CN115508718B - Method and device for monitoring self-discharge of power battery - Google Patents

Abstract

The invention discloses a method and a device for monitoring self-discharge of a power battery, which are used for determining the short-circuit resistance of each battery string in a plurality of battery strings included in the power battery when a preset monitoring period is reached, and then determining whether the self-discharge abnormality of each battery string occurs or not based on the short-circuit resistance, so that the self-discharge condition of each battery string can be monitored, thermal runaway is avoided, and the safety and the reliability of the power battery are improved.

Description

Method and device for monitoring self-discharge of power battery

technical field

The invention relates to the technical field of power batteries, in particular to a method and device for monitoring the self-discharge of a power battery.

Background technique

As the power storage unit of new energy vehicles, the power battery has a self-discharge phenomenon when no load is connected, which reduces the power of the power battery. A certain amount of self-discharge is the natural result of the chemical reaction of the power battery, but abnormal self-discharge not only makes the power battery's ability to store energy worse and worse, and the battery life becomes shorter, it may also cause thermal runaway, resulting in power battery failure. Security risks.

Contents of the invention

The embodiment of the present invention provides a method and device for monitoring the self-discharge of a power battery, which is used to determine whether each battery string in a plurality of battery strings included in the power battery is abnormal in self-discharge, so as to avoid thermal runaway, thereby improving the safety of the power battery and reliability.

In the first aspect, an embodiment of the present invention provides a method for monitoring the self-discharge of a power battery, including:

When the power battery includes a plurality of battery strings, and the preset monitoring period includes two sub-times equally divided, and the sub-times include a plurality of preset acquisition periods, when any of the monitoring periods is reached and for any of the The above battery strings all perform the following process:

Determine the leakage current of the battery string in the current monitoring cycle according to the SOC change value of the battery string in the current monitoring cycle and the rated capacity of the battery string;

According to the average value of the voltage values collected by the battery string in each of the collection periods in one of the sub-times in the current monitoring period and the leakage current of the battery string in the current monitoring period, determine the battery string short circuit resistance during said current monitoring period;

According to the short-circuit resistance, it is determined whether the battery string has abnormal self-discharge.

In the second aspect, an embodiment of the present invention provides a self-discharging monitoring device for a power battery, including:

memory for storing program instructions;

The processor is configured to call the program instructions stored in the memory, and execute the above-mentioned monitoring method provided by the embodiment of the present invention according to the obtained program.

In a third aspect, an embodiment of the present invention provides a vehicle, including: the above monitoring device as provided in the embodiment of the present invention.

In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium, the computer-readable storage medium stores a computer program, and the computer program is used to execute the above-mentioned monitoring method provided by the embodiment of the present invention.

The beneficial effects of the present invention are as follows:

A method and device for monitoring the self-discharge of a power battery provided by an embodiment of the present invention determines the short-circuit resistance of each of the multiple battery strings included in the power battery when the preset monitoring period is reached, and then determines the short-circuit resistance based on the short-circuit resistance Whether each battery string has abnormal self-discharge, so that the self-discharge of each battery string can be monitored to avoid thermal runaway, thereby improving the safety and reliability of the power battery.

Description of drawings

Fig. 1 is a flowchart of a self-discharging monitoring method of a power battery provided in an embodiment of the present invention;

Fig. 2 is a schematic diagram of the variation trend of the short-circuit resistance provided in the embodiment of the present invention;

Fig. 3 is a schematic diagram of the variation trend of the leakage current provided in the embodiment of the present invention;

Fig. 4 is a schematic structural diagram of a power battery self-discharge monitoring device provided in an embodiment of the present invention;

Fig. 5 is a schematic structural diagram of a vehicle provided in an embodiment of the present invention.

Detailed ways

The specific implementation of a method and device for monitoring self-discharge of a power battery provided by an embodiment of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the described embodiments are only some of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

An embodiment of the present invention provides a self-discharge monitoring method for a power battery, as shown in FIG. 1 , including:

When the power battery includes multiple battery strings, and the preset monitoring cycle includes two equal sub-times, and the sub-time includes multiple preset acquisition cycles, any monitoring cycle is reached and the following process is performed for any battery string:

S101. Determine the leakage current of the battery string in the current monitoring cycle according to the SOC change value of the battery string in the current monitoring cycle and the rated capacity of the battery string;

S102. Determine the short circuit of the battery string in the current monitoring cycle according to the average value of the voltage values collected in each collection cycle of the battery string in one of the sub-times in the current monitoring cycle and the leakage current of the battery string in the current monitoring cycle resistance;

S103. Determine whether the battery string has self-discharge abnormality according to the short-circuit resistance.

In this way, when the preset monitoring period is reached, the short-circuit resistance of each battery string among the plurality of battery strings included in the power battery is determined, and then based on the short-circuit resistance, it is determined whether each battery string has abnormal self-discharge, so that the Self-discharge is monitored to avoid thermal runaway, thereby improving the safety and reliability of the power battery.

In some embodiments, a monitoring period can be set during the monitoring process. Every time a monitoring period is reached, it is judged once whether each battery string has an abnormal self-discharge; wherein, the monitoring period can be determined according to factors such as the strictness of the monitoring, and is not used here. Not limited. For example, but not limited to, when strict monitoring of the power battery is required, the monitoring period can be set shorter, such as the monitoring period is 5h, and monitoring is performed every 5h; if strict monitoring of the power battery is not required, the monitoring period can be set to If the monitoring period is 2 days, monitor once every 2 days.

1. The specific implementation process of the above steps S101 and S102 will be described below.

In some embodiments, in order to realize the above steps S101 and S102, the following process may be included:

Step 1. According to the SOC corresponding to the average value of the voltage values collected by the power battery in each collection cycle in each sub-time in the current monitoring cycle, and the voltage collected by the battery string in each collection cycle in each sub-time in the current monitoring cycle The SOC corresponding to the average value of the value, determine the SOC change value of the battery string in the current monitoring cycle;

In some embodiments, in order to realize step 1, it may specifically include:

Step 1.1, determine the average value of the voltage values collected by the power battery in each acquisition cycle in any sub-time in the current monitoring cycle, and define it as the first voltage value;

Step 1.2, determine the average value of the voltage values collected in each collection cycle of the battery string in any sub-time in the current monitoring cycle, and define it as the second voltage value;

Step 1.3, find out the SOC corresponding to the first voltage value and the second voltage value respectively from the preset OCV-SOC curve;

Step 1.4, according to the SOC corresponding to the found first voltage value and the second voltage value, determine the SOC change value of the battery string in the current monitoring period.

For example, assuming that two sub-times are defined as T1 sub-time and T2 sub-time respectively, and T1 sub-time is earlier than T2 sub-time, when the xth monitoring period is reached, then:

According to the acquisition cycle, within the T1 sub-time, n voltage values of the power battery are collected, and by integrating the n voltage values and time, and then averaging the integral value and time, the power battery within the T1 sub-time can be determined. The corresponding first voltage value (denoted as U _ave1x ); similarly, the corresponding first voltage value of the power battery (denoted as U _ave2x ) within the T2 sub-time can be determined; of course, the power battery sub-time and T2 within the T1 sub-time The first voltage value within a sub-time is not limited to being determined by means of integration, but can also be determined based on the sum of n voltage values and the average value of time or other means of calculating the average value;

According to the acquisition period, in the T1 sub-time, collect n voltage values of each battery string, calculate the average value of the n voltage values, and then determine the second voltage value corresponding to each battery string in the T1 sub-time (record is U _m1x ); similarly, the second voltage value corresponding to each battery string in the T2 sub-time (denoted as U _m2x ); of course, the second voltage of the battery string in the T1 sub-time and T2 sub-time The value is not limited to be determined by summing and re-averaging, but can also be determined based on the average value of the integral value of n voltage values and time or other means of calculating the average value;

Next, find out the SOC corresponding to U _m1x , U _m2x , U _ave1x and U _ave2x from the static OCV-SOC curve (that is, the preset OCV-SOC curve mentioned in step 1.3 above), and use the found U _m1x The corresponding SOC is recorded as SOC _m1x , the SOC corresponding to the found U _m2x is recorded as SOC _m2x , the SOC corresponding to the found U _ave1x is recorded as SOC _ave1x , and the SOC corresponding to the found U _ave2x is recorded as SOC _ave2x ;

After that, formula 1: △SOC _x =|(SOC _ave1x -SOC _m1x )-(SOC _ave2x -SOC _m2x )| is used to determine the SOC change value of the power battery in the current monitoring period (ie △SOC _x ).

In this way, based on the average voltage values of the power battery and each battery string in each sub-time, the SOC change value of the battery string in the current monitoring period can be determined, so as to subsequently determine the leakage current based on the SOC change value. Moreover, since the calculation of the SOC change value is based on the SOC corresponding to the first voltage value and the second voltage value, and the SOC is found from the static OCV-SOC curve, the found SOC is closer to and conforms to The real situation of the power battery and each battery string, so that the subsequent calculated leakage current is more accurate, and the accuracy of self-discharge abnormal judgment is improved.

In some embodiments, the OCV-SOC curve preset in step 1.3 above can be determined in the following manner, but not limited to:

Step 1.3.1. Place the power battery at a constant temperature of 25°C for a certain period of time, such as but not limited to 20 hours;

Step 1.3.2, charge the power battery to the upper limit voltage with a charging rate of 0.05C and a constant current to obtain the first charging curve; wherein, the upper limit voltage refers to the voltage when the power battery is fully charged;

Step 1.3.3, discharge the power battery to the end voltage with a discharge rate of 0.05C and a constant current to obtain the first discharge curve; wherein, the end voltage refers to the lowest voltage when the power battery is discharged;

Step 1.3.4, according to the average value of the first charge curve and the first discharge curve, obtain the SOC-OCV curve of the power battery at 25°C.

Among them, different types of power batteries may have different corresponding SOC-OVC curves; and, the SOC-OVC curves for different types of power batteries can be pre-written and stored in the memory of the detection device, so as to be extracted when needed .

Step 2. According to the SOC change value of the battery string in the current monitoring period and the rated capacity of the battery string, determine the leakage current of the battery string in the current monitoring period;

In some embodiments, in order to realize step 2, it may specifically include:

Use the following formula (that is, formula 2) to determine the leakage current of the battery string in the xth monitoring period:

I _dx =△SOC _x ×C/T;

Among them, I _dx represents the leakage current of the battery string in the xth monitoring period, T represents the sub-time, C represents the rated capacity of the battery string, and △SOC _x represents the SOC change value of the battery string in the xth monitoring cycle.

In this formula 2, the value of C in each monitoring period is the same, and the value of T in each monitoring period is also the same. It only needs to determine △SOC _x to calculate I _dx , thereby determining the battery The leakage current in series in each monitoring cycle, and then subsequently calculate the short-circuit resistance.

Step 3. According to the average value of the voltage values collected in each acquisition cycle of the battery string in one of the sub-times in the current monitoring cycle and the leakage current of the battery string in the current monitoring cycle, determine the current monitoring cycle of the battery string. short circuit resistance.

In some embodiments, in order to realize step 3, it may specifically include:

Use the following formula (that is, formula 3) to determine the short-circuit resistance of the battery string in the xth monitoring cycle:

R _ix =U _mkx /I _dx ;

Among them, i represents the number of the battery string, R _ix represents the short-circuit resistance of the battery string in the xth monitoring period, I _dx represents the leakage current of the battery string in the xth monitoring cycle; U _mkx represents the battery string in the current monitoring the second voltage value within one of the sub-times in the cycle;

Moreover, assuming that the two sub-times are respectively defined as T1 sub-time and T2 sub-time, and when the T1 sub-time is earlier than the T2 sub-time, U _mkx can be the second voltage value of the battery string in the T1 sub-time, or can be Of course, the second voltage value in the T2 sub-time may also be the smaller value of the second voltage value in the T1 sub-time and the second voltage value in the T2 sub-time.

In this way, based on the leakage current of the battery string in the current monitoring period and the second voltage value of the battery string in one of the sub-times in the current detection period, combined with Ohm's law, it can be determined that the battery string is in the current monitoring period. The short-circuit resistance of the cycle provides a basis for judging whether an abnormal self-discharge occurs in the future.

Moreover, the above steps 1 to 3 are executed every time a monitoring cycle is reached, so that the short-circuit resistance of each battery string can be determined.

2. The specific implementation process of the above step S103 will be described below.

In some embodiments, for a certain battery string, when determining whether the battery string has abnormal self-discharge according to the short-circuit resistance, the following methods may be included:

Method 1:

When the short-circuit resistance of the battery string in the current monitoring period is less than or equal to the first preset value, it is determined that the battery string is currently abnormally self-discharged.

That is to say: compare the short-circuit resistance of the battery string determined in the xth monitoring cycle with the first preset value, if it is less than or equal to the first preset value, it means that the short-circuit resistance of the battery string is small, indicating that a short-circuit resistance has occurred Self-discharge is abnormal, so it can be determined that the battery string has an abnormal self-discharge in the xth monitoring cycle. At this time, the user and maintenance personnel can be alerted to remind the user and maintenance personnel that the power battery is abnormal. , so that users and maintenance personnel can take relevant measures to avoid danger.

For example, as shown in Figure 2, the test results of the short-circuit resistance of a certain battery string (denoted as battery string M) in each monitoring cycle, the broken line 1 in the figure shows the short-circuit resistance corresponding to 8 monitoring cycles, in 2/ The short-circuit resistance calculated before 10 (meaning February 10) is 1474Ω, and the short-circuit resistance calculated after 2/10 is 88Ω. If the first preset value is 1000Ω, obviously in the third monitoring cycle (that is, 2 /10, and before 2/12), the calculated short-circuit resistance is less than the first preset value, so in the third monitoring cycle, it can be judged that the battery string M has an abnormal self-discharge.

Moreover, in Fig. 3, the leakage current of the battery string M in each monitoring cycle is shown. Obviously, the leakage current of the battery string M in the third monitoring cycle (that is, between 2/10 and 2/12) There is an obvious increase in the current, and the increase range is relatively large, indicating that the battery string M has an abnormal self-discharge at this time.

Continuing to refer to Fig. 2, broken line 2 shows the first voltage value corresponding to the power battery in 9 monitoring cycles, and broken line 3 shows the second voltage value corresponding to the battery string M in 9 monitoring cycles, from the broken line 2 and broken line 3, in the fourth monitoring cycle around 2/12 (indicating February 12th), it was determined that the first voltage value and the second voltage value deviated, and as time went on, the two The deviation between them is getting bigger and bigger; if the self-discharge abnormality is judged based on the first voltage value and the second voltage value, the battery string M has self-discharge abnormality in the fourth monitoring cycle around 2/12.

Therefore, from the results shown in line 1 to line 3, it can be determined that:

When judging whether a battery string has an abnormal self-discharge, the short-circuit resistance can detect whether an abnormal self-discharge occurs earlier than the voltage value, and then the user and maintenance personnel can be alerted earlier, and measures can be taken earlier. The occurrence of danger is greatly avoided, thereby effectively improving the safety and reliability of the power battery.

In some embodiments, it may further include:

Determine the first difference between the short-circuit resistance of the battery string in the current monitoring period and the first preset value;

According to the first corresponding relationship between the preset difference range and the warning level, the warning level corresponding to the current first difference value of the battery string is determined.

That is to say: when calculating the first difference between the short-circuit resistance determined in the xth monitoring cycle of a certain battery string and the first preset value, find out the difference corresponding to the first difference from the first correspondence Value range, and then find the alarm level corresponding to the difference range, and then give an alarm to the battery string, so that users and maintenance personnel can grasp the information of the power battery in time and avoid danger.

In some embodiments, the first corresponding relationship may be as shown in Table 1 below, and the difference range may be the first preset value minus the value of the short-circuit resistance.

Table 1

It can be seen from the above table 1 that:

When the first difference is at [c1-c2), it means that the alarm level of the battery string in the current monitoring cycle is low, indicating that the current self-discharge abnormality of the battery string is relatively small, so as to warn the user that the power battery may be in danger ;

When the first difference is in [c2-c3), it means that the alarm level of the battery string in the current monitoring period is medium, indicating that the current self-discharge abnormality of the battery string is moderate, so as to warn the user of the possibility of danger in the power battery High, need to take relevant measures as soon as possible;

When the first difference is at [c3-c4), it means that the alarm level of the battery string in the current monitoring period is high, indicating that the current self-discharge abnormality of the battery string is relatively large, so as to warn the user that the power battery may be damaged immediately. In case of danger, it is necessary to stop using the power battery immediately.

Of course, the first corresponding relationship is not limited to that shown in Table 1, and can also be set according to actual needs, as long as different alarm levels can be provided to users and maintenance personnel, so that users and maintenance personnel can take relevant measures, all It belongs to the protection scope of the embodiments of the present invention.

Method 2:

Determine the rate of change of the short-circuit resistance of the battery string in the current monitoring period;

When the rate of change is greater than or equal to the second preset value, it is determined that the battery string is currently experiencing self-discharge abnormality.

Among them, assuming that the short-circuit resistance calculated in the x-1 monitoring cycle is represented by R _ix-1 , and the short-circuit resistance calculated in the x-th monitoring cycle is represented by R _ix , the rate of change can be understood as: |(R _ix-1 - R _ix )|/t, t represents the monitoring period, that is, the ratio of the absolute value of the difference between the short-circuit resistance calculated in the x-1th monitoring period and the short-circuit resistance calculated in the xth monitoring period to the monitoring period. For example, continue referring to FIG. 2 , the rate of change is the slope of the line connecting two adjacent points in the polyline 1 . And, for the first monitoring period, the rate of change can be regarded as 0 or no rate of change.

In this way, the rate of change of the short-circuit resistance of a certain battery string determined in the xth monitoring cycle is compared with the second preset value, and if it is greater than or equal to the second preset value, it means that the short-circuit resistance of the battery string has a large change , indicating that self-discharge abnormality has occurred, so it can be determined that the battery string has self-discharge abnormality in the xth monitoring cycle, and at this time, an alarm can be given to the user and maintenance personnel to remind the user and maintenance personnel of the power If the battery is abnormal, it is convenient for users and maintenance personnel to take relevant measures to avoid danger.

In some embodiments, it may further include:

determining a second difference between the rate of change and a second preset value;

According to the second corresponding relationship between the preset difference range and the warning level, the warning level corresponding to the current second difference value of the battery string is determined.

That is to say: when calculating the second difference between the change rate of the short-circuit resistance determined in the xth monitoring cycle of a certain battery string and the second preset value, the second difference is found from the second correspondence The corresponding difference range, and then find the alarm level corresponding to the difference range, and then send an alarm to the battery string, so that users and maintenance personnel can grasp the information of the power battery in time and avoid danger.

In some embodiments, the second corresponding relationship may be as shown in Table 2 below, and the difference range may be the change rate of the short-circuit resistance minus the value of the second preset value.

Table 2

It can be seen from the above table 2 that:

When the second difference is at [d1-d2), it means that the alarm level of the battery string in the current monitoring cycle is low, indicating that the current short-circuit resistance change rate of the battery string is relatively small, which in turn indicates that the degree of abnormal self-discharge is relatively small. To warn users that the power battery may be in danger;

When the second difference is at [d2-d3), it means that the alarm level of the battery string in the current monitoring period is medium, indicating that the current short-circuit resistance of the battery string has a medium change rate, and then indicating that the degree of self-discharge abnormality is medium, and the warning The user's power battery has a high possibility of danger, and relevant measures need to be taken as soon as possible;

When the second difference is at [d3-d4), it means that the alarm level of the battery string in the current monitoring period is high, indicating that the current short-circuit resistance of the battery string has a relatively large change rate, which in turn indicates that the degree of self-discharge abnormality is relatively large. In order to warn the user that the power battery may be in danger immediately, it is necessary to stop using the power battery immediately.

Of course, the second corresponding relationship is not limited to that shown in Table 2, and can also be set according to actual needs, as long as different alarm levels can be provided to users and maintenance personnel, so that users and maintenance personnel can take relevant measures. It belongs to the protection scope of the embodiments of the present invention.

Based on the same inventive concept, an embodiment of the present invention provides a self-discharge monitoring device for a power battery. The implementation principle of the monitoring device is similar to that of the aforementioned monitoring method. For the specific implementation of the monitoring device, please refer to the specific implementation of the aforementioned monitoring method. Embodiment, repeated description will not be repeated.

Specifically, a power battery self-discharge monitoring device provided in an embodiment of the present invention, as shown in FIG. 4 , includes:

Memory 401, used to store program instructions;

The processor 402 is configured to call the program instructions stored in the memory 401, and execute the above monitoring method as provided by the embodiment of the present invention according to the obtained program.

Based on the same inventive concept, an embodiment of the present invention provides a vehicle, as shown in FIG. 5 , including: the above-mentioned monitoring device 10 provided by the embodiment of the present invention.

In some embodiments, as shown in FIG. 5 , in addition to the monitoring device, the vehicle may also include: a power battery 20 , wheels 30 and other structures for realizing vehicle functions, which are not limited herein.

Based on the same inventive concept, an embodiment of the present invention provides a computer-readable storage medium, where a computer program is stored in the computer-readable storage medium, and the computer program is used to execute the above-mentioned monitoring method provided by the embodiment of the present invention.

It should be emphasized that the above solutions provided by the embodiments of the present invention have the following advantages:

1. By monitoring the short-circuit resistance to judge whether self-discharge abnormality occurs, it can more directly reflect the level and development trend of the short-circuit resistance, evaluate the heating power level caused by the short-circuit more directly, and provide favorable data support for risk assessment for big data early warning.

2. By obtaining the second voltage value in the sub-time, the influence of the current difference on the second voltage value at different times can be reduced, and the accuracy of the variation of the deviation of the second voltage value in the two sub-times can be improved, which can better reflect the short circuit The level and development trend of resistance;

3. There is an SOC plateau area in the OCV-SOC curve, and in this SOC plateau area, the OCV changes little. If the voltage value is used to judge whether self-discharge abnormality occurs, it is easy to misjudgment, and the judgment result has a large delay. That is to say, when it is judged that an abnormal self-discharge occurs, it is possible that a certain battery string may already have an abnormal self-discharge, which increases the danger of the power battery during use. In the technical solution provided by the embodiment of the present invention, based on the short-circuit resistance to judge whether self-discharge abnormality occurs, the SOC can be adjusted to eliminate the influence of the SOC plateau area, and the power battery leakage current and the change of the short-circuit resistance can be monitored in real time, which can not only improve the judgment It can also give judgment results as early as possible and take measures early, thereby reducing the danger of power batteries during use and improving the safety and reliability of use.

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims (9)

1. A method for monitoring the self-discharge of a power battery, characterized in that, comprising When the power battery includes a plurality of battery strings, and the preset monitoring period includes two sub-times equally divided, and the sub-times include a plurality of preset acquisition periods, when any of the monitoring periods is reached and for any of the The above battery strings all perform the following process: Determine the leakage current of the battery string in the current monitoring cycle according to the SOC change value of the battery string in the current monitoring cycle and the rated capacity of the battery string; According to the average value of the voltage values collected by the battery string in each of the collection periods in one of the sub-times in the current monitoring period and the leakage current of the battery string in the current monitoring period, determine the battery string short circuit resistance during said current monitoring period; According to the short-circuit resistance, determine whether the battery string has abnormal self-discharge; The SOC change value of the battery string in the current monitoring period is determined in the following manner: The average value of the voltage values collected by the power battery in each of the acquisition periods in any of the sub-times in the current monitoring period is defined as the first voltage value, and the battery string is in the current monitoring period. When the average value of the voltage values collected in each of the acquisition periods in any of the sub-times in the period is defined as the second voltage value, the first voltage value and the first voltage value are respectively found from the preset OCV-SOC curve The SOC corresponding to the second voltage value; The following formula is used to determine the SOC change value of the battery string in the current monitoring period: △SOC _x =|(SOC _ave1x -SOC _m1x )-(SOC _ave2x -SOC _m2x )|; Among them, ΔSOC _x represents the SOC change value of the battery string in the current monitoring period, and SOC _ave1x represents the first voltage value corresponding to the first voltage value of the power battery in the sub-time earlier in the current monitoring period. SOC, SOC _ave2x indicates the SOC corresponding to the first voltage value of the power battery in the sub-time later in the current monitoring period, and SOC _m1x indicates that the battery string is earlier in the current monitoring period The SOC corresponding to the second voltage value in the sub-time of , SOC _m2x represents the SOC corresponding to the second voltage value of the battery string in the sub-time later in the current monitoring period. 2. The monitoring method according to claim 1, wherein, according to the short-circuit resistance, determining whether the battery string has an abnormal self-discharge includes: When the short-circuit resistance of the battery string in the current monitoring period is less than or equal to the first preset value, it is determined that the battery string is currently abnormally self-discharged. 3. The monitoring method according to claim 2, further comprising: determining a first difference between the short-circuit resistance of the battery string in the current monitoring period and the first preset value; According to the first corresponding relationship between the preset difference range and the warning level, the warning level corresponding to the current first difference value of the battery string is determined. 4. The monitoring method according to claim 1, wherein, according to the short-circuit resistance, determining whether the battery string has an abnormal self-discharge includes: Determine the rate of change of the short-circuit resistance of the battery string in the current monitoring period; When the rate of change is greater than or equal to the second preset value, it is determined that the battery string is currently experiencing an abnormal self-discharge. 5. The monitoring method according to claim 4, further comprising: determining a second difference between the rate of change and the second preset value; According to the second corresponding relationship between the preset difference range and the warning level, the warning level corresponding to the current second difference value of the battery string is determined. 6. The monitoring method according to claim 1, characterized in that, according to the average value of the voltage values collected by the battery string in each of the acquisition periods in one of the sub-times in the current monitoring period, and the The leakage current of the battery string in the current monitoring period is determined to determine the short-circuit resistance of the battery string in the current monitoring period, including: The following formula is used to determine the short-circuit resistance of the battery string in the current monitoring period: R _ix =U _mkx /I _dx ; Wherein, i represents the number of the battery string, x represents the current monitoring cycle, R _ix represents the short-circuit resistance of the battery string in the current monitoring cycle, and U _mkx represents one of the battery strings in the current monitoring cycle. The average value of the voltage values collected in each of the collection cycles within the sub-time, _Idx represents the leakage current of the battery string in the current monitoring cycle. 7. A self-discharging monitoring device for a power battery, characterized in that it comprises: memory for storing program instructions; A processor, configured to call the program instructions stored in the memory, and execute the monitoring method according to any one of claims 1-6 according to the obtained program. 8. A vehicle, characterized by comprising: the monitoring device according to claim 7. 9. A computer-readable storage medium, wherein a computer program is stored in the computer-readable storage medium, and the computer program is used to execute the monitoring method according to any one of claims 1-6.

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