Battery system equalization effect evaluation method and computer equipment

Abstract

The invention belongs to the technical field of battery systems, and particularly relates to a battery system equalization effect evaluation method and computer equipment. The method comprises the following steps: when a single battery with the highest SOC during charging cut-off and a single battery with the lowest SOC during discharging cut-off in a battery system are not the same single battery, evaluating the equalization effect of the battery system as effective, and obtaining the maximum value of the SOC difference value of the single batteries during charging cut-off and the maximum value of the SOC difference value of the single batteries during discharging cut-off; the effective degree of the equalization effect of the battery system is evaluated according to the smaller value in the two obtained maximum values; and when the battery cell with the highest SOC when the charging is cut off and the battery cell with the lowest SOC when the discharging is cut off in the batteries are the same battery cell, the equalization effect of the battery system is evaluated to be invalid.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery systems, and in particular relates to a battery system balancing effect evaluation method and computer equipment. Background Art

[0002] In the prior art, when the battery life decreases, it is usually necessary to balance the battery, and the battery life can be improved by improving the consistency between different battery cells in the battery system through balancing.

[0003] In order to evaluate the equalization effect of the battery system, the Chinese invention patent with the authorization announcement number CN118630347B proposes a technical solution for determining the equalization efficiency based on the data in the battery system equalization process, thereby evaluating the effect of the equalization strategy. However, this solution requires the use of battery system data in the equalization process, and it needs to be equalized first to obtain the equalization effect, and it is impossible to pre-evaluate the equalization effect. When the battery system is equalized, the equalization result may be completely invalid, and even if the equalization effect is effective, it may be less effective. These situations cannot significantly improve the battery life of the battery system. Only when the equalization effect is effective to a good degree can the battery life of the battery system be significantly improved. Therefore, performing equalization operations on battery systems with invalid or poor equalization effects cannot achieve the expected equalization effect, which will result in a waste of time and manpower costs. Summary of the invention

[0004] The object of the present invention is to provide a battery system balancing effect evaluation method and computer equipment to solve the technical problem in the prior art that the balancing effect evaluation needs to use the data in the balancing process, so the balancing effect cannot be evaluated in advance before balancing.

[0005] In order to solve the above technical problems, the present invention provides a method for evaluating the equalization effect of a battery system, comprising the following steps: When the battery cell with the highest SOC at the end of charging and the battery cell with the lowest SOC at the end of discharging in the battery system are not the same battery cell, the balancing effect of the battery system is evaluated as effective, and the maximum value of the difference in SOC of the battery cells at the end of charging and the maximum value of the difference in SOC of the battery cells at the end of discharging are obtained, and the effectiveness of the balancing effect of the battery system is evaluated according to the smaller value of the two obtained maximum values; When the battery cell with the highest SOC when charging is terminated and the battery cell with the lowest SOC when discharging is terminated in the battery are the same battery cell, the equalization effect of the battery system is evaluated as invalid.

[0006] The present invention is a pioneering invention, and its beneficial effects are as follows: the present invention proposes a new method for evaluating the equalization effect of a battery system. The method does not need to use the battery system data during the equalization process, but only needs to use the data during the normal operation of the battery system. Therefore, the equalization effect can be evaluated before equalization. The specific evaluation method is: first determine whether the battery cell with the highest SOC when the battery system is charged and the battery cell with the lowest SOC when the battery system is discharged are the same. If they are the same, then balancing the battery system will no longer have any effect, and the equalization effect is evaluated as invalid. If they are not the same, the battery system's endurance can be improved by balancing, and the equalization effect is evaluated as effective. In addition, the degree of effectiveness is obtained according to the smaller value of the maximum value of the difference between the battery cell SOC when the charging is cut off and the maximum value of the difference between the battery cell SOC when the discharging is cut off. The present invention can realize pre-evaluation before equalization. If the battery system equalization effect is not good, it cannot be equalized, which can prevent the waste of manpower and resources caused by invalid or poor equalization of the battery system.

[0007] Furthermore, the method for obtaining the maximum value of the battery cell SOC difference when the discharge is cut off includes: screening out a group of data from the battery system data in which the battery system is in a static state and the lowest voltage of the battery cells is lower than the set battery cell low voltage threshold, determining the maximum value of the battery cell SOC difference according to the screened group of data, and using the determined maximum value of the battery cell SOC difference as the maximum value of the battery cell SOC difference when the discharge is cut off in the battery system; setting the battery cell low voltage threshold as a threshold for determining that the lowest voltage of the battery cells in the battery system is close to the discharge cut off voltage.

[0008] Furthermore, the method for obtaining the maximum SOC difference of the battery cells at the time of charging cutoff includes: obtaining the time when the battery cell with the highest voltage is charged to the charging cutoff voltage, determining the time as the calculation end time, and obtaining the voltage of the battery cell with the lowest voltage at this time; determining the time when the voltage of the battery cell with the highest voltage is equal to the obtained voltage as the calculation start time, and the SOC value charged into the battery cell with the highest voltage from the calculation start time to the calculation end time is the maximum SOC difference of the battery cells at the time of charging cutoff.

[0009] Furthermore, the process of determining the maximum value of the battery cell SOC difference according to a set of screened data includes: obtaining the highest battery cell voltage and the lowest battery cell voltage in the set of data, and calculating the highest battery cell SOC value and the lowest battery cell SOC value according to the highest battery cell voltage and the lowest battery cell voltage, and the difference between the two SOC values ​​is the maximum value of the battery cell SOC difference when charging is cut off.

[0010] Furthermore, the process of filtering out a group of data from the battery system data in which the battery system is in a static state and the lowest voltage of the battery cells is lower than the set battery cell low voltage threshold includes: filtering the battery system data in which the battery system is in a static state and the lowest voltage of the battery cells is lower than the set battery cell low voltage threshold in units of pieces, filtering out multiple pieces of battery system data that are within a normal range, grouping the filtered data pieces, filtering the data in units of groups, and filtering out a group of data that is continuous, has a static time that meets the standard, and has a stable lowest voltage of the battery cells.

[0011] Furthermore, a method for determining whether a battery cell minimum voltage of a group of data is stable is as follows: if, in the group of data, within a set time period, the difference between the battery cell minimum voltages in any two adjacent data is less than a set battery cell voltage difference threshold, then the battery cell minimum voltage of the group of data is stable; otherwise, the battery cell minimum voltage of the group of data is unstable; the battery cell voltage difference threshold is set to a threshold that can ensure that the battery cell voltage changes in any two adjacent data are small.

[0012] Furthermore, the method for determining whether a group of data is continuous includes: if the battery system SOC difference between any two adjacent data in the group of data is less than a first set battery system SOC difference threshold, and the average difference in sequence numbers is equal to 1, then the group of data is continuous, otherwise the group of data is discontinuous; the first set battery system SOC difference threshold is a threshold that ensures that the battery system SOC change value between any two adjacent data is small, thereby ensuring the continuity of the group of data.

[0013] Furthermore, the calculation method of the static time is: the time corresponding to the previous data of the first data of each group of data is the static start time of the group of data, the time corresponding to the next data of the last data of each group of data is the static end time of the group of data, and the static end time of the group of data minus the static start time of the group of data is obtained by subtracting the static end time of the group of data from the static start time of the group of data.

[0014] Further, the process of determining the calculation start time and the calculation end time includes: obtaining a group of charging data in which the data is normal and continuous, the highest voltage of the battery cell is greater than the set battery cell high voltage threshold, the charging current is stable, and the charging time is up to the standard; obtaining the battery cell voltage whose highest voltage is greater than the set battery cell high voltage threshold and the lowest battery cell voltage belonging to the same data from the group of charging data, and determining the time corresponding to the data as the calculation end time; looking forward for a data in the same group of data in which the highest battery cell voltage is equal to the lowest battery cell voltage at the end time, and determining the time corresponding to the data as the calculation start time; The battery cell high voltage threshold is set as a threshold for determining that the highest battery cell voltage in the battery system is close to the charging cut-off voltage; The charging time is the time from the start of charging to the start of calculation.

[0015] Furthermore, the process of obtaining a set of data that is normal and continuous, the maximum voltage of the battery cell is greater than the set battery cell high-voltage threshold, the charging current is stable, and the charging time is up to the standard includes: obtaining charging data in which the battery system is in a charging state and the maximum voltage of the battery cell is greater than the set battery cell high-voltage threshold, filtering the obtained charging data in units of pieces, filtering out multiple charging data in which all data are normal, grouping the filtered charging data, filtering the charging data in units of groups, and filtering out charging data that is continuous, the charging current is stable, and the charging time is up to the standard.

[0016] Further, when the data is filtered in groups, the method for judging whether a group of data is continuous is as follows: if the difference in battery system SOC between any two adjacent data in the group of data is less than a second set battery system SOC difference threshold, and the sequence number difference is equal to 1, then the group of data is continuous, otherwise the data is discontinuous; the second set battery system SOC difference threshold is a threshold that ensures that the change in battery system SOC between any two adjacent data in a group of data is small, thereby ensuring the continuity of the group of data.

[0017] Furthermore, the method for determining whether the charging current in the group of data is stable is: if the ratio of the absolute value of the difference between the maximum charging current and the minimum charging current of the battery cell with the highest voltage in the group of data to the capacity of the battery cell is less than a set ratio threshold, then the charging current of the group of data is stable; otherwise, the charging current of the group of data is unstable.

[0018] Furthermore, the process of calculating the SOC value charged into the battery cell with the highest voltage from the calculation start time to the calculation end time includes: summing up the amount of electricity charged into the battery cell with the highest voltage between all data from the calculation start time to the calculation end time and the corresponding previous data, to obtain the total amount of electricity charged into the battery cell with the highest voltage from the calculation start time to the calculation end time, and using the total amount of electricity divided by the capacity of the battery cell with the highest voltage to obtain the corresponding SOC value.

[0019] Furthermore, if the calculation start time is the time of the first data of the group of data, the charging current of the battery cell with the highest voltage in the data is calculated by multiplying it by the set interval time, and the calculation result is used as the amount of electricity charged into the battery cell with the highest voltage between the data and the previous data.

[0020] To solve the above technical problems, the present invention further provides a computer device, including a processor, wherein the processor implements the method steps described in the battery system balancing effect evaluation method of the present invention when executing a computer program.

[0021] The present invention is an improved invention, and its beneficial effects are as follows: the present invention proposes a new method for evaluating the equalization effect of a battery system. The method does not need to use the battery system data during the equalization process, but only needs to use the data during the normal operation of the battery system. Therefore, the equalization effect can be evaluated before equalization. The specific evaluation method is: first determine whether the battery cell with the highest SOC when the battery system is charged and the battery cell with the lowest SOC when the discharge is cut off are the same. If they are the same, then balancing the battery system will no longer have any effect, and the equalization effect is evaluated as invalid. If they are not the same, the battery system's endurance can be improved by balancing, and the equalization effect is evaluated as effective. In addition, the degree of effectiveness is obtained according to the smaller value of the maximum value of the battery cell SOC difference when the charging is cut off and the maximum value of the battery cell SOC difference when the discharge is cut off. The present invention can realize pre-evaluation before equalization. If the battery system equalization effect is not good, it cannot be equalized, which can prevent the waste of manpower and resources caused by invalid or poor equalization of the battery system. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic diagram of an equivalent model of a battery system with equal capacity according to an embodiment of the method of the present invention; Figure 2 is a schematic diagram of an equivalent model of an aligned battery system with unequal capacities according to a method embodiment of the present invention; Figure 3 is a schematic diagram of an equivalent model of a battery system with unequal capacities included in an embodiment of the method of the present invention; Figure 4 is a schematic diagram of an equivalent model of a misaligned battery system with unequal capacities according to a method embodiment of the present invention; Figure 5 It is a flow chart of a battery system balancing effect evaluation method according to a method embodiment of the present invention. DETAILED DESCRIPTION

[0023] A battery system balancing effect evaluation method and computer equipment of the present invention propose a new battery system balancing effect evaluation method. This method does not need to use the battery system data in the balancing process, but only needs to use the data during the normal operation of the battery system. Therefore, the balancing effect can be evaluated before balancing. The specific evaluation method is: first determine whether the battery cell with the highest SOC when the battery system is charged and the battery cell with the lowest SOC when the battery system is discharged are the same. If they are the same, then balancing the battery system will no longer have any effect, and the balancing effect is evaluated as invalid. If they are not the same, the battery system's endurance can be improved by balancing, and the balancing effect is evaluated as effective. In addition, the effectiveness is obtained according to the smaller value of the maximum value of the battery cell SOC difference when the charging is cut off and the maximum value of the battery cell SOC difference when the discharging is cut off. The present invention can realize pre-evaluation before balancing. If the battery system balancing effect is not good, it cannot be balanced, which can prevent the waste of manpower and resources caused by invalid or poor balancing of the battery system.

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0025] Method Example: A battery system generally includes many cells connected in series and in parallel. For ease of explanation and understanding, this embodiment simplifies the battery system into a series structure of two cells for explanation. There are two cases depending on whether the capacity of the cells is equal. The first case assumes that the capacity of the two battery cells is equal. The model is as follows: Figure 1 As shown; the second assumption is that the two battery capacities are not equal, the battery capacity of monomer 2 is equal to 80% of the battery capacity of monomer 1, the model is as follows Figure 2 The number next to the battery cell in the figure is the SOC value of the battery cell.

[0026] Figure 1 In the process, cell 1 and cell 2 are misaligned. Cell 2 is charged to 100% and the charging is stopped. At this time, cell 1 only has 80% of the power and the remaining 20% ​​cannot be fully charged. During discharge, cell 1 is discharged to 0% and the discharge is stopped. At this time, there is still 20% of the power in cell 2 that cannot be used. Therefore, the actual available power of the entire battery system is only the part where the two cells are aligned. The balancing operation is to charge and discharge the battery cells separately so that more parts of cell 1 and cell 2 are aligned, usually the high end (100% SOC) or low end (0% SOC) of the battery cells are aligned, that is, charging is stopped at the same time or discharging is stopped at the same time. Figure 1Since the capacities of cell 1 and cell 2 are equal, the high end of the battery system is aligned at the same time as the low end, so that the two cells are charged and discharged at the same time. Before balancing, the consistency difference of the high end is 20%, and the consistency difference of the low end is also 20%. After alignment, the 20% difference is made up. When the battery system is charged, the SOC of the two battery cells is 100%, and the SOC of the discharge is 0%, which is equivalent to an increase of 20% in the available capacity. Therefore, the balancing effect is 20%.

[0027] Figure 2 The alignment is shown when the capacities of two battery cells are not equal. Figure 2 In the case shown in the figure, the high ends of cell 1 and cell 2 are aligned, and the high end consistency difference is 0, indicating that the charging of cell 1 and cell 2 is terminated at the same time. Both charging and discharging are terminated first by cell 2. At this time, the aligned parts in cell 1 and cell 2 have reached the maximum value, and the battery life can no longer be improved by balancing.

[0028] Figure 3 The following figure shows the situation when the capacities of two battery cells are not equal. In the figure, when cell 2 is charged to 100%, the SOC value charged into cell 1 is 90%, and the high-end consistency difference is 10%; when cell 2 is discharged to 0%, the remaining SOC value of cell 1 is 0%, and the low-end consistency difference is 10. However, at this time, since charging and discharging are both terminated by cell 2 first, the maximum number of aligned SOC nodes of the two has been reached, and the battery system endurance can no longer be improved through balancing.

[0029] Figure 4 The case of misalignment when the capacities of two battery cells are not equal is given. When discharging, cell 2 is cut off first. When the discharge of cell 2 is cut off (SOC=0%), the remaining SOC value of cell 1 is 30%, and the low-end consistency difference is 30%; when charging, cell 1 is cut off first. When cell 1 is cut off (SOC=100%), the charged power of cell 2 is 87.5%, and the high-end consistency difference is 12.5%. After balancing, after aligning the high or low ends of cell 1 and cell 2, the battery system can improve the endurance by 12.5%, which is equal to the smaller value of the high-end consistency difference and the low-end consistency difference.

[0030] According to the above analysis, when the battery cells are contained or aligned, the aligned SOC node has reached the maximum, and the balancing effect is 0. When the battery cells are misaligned, the balancing effect is equal to the minimum value of the high-end difference and the low-end difference. The core of the battery balancing effect evaluation method of the present invention is as follows: According to the analysis process, the actual meaning of the high-end consistency difference is the maximum value of the battery cell SOC difference when charging is cut off, and the low-end consistency difference is the maximum value of the battery cell SOC difference when discharging is cut off. Therefore, the battery system balancing effect evaluation method of the present invention includes: when the battery cell with the highest SOC when charging is cut off and the battery cell with the lowest SOC when discharging is cut off in the battery system are not the same battery cell, the balancing effect of the battery system is evaluated as effective, and the maximum value of the battery cell SOC difference when charging is cut off and the maximum value of the battery cell SOC difference when discharging is cut off are obtained, and the effectiveness of the battery system balancing effect is evaluated according to the smaller value of the two maximum values ​​obtained; when the battery cell with the highest SOC when charging is cut off and the battery cell with the lowest SOC when discharging is cut off in the battery are the same battery cell, the balancing effect of the battery system is evaluated as invalid.

[0031] Specifically, Figure 5 As shown, the steps of the battery balancing effect evaluation method of the present invention are as follows: Step 1: Obtain the battery cells with the lowest and highest SOC at the end of discharge, as well as the SOC difference between the two.

[0032] This embodiment processes the data when the lowest voltage of the battery cell in the battery system is lower than the set battery cell low voltage threshold (3.28v) when the battery system is in a static state, and selects a group of data, obtains the highest and lowest battery cell voltages and the corresponding battery cells from the group of data, and calculates the corresponding SOC value according to the maximum and minimum battery cell voltages, thereby obtaining the low-end SOC difference. The battery cell low voltage threshold is set as a threshold for determining that the lowest voltage of the battery cell in the battery system is close to the discharge cut-off voltage.

[0033] The specific steps are as follows: 1) Obtain battery system data. The battery system data appears in pieces. Each piece of data is numbered according to time. Each piece of data includes: time, highest (lowest) battery cell voltage, current, battery system SOC, and highest (lowest) cell position.

[0034] The acquired data is filtered in units of bars, and the filtering conditions include: the highest (lowest) single cell voltage is between 0-5V (in the voltage range of normal operation), the highest single cell voltage ≥ the lowest single cell voltage, and the highest (lowest) single cell position is not empty. These conditions ensure that the battery system data finally obtained is valid data, and the data is within the normal operation range, and unreasonable bad data is eliminated. When a certain data in a data does not meet the filtering conditions, the entire data needs to be eliminated.

[0035] 2) Process the acquired data to obtain: the previous time, the previous highest (lowest) single cell voltage, the previous highest (lowest) single cell position, the previous two (three) lowest single cell positions, the previous battery system SOC, and calculate the difference between the current battery system SOC and the previous battery system SOC (battery system SOC change value).

[0036] 3) Group the filtered data and divide the continuous data into one group.

[0037] In this embodiment, the method of grouping continuous data is as follows: subtract the sequence number of the previous data from the sequence number of the current data. If the difference is greater than 1, the current data is the starting data of a group of data; if it is equal to 1, it means that the current data is continuous with the previous data.

[0038] After the filtered data is grouped according to this method, a group number is established for each group of data, the previous data of each group start data is used as the static start time, and the next data of each group end data is used as the static end time.

[0039] 4) Filter the groups.

[0040] Each group of data shall meet the following conditions: the battery system SOC change value in any adjacent data within the group is less than the first set battery system SOC difference threshold of 1%, the standing time is greater than or equal to the set standing time threshold of 3 minutes, and the difference between the lowest battery cell voltages of the first, second, and third (set time periods) before standing does not exceed the set battery cell voltage difference threshold of 5mV.

[0041] The first setting of the battery system SOC difference threshold is a threshold that ensures that the battery system SOC change value between any two adjacent data is small, thereby ensuring the continuity of the group of data, and the setting of the battery cell voltage difference threshold is a threshold that can ensure that the battery cell voltage change between any two adjacent data is small.

[0042] The purpose of the resting time being greater than or equal to 3 minutes is to ensure that the resting time lasts for a period of time, and the system depolarization process is more thorough. The simple time is not enough to ensure that the system is in a truly depolarized state, so from the voltage performance, it is also required that the difference between the lowest voltages of the first, second, and third bars before resting does not exceed 5mV, which can further ensure that the battery has been depolarized. As another embodiment, the first, second, and third bars before resting can also be a specific period of time.

[0043] In this embodiment, the calculation method of the static time of a group of data is as follows: the time corresponding to the previous data of the first data of each group of data is the static start time of the group of data, the time corresponding to the next data of the last data of each group of data is the static end time of the group of data, and the static end time of the group of data minus the static start time of the group of data is used to obtain the static time of the group of data. For example: the vehicle is powered off at 8:00 and powered on at 8:15. From 8:15 to 8:20, the current is always less than 5A. At 8:20, the current is greater than 5A, and the static end is obtained. At this time, the static time is not 5 minutes, but 20 minutes, so the static start time is not the first time of each group, but the time before the first time of each group. There is no current when the power is turned off, and this period of time should be included. In this way, in addition to accurately calculating the static time, the conditions that meet the conditions can be included to the maximum extent, increasing the opportunity to calculate the static voltage.

[0044] There are several situations where a voltage close to the depolarization completion cannot be obtained by passing a current less than 5A for 3 minutes. First, when the sampling interval is not dense enough, a current greater than 5A may appear but not be collected, which can be called invisible current.

[0045] As another implementation, even if the sampling interval is dense enough, if a current with a very high rate appears before 3 minutes, then even if the current is less than 5A within 3 minutes, it cannot be guaranteed that the depolarization is nearly completed. However, for the first, second, and third rules where the difference between the lowest static voltages is small enough, this situation that is prone to misjudgment can be avoided. In other words, the depolarization is nearly completed not only from the peripheral conditions (less than 5A for 3 minutes) but also from the battery performance (the final voltage fluctuation is very small).

[0046] 5) According to the finally filtered group data, the maximum voltage and the minimum voltage of the battery cell are obtained, and then the corresponding SOC is calculated according to the SOC-OCV curve, and the SOC difference is obtained. The SOC difference is the maximum value of the battery cell SOC difference at the final discharge cutoff.

[0047] Step 2: Obtain the battery cells with the lowest and highest SOCs at the end of charging, as well as the SOC difference between the two.

[0048] For lithium batteries, when the SCO value is large, the slope of the SOC-OCV curve is small. Using SOC-OCV to calculate the SOC value will result in a large error. Therefore, the charging method is used in this embodiment to determine the SOC value of each battery cell when charging is terminated. The specific steps are as follows: 1) Obtain data on the battery charging process.

[0049] 2) Obtain the charging group number, time, highest and lowest cell voltage, the battery cell with the highest and lowest voltage, charging current and charging start mark for each set of data.

[0050] 3) Filter the acquired charging data in units of pieces, and filter out the battery system charging data with normal data. In this embodiment, only the data with a charging current greater than the set charging current threshold (1A) is retained. After the screening is completed, the consecutive pieces of data are grouped together. The specific grouping method is: use the sequence number of the current piece of data minus the sequence number of the previous piece of data. If the difference is greater than 1, the current piece of data is the starting data of a group of data; if it is equal to 1, it means that the current piece of data is continuous with the previous piece of data.

[0051] 4) Filter the grouped data, and count the maximum value of the highest single cell voltage, charging start time, and BMS-SOC change value in each group. When calculating the BMS-SOC change value, it is necessary to use data with a required time interval of less than 5 minutes and a charging start position mark of 1 for calculation; the screening conditions include: the highest voltage during the charging process is greater than the set battery cell high voltage threshold of 3.55V, any two adjacent data battery system SOC change values ​​are less than the second set battery system SOC difference threshold of 2%, the ratio of the absolute value of the maximum current and the minimum current difference to the rated capacity is less than 0.1, the charging time is greater than the set charging time of 5min, and the charging time is the time from the charging start time to the calculation start time. The data filtered out in this embodiment meets the above four conditions at the same time. Among them, the highest voltage during the charging process is greater than the set battery cell high voltage threshold to ensure that the battery is almost fully charged, and the voltage of the battery cell is close to the cut-off voltage. Therefore, the battery cell high voltage threshold is set close to the cut-off voltage, and the cut-off voltage in this embodiment is 3.56v. The change value of the battery system SOC of any two adjacent data is less than the second set battery system SOC difference threshold of 2%, which can prevent data loss and ensure data continuity. The absolute value of the difference between the maximum current and the minimum current and the rated capacity is less than 0.1, which can ensure the stability of the charging current. The difference between the maximum battery rate and the minimum battery rate is less than 0.1C, which ensures that the charging current is stable and the polarization degree remains unchanged, and the battery rate is equal to the current ratio to the rated capacity. The charging time is greater than the set charging time of 5min to avoid the process of polarization instability at the beginning of charging.

[0052] In this embodiment, it is not enough to ensure data continuity only by the difference between the sequence numbers of two adjacent data. Therefore, the battery system SOC change value between any two adjacent data is added for judgment. Only when both conditions are judged as continuous at the same time can the continuity of the group of data be guaranteed.

[0053] The charging process may experience a jump due to SOC correction, and the time difference between the upper and lower times is small. What we want to filter here is not this normal jump, but a large jump in SOC with a time interval greater than 5 minutes, which represents data loss.

[0054] In addition, the charging start position marked as 1 represents the first data of the group. Because the battery system often loses power for a period of time before charging begins, the time is generally more than 5 minutes, and no judgment is made at this time.

[0055] 5) Determine the calculation end time from the filtered data. Calculate the earliest time when the highest cell voltage is greater than the set battery cell high voltage threshold of 3.55V. Keep the data earlier than this time, when the highest battery cell voltage is about to reach the charging cut-off voltage. Define this time as the end time of the calculation. And determine the lowest battery cell voltage at this time.

[0056] 6) Determine the calculation start time in the same group of data. The calculation start time is the latest time that satisfies the highest battery cell voltage less than the lowest battery cell voltage at the calculation end time. In this way, the SOC value of the battery cell with the highest voltage charged from the start time to the end time is approximately equal to the SOC value required to fully charge from the battery cell with the lowest voltage charging end time, that is, the maximum value of the battery cell SOC difference at the end of charging.

[0057] The calculation end time and the calculation start time belong to the same set of data after filtering.

[0058] 7) From the start time to the end time of calculation, the amount of electricity charged between each piece of data and the previous piece of data is accumulated to obtain the total amount of electricity charged into the battery cell with the highest voltage in the entire calculation process. This amount of electricity is divided by the capacity of the highest battery cell to obtain the maximum SOC difference of the battery cell when charging is terminated.

[0059] Theoretically, the calculation end time is the time when the highest cell voltage is equal to the set cell high voltage threshold, and the calculation start time is the time when the highest cell voltage is equal to the lowest cell voltage at the calculation end time. However, in actual use, it is not always possible to find data that exactly meets the equal conditions. Therefore, in this embodiment, the earliest time when the highest cell voltage is greater than the set cell high voltage threshold is used as the calculation end time, and the latest time when the highest cell voltage is less than the lowest cell voltage at the calculation end time is used as the calculation start time. Therefore, there may be a difference between the calculation start time obtained in this embodiment and the actual calculation start time. In order to correct this deviation, this embodiment introduces the following method: If the calculation start time is the time of the first data of the group of data, the charging current of the battery cell with the highest voltage in the data is calculated and multiplied by the set interval time, and the calculation result is used as the power charged into the battery cell with the highest voltage between the data and the previous data.

[0060] Step 3: Evaluate the balancing effect of the battery system based on the acquired data.

[0061] First, determine whether the battery cell lowest voltage in step one and the battery cell highest voltage and the battery cell highest voltage at the end of the calculation in step two are the same battery cell; if so, the balancing effect of the battery system is invalid; if the corresponding battery cells are not the same battery cell, the balancing effect is evaluated as effective, and the effectiveness of the balancing effect is obtained according to the minimum value of the calculation results of step one and step two.

[0062] Computer equipment example: A computer device of the present invention includes a processor, and the processor implements the steps of a battery system equalization effect evaluation method as described in the method embodiment of the present invention when executing a computer program. The specific process, principle and beneficial effects of the method have been described in detail in the method embodiment, and will not be repeated in this embodiment.

[0063] The processor may be a microprocessor MCU, a programmable logic device FPGA or other processing device.

Claims

1. A battery system balancing effect evaluation method, characterized in that: The following steps are involved: When the battery cell with the highest SOC at the end of charging and the battery cell with the lowest SOC at the end of discharging in the battery system are not the same battery cell, the balancing effect of the battery system is evaluated as effective, and the maximum value of the difference in SOC of the battery cells at the end of charging and the maximum value of the difference in SOC of the battery cells at the end of discharging are obtained, and the effectiveness of the balancing effect of the battery system is evaluated according to the smaller value of the two obtained maximum values; When the battery cell with the highest SOC when charging is terminated and the battery cell with the lowest SOC when discharging is terminated in the battery are the same battery cell, the equalization effect of the battery system is evaluated as invalid.

2. The battery system equalization effect evaluation method according to claim 1, characterized in that: The method for obtaining the maximum value of the SOC difference of the battery cells when the discharge is cut off includes: selecting a group of data from the battery system data in which the battery system is in a static state and the lowest voltage of the battery cells is lower than the set battery cell low voltage threshold, determining the maximum value of the SOC difference of the battery cells according to the selected group of data, and using the determined maximum value of the SOC difference of the battery cells as the maximum value of the SOC difference of the battery cells when the discharge is cut off in the battery system; setting the battery cell low voltage threshold as a threshold for determining that the lowest voltage of the battery cells in the battery system is close to the discharge cut off voltage.

3. The battery system equalization effect evaluation method according to claim 1, characterized in that: The method for obtaining the maximum SOC difference value of the battery cells at the end of charging includes: obtaining the time when the battery cell with the highest voltage is charged to the charging cut-off voltage, determining the time as the calculation end time, and obtaining the voltage of the battery cell with the lowest voltage at the time; determining the time when the voltage of the battery cell with the highest voltage is equal to the obtained voltage as the calculation start time, and the SOC value charged by the battery cell with the highest voltage from the calculation start time to the calculation end time is the maximum SOC difference value of the battery cell at the end of charging.

4. The battery system equalization effect evaluation method according to claim 2, characterized in that: The process of determining the maximum value of the SOC difference of the battery cells according to a set of screened data includes: obtaining the highest voltage of the battery cells and the lowest voltage of the battery cells in the set of data, calculating the highest SOC value of the battery cells and the lowest SOC value of the battery cells according to the highest voltage of the battery cells and the lowest voltage of the battery cells, and the difference between the two SOC values ​​is the maximum value of the SOC difference of the battery cells when charging is cut off.

5. The battery system equalization effect evaluation method according to claim 2, characterized in that: The process of filtering out a group of data from battery system data in which the battery system is in a static state and the lowest voltage of the battery cell is lower than a set battery cell low voltage threshold comprises: filtering the battery system data in which the battery system is in a static state and the lowest voltage of the battery cell is lower than the set battery cell low voltage threshold in units of pieces, filtering out multiple pieces of battery system data that are within a normal range, grouping the filtered pieces of data, filtering the data in units of groups, and filtering out a group of data that is continuous, has a static time that meets the standard, and has a stable lowest voltage of the battery cell.

6. The battery system equalization effect evaluation method according to claim 5, characterized in that: The method for judging whether the minimum voltage of a battery cell in a group of data is stable is as follows: if, in the group of data, within a set time period, the difference between the minimum voltage of a battery cell in any two adjacent data is less than a set battery cell voltage difference threshold, then the minimum voltage of the battery cell in the group of data is stable; otherwise, the minimum voltage of the battery cell in the group of data is unstable; the battery cell voltage difference threshold is set to a threshold that can ensure that the battery cell voltage in any two adjacent data changes less.

7. The battery system equalization effect evaluation method according to claim 5, characterized in that: The method for determining whether a group of data is continuous includes: if the difference in battery system SOC between any two adjacent data in the group of data is less than a first set battery system SOC difference threshold, and the average difference in sequence numbers is equal to 1, then the group of data is continuous, otherwise the group of data is discontinuous; the first set battery system SOC difference threshold is a threshold that ensures that the battery system SOC change value between any two adjacent data is small, thereby ensuring the continuity of the group of data.

8. The battery system equalization effect evaluation method according to claim 5, characterized in that: The calculation method of the static time is: the time corresponding to the previous data of the first data of each group of data is the static start time of the group of data, the time corresponding to the next data of the last data of each group of data is the static end time of the group of data, and the static end time of the group of data minus the static start time of the group of data is the static time of the group of data.

9. The battery system equalization effect evaluation method according to claim 3, characterized in that: The process of determining the calculation start time and the calculation end time includes: obtaining a group of charging data in which the data is normal and continuous, the highest voltage of the battery cell is greater than the set battery cell high voltage threshold, the charging current is stable, and the charging time is up to the standard; obtaining the battery cell voltage whose highest voltage is greater than the set battery cell high voltage threshold and the lowest battery cell voltage belonging to the same data from the group of charging data, and determining the time corresponding to the data as the calculation end time; looking forward for a data in the same group of data in which the highest battery cell voltage is equal to the lowest battery cell voltage at the end time, and determining the time corresponding to the data as the calculation start time; The battery cell high voltage threshold is set as a threshold for determining that the highest battery cell voltage in the battery system is close to the charging cut-off voltage; The charging time is the time from the start of charging to the start of calculation.

10. The battery system equalization effect evaluation method according to claim 9, characterized in that: The process of obtaining a set of data that is normal and continuous, the highest voltage of the battery cell is greater than the set battery cell high-voltage threshold, the charging current is stable, and the charging time is up to the standard includes: obtaining charging data in which the battery system is in a charging state and the highest voltage of the battery cell is greater than the set battery cell high-voltage threshold, filtering the obtained charging data in units of pieces, filtering out multiple charging data in which all data are normal, grouping the filtered charging data, filtering the charging data in units of groups, and filtering out charging data that is continuous, the charging current is stable, and the charging time is up to the standard.

11. The battery system equalization effect evaluation method according to claim 10, characterized in that: When data is screened in groups, the method for judging whether a group of data is continuous is as follows: if the difference in battery system SOC between any two adjacent data in the group of data is less than a second set battery system SOC difference threshold, and the sequence number difference is equal to 1, then the group of data is continuous, otherwise the data is discontinuous; the second set battery system SOC difference threshold is a threshold that ensures that the change in battery system SOC between any two adjacent data in a group of data is small, thereby ensuring the continuity of the group of data.

12. The battery system equalization effect evaluation method according to claim 10, characterized in that: The method for judging whether the charging current in the group of data is stable is: if the ratio of the absolute value of the difference between the maximum charging current and the minimum charging current of the battery cell with the highest voltage in the group of data to the capacity of the battery cell is less than the set ratio threshold, then the charging current of the group of data is stable; otherwise, the charging current of the group of data is unstable.

13. The battery system equalization effect evaluation method according to claim 3, characterized in that: The process of calculating the SOC value charged into the battery cell with the highest voltage from the calculation start time to the calculation end time includes: summing up the amount of electricity charged into the battery cell with the highest voltage between all data from the calculation start time to the calculation end time and the corresponding previous data, to obtain the total amount of electricity charged into the battery cell with the highest voltage from the calculation start time to the calculation end time, and using the total amount of electricity divided by the capacity of the battery cell with the highest voltage to obtain the corresponding SOC value.

14. The battery system equalization effect evaluation method according to claim 13, characterized in that: If the calculation start time is the time of the first data of the group of data, the charging current of the battery cell with the highest voltage in the data is calculated and multiplied by the set interval time, and the calculation result is used as the power charged into the battery cell with the highest voltage between the data and the previous data.

15. A computer device comprising a processor, characterized in that: The processor implements the steps of the battery system balancing effect evaluation method as described in any one of claims 1 to 14 when executing the computer program.

Images