A battery thermal runaway early warning method and a new energy vehicle

Abstract

The application discloses a battery thermal runaway early warning method and a new energy vehicle, and belongs to the technical field of new energy vehicle batteries. The method comprises the following steps: recording the maximum voltage and minimum voltage of a battery cell each time when the new energy vehicle is fully charged through a battery management system (BMS), calculating the capacity difference each time according to the maximum voltage and minimum voltage of the battery cell recorded each time, calculating the leakage current of the battery cell through two adjacent capacity differences, and calculating the average voltage of the battery cell with the lowest voltage in the battery pack within the time interval of two adjacent full charges, so as to calculate the short-circuit resistance of the battery cell with the lowest voltage in the battery pack within the time interval of two adjacent full charges. When two adjacent short-circuit resistances are calculated, the battery management system (BMS) judges whether battery thermal runaway early warning is needed according to relevant conditions. If it is judged that the relevant conditions are met, battery thermal runaway early warning is performed. That is, the application can perform early warning before battery thermal runaway occurs.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy vehicle batteries. Specifically, the present invention relates to a battery thermal runaway early warning method and a new energy vehicle. Background Art

[0002] Battery safety is crucial in new energy vehicles. As a core component, batteries not only impact the vehicle's power performance but also directly affect the safety of drivers and passengers. Battery safety issues such as thermal runaway and short circuits can cause fires or even explosions, with devastating consequences. Therefore, ensuring battery safety is a prerequisite and foundation for the development of new energy vehicles.

[0003] Currently, new energy vehicles can only sound an alarm when battery thermal runaway has occurred and cannot provide early warning. The current monitoring and alarm methods for battery thermal runaway in new energy vehicles mainly rely on monitoring the sudden drop in battery voltage and the temperature of the associated battery cells, or monitoring the smoke concentration in the battery pack through smoke sensors. However, these methods have obvious limitations because they can usually only sound an alarm when a fault has occurred. When the battery voltage suddenly drops or the battery cell temperature rises abnormally, or the smoke sensor can only sound an alarm after smoke is generated, although the alarm system can be triggered, the time window left for the driver and passengers to take countermeasures is often very short, which can easily cause property damage and casualties.

[0004] Patent CN117465222B discloses a power battery fault warning method and a fault warning system. The power battery fault warning method is applied to the cloud, including: obtaining the cell detection data of the target vehicle power battery and the rated parameters of the power battery to perform a first fault judgment; based on the first fault judgment result, obtaining load status information; and performing a small current over-discharge fault judgment based on the load status information to generate a warning result.

[0005] However, the technology disclosed in the above patent cannot provide early warning before the battery undergoes thermal runaway. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a battery thermal runaway warning method and a new energy vehicle in view of the shortcomings of the existing technology, so as to achieve the purpose of providing a warning before the battery thermal runaway occurs.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] The present invention provides a battery thermal runaway early warning method, the method comprising the following steps:

[0009] S1: Charging the new energy vehicle for the first time;

[0010] S2: continuously collecting the voltage of the battery cell through the battery management system (BMS);

[0011] S3: when the new energy vehicle is fully charged for the first time, the battery management system (BMS) records the highest voltage and the lowest voltage of the battery cell, and calculates the first capacity difference C1 according to the recorded highest voltage and the lowest voltage of the battery cell;

[0012] S4: charging the new energy vehicle for the second time;

[0013] S5: continuously collecting the voltage of the battery cell through the battery management system (BMS);

[0014] S6: when the new energy vehicle is fully charged for the second time, the battery management system (BMS) records the highest voltage and the lowest voltage of the battery cell, and calculates the second capacity difference C2 according to the recorded highest voltage and the lowest voltage of the battery cell;

[0015] S7: the battery management system (BMS) calculates the leakage current I1 of the battery cell according to the first time interval T1, the first capacity difference C1 and the second capacity difference C2;

[0016] S8: the battery management system (BMS) calculates the average voltage U1 of the battery cell with the lowest voltage in the battery pack within the first time interval T1;

[0017] S9: the battery management system (BMS) calculates the short-circuit resistance R1 of the battery cell with the lowest voltage in the battery pack;

[0018] S10: charging the new energy vehicle for the third time;

[0019] S11: continuously collecting the voltage of the battery cell through the battery management system (BMS);

[0020] S12: when the new energy vehicle is fully charged for the third time, the battery management system (BMS) records the highest voltage and the lowest voltage of the battery cell, and calculates the third capacity difference C3 according to the recorded highest voltage and the lowest voltage of the battery cell;

[0021] S13: the battery management system (BMS) calculates the leakage current I2 of the battery cell according to the second time interval T2, the second capacity difference C2 and the third capacity difference C3;

[0022] S14: the battery management system (BMS) calculates the average voltage U2 of the battery cell with the lowest voltage in the battery pack within the second time interval T2;

[0023] S15: the battery management system (BMS) calculates the short-circuit resistance R2 of the battery cell with the lowest voltage in the battery pack;

[0024] S16: The battery management system (BMS) determines whether the first condition, the second condition and the third condition are all met, if yes, enters S17, if not, enters S18;

[0025] S17: The battery management system (BMS) performs a battery thermal runaway warning, and after the warning is over, enters S26;

[0026] S18: The new energy vehicle is charged for the N+1th time;

[0027] S19: The voltage of the battery cell is continuously collected by the battery management system (BMS);

[0028] S20: When the new energy vehicle is fully charged for the N+1th time, the battery management system (BMS) records the highest voltage and the lowest voltage of the battery cell, and calculates the N+1th capacity difference C N+1 according to the recorded highest voltage and the lowest voltage of the battery cell;

[0029] S21: The battery management system (BMS) calculates the leakage current I N of the battery cell according to the Nth time interval T N , the Nth capacity difference C N and the N+1th capacity difference C N+1 ;

[0030] S22: The battery management system (BMS) calculates the average voltage U N of the battery cell with the lowest voltage in the battery pack within the Nth time interval T N ;

[0031] S23: The battery management system (BMS) calculates the short-circuit resistance R N of the battery cell with the lowest voltage in the battery pack;

[0032] S24: The battery management system (BMS) determines whether the first condition, the second condition and the fourth condition are all met, if yes, enters S17, if not, enters S25;

[0033] S25: N=N+1 is taken;

[0034] S26: Enters S18.

[0035] Further, N is a positive integer greater than 2, and N takes a value from 3.

[0036] Further, I1=(C2-C1) / T1, I2=(C3-C2) / T2, I N =(C N+1 -C N ) / T N , wherein T1 is the first time interval, T2 is the second time interval, T Nis the Nth time interval, C1 is the first capacity difference, C2 is the second capacity difference, C3 is the third capacity difference, C N is the Nth capacity difference, C N+1 is the N+1th capacity difference, I1 is the leakage current of the battery cell in the first time interval T1, I2 is the leakage current of the battery cell in the second time interval T2, I N is the Nth time interval T N Leakage current of the internal battery.

[0037] Furthermore, R1=U1 / I1,R2=U2 / I2,R N =U N / I N , where I1 is the leakage current of the cell in the first time interval T1, I2 is the leakage current of the cell in the second time interval T2, and I N is the Nth time interval T N Leakage current of the inner cell, U1 is the average voltage of the lowest voltage cell in the battery pack during the first time interval T1, U2 is the average voltage of the lowest voltage cell in the battery pack during the first time interval T2, U N is the Nth time interval T N The average voltage of the lowest voltage cell in the battery pack, R1 is the short-circuit resistance of the lowest voltage cell in the battery pack during the first time interval T1, R2 is the short-circuit resistance of the lowest voltage cell in the battery pack during the second time interval T2, R N is the Nth time interval T N The short-circuit resistance of the lowest voltage cell in the battery pack.

[0038] Furthermore, the first time interval T1 is the time difference between the first time the new energy vehicle is fully charged and the second time the new energy vehicle is fully charged, the second time interval T2 is the time difference between the second time the new energy vehicle is fully charged and the third time the new energy vehicle is fully charged, and the Nth time interval T N It is the time difference between the Nth time a new energy vehicle is fully charged and the N+1th time a new energy vehicle is fully charged.

[0039] Furthermore, the first condition is that the state of charge (SOC) of the battery is greater than a preset threshold.

[0040] Furthermore, the second condition is that the voltage drop rate of the lowest voltage cell in the battery pack is greater than a preset voltage drop rate and lasts for a time greater than a preset time.

[0041] Furthermore, the third condition is that the value of |R2-R1| / R1 is greater than 0.5.

[0042] Furthermore, the fourth condition is |R N -R N-1 | / R N-1 The value of is greater than 0.5.

[0043] The application also provides a new energy vehicle, which adopts the battery thermal runaway early warning method.

[0044] The battery thermal runaway early warning method has the following advantages:

[0045] (1) The battery thermal runaway early warning method can early warn before the battery thermal runaway, and further can gain more time window for the user.

[0046] (2) Through the application, after the battery management system (BMS) judges that the battery thermal runaway early warning is needed, the battery management system (BMS) pushes the battery thermal runaway early warning information to the enterprise platform and the user, so as to subsequently carry out safety maintenance on the battery, and also can avoid property loss and personnel casualty.

[0047] (3) The application early warns before the battery thermal runaway, and improves the safety of the vehicle.

[0048] (4) The battery management system (BMS) of the application combines multiple judgment conditions before the battery thermal runaway early warning, better avoids misjudgment, and improves the accuracy of early warning before the battery thermal runaway.

[0049] (5) The application detects the leakage current between two adjacent charges of the new energy vehicle, which can solve the problem that the early short circuit phenomenon is not obvious, and also takes into account the detection in the middle and late stages. BRIEF DESCRIPTION OF DRAWINGS

[0050] The present specification includes the following drawings, and the contents shown are as follows:

[0051] Figure 1 is a flow chart of a battery thermal runaway early warning method of the application. DETAILED DESCRIPTION

[0052] The specific embodiments of the application will be further described below by comparing the drawings and the embodiments, and the purpose is to help the skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the application, and to help its implementation.

[0053] Figure 1 is a flow chart of a battery thermal runaway early warning method of the application, and the method comprises the following steps:

[0054] S1: first charge the new energy vehicle, that is, corresponding to S1 in the above embodiment. Figure 1

[0055] ​S2: The battery management system (BMS) continuously collects the voltage of the battery cell, which corresponds to Figure 1 Specifically, during the charging process of the new energy vehicle, the voltage of the battery cell is continuously collected through the battery management system (BMS). For example, the voltage of the battery cell can be collected every 0.01 seconds.

[0056] S3: When the new energy vehicle is fully charged for the first time, the battery management system (BMS) records the highest and lowest voltages of the battery cell, and calculates the first capacity difference C1 based on the recorded highest and lowest voltages of the battery cell, which corresponds to Figure 1 Specifically, when the new energy vehicle is fully charged for the first time, the capacity difference between the highest voltage cell and the lowest voltage cell is calculated by the highest voltage and the lowest voltage among the voltages collected by the battery management system (BMS), and is recorded as the first capacity difference C1.

[0057] S4: The second time to charge the new energy vehicle, that is, Figure 1 S4 in.

[0058] S5: The battery management system (BMS) continuously collects the voltage of the battery cell, which corresponds to Figure 1 Specifically, during the charging process of the new energy vehicle, the voltage of the battery cell is continuously collected through the battery management system (BMS). For example, the voltage of the battery cell can be collected every 0.01 seconds.

[0059] S6: When the new energy vehicle is fully charged for the second time, the battery management system (BMS) records the highest voltage and the lowest voltage of the battery cell, and calculates the second capacity difference C2 based on the recorded highest voltage and the lowest voltage of the battery cell, which corresponds to Figure 1 Specifically, when the new energy vehicle is fully charged for the second time, the capacity difference between the highest voltage cell and the lowest voltage cell is calculated by the highest voltage and the lowest voltage among the voltages collected by the battery management system (BMS), and is recorded as the second capacity difference C2.

[0060] S7: The battery management system (BMS) calculates the leakage current I1 of the battery cell according to the first time interval T1, the first capacity difference C1 and the second capacity difference C2, which corresponds to Figure 1S7: the battery management system (BMS) calculates the leakage current I1 of the battery cell according to I1 = (C2-C1) / T1, wherein T1 is the first time interval, the first time interval T1 is not a fixed time value, the first time interval T1 is the time difference between the first time when the new energy vehicle is fully charged and the second time when the new energy vehicle is fully charged, the time difference is recorded by the battery management system (BMS), and the specific value of the time difference depends on how long the vehicle owner waits to charge the new energy vehicle after the first time when the new energy vehicle is fully charged, in addition, C1 is the first capacity difference, C2 is the second capacity difference, and I1 is the leakage current of the battery cell in the first time interval T1.

[0061] S8: the battery management system (BMS) calculates the average voltage U1 of the lowest voltage battery cell in the battery pack in the first time interval T1, that is, corresponds to Figure 1 S8 in the above. Specifically, the battery management system (BMS) obtains the average voltage U1 of the lowest voltage battery cell in the battery pack in the first time interval T1 by dividing the sum of the voltages of the lowest voltage battery cell in the battery pack collected in the first time interval T1 by the total number of times the battery management system (BMS) collects the voltage of the battery cell in the first time interval T1.

[0062] S9: the battery management system (BMS) calculates the short-circuit resistance R1 of the lowest voltage battery cell in the battery pack, that is, corresponds to Figure 1 S9 in the above. Specifically, the battery management system (BMS) calculates the short-circuit resistance R1 of the lowest voltage battery cell in the battery pack according to R1 = U1 / I1, wherein I1 is the leakage current of the battery cell in the first time interval T1, U1 is the average voltage of the lowest voltage battery cell in the battery pack in the first time interval T1, and R1 is the short-circuit resistance of the lowest voltage battery cell in the battery pack in the first time interval T1.

[0063] S10: the new energy vehicle is charged for the third time, that is, corresponds to Figure 1 S10 in the above.

[0064] S11: the voltage of the battery cell is continuously collected by the battery management system (BMS), that is, corresponds to Figure 1 S11 in the above. Specifically, during the charging of the new energy vehicle, the voltage of the battery cell is continuously collected by the battery management system (BMS), for example, the voltage of the battery cell can be collected every 0.01 seconds.

[0065] S12: when the new energy vehicle is fully charged for the third time, the battery management system (BMS) records the highest voltage and the lowest voltage of the battery cell, and calculates the third capacity difference C3 according to the recorded highest voltage and the lowest voltage of the battery cell, that is, corresponds to Figure 1S12: the battery management system (BMS) calculates the capacity difference between the highest voltage cell and the lowest voltage cell in the battery pack, i.e., corresponds to S12 in FIG. 1. Specifically, the capacity difference between the highest voltage cell and the lowest voltage cell is calculated by the highest voltage and the lowest voltage collected by the battery management system (BMS) when the new energy vehicle is charged for the third time, and is recorded as the third capacity difference C3.

[0066] S13: the battery management system (BMS) calculates the leakage current I2 of the cell according to the second time interval T2, the second capacity difference C2 and the third capacity difference C3, i.e., corresponds to S13 in FIG. 1. Figure 1

[0066] S13: the battery management system (BMS) calculates the leakage current I2 of the cell according to the second time interval T2, the second capacity difference C2 and the third capacity difference C3, i.e., corresponds to S13 in FIG. 1.

[0067] S14: the battery management system (BMS) calculates the average voltage U2 of the lowest voltage cell in the battery pack in the second time interval T2, i.e., corresponds to S14 in FIG. 1. Figure 1

[0067] S14: the battery management system (BMS) calculates the average voltage U2 of the lowest voltage cell in the battery pack in the second time interval T2, i.e., corresponds to S14 in FIG. 1.

[0068] S15: the battery management system (BMS) calculates the short-circuit resistance R2 of the lowest voltage cell in the battery pack, i.e., corresponds to S15 in FIG. 1. Figure 1

[0068] S15: the battery management system (BMS) calculates the short-circuit resistance R2 of the lowest voltage cell in the battery pack, i.e., corresponds to S15 in FIG. 1.

[0069] S16: the battery management system (BMS) determines whether the first condition, the second condition and the third condition are all met, if yes, it goes to S17, if not, it goes to S18, i.e., corresponds to S16 in FIG. 1. Figure 1S16 in the above description. The first condition is that the state of charge (SOC) of the battery is greater than a preset threshold value, the second condition is that the voltage drop rate of the lowest voltage cell in the battery pack is greater than a preset voltage drop rate and lasts for a duration greater than a preset time, and the third condition is that the value of |R2-R1| / R1 is greater than 0.5.

[0070] S17: The battery management system (BMS) issues a battery thermal runaway warning. After the warning is completed, it enters S26, which corresponds to Figure 1 Specifically, the battery management system (BMS) pushes warning information about battery thermal runaway to the enterprise platform and users, allowing for subsequent safety inspections of the battery. This means it can issue a warning before thermal runaway occurs, thereby buying users more time to avoid property damage and casualties, and improving vehicle safety. Furthermore, it also better avoids misjudgments and improves the accuracy of warnings before thermal runaway occurs.

[0071] S18: Charging the new energy vehicle for the N+1th time, corresponding to Figure 1 S18 in.

[0072] S19: The battery management system (BMS) continuously collects the voltage of the battery cell, which corresponds to Figure 1 Specifically, during the charging process of the new energy vehicle, the voltage of the battery cell is continuously collected through the battery management system (BMS). For example, the voltage of the battery cell can be collected every 0.01 seconds.

[0073] S20: When the new energy vehicle is fully charged for the N+1th time, the battery management system (BMS) records the highest and lowest voltages of the battery cell and calculates the N+1 capacity difference C based on the recorded highest and lowest voltages of the battery cell. N+1 , that is, corresponding to Figure 1 Specifically, when the new energy vehicle is fully charged for the N+1th time, the capacity difference between the highest voltage cell and the lowest voltage cell is calculated by the highest voltage and the lowest voltage among the voltages collected by the battery management system (BMS), and is recorded as the N+1th capacity difference C N+1 .

[0074] S21: The battery management system (BMS) performs the following operations according to the Nth time interval T: N , Nth capacity difference C N and the N+1 capacity difference C N+1 Calculate the leakage current I of the battery cell N , that is, corresponding to Figure 1 Specifically,

[0075] Battery Management System (BMS) according to I N =(C N+1 -CN ) / T N calculating the leakage current I of the battery cell N , wherein T N is the Nth time interval, the Nth time interval T N is not a fixed time value, the Nth time interval T N is the time difference between the Nth time when the new energy vehicle is fully charged and the N+1th time when the new energy vehicle is fully charged, the time difference is recorded by the battery management system (BMS), and the specific value of the time difference depends on how long the vehicle owner waits to charge the new energy vehicle after the Nth time when the new energy vehicle is fully charged, in addition, C N is the Nth capacity difference, C N+1 is the N+1th capacity difference, I N is the leakage current of the battery cell in the Nth time interval T N .

[0076] S22: The battery management system (BMS) calculates the average voltage U N of the battery cell with the lowest voltage in the battery pack in the Nth time interval T N , that is, corresponding to S22 in Figure 1 . Specifically, the battery management system (BMS) calculates the average voltage U N of the battery cell with the lowest voltage in the battery pack in the Nth time interval T N by dividing the sum of the voltages of the battery cell with the lowest voltage in the battery pack collected in the Nth time interval T N by the total number of times the voltage of the battery cell is collected by the battery management system (BMS) in the Nth time interval T N .

[0077] S23: The battery management system (BMS) calculates the short-circuit resistance R N of the battery cell with the lowest voltage in the battery pack, that is, corresponding to S23 in Figure 1 . Specifically, the battery management system (BMS) calculates the short-circuit resistance R N of the battery cell with the lowest voltage in the battery pack according to R N = U N / I N , wherein I N is the leakage current of the battery cell in the Nth time interval T N , U N is the average voltage of the battery cell with the lowest voltage in the battery pack in the Nth time interval T N , and R N is the short-circuit resistance of the battery cell with the lowest voltage in the battery pack in the Nth time interval T N .

[0078] S24: the battery management system (BMS) judges whether the first condition, the second condition and the fourth condition are all met, if yes, S17 is entered, if not, S25 is entered, that is, corresponding to S24 in the embodiment. Figure 1 The first condition is that the state of charge (SOC) of the battery is greater than a preset threshold, the second condition is that the voltage abrupt drop speed of the lowest voltage cell in the battery pack is greater than a preset voltage abrupt drop speed and the duration is greater than a preset time, and the fourth condition is that the value of |R2-R1| / R1 is greater than 0.5. N -R N-1 | / R N-1 .

[0079] S25: N=N+1 is taken, that is, corresponding to S25 in the embodiment. Figure 1 After N=N+1 is taken, the N+1th charging of the new energy vehicle becomes the N+2th charging of the new energy vehicle, and other parameters with N are also taken in this way.

[0080] S26: S18 is entered, that is, corresponding to S26 in the embodiment. ​

[0081] In the embodiment, N is a positive integer greater than 2, and N starts from 3.

[0082] In the embodiment, the preset threshold is 15%, the preset voltage abrupt drop speed is 0.2V / S, and the preset time is 1 second.

[0083] In addition, the application also provides a new energy vehicle, which adopts the above-mentioned battery thermal runaway early warning method for battery thermal runaway early warning.

[0084] Effects of the embodiment

[0085] The battery management system (BMS) judges whether the first condition, the second condition and the third condition are all met, if yes, the battery management system (BMS) pushes the early warning information of the battery thermal runaway to the enterprise platform and the user, so as to subsequently carry out safety maintenance on the battery, that is, the early warning can be carried out before the battery thermal runaway, thereby more time windows can be obtained for the user, property loss and personnel casualty can be avoided, and the safety of the vehicle is improved; in addition, the misjudgment is better avoided, and the accuracy of the early warning before the battery thermal runaway is improved. The first condition is that the state of charge (SOC) of the battery is greater than a preset threshold, the second condition is that the voltage abrupt drop speed of the lowest voltage cell in the battery pack is greater than a preset voltage abrupt drop speed and the duration is greater than a preset time, and the third condition is that the value of |R2-R1| / R1 is greater than 0.5.

[0086] ​The battery management system (BMS) judges whether the first condition, the second condition and the fourth condition are all satisfied, if yes, the battery management system (BMS) pushes the early warning information of the battery thermal runaway to the enterprise platform and the user, so as to carry out subsequent safety maintenance on the battery, that is, early warning can be carried out before the battery thermal runaway, and then more time windows can be obtained for the user, property loss and personnel casualty can be avoided, and the safety of the whole vehicle is improved; in addition, false judgment is better avoided, and the accuracy of early warning before the battery thermal runaway is improved. The first condition is that the state of charge (SOC) of the battery is greater than a preset threshold, the second condition is that the voltage abrupt drop speed of the lowest voltage cell in the battery pack is greater than a preset voltage abrupt drop speed and the duration is greater than a preset time, and the fourth condition is that the value of R N -R N-1 | / R N-1 is greater than 0.5.

[0087] In addition, through detection of the leakage current between two adjacent charging of the new energy vehicle, the present application can solve the problem that the early internal short circuit phenomenon is not obvious, and also takes into account the detection of the middle and late stages.

[0088] The above is an exemplary description of the present application in combination with the drawings. Obviously, the specific implementation of the present application is not limited by the above method. As long as various non-essential improvements are made by adopting the method concept and technical scheme of the present application; or the above concept and technical scheme of the present application are directly applied to other occasions without improvement, they are all within the protection scope of the present application.

Claims

1. A battery thermal runaway early warning method, characterized by: The method comprises the following steps: S1: Charging the new energy vehicle for the first time; S2: Continuously collect the voltage of the battery cell through the battery management system; S3: When the new energy vehicle is fully charged for the first time, the battery management system records the maximum voltage and the minimum voltage of the battery cell, and calculates the first capacity difference C1 based on the recorded maximum voltage and minimum voltage of the battery cell; S4: charging the new energy vehicle for the second time; S5: Continuously collect the voltage of the battery cell through the battery management system; S6: When the new energy vehicle is fully charged for the second time, the battery management system records the maximum voltage and the minimum voltage of the battery cell, and calculates the second capacity difference C2 based on the recorded maximum voltage and the minimum voltage of the battery cell; S7: The battery management system calculates the leakage current I1 of the battery cell according to the first time interval T1, the first capacity difference C1 and the second capacity difference C2; S8: The battery management system calculates the average voltage U1 of the lowest voltage cell in the battery pack within the first time interval T1; S9: The battery management system calculates the short-circuit resistance R1 of the lowest voltage cell in the battery pack; S10: Charging the new energy vehicle for the third time; S11: Continuously collect the voltage of the battery cell through the battery management system; S12: When the new energy vehicle is fully charged for the third time, the battery management system records the highest voltage and the lowest voltage of the battery cell, and calculates a third capacity difference C3 based on the recorded highest voltage and the lowest voltage of the battery cell; S13: The battery management system calculates the leakage current I2 of the battery cell according to the second time interval T2, the second capacity difference C2, and the third capacity difference C3; S14: The battery management system calculates the average voltage U2 of the lowest voltage cell in the battery pack within the second time interval T2; S15: The battery management system calculates the short-circuit resistance R2 of the lowest voltage cell in the battery pack; S16: The battery management system determines whether the first condition, the second condition and the third condition are all satisfied. If so, the process proceeds to S17; if not, the process proceeds to S18. The first condition is that the state of charge of the battery is greater than a preset threshold; The second condition is that the voltage drop rate of the lowest voltage cell in the battery pack is greater than a preset voltage drop rate and lasts for a time greater than a preset time; The third condition is that the value of |R2 -R1| / R1 is greater than 0.5; S17: The battery management system issues a battery thermal runaway warning, and after the warning is over, it enters S26; S18: charging the new energy vehicle for the N+1th time; S19: Continuously collect the voltage of the battery cell through the battery management system; S20: When the new energy vehicle is fully charged for the N+1th time, the battery management system records the highest and lowest voltages of the battery cell, and calculates the N+1th capacity difference C based on the recorded highest and lowest voltages of the battery cell. N ＋ 1 ; S21: The battery management system calculates the battery status according to the Nth time interval T. N , Nth capacity difference C N and N+1 capacity difference C N ＋ 1 Calculate the leakage current I of the battery cell N ; S22: The battery management system calculates the Nth time interval T N The average voltage U of the lowest voltage cell in the battery pack N ; S23: The battery management system calculates the short-circuit resistance R of the lowest voltage cell in the battery pack N ; S24: The battery management system determines whether the first condition, the second condition, and the fourth condition are all satisfied. If so, the process proceeds to S17; if not, the process proceeds to S25. The fourth condition is |R N -R N-1 | / R N-1 The value of is greater than 0.5; S25: Take N=N+1; N is a positive integer greater than 2, and N starts at 3; S26: Enter S18.

2. The battery thermal runaway warning method according to claim 1, characterized in that: The I1 = (C2 - C1) / T1, the I2 = (C3 - C2) / T2, the IN = (C N + 1 -CN) / T N , where T1 is the first time interval, T2 is the second time interval, and T N is the Nth time interval, C1 is the first capacity difference, C2 is the second capacity difference, C3 is the third capacity difference, C N is the Nth capacity difference, C N ＋ 1 is the N+1th capacity difference, I1 is the leakage current of the battery cell in the first time interval T1, I2 is the leakage current of the battery cell in the second time interval T2, I N is the Nth time interval T N Leakage current of the internal battery.

3. The battery thermal runaway warning method according to claim 2, characterized in that: The R1=U1 / I1, the R2=U2 / I2, the R N = U N / I N , where I1 is the leakage current of the cell in the first time interval T1, I2 is the leakage current of the cell in the second time interval T2, and I N is the Nth time interval T N The leakage current of the inner battery cell, U1 is the average voltage of the lowest voltage battery cell in the battery pack during the first time interval T1, U2 is the average voltage of the lowest voltage battery cell in the battery pack during the first time interval T2, U N is the Nth time interval T N The average voltage of the lowest voltage cell in the battery pack in the first time interval T1, R1 is the short-circuit resistance of the lowest voltage cell in the battery pack in the first time interval T1, R2 is the short-circuit resistance of the lowest voltage cell in the battery pack in the second time interval T2, R N is the Nth time interval T N The short-circuit resistance of the lowest voltage cell in the battery pack.

4. The battery thermal runaway warning method according to claim 3, characterized in that: The first time interval T1 is the time difference between the first time the new energy vehicle is fully charged and the second time the new energy vehicle is fully charged. The second time interval T2 is the time difference between the second time the new energy vehicle is fully charged and the third time the new energy vehicle is fully charged. The Nth time interval T N It is the time difference between the Nth time of fully charging the new energy vehicle and the N+1th time of fully charging the new energy vehicle.

5. A new energy vehicle, characterized by: The new energy vehicle uses the battery thermal runaway warning method according to any one of claims 1 to 4 to provide battery thermal runaway warning.

Images