Balanced maintenance method for nickel-metal hydride battery system

Abstract

The invention provides a nickel-metal hydride battery system equalization maintenance method, which comprises the following steps: S1, acquiring battery cell voltage difference during high-rate charging and discharging of a battery system, and recording a plurality of battery cells with highest voltage during charging and a plurality of battery cells with lowest voltage during discharging; s2, if the charging state voltage difference and the discharging state voltage difference both exceed a voltage difference threshold value, the battery system needs to be maintained; s3, judging whether the recorded high-voltage battery cell and the recorded low-voltage battery cell coincide or not, and if yes, carrying out single battery cell maintenance on the coincident battery cells; and S4, if the high-voltage cell does not coincide with the low-voltage cell, carrying out full-charge state equalization on the battery system in a low-rate and small-range overcharge mode.

Description

Technical Field

[0001] This invention belongs to the field of battery system maintenance technology, and particularly relates to a method for equalization maintenance of nickel-metal hydride battery systems. Background Technology

[0002] Battery balancing technology is a technique that uses power electronics and other methods to maintain the consistency of voltage and SOC among the cells in a battery system. When the consistency of cells in a battery system is poor, in addition to easily causing low system capacity and reduced rate performance, more seriously, it can easily lead to frequent overcharging of battery cells with high SOC and frequent over-discharging of battery cells with low SOC, thereby inducing safety accidents.

[0003] The prior art disclosure CN120150321A discloses a battery balancing method, apparatus, electronic device, and storage medium. The method includes: acquiring the initial voltage information of each battery in a battery pack; performing pre-charge and pre-discharge processing on each battery when each battery is in a float charge state and the initial voltage information of the battery pack meets a first preset condition, and determining the first voltage change rate of each battery during the pre-charge process; identifying a target battery from the battery pack; and charging or discharging the other batteries based on a first difference information between the first voltage change rate of the other batteries and the target battery, so that the voltage change rate of the other batteries meets a second preset condition during the charging or discharging process, and the capacity of each battery is balanced; the other batteries are the batteries in the battery pack other than the target battery. Summary of the Invention

[0004] Existing equalization technologies typically use cell voltage sampling and voltage difference calculation as the basis for determining whether to initiate equalization. However, because the charge-discharge voltage curve of nickel-metal hydride batteries is relatively flat, differences in state of charge (SOC) are difficult to reflect through cell voltage difference. Furthermore, in practical use, due to factors such as inconsistent cell impedance, differences in connection internal resistance, and cell degradation, some cells may simultaneously exhibit high voltage during charging and low voltage during discharging, interfering with the judgment and execution of the equalization strategy.

[0005] To solve the above-mentioned technical problems, the present invention provides a technical solution: a method for equalization maintenance of a nickel-metal hydride battery system, comprising the following steps: S1. Collect the cell voltage difference during high-rate charging and discharging of the battery system, and record the cells with the highest voltage during charging and the cells with the lowest voltage during discharging. S2. If both the charging and discharging voltage differences exceed the voltage difference threshold, the battery system needs to be maintained. S3. Determine whether there is overlap between the recorded high-voltage cells and low-voltage cells. If there is, individual cell maintenance is required for the overlapping cells. S4. If there is no overlap between high-voltage and low-voltage cells, the battery system needs to be fully charged and balanced by overcharging at a small rate within a small range.

[0006] Specifically, the high-rate charging and discharging in S1 is a charging rate of 3C or higher, and at least 5 cells with the highest voltage during charging and at least 5 cells with the lowest voltage during discharging are recorded.

[0007] Specifically, in S3, it is determined whether there are individual battery cells with high voltage during charging and low voltage during discharging. For these deteriorated individual cells, electrolyte replenishment or replacement is selected to maintain the individual cell.

[0008] Specifically, the S4 uses a stepped charging method for equalization maintenance. During the charging process, the power of the heat dissipation components is adjusted according to a pre-defined battery thermal management strategy to control the temperature.

[0009] Specifically, during equalization maintenance in S4, if the battery system SOC ≤ 70%, the system is first charged at a 1-hour rate current for (70% - SOC) * 60 minutes, then charged at a 2-hour rate current for 30 minutes, and finally charged at a 3-hour rate current for 25 minutes.

[0010] Specifically, during equalization maintenance in S4, if the battery system SOC ≤ 95%, the system is first charged at a 2-hour rate current for (95% - SOC) * 120 minutes, and then charged at a 3-hour rate current for 25 minutes.

[0011] Specifically, during equalization maintenance in S4, if the battery system SOC > 95%, the system is charged at a 3-hour rate current for 25 minutes.

[0012] Specifically, during the charging process of the battery system in S1, when the instantaneous charging current I is greater than 3 times the 1-hour rate current, the charging state voltage difference and the numbers of several cells with the highest voltage during charging are recorded.

[0013] Specifically, during the charging process of the battery system in S1, when the instantaneous discharge current I is greater than 3 times the 1-hour rate current, the discharge state voltage difference and the numbers of several cells with the highest voltage during charging are recorded.

[0014] Specifically, battery system maintenance will only be performed in S2 when both the charging and discharging voltage differences exceed 50mV, which will then lead to S3 and subsequent steps.

[0015] The beneficial effects of this invention are: the method provided by this invention does not require an external equalization module, nor does it require a pre-provided cell voltage-SOC corresponding curve. It utilizes the overcharge tolerance of nickel-metal hydride batteries, amplifies the voltage difference signal by high-rate charging and discharging to reduce misjudgments, and improves the effectiveness of strategy execution by comparing high and low voltage cell numbers and comprehensively judging the voltage difference signal. It has significant practicality in actual battery maintenance. Attached Figure Description

[0016] Figure 1 This is a flowchart of the method of the present invention.

[0017] Figure 2 This is a flowchart of the balanced maintenance process of the present invention. Detailed Implementation

[0018] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0019] Example 1: A method for equalization maintenance of a nickel-metal hydride battery system, such as... Figure 1 As shown, it includes the following steps: S1. Collect the cell voltage difference during high-rate charging and discharging of the battery system, and record the cell numbers with the highest voltage during charging and the cell numbers with the lowest voltage during discharging. S2. If both the charging and discharging voltage differences exceed the voltage difference threshold, the battery system needs to be maintained. S3. Determine whether the recorded high-voltage cell number and low-voltage cell number overlap. If they do, individual cell maintenance is required for the overlapping cells. S4. If the high-voltage cell number does not overlap with the low-voltage cell number, the battery system needs to be fully charged and balanced by overcharging at a small rate.

[0020] In the specific implementation of this embodiment, the charging process of the nickel-metal hydride battery system is monitored in real time, data is collected, and the system's operating status is identified. During the operation of the nickel-metal hydride battery system, data is collected in real time, and it is simultaneously identified whether the charging or discharging current of the system exceeds 3C.

[0021] Each time the nickel-metal hydride battery system is charged and discharged, a set of charging and discharging data is collected and recorded. If the charging current exceeds 3C, the cell voltages at that moment are arranged from high to low, and the maximum charging voltage difference ΔV within the battery system is recorded. chg The numbers of the n cells with the highest voltage (5≤n≤10) are denoted as N. max-1 ~N max-n If the discharge current exceeds 3C, arrange the cell voltages at that moment from low to high, and record the maximum discharge voltage difference ΔV within the battery system. dchg The n cells with the lowest voltage (5≤n≤10) are numbered as N. min-1 ~N min-n .

[0022] Based on the collected data, a determination is made as to whether the battery system requires equalization maintenance. This involves comparing ΔV. chg ΔV dchg The difference between the preset charge / discharge voltage threshold ΔVt-chg ΔV t-dchg When ΔV chg ≥ΔV t-chg And ΔV dchg ≥ΔV t-dchg The system needs maintenance at times.

[0023] When it is determined that battery system maintenance is required, select the maintenance method as follows: If there exist i and j such that N max-i =N min-j If a battery cell has a high voltage during charging and a low voltage during discharging, it indicates that the cell has deteriorated during use. In this case, cell maintenance can be performed by adding electrolyte or replacing the cell. If there are no i, j such that N max-i =N min-j This means that the performance degradation of the system is mainly caused by inconsistencies between the cells, and equalization can be selected.

[0024] During individual cell maintenance, the system issues a cell abnormality warning and outputs the cell number. If the system is not shut down due to other faults, it continues to operate normally until maintenance personnel can inspect and repair the deteriorated cells, either by adding electrolyte or replacing them. Specifically, if ΔV remains after individual cell maintenance... chg ≥ΔV t-chg And ΔV dchg ≥ΔV t-dchg Then it enters the balance maintenance phase.

[0025] During equalization maintenance, the battery system will issue an equalization prompt message. If the system has not been shut down due to other faults, it will continue to operate normally until maintenance personnel confirm the information and initiate equalization. Equalization maintenance is as follows: Figure 2 As shown, a stepped charging method is used: a) When the battery system SOC ≤ 70%, the system is first charged with current I1 (70% - SOC) for 60 minutes, then with current I2 for 30 minutes, and finally with current I3 for 25 minutes; b) When the battery system SOC ≤ 95%, the system is first charged with current I2 (95% - SOC) for 120 minutes, then with current I2 for 25 minutes; c) When the battery system SOC > 95%, the system is charged with current I3 for 25 minutes. In this case, the nickel-metal hydride battery is overcharged by approximately 8% with a small current, which has no negative impact on battery performance. Because the battery temperature rises rapidly during overcharging, a battery system thermal management strategy should be activated during the above charging process. Here, I1 represents the 1-hour rate current, I2 represents the 2-hour rate current, and I3 represents the 3-hour rate current.

[0026] Example 2: A method for equalization maintenance of a nickel-metal hydride battery system, such as... Figure 1 As shown, it includes the following steps: S1. Collect the cell voltage difference during high-rate charging and discharging of the battery system, and record the cell numbers with the highest voltage during charging and the cell numbers with the lowest voltage during discharging. S2. If both the charging and discharging voltage differences exceed the voltage difference threshold, the battery system needs to be maintained. S3. Determine whether the recorded high-voltage cell number and low-voltage cell number overlap. If they do, individual cell maintenance is required for the overlapping cells. S4. If the high-voltage cell number does not overlap with the low-voltage cell number, the battery system needs to be fully charged and balanced by overcharging at a small rate.

[0027] In the specific implementation of this embodiment, the charging process of the nickel-metal hydride battery system is monitored in real time, data is collected, and the system's operating status is identified. During the operation of the nickel-metal hydride battery system, data is collected in real time, and it is simultaneously identified whether the charging or discharging current of the system exceeds 3C.

[0028] Each time the nickel-metal hydride battery system is charged and discharged, a set of charging and discharging data is collected and recorded. If the charging current exceeds 3C, the cell voltages at that moment are arranged from high to low, and the maximum charging voltage difference ΔV within the battery system is recorded. chg The numbers of the n cells with the highest voltage (5≤n≤10) are denoted as N. max-1 ~N max-n If the discharge current exceeds 3C, arrange the cell voltages at that moment from low to high, and record the maximum discharge voltage difference ΔV within the battery system. dchg The n cells with the lowest voltage (5≤n≤10) are numbered as N. min-1 ~N min-n .

[0029] In this embodiment, n=5 and ΔV are pre-written into the battery system. t-chg =50mV, ΔV t-dchg =50mV.

[0030] Based on the collected data, a determination is made as to whether the battery system requires equalization maintenance. This involves comparing ΔV. chg ΔV dchg The difference between the preset charge / discharge voltage threshold ΔV t-chg ΔV t-dchg When ΔV chg ≥ΔV t-chg And ΔV dchg ≥ΔV t-dchg The system needs maintenance at times.

[0031] When it is determined that battery system maintenance is required, select the maintenance method as follows: If there exist i and j such that N max-i =N min-j If a battery cell has a high voltage during charging and a low voltage during discharging, it indicates that the cell has deteriorated during use. In this case, cell maintenance can be performed by adding electrolyte or replacing the cell. If there are no i, j such that N max-i =N min-j This means that the performance degradation of the system is mainly caused by inconsistencies between the cells, and equalization can be selected.

[0032] During individual cell maintenance, the system issues a cell abnormality warning and outputs the cell number. If the system is not shut down due to other faults, it continues to operate normally until maintenance personnel can inspect and repair the deteriorated cells, either by adding electrolyte or replacing them. Specifically, if ΔV remains after individual cell maintenance... chg ≥ΔV t-chg And ΔV dchg ≥ΔV t-dchg Then it enters the balance maintenance phase.

[0033] During equalization maintenance, the battery system will issue an equalization prompt. If the system has not been shut down due to other faults, it will continue to operate normally until maintenance personnel confirm the information and initiate equalization. Equalization is performed using a stepped charging method: a) If the battery system SOC ≤ 70%, the system will first charge at current I1 for (70% - SOC) * 60 min, then at current I2 for 30 min, and finally at current I3 for 25 min; b) If the battery system SOC ≤ 95%, the system will first charge at current I2 for (95% - SOC) * 120 min, then at current I2 for 25 min; c) If the battery system SOC > 95%, the system will charge at current I3 for 25 min. In this case, the nickel-metal hydride battery will be overcharged by approximately 8% with a small current, which will not negatively impact battery performance. Because the battery temperature rises rapidly during overcharging, the battery system thermal management strategy should be activated during the above charging process. Here, I1 represents the 1-hour rate current, I2 represents the 2-hour rate current, and I3 represents the 3-hour rate current.

[0034] In one application scenario of this embodiment, during the normal operation of the battery system, a charging instantaneous current I > 3I1 is detected. The voltage of each cell at this time, and N, are recorded. max-1 ~N max-5 Calculate the charging state voltage difference ΔV chg >50mV. The system continues to run. When the instantaneous discharge current I > 3I1 is detected, record the voltage of each cell at this time, as well as N. min-1 ~N min-5 Calculate the discharge state voltage difference ΔV dchg <50mV. Due to ΔV dchg<50mV, therefore the system maintenance conditions are not met.

[0035] Example 3: A method for equalization maintenance of a nickel-metal hydride battery system, comprising the following steps: S1. Collect the cell voltage difference during high-rate charging and discharging of the battery system, and record the cell numbers with the highest voltage during charging and the cell numbers with the lowest voltage during discharging. S2. If both the charging and discharging voltage differences exceed the voltage difference threshold, the battery system needs to be maintained. S3. Determine whether the recorded high-voltage cell number and low-voltage cell number overlap. If they do, individual cell maintenance is required for the overlapping cells. S4. If the high-voltage cell number does not overlap with the low-voltage cell number, the battery system needs to be fully charged and balanced by overcharging at a small rate.

[0036] Specifically, S1 collects the voltage difference of each cell during high-rate charging and discharging (above 3C) and the battery numbers of the highest and lowest voltage cells.

[0037] Specifically, in S3, it is determined whether there are individual battery cells with high voltage during charging and low voltage during discharging. For these deteriorated individual cells, electrolyte replenishment or replacement is selected to maintain the individual cell.

[0038] Specifically, the S4 uses a stepped charging method for equalization maintenance. During the charging process, the power of the heat dissipation components is adjusted according to a pre-defined battery thermal management strategy to control the temperature.

[0039] Specifically, during equalization maintenance in S4, if the battery system SOC ≤ 70%, the system is first charged at a 1-hour rate current for (70% - SOC) * 60 minutes, then charged at a 2-hour rate current for 30 minutes, and finally charged at a 3-hour rate current for 25 minutes.

[0040] Specifically, during equalization maintenance in S4, if the battery system SOC ≤ 95%, the system is first charged at a 2-hour rate current for (95% - SOC) * 120 minutes, and then charged at a 3-hour rate current for 25 minutes.

[0041] Specifically, during equalization maintenance in S4, if the battery system SOC > 95%, the system is charged at a 3-hour rate current for 25 minutes.

[0042] Specifically, during the charging process of the battery system in S1, when the instantaneous charging current I is greater than 3 times the 1-hour rate current, the charging state voltage difference and the numbers of several cells with the highest voltage during charging are recorded.

[0043] Specifically, during the charging process of the battery system in S1, when the instantaneous discharge current I is greater than 3 times the 1-hour rate current, the discharge state voltage difference and the numbers of several cells with the highest voltage during charging are recorded.

[0044] Specifically, battery system maintenance will only be performed in S2 when both the charging and discharging voltage differences exceed 50mV, which will then lead to S3 and subsequent steps.

[0045] In one application scenario of this embodiment, a set of charging and discharging data is collected and recorded each time the nickel-metal hydride battery system is charged and discharged. If the charging current exceeds 3C, the cell voltages at that moment are arranged from high to low, and the maximum charging voltage difference ΔV within the battery system is recorded. chg The numbers of the n cells with the highest voltage (5≤n≤10) are denoted as N. max-1 ~N max-n If the discharge current exceeds 3C, arrange the cell voltages at that moment from low to high, and record the maximum discharge voltage difference ΔV within the battery system. dchg The n cells with the lowest voltage (5≤n≤10) are numbered as N. min-1 ~N min-n .

[0046] In this embodiment, n=5 and ΔV are pre-written into the battery system. t-chg =50mV, ΔV t-dchg =50mV. During normal operation of the battery system, a charging instantaneous current I > 3I1 is detected. Record the voltage of each cell at this time, and N. max-1 ~N max-5 Calculate the charging state voltage difference ΔV chg >50mV. The system continues to run. When the instantaneous discharge current I > 3I1 is detected, record the voltage of each cell at this time, as well as N. min-1 ~N min-5 Calculate the discharge state voltage difference ΔV dchg >50mV. Due to ΔV chg and ΔV dchg All values ​​exceeded 50mV, meeting the system maintenance requirements.

[0047] Comparison N max-1 ~N max-5 and N min-1 ~N min-5 The system detected that all cell serial numbers were different, indicating inconsistencies among the cells and requiring balancing. The system issued a balancing prompt. Since no other abnormal alarms were detected, the system continued normal operation.

[0048] Maintenance personnel selected the battery system during the planned maintenance period, confirmed the equalization prompt, and initiated the equalization process. The battery system's SOC was checked and found to be below 70%. A stepped charging strategy was then implemented, charging sequentially with currents I1, I2, and I3 until equalization was complete.

[0049] Example 4: A method for equalization maintenance of a nickel-metal hydride battery system, such as... Figure 1 As shown, it includes the following steps: S1. Collect the cell voltage difference during high-rate charging and discharging of the battery system, and record the cell numbers with the highest voltage during charging and the cell numbers with the lowest voltage during discharging. S2. If both the charging and discharging voltage differences exceed the voltage difference threshold, the battery system needs to be maintained. S3. Determine whether the recorded high-voltage cell number and low-voltage cell number overlap. If they do, individual cell maintenance is required for the overlapping cells. S4. If the high-voltage cell number does not overlap with the low-voltage cell number, the battery system needs to be fully charged and balanced by overcharging at a small rate.

[0050] In the specific implementation of this embodiment, the charging process of the nickel-metal hydride battery system is monitored in real time, data is collected, and the system's operating status is identified. During the operation of the nickel-metal hydride battery system, data is collected in real time, and it is simultaneously identified whether the charging or discharging current of the system exceeds 3C.

[0051] Each time the nickel-metal hydride battery system is charged and discharged, a set of charging and discharging data is collected and recorded. If the charging current exceeds 3C, the cell voltages at that moment are arranged from high to low, and the maximum charging voltage difference ΔV within the battery system is recorded. chg The numbers of the n cells with the highest voltage (5≤n≤10) are denoted as N. max-1 ~N max-n If the discharge current exceeds 3C, arrange the cell voltages at that moment from low to high, and record the maximum discharge voltage difference ΔV within the battery system. dchg The n cells with the lowest voltage (5≤n≤10) are numbered as N. min-1 ~N min-n .

[0052] In this embodiment, n=5 and ΔV are pre-written into the battery system. t-chg =50mV, ΔV t-dchg =50mV.

[0053] Based on the collected data, a determination is made as to whether the battery system requires equalization maintenance. This involves comparing ΔV. chg ΔV dchg The difference between the preset charge / discharge voltage threshold ΔVt-chg ΔV t-dchg When ΔV chg ≥ΔV t-chg And ΔV dchg ≥ΔV t-dchg The system needs maintenance at times.

[0054] When it is determined that battery system maintenance is required, select the maintenance method as follows: If there exist i and j such that N max-i =N min-j If a battery cell has a high voltage during charging and a low voltage during discharging, it indicates that the cell has deteriorated during use. In this case, cell maintenance can be performed by adding electrolyte or replacing the cell. If there are no i, j such that N max-i =N min-j This means that the performance degradation of the system is mainly caused by inconsistencies between the cells, and equalization can be selected.

[0055] During individual cell maintenance, the system issues a cell abnormality warning and outputs the cell number. If the system is not shut down due to other faults, it continues to operate normally until maintenance personnel can inspect and repair the deteriorated cells, either by adding electrolyte or replacing them. Specifically, if ΔV remains after individual cell maintenance... chg ≥ΔV t-chg And ΔV dchg ≥ΔV t-dchg Then it enters the balance maintenance phase.

[0056] During equalization maintenance, the battery system will issue an equalization prompt. If the system has not been shut down due to other faults, it will continue to operate normally until maintenance personnel confirm the information and initiate equalization. Equalization is performed using a stepped charging method: a) If the battery system SOC ≤ 70%, the system will first charge at current I1 for (70% - SOC) * 60 min, then at current I2 for 30 min, and finally at current I3 for 25 min; b) If the battery system SOC ≤ 95%, the system will first charge at current I2 for (95% - SOC) * 120 min, then at current I2 for 25 min; c) If the battery system SOC > 95%, the system will charge at current I3 for 25 min. In this case, the nickel-metal hydride battery will be overcharged by approximately 8% with a small current, which will not negatively impact battery performance. Because the battery temperature rises rapidly during overcharging, the battery system thermal management strategy should be activated during the above charging process. Here, I1 represents the 1-hour rate current, I2 represents the 2-hour rate current, and I3 represents the 3-hour rate current.

[0057] In one application scenario of this embodiment, n=5 and ΔV are pre-written. t-chg =50mV, ΔV t-dchg =50mV.

[0058] During normal operation of the battery system, a charging instantaneous current I > 3I1 is detected. The voltage of each cell at this time, and N, are recorded. min-1 ~N min-5 Calculate the charging state voltage difference ΔV chg >50mV. The system continues to run. When the instantaneous discharge current I > 3I1 is detected, record the voltage of each cell at this time, as well as N. min-1 ~N min-5 Calculate the discharge state voltage difference ΔV dchg <50mV. Due to ΔV chg and ΔV dchg All values ​​exceeded 50mV, meeting the system maintenance requirements.

[0059] Comparison N max-1 ~N max-5 and N min-1 ~N min-5 N was found max-1 =N min-1 This indicates that the battery cell has deteriorated. Since there are no other abnormal alarm messages, the system continues to operate normally.

[0060] Maintenance personnel selected a scheduled maintenance period for the battery system to perform individual cell maintenance, replacing any faulty cells. This was due to the ΔV of the remaining cells (excluding the faulty one). chg and ΔV dchg If the voltage still exceeds 50mV, it indicates inconsistency among the battery cells, requiring balancing. The system issues a balancing prompt. After confirming the balancing prompt, maintenance personnel initiate the balancing process. The battery system's SOC is checked and found to be below 95%. A stepped charging strategy is then implemented, charging with currents I2 and I3 sequentially until balancing is complete.

[0061] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for equalization maintenance of a nickel-metal hydride battery system, characterized in that, Includes the following steps: S1. Collect the cell voltage difference during high-rate charging and discharging of the battery system, and record the cells with the highest voltage during charging and the cells with the lowest voltage during discharging. S2. If both the charging and discharging voltage differences exceed the voltage difference threshold, the battery system needs to be maintained. S3. Determine whether there is overlap between the recorded high-voltage cells and low-voltage cells. If there is, individual cell maintenance is required for the overlapping cells. S4. If there is no overlap between high-voltage and low-voltage cells, the battery system needs to be fully charged and balanced by overcharging at a small rate within a small range.

2. The method for equalization and maintenance of a nickel-metal hydride battery system according to claim 1, characterized in that, The high-rate charging and discharging in S1 is a charging rate of 3C or higher, and records at least 5 cells with the highest voltage during charging and at least 5 cells with the lowest voltage during discharging.

3. The method for equalization maintenance of a nickel-metal hydride battery system according to claim 1, characterized in that, In S3, it is determined whether there is a battery cell with a high voltage during charging and a low voltage during discharging. For this deteriorated battery cell, electrolyte replenishment or replacement is selected to perform battery cell maintenance.

4. The method for equalization and maintenance of a nickel-metal hydride battery system according to claim 1, characterized in that, The S4 uses a stepped charging method for equalization maintenance. During the charging process, it adjusts the power of the heat dissipation components and controls the temperature according to a pre-defined battery thermal management strategy.

5. The method for equalization and maintenance of a nickel-metal hydride battery system according to claim 4, characterized in that, When performing equalization maintenance in S4, if the battery system SOC≤70%, the system is first charged at a 1-hour rate current for (70% - SOC)*60min, then charged at a 2-hour rate current for 30min, and finally charged at a 3-hour rate current for 25min.

6. The method for equalization and maintenance of a nickel-metal hydride battery system according to claim 4, characterized in that, When performing equalization maintenance in S4, if the battery system SOC≤95%, the system is first charged at a 2-hour rate current for (95% - SOC)*120min, and then charged at a 3-hour rate current for 25min.

7. The method for equalization maintenance of a nickel-metal hydride battery system according to claim 4, characterized in that, When performing equalization maintenance in S4, if the battery system SOC > 95%, the system is charged at a 3-hour rate current for 25 minutes.

8. The method for equalization maintenance of a nickel-metal hydride battery system according to claim 1 or 2, characterized in that, During the charging process of the battery system in S1, when the instantaneous charging current I is greater than 3 times the 1-hour rate current, the charging state voltage difference and the cells with the highest voltage during charging are recorded.

9. The method for equalization maintenance of a nickel-metal hydride battery system according to claim 8, characterized in that, During the charging process of the battery system in S1, when the instantaneous discharge current I is greater than 3 times the 1-hour rate current, the discharge state voltage difference and the several cells with the highest voltage during charging are recorded.

10. The method for equalization maintenance of a nickel-metal hydride battery system according to claim 1, characterized in that, Battery system maintenance will only be performed when both the charging and discharging voltage differences exceed 50mV in S2, which will then lead to S3 and subsequent steps.

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