A SOC estimation method for a self-heating battery

Abstract

The present application relates to the field of battery technology, and provides a method for estimating the SOC of a self-heating battery, the method comprising: determining that the battery starts self-heating, obtaining a first current temperature and a current SOC of the battery; determining that the battery exits self-heating, obtaining a second current temperature of the battery; and determining an updated SOC based on the temperature difference between the second current temperature and the first current temperature, and a first preset value. The method for estimating the SOC of a self-heating battery provided in the present application can estimate the SOC of the battery after self-heating more accurately, which helps to improve the safety of battery use and the driving experience of the user.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a method for estimating the SOC of a self-heating battery. Background Art

[0002] Electric vehicles have made great progress in recent years, and battery thermal management, as one of the key technologies, is crucial to the safe and stable driving of electric vehicles. In related technologies, the battery achieves self-heating through high-frequency current, and its power consumption cannot be calculated by BMS. Moreover, the longer the self-heating time, the greater the estimation error of the battery's SOC, which poses a certain risk to the user's normal use. Summary of the invention

[0003] In view of this, an embodiment of the present application hopes to provide a method for estimating the SOC of a self-heating battery, which can improve the accuracy of estimating the SOC of the battery.

[0004] In order to achieve the above-mentioned purpose, the technical solution of the embodiment of the present application is implemented as follows:

[0005] The present application embodiment discloses a method for estimating the SOC of a self-heating battery, comprising:

[0006] Determine that the battery starts self-heating, and obtain a first current temperature and a current SOC of the battery;

[0007] Determine that the battery exits self-heating, and obtain a second current temperature of the battery;

[0008] An updated SOC is determined according to a temperature difference between the second current temperature and the first current temperature and a first preset value.

[0009] In one embodiment, determining to update the SOC according to the temperature difference between the second current temperature and the first current temperature and a first preset value includes:

[0010] When the temperature difference is less than the first preset value, the updated SOC is determined to be the current SOC.

[0011] In one embodiment, determining to update the SOC according to the temperature difference between the second current temperature and the first current temperature and a first preset value includes:

[0012] When the temperature difference is not less than the first preset value, the updated SOC is determined as a ratio of the current SOC minus the self-heating power consumption to the rated capacity of the battery.

[0013] In one embodiment, the method comprises:

[0014] Based on the current SOC, the first current temperature, and the second current temperature, a set correspondence table is queried to obtain the self-heating power consumption; the correspondence table includes at least one set of correspondence between the set power, the first set temperature, the second set temperature and the test power consumption.

[0015] In one embodiment, the method comprises:

[0016] For each of the set electric quantities in the set electric quantity set, each of the first set temperature in the first temperature set, and each of the second set temperature in the second temperature set, determining the test power consumption required to self-heat the test battery having the set electric quantity from the first set temperature to the second set temperature;

[0017] Adding the correspondence between the set power, the first set temperature, the second set temperature and the test power consumption to the correspondence table;

[0018] Determine that the current SOC is the same as the set power, the first current temperature is the same as the first set temperature, the second current temperature is the same as the second set temperature, and determine that the self-heating power consumption is equal to the test power consumption.

[0019] In one embodiment, the method comprises:

[0020] Discharging the test battery to a cut-off voltage at a set rate at a third set temperature, then charging the test battery to the set power at the set rate, and obtaining the charged power;

[0021] Adjusting the real-time temperature of the test battery to the first set temperature, and the test battery self-heating to the second set temperature;

[0022] adjusting the real-time temperature of the test battery to the third set temperature;

[0023] Discharging the test battery again to the cut-off voltage at the set rate at the third set temperature, and obtaining the amount of electricity discharged again;

[0024] The test power consumption is obtained according to the discharged power and the charged power.

[0025] In one embodiment, the set rate is 1 / 6 to 1 / 3 of the rated capacity of the test battery.

[0026] In one embodiment, the third set temperature is between 25°C and 35°C.

[0027] In one embodiment, after adjusting the real-time temperature of the test battery to the third set temperature, the method includes:

[0028] The test battery is kept at rest for a time greater than a second preset value.

[0029] In one embodiment, the method comprises:

[0030] Discharging the test battery to a cut-off voltage at a set rate at a third set temperature, and then charging the test battery to the set power at the set rate to obtain charged energy;

[0031] The test battery is discharged again to the cut-off voltage at the set rate at the third set temperature to obtain discharged energy.

[0032] In one embodiment, the method comprises:

[0033] The charging energy and the discharging energy are acquired through a current sensor, a voltage sensor and a power analyzer.

[0034] In one embodiment, the method comprises:

[0035] The real-time temperature of the test battery is adjusted to the first set temperature, and the test battery is self-heated to the second set temperature to obtain the self-heating time of the test battery.

[0036] In one embodiment, the method comprises:

[0037] The charged amount and the discharged amount are obtained through a current sensor and a power analyzer.

[0038] In one embodiment, the range of the first temperature set is between -30°C and 0°C, and the range of the second temperature set is between -25°C and 25°C.

[0039] The embodiment of the present application discloses a method for estimating the SOC of a self-heating battery. The method obtains a first current temperature and a current SOC of the battery after self-heating starts, and a second current temperature after self-heating ends, compares the temperature difference between the second current temperature and the first current temperature with a first preset value, and then determines the updated SOC of the battery after self-heating. This method can more accurately estimate the SOC of the battery after self-heating, which helps to improve the safety of battery use and the driving experience of the user. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A schematic flow chart of a method for estimating the SOC of a self-heating battery provided in an embodiment of the present application;

[0041] Figure 2 A test principle diagram of a test device provided in another embodiment of the present application.

[0042] Description of Reference Numerals

[0043] Test device 1; charging and discharging equipment 11; electric drive system 12; current sensor 13; voltage sensor 14; power analyzer 15; constant temperature box 16; water cooling unit 17; test battery 2. DETAILED DESCRIPTION

[0044] It should be noted that, in the absence of conflict, the embodiments and technical features in the embodiments of the present application can be combined with each other, and the detailed description in the specific implementation method should be understood as an explanation of the purpose of the present application and should not be regarded as an improper limitation on the present application.

[0045] The present application is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The descriptions of "first", "second", etc. in the embodiments of the present application are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly including at least one feature. In the description of the embodiments of the present application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically limited.

[0046] The present application embodiment provides a method for estimating the SOC of a self-heating battery. Figure 1 , estimation methods include:

[0047] S1. Determine that the battery starts self-heating, and obtain a first current temperature and a current SOC of the battery.

[0048] Exemplarily, a first current temperature of the battery may be collected by a temperature sensor, and a current SOC (State of Charge, remaining power) and the first current temperature may be latched.

[0049] In some embodiments, the first current temperature may be an average temperature, that is, the first current temperature may be an arithmetic average of temperatures at multiple locations on the battery surface.

[0050] S2. determining that the battery exits self-heating, and obtaining a second current temperature of the battery;

[0051] In some embodiments, the second current temperature may be an average temperature, that is, the second current temperature may be an arithmetic average of temperatures at multiple locations on the battery surface.

[0052] S3. Determine to update the SOC according to the temperature difference between the second current temperature and the first current temperature and a first preset value.

[0053] It should be noted that during the self-heating process of the battery, such as the battery is in the process of high-frequency current self-heating, for the high-frequency current changing from several hundred Hz (Hz) to several thousand Hz (Hz), since the current operating frequency of the BMS is around 10Hz to 100Hz, the current of the battery during the self-heating process cannot be accurately obtained through the BMS. In other words, the SOC after heating cannot be accurately obtained through traditional methods such as the ampere-hour integration method or the Kalman filter method. For example, the SOC of the battery before self-heating is 70%. After self-heating, due to battery losses such as power consumption, the actual SOC of the battery will be less than 70%, but the BMS cannot perform detection during the self-heating process, resulting in the obtained SOC still being 70%, resulting in a "false label" situation, and this "false label" will affect the safety of battery use and the user's driving experience.

[0054] It should be noted that the Kalman filter algorithm consists of four parts: initialization, calculation, filtering, and loop iteration. Each SOC calculation must be adjusted and corrected by the actual voltage, current, and filter gain value. When the SOC error is large, the filter gain coefficient is large, and the correction effect of the measured value on the SOC is strong; conversely, the correction effect of the measured value on the SOC is weak. In the initial stage of the algorithm, the initial SOC value is randomly input at K=0, and then the SOC value at K+1 is estimated and compared with the SOC obtained by the actual detection to obtain the estimated error. The error is corrected by the Kalman gain to obtain the corrected K+1 SOC estimate. Through this estimate, the K+2 SOC value is continued to be estimated. The ampere-hour integration method can update the battery SOC in real time through the SOC value of the previous moment, the current sampling value of the current moment, and the rated capacity of the battery cell.

[0055] This embodiment obtains the first current temperature and current SOC of the battery after self-heating starts, and the second current temperature after self-heating ends, compares the temperature difference between the second current temperature and the first current temperature with the first preset value, and then determines the updated SOC of the battery after self-heating. This can more accurately estimate the SOC of the battery after self-heating, which helps to improve the battery's safety and the user's driving experience.

[0056] In one embodiment, S3, determining to update the SOC according to the temperature difference between the second current temperature and the first current temperature and a first preset value, includes:

[0057] S31. When the temperature difference is less than the first preset value, determine that the updated SOC is the current SOC.

[0058] In this way, when the temperature difference between the second current temperature and the first current temperature is less than the first preset value, the SOC of the battery is not updated, that is, the loss of the battery during the self-heating process, such as power consumption, can be ignored, and the current SOC at the start of self-heating is used as the SOC after the battery self-heating is completed. It can be understood that the value of the first preset value here depends on the acquisition accuracy of the battery self-heating starting temperature. For example, if the acquisition is from 5°C to 8°C, then the accuracy of the first preset value is 3. When the temperature difference between the second current temperature and the first current temperature is less than 3, the loss of the battery during this self-heating process, such as power consumption, is ignored.

[0059] In one embodiment, after determining to update the SOC, the estimation method includes:

[0060] S4. Determine the real-time SOC based on the ampere-hour integration method or the Kalman filter algorithm.

[0061] In this way, the updated SOC can be updated to the real-time SOC of the electric vehicle through the BMS according to the ampere-hour integration method or the Kalman filter algorithm, thereby improving the safety of battery use.

[0062] In one embodiment, the current SOC is determined according to an ampere-hour integration method or a Kalman filter algorithm.

[0063] Exemplarily, when the battery is not detected to be in a self-heating state, the current SOC can be obtained according to the ampere-hour integration method or the Kalman filter algorithm and the current SOC can be obtained and the SOC of the battery can be updated in real time through the BMS.

[0064] In one embodiment, determining to update the SOC according to the temperature difference between the second current temperature and the first current temperature and a first preset value includes:

[0065] S31', when the temperature difference is not less than the first preset value, determining the updated SOC as the ratio of the current SOC minus the self-heating power consumption to the rated capacity of the battery.

[0066] In this way, when the temperature difference between the second current temperature and the first current temperature is greater than or equal to the first preset value, the BMS uses the ratio of the current SOC minus the self-heating power consumption to the rated capacity of the battery as the updated SOC.

[0067] In one embodiment, the method includes: S31'1, based on the current SOC, the first current temperature, and the second current temperature, query the set correspondence table to obtain the self-heating power consumption; the correspondence table includes at least one set of correspondence between the set power, the first set temperature, the second set temperature and the test power consumption.

[0068] In this way, by establishing a correspondence table between the set power, the first set temperature, the second set temperature and the test power consumption, after detecting the current SOC, the first current temperature and the second current temperature, the self-heating power consumption of the battery during the self-heating process can be obtained in time by querying the correspondence table, and then the updated SOC is obtained through the self-heating power consumption, with short acquisition time and high efficiency.

[0069] In one embodiment, the method includes: S31'11, for each of the set power in the set power set, each of the first set temperature in the first temperature set, and each of the second set temperature in the second temperature set, determining the test power consumption required to self-heat the test battery having the set power from the first set temperature to the second set temperature;

[0070] Adding the correspondence between the set power, the first set temperature, the second set temperature and the test power consumption to the correspondence table;

[0071] Determine that the current SOC is the same as the set power, the first current temperature is the same as the first set temperature, the second current temperature is the same as the second set temperature, and determine that the self-heating power consumption is equal to the test power consumption.

[0072] Exemplarily, the set power set may be a set of the first vertical row values ​​in the correspondence table, so that the first value corresponding to each horizontal row in the correspondence table is the set power; the first temperature set may be the second vertical row in the correspondence table, and the second value corresponding to each horizontal row in the correspondence table is the first set temperature; the second temperature set may be the third vertical row in the correspondence table, and the third value corresponding to each horizontal row in the correspondence table is the second set temperature; the fourth vertical row in the correspondence table may be a test power consumption set, that is, the fourth value of each horizontal row in the correspondence table is the test power consumption required for the test battery 2 to self-heat from the first set temperature to the second set temperature based on the set power. In this way, in the actual self-heating process, the current SOC of the battery, the first current temperature when the self-heating starts, and the second current temperature after the self-heating ends can be obtained, and the corresponding relationship table can be queried to find the horizontal row in which the current SOC is the same as the set power, the first current temperature and the first set temperature, and the second current temperature and the second set temperature. Then the corresponding fourth value (test power consumption) in the horizontal row is the self-heating power consumption of the battery, and then the updated SOC is calculated by the BMS according to the self-heating power consumption and the SOC of the battery is updated in real time.

[0073] In one embodiment, the range of the first temperature set is between -30°C and 0°C, and the range of the second temperature set is between -25°C and 25°C. In this way, the sample capacity of the corresponding relationship table can be expanded, so that the self-heating power consumption query has high accuracy; of course, the range of the first temperature set and the second temperature set can also be adjusted according to the threshold of the thermal management of the whole vehicle.

[0074] It should be noted that when the set power is lower than 30%, the discharge of the test battery 2 is likely to cause damage to the battery cell, so it is forbidden to turn on the high-frequency current self-heating.

[0075] In one embodiment, the method includes: S31-111, discharging the test battery to a cut-off voltage at a set rate at a third set temperature, then charging the test battery to the set power at the set rate, and obtaining the charged power;

[0076] It should be noted that the test battery 2 is discharged to the cut-off voltage, that is, the SOC of the test battery 2 is discharged to 0%, so as to eliminate the interference of the test battery 2 with the charge before the test on the test, and the measurement accuracy is high.

[0077] S31'112, adjusting the real-time temperature of the test battery to the first set temperature, and the test battery is heated to the second set temperature by self-heating;

[0078] S31'113, adjusting the real-time temperature of the test battery to the third set temperature;

[0079] S31′114, discharging the test battery again to the cut-off voltage at the set rate at the third set temperature, and obtaining the amount of electricity discharged again;

[0080] S31'115, obtaining the test power consumption according to the discharged power and the charged power.

[0081] In this way, the difference between the discharged power and the charged power is calculated as the test power consumption of the test battery 2 during the self-heating process, which is simple to calculate and has high accuracy.

[0082] It should be noted that the third set temperature simulates the actual temperature of the battery when the electric vehicle is running.

[0083] In one embodiment, the third set temperature is between 25° C. and 35° C. Exemplarily, the third set temperature may be 25° C., so that the actual temperature of the battery under the operation of the electric vehicle can be simulated, so that the charge and discharge power obtained at the third temperature are more realistic, close to the actual application scenario, and have high accuracy.

[0084] In one embodiment, after S31-113, adjusting the real-time temperature of the test battery to the third set temperature, the method includes:

[0085] S31'116, maintaining the test battery at rest for a time greater than a second preset value.

[0086] Exemplarily, the second preset value may be 3 hours (h), so that the acquisition accuracy of the discharged electricity can be higher. It is understandable that during the self-heating process and the temperature adjustment process, the polarization voltage of the test battery 2 will undergo a large change, and this change will affect the subsequent measurement of the discharged electricity, resulting in an inaccurate measured value of the discharged electricity. By leaving the test battery 2 to stand for 3 hours, the influence of the polarization effect on the discharged electricity can be reduced, and the measurement accuracy is high.

[0087] In one embodiment, S31′111, discharging the test battery to a cutoff voltage at a set rate at a third set temperature, and then charging the test battery to the set power at the set rate, and obtaining the charged power, comprises:

[0088] S31'117, maintaining the test battery at rest for a time greater than a second preset value.

[0089] Exemplarily, the second preset value may be 3 hours (h), so that the accuracy of obtaining the charged power can be improved.

[0090] In one embodiment, the setting rate is 1 / 6 to 1 / 3 of the rated capacity of the test battery 2. Exemplarily, the setting rate may be 1 / 3 of the rated capacity of the test battery 2, so that the test battery 2 can be charged and discharged at a faster and safer setting rate, thereby reducing the test time and increasing the service life of the test battery 2.

[0091] In one embodiment, the method includes: S31'111', discharging the test battery to a cut-off voltage at a set rate at a third set temperature, and then charging the test battery to the set power at the set rate to obtain charged energy;

[0092] S31′114′, discharging the test battery again to the cut-off voltage at the set rate at the third set temperature to obtain discharged energy.

[0093] In this way, by acquiring the charging energy and the discharging energy of the test battery 2 , the subsequent calculation of the service life cycle of the battery can be participated in.

[0094] In one embodiment, the method includes: adjusting the real-time temperature of the test battery to the first set temperature, and the test battery self-heats to the second set temperature to obtain the self-heating time of the test battery.

[0095] In this way, by obtaining the self-heating time of the test battery 2, a correspondence table can be set, and the set correspondence table can be queried based on the current SOC, the first current temperature, and the self-heating time to obtain the self-heating power consumption; the correspondence table includes at least one set of correspondence between the set power, the first set temperature, the test self-heating time and the test power consumption.

[0096] In some embodiments, for each of the set power in the set power set, each of the first set temperature in the first temperature set, and each of the test self-heating time in the test self-heating time set, determine the test power consumption required to self-heat the test battery 2 with the set power from the first set temperature to the test self-heating time;

[0097] Adding the correspondence between the set power, the first set temperature, the test self-heating time and the test power consumption to the correspondence table;

[0098] Determine that the current SOC is the same as the set power, the first current temperature is the same as the first set temperature, the self-heating time is the same as the test self-heating time, and determine that the self-heating power consumption is equal to the test power consumption.

[0099] Exemplarily, the set power set can be a set of the first vertical row values ​​in the correspondence table, so that the first value corresponding to each horizontal row in the correspondence table is the set power; the first temperature set can be the second vertical row in the correspondence table, and the second value corresponding to each horizontal row in the correspondence table is the first set temperature; the test self-heating time set can be the third vertical row in the correspondence table, and the third value corresponding to each horizontal row in the correspondence table is the test self-heating time; the fourth vertical row in the correspondence table can be the test power consumption set, that is, the fourth value of each horizontal row in the correspondence table is the test power consumption required for the test battery 2 to self-heat from the first set temperature to the test self-heating time based on the set power. In this way, in the actual self-heating process, the current SOC of the battery, the first current temperature when self-heating starts, and the self-heating time after self-heating is completed can be obtained, and the correspondence table can be queried to find the horizontal row in which the current SOC and the set power, the first current temperature and the first set temperature, as well as the self-heating time and the test self-heating time are the same. Then the corresponding fourth value in the horizontal row (test power consumption) is the self-heating power consumption of the battery. Then, the updated SOC is calculated by the BMS based on the self-heating power consumption and the battery SOC is updated in real time.

[0100] In one embodiment, the method includes: obtaining the charged amount and the discharged amount by using a current sensor and a power analyzer.

[0101] Exemplarily, the current sensor 13 and the power analyzer 15 can be connected by a wire. The current sensor 13 can collect the bus current of the test battery 2 within a fixed time (charging time and discharging time), and then transmit it to the power analyzer 15. The power analyzer 15 accumulates the collected bus current within a fixed time, that is, the charged power and discharged power can be obtained.

[0102] In one embodiment, the method includes: acquiring the charging energy and the discharging energy through a current sensor, a voltage sensor and a power analyzer.

[0103] Exemplarily, the current sensor 13 and the current sensor 13 can be connected to the power analyzer 15 respectively through wires, and the current sensor 13 and the voltage sensor 14 can respectively collect the bus voltage and bus current of the test battery 2 within a fixed time (charging time and discharging time), and then transmit them to the power analyzer 15. The power analyzer 15 calculates the product of the collected bus voltage and bus current to obtain power, and can accumulate the calculated power within a fixed time, that is, the charged energy and released energy can be obtained.

[0104] Another embodiment of the present application provides a testing device, which can be used to obtain the test power consumption corresponding to the set current machine, the first temperature set and the second temperature set of the test battery 2. Figure 2 The test device 1 includes a charging and discharging device 11, an electric drive system 12, a current sensor 13, a voltage sensor 14, a power analyzer 15, a thermostat 16 and a water cooling unit 17. The charging and discharging device 11 can charge and discharge the test battery 2 at a set rate. The electric drive system 12 is connected to the test battery 2 for self-heating the test battery 2. The current sensor 13 is used to collect the bus. The voltage sensor 14 is used to collect the bus voltage. The power analyzer 15 is connected to the current sensor 13 and the voltage sensor 14 respectively, and calculates the charged and discharged electricity according to the bus current, and calculates the charged energy and discharged energy according to the bus current and the bus voltage. The electric drive system 12, the current sensor 13 and the voltage sensor 14 are all located in the thermostat 16, which is used to adjust the temperature of the test battery 2. The water cooling unit 17 is connected to the electric drive system 12 and the test battery 2 through the water channel respectively, and is used to cool the test current to prevent the test battery 2 from overheating.

[0105] The test device 1 provided in the embodiment of the present application can effectively obtain the test power consumption of the test battery 2 during the self-heating process and establish a corresponding relationship table to facilitate the subsequent query of the self-heating power consumption of the battery in the actual process, and facilitate accurate estimation of the updated SOC of the battery after self-heating.

[0106] The above is only a preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. All modifications, equivalent substitutions, improvements, etc. within the spirit and principles of the present application are included in the protection scope of the present application.

Claims

1. A method for estimating the SOC of a self-heating battery, characterized in that: include: Determine that the battery starts self-heating, and obtain a first current temperature and a current SOC of the battery; Determine that the battery exits self-heating, and obtain a second current temperature of the battery; Determine to update the SOC according to a temperature difference between the second current temperature and the first current temperature and a first preset value; When the temperature difference is not less than the first preset value, based on the current SOC, the first current temperature, and the second current temperature, a set corresponding relationship table is queried to obtain the self-heating power consumption, and the updated SOC is determined to be the ratio of the current SOC minus the self-heating power consumption to the rated capacity of the battery; The correspondence table includes at least one set of correspondences between a set power, a first set temperature, a second set temperature and a test power consumption, and for each set power in the set power set, each first set temperature in the first temperature set and each second set temperature in the second temperature set, determines the test power consumption required to self-heat the test battery having the set power from the first set temperature to the second set temperature; Discharging the test battery to a cutoff voltage at a set rate at a third set temperature, then charging the test battery to the set power at the set rate, and obtaining the charged power; adjusting the real-time temperature of the test battery to the first set temperature, and the test battery self-heating to the second set temperature; adjusting the real-time temperature of the test battery to the third set temperature; discharging the test battery again to the cutoff voltage at the set rate at the third set temperature, and obtaining the discharged power; obtaining the test power consumption according to the discharged power and the charged power; Adding the correspondence between the set power, the first set temperature, the second set temperature and the test power consumption to the correspondence table; Determine that the current SOC is the same as the set power, the first current temperature is the same as the first set temperature, the second current temperature is the same as the second set temperature, and determine that the self-heating power consumption is equal to the test power consumption.

2. The SOC estimation method according to claim 1, characterized in that: Determining to update the SOC according to the temperature difference between the second current temperature and the first current temperature and a first preset value includes: When the temperature difference is less than the first preset value, the updated SOC is determined to be the current SOC.

3. The SOC estimation method according to claim 1, characterized in that: The set rate is 1 / 6 to 1 / 3 of the rated capacity of the test battery.

4. The SOC estimation method according to claim 1, characterized in that: The third set temperature is between 25°C and 35°C.

5. The SOC estimation method according to claim 1, characterized in that: After adjusting the real-time temperature of the test battery to the third set temperature, the method includes: The test battery is kept at rest for a time greater than a second preset value.

6. The SOC estimation method according to claim 1, characterized in that: The method comprises: Discharging the test battery to a cut-off voltage at a set rate at a third set temperature, and then charging the test battery to the set power at the set rate to obtain charged energy; The test battery is discharged again to the cut-off voltage at the set rate at the third set temperature to obtain discharged energy.

7. The SOC estimation method according to claim 6, characterized in that: The method comprises: The charging energy and the discharging energy are acquired through a current sensor, a voltage sensor and a power analyzer.

8. The SOC estimation method according to claim 1, characterized in that: The method comprises: The real-time temperature of the test battery is adjusted to the first set temperature, and the test battery is self-heated to the second set temperature to obtain the self-heating time of the test battery.

9. The SOC estimation method according to claim 1, characterized in that: The method comprises: The charged amount and the discharged amount are obtained through a current sensor and a power analyzer.

10. The SOC estimation method according to claim 1, characterized in that: The first temperature set ranges from -30°C to 0°C, and the second temperature set ranges from -25°C to 25°C.

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