

9. A battery system, characterized in that, The battery system includes a battery pack and a detection component connected in communication, wherein the detection component is the detection component as described in claim 8.

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