Test method, device and equipment for improving the accuracy of power battery state of charge estimation

Abstract

This application discloses a test method, device, and equipment for improving the accuracy of power battery state-of-charge estimation, relating to the field of power battery technology. The method comprises: discharging the power battery to a first state-of-charge using a constant current, and then charging it to a second state-of-charge using a stepwise constant current; discharging the rested power battery to a third state-of-charge under variable temperature conditions; performing a charge-discharge cycle test on the power battery based on the third and fourth states of charge; discharging the power battery to the first state-of-charge; and determining a relative state-of-charge error based on the state-of-charge ampere-hour integral value obtained by the charging and discharging device and the state-of-charge (BMS) value obtained by the power battery management system, and determining a state-of-charge evaluation result to improve the state-of-charge estimation accuracy of the power battery management system. The relative state-of-charge error is determined using the ampere-hour integral method of the charging device, and SOC correction is performed in real time to improve the state-of-charge estimation accuracy of the power battery management system.

Description

Technical Field

[0001] The present application relates to the field of power battery technology, and in particular to a test method, device, and equipment for improving the accuracy of power battery state of charge estimation. Background Art

[0002] The battery management system (BMS) ensures the safe and efficient operation of batteries and is crucial to improving the overall performance, safety, and cycle life of electric vehicles. The BMS's estimation of the battery's state of charge (SOC) is a crucial component of battery management. It provides drivers or operators with accurate battery usage information, understanding the battery's remaining charge, and providing basic data for battery charge and discharge management, thermal management, and health management. Due to the complex structure of batteries and the numerous factors that influence their SOC, there is currently limited research on test methods for SOC estimation in battery management systems. The calculation methods for SOC estimation in battery management systems are complex and lack precision.

[0003] The above content is only used to assist in understanding the technical solution of the present invention and does not constitute an admission that the above content is prior art. Summary of the Invention

[0004] The main purpose of this application is to provide a test method, device and equipment for improving the accuracy of power battery state of charge estimation, aiming to solve the technical problems of complex calculation methods and insufficient accuracy of power battery management system state of charge estimation in the existing technology.

[0005] To achieve the above objectives, the present application provides a test method for improving the accuracy of power battery state of charge estimation, which is applied to a test system for improving the accuracy of power battery state of charge estimation. The test system for improving the accuracy of power battery state of charge estimation includes at least a variable temperature box, a power battery management system, and a charging and discharging device. The power battery is placed in the variable temperature box, and the power battery management system and the charging and discharging device are respectively connected to the power battery. The charging and discharging device is used to perform charge and discharge tests on the power battery and record the ampere-hour integral value of the power battery state of charge during the charge and discharge tests. The power battery management system is used to obtain the state of charge (BMS) value of the power battery during the charge and discharge tests. The test method for improving the accuracy of power battery state of charge estimation includes:

[0006] After the variable temperature box is set to the constant temperature mode and the temperature is adjusted to room temperature, the power battery is discharged at a constant current to the first state of charge, and then charged at a stepwise constant current to the second state of charge to complete full discharge and full charge;

[0007] The variable temperature box is set to the temperature dynamic cycle mode to perform a temperature cycle test, and the power battery that has been left at rest is discharged to the third state of charge;

[0008] Based on the third state of charge and the fourth state of charge, performing a charge and discharge cycle test on the power battery under a preset cycle condition;

[0009] After the charge and discharge cycle test is completed, the power battery is discharged to the first state of charge to complete full discharge;

[0010] Determine the relative error of the state of charge based on the ampere-hour integral value of the state of charge of the charging and discharging equipment during the charge and discharge test and the state of charge BMS value obtained by the power battery management system;

[0011] Based on the relative error of the state of charge, the state of charge evaluation result is determined to improve the state of charge estimation accuracy of the power battery management system.

[0012] In one embodiment, after the variable temperature box is set to a constant temperature mode and the temperature is adjusted to room temperature, the steps of discharging the power battery at a constant current to a first state of charge and charging the power battery at a stepwise constant current to a second state of charge to complete full discharge and full charge include:

[0013] After the variable temperature box is set to a constant temperature mode and the temperature is adjusted to room temperature, the power battery is discharged at a constant current to a first state of charge based on a first preset discharge rate to complete full discharge;

[0014] After the full discharge is completed, the power battery is charged to the second state of charge based on the preset step current to complete the full charge.

[0015] In one embodiment, the variable temperature box is set to a temperature dynamic cycle mode to perform a temperature cycle test, and the step of discharging the power battery after being left at rest to the third state of charge includes:

[0016] Setting the variable temperature box to a temperature dynamic cycle mode, performing a temperature cycle test, and performing a rest treatment on the power battery based on a first rest time;

[0017] After the resting is completed, the power battery in the second state of charge is discharged to a third state of charge based on a second preset discharge rate.

[0018] In one embodiment, based on the third state of charge and the fourth state of charge, the step of performing a charge-discharge cycle test on the power battery under a preset cycle condition includes:

[0019] Under the preset cycle condition, discharging the power battery to a fourth state of charge based on a third preset discharge rate, and performing a rest treatment on the power battery based on a second rest time;

[0020] charging the power battery to a third state of charge based on a fast charging strategy, and performing a rest process on the power battery based on a third rest time;

[0021] Update the number of cycles and repeat the above steps until the number of cycles meets the preset number of cycles.

[0022] In one embodiment, after the charge-discharge cycle test is completed, the step of discharging the power battery to the first state of charge to complete full discharge includes:

[0023] After the charge-discharge cycle test is completed, discharging the power battery to a discharge cut-off voltage based on a fourth preset discharge rate;

[0024] After the variable temperature box is set to a constant temperature mode and the temperature is adjusted to room temperature, the power battery is subjected to a rest treatment based on a fourth rest time;

[0025] After the resting is completed, the power battery is discharged to the first state of charge based on the fifth preset discharge rate to complete full discharge.

[0026] In one embodiment, the step of determining the relative error of the state of charge based on the ampere-hour integral value of the state of charge of the charging and discharging device during the charge and discharge test and the state of charge BMS value obtained by the power battery management system includes:

[0027] Obtain temperature correction factor, rate correction factor, and charge and discharge current data, charge and discharge time data, and state of charge data recorded by the charge and discharge equipment during the charge and discharge test;

[0028] Obtaining a first correspondence between a temperature correction factor, a rate correction factor, charge and discharge current data, charge and discharge time data, state of charge data, and a battery rated capacity and a state of charge ampere-hour integral value;

[0029] Obtaining a state-of-charge ampere-hour integral value based on the temperature correction factor, the rate correction factor, the charge and discharge current data, the charge and discharge time data, the state-of-charge data, the battery rated capacity, and the first corresponding relationship;

[0030] The state of charge (BMS) value obtained by the power battery management system is obtained, and the difference between the state of charge ampere-hour integral value and the state of charge BMS value is used as the state of charge relative error.

[0031] In one embodiment, the test method for improving the accuracy of power battery state of charge estimation further includes:

[0032] Obtaining a second correspondence between battery temperature data, the temperature of the variable temperature box, a battery operating temperature threshold, a battery characteristic correction parameter, and a temperature correction factor;

[0033] Obtaining a temperature correction factor based on battery temperature data, the temperature of the variable temperature box, a battery operating temperature threshold, a battery characteristic correction parameter, and a second corresponding relationship;

[0034] Obtain battery temperature data, temperature of the variable temperature box, battery operating temperature threshold, charge and discharge current data, battery rated capacity, battery peak charge and discharge current, battery temperature correction coefficient, ambient temperature correction coefficient, and the third correspondence between the charge and discharge current correction coefficient and the rate correction factor;

[0035] The rate correction factor is obtained based on the battery temperature data, the temperature of the variable temperature box, the battery operating temperature threshold, the charge and discharge current data, the battery rated capacity, the battery peak charge and discharge current, the battery temperature correction coefficient, the ambient temperature correction coefficient, the charge and discharge current correction coefficient and the third corresponding relationship.

[0036] In one embodiment, the state of charge relative error includes the state of charge relative error of the charge-discharge cycle test and the state of charge relative error of the overall charge-discharge test;

[0037] The steps of determining a state of charge evaluation result based on the state of charge relative error to improve the state of charge estimation accuracy of the power battery management system include:

[0038] When the relative error of the state of charge of the charge-discharge cycle test is greater than a preset error threshold, determining that the state of charge evaluation result of the charge-discharge cycle test does not meet the accuracy requirement, and correcting the state of charge of the power battery management system to improve the state of charge estimation accuracy of the power battery management system;

[0039] When the relative error of the state of charge of the overall charge and discharge test is greater than the preset error threshold, it is determined that the state of charge evaluation result of the overall charge and discharge test does not meet the accuracy requirements, and the state of charge of the power battery management system is corrected to improve the state of charge estimation accuracy of the power battery management system.

[0040] In addition, to achieve the above-mentioned purpose, the present application also proposes a test device for improving the accuracy of power battery state of charge estimation. The test device for improving the accuracy of power battery state of charge estimation includes:

[0041] The test module is used to discharge the power battery to a first state of charge with a constant current, and to charge the power battery to a second state of charge with a stepwise constant current, after the variable temperature box is set to a constant temperature mode and the temperature is adjusted to room temperature, so as to complete full discharge and full charge;

[0042] The test module is further used to set the variable temperature box to a temperature dynamic cycle mode, perform a temperature cycle test, and discharge the power battery after standing to the third state of charge;

[0043] The test module is further configured to perform a charge-discharge cycle test on the power battery under a preset cycle condition based on the third state of charge and the fourth state of charge;

[0044] The test module is further configured to discharge the power battery to a first state of charge after the charge-discharge cycle test is completed, so as to achieve full discharge;

[0045] An evaluation module is used to determine the relative error of the state of charge based on the ampere-hour integral value of the state of charge of the charging and discharging equipment during the charge and discharge test and the state of charge BMS value obtained by the power battery management system;

[0046] The evaluation module is also used to determine the state of charge evaluation result based on the relative error of the state of charge, so as to improve the state of charge estimation accuracy of the power battery management system.

[0047] In addition, to achieve the above-mentioned purpose, the present application also proposes a test device for improving the accuracy of power battery state of charge estimation. The test device for improving the accuracy of power battery state of charge estimation includes: a memory, a processor, and a computer program stored in the memory and runnable on the processor. The computer program is configured to implement the steps of the test method for improving the accuracy of power battery state of charge estimation as described above.

[0048] In addition, to achieve the above-mentioned purpose, the present invention also proposes a storage medium, which is a computer-readable storage medium. A computer program is stored on the storage medium. When the computer program is executed by a processor, the steps of the test method for improving the accuracy of power battery state of charge estimation as described above are implemented.

[0049] In addition, to achieve the above-mentioned purpose, the present application also provides a computer program product, which includes a computer program. When the computer program is executed by a processor, it implements the steps of the test method for improving the accuracy of power battery state of charge estimation as described above.

[0050] The present application provides a test method for improving the accuracy of state-of-charge estimation of a power battery. After a variable temperature box is set to a constant temperature mode and the temperature is adjusted to room temperature, the power battery is discharged to a first state of charge with a constant current, and is charged to a second state of charge with a step-by-step constant current to complete full discharge and full charge; the variable temperature box is set to a temperature dynamic cycle mode, and a temperature cycle test is performed, and the power battery that has been stationary is discharged to a third state of charge; based on the third state of charge and a fourth state of charge, a charge and discharge cycle test is performed on the power battery under preset cycle conditions; after the charge and discharge cycle test is completed, the power battery is discharged to the first state of charge to complete full discharge; based on the state-of-charge ampere-hour integral value of the charge and discharge equipment in the charge and discharge test and the state-of-charge BMS value obtained by the power battery management system, the relative error of the state of charge is determined; based on the relative error of the state of charge, a state-of-charge evaluation result is determined to improve the accuracy of state-of-charge estimation of the power battery management system. This application targets variable temperature working conditions and uses the state-of-charge ampere-hour integral value obtained by the charging and discharging equipment based on the ampere-hour integral method to determine the relative error of the state of charge. Based on the designed threshold of the relative error of the state of charge, the state of charge evaluation result is determined, and the SOC correction is performed in real time to improve the state-of-charge estimation accuracy of the power battery management system. The test method is simple, convenient, and easy to operate, effectively saving development costs, and solving the technical problems of complex calculation methods and insufficient accuracy of the state-of-charge estimation of the power battery management system. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0052] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0053] Figure 1 A schematic diagram of the structure of a test system for improving the accuracy of power battery state of charge estimation, as involved in the test method for improving the accuracy of power battery state of charge estimation in this application;

[0054] Figure 2 A schematic diagram of a detailed structure of a test system for improving the accuracy of power battery state of charge estimation, as involved in the test method for improving the accuracy of power battery state of charge estimation in this application;

[0055] Figure 3 This is a flow chart of a first embodiment of a test method for improving the accuracy of power battery state of charge estimation in this application;

[0056] Figure 4A schematic diagram of a step constant current charging method for improving the accuracy of power battery state of charge estimation provided in Example 1 of the present application;

[0057] Figure 5 This is a flow chart of Example 2 of a test method for improving the accuracy of power battery state of charge estimation in this application;

[0058] Figure 6 A schematic diagram of a simplified flow chart of a test method for improving the accuracy of power battery state of charge estimation provided in the second embodiment of the present application;

[0059] Figure 7 A schematic diagram of the module structure of a test device for improving the accuracy of power battery state of charge estimation according to an embodiment of the present application;

[0060] Figure 8 Schematic diagram of the device structure of the hardware operating environment involved in the test method for improving the accuracy of power battery state of charge estimation in an embodiment of the present application.

[0061] The realization of the objectives, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0062] It should be understood that the specific embodiments described herein are merely used to explain the technical solutions of the present application and are not intended to limit the present application.

[0063] In order to better understand the technical solution of the present application, a detailed description will be given below in conjunction with the accompanying drawings and specific implementation methods.

[0064] The main solution of the embodiment of the present application is: after the variable temperature box is set to the constant temperature mode and the temperature is adjusted to room temperature, the power battery is discharged to the first state of charge with a constant current, and is charged to the second state of charge with a step-by-step constant current to complete full discharge and full charge; the variable temperature box is set to the temperature dynamic cycle mode, and a temperature cycle test is performed to discharge the power battery that has been stationary to the third state of charge; based on the third state of charge and the fourth state of charge, a charge and discharge cycle test is performed on the power battery under preset cycle conditions; after the charge and discharge cycle test is completed, the power battery is discharged to the first state of charge to complete full discharge; based on the state of charge ampere-hour integral value of the charge and discharge equipment in the charge and discharge test and the state of charge BMS value obtained by the power battery management system, the relative error of the state of charge is determined; based on the relative error of the state of charge, the state of charge evaluation result is determined to improve the state of charge estimation accuracy of the power battery management system.

[0065] Currently, there is little research on test methods for state of charge estimation of power battery management systems. The calculation methods for state of charge estimation of power battery management systems are complex and lack accuracy.

[0066] The present application provides a solution for variable temperature working conditions. It uses the state-of-charge ampere-hour integral value obtained by the charging and discharging equipment based on the ampere-hour integral method to determine the relative error of the state of charge. Based on the design threshold of the relative error of the state of charge, the state of charge evaluation result is determined, and the SOC correction is performed in real time to improve the state-of-charge estimation accuracy of the power battery management system. The test method is simple, convenient and easy to operate, effectively saving development costs, and solving the technical problems of complex calculation methods and insufficient accuracy of the state of charge estimation of the power battery management system.

[0067] It should be noted that this embodiment is applied to a test system for improving the accuracy of power battery state of charge estimation. Figure 1 The test system for improving the accuracy of power battery state of charge estimation includes at least a variable temperature box 1, a power battery management system (BMS) 2, a charging and discharging device 3, a power battery 4 and a CAN bus 5. The power battery 4 is placed in the variable temperature box 1, and the power battery management system 2 and the charging and discharging device 3 are respectively connected to the power battery 4 through the CAN bus 5.

[0068] It is understandable that a BMS can generally implement online battery status monitoring, SOC estimation, battery health status analysis, and necessary thermal management functions to ensure the safe operation of the battery pack and extend the battery cycle life. For example, a BMS can collect the terminal voltage and temperature, charge and discharge current, and total battery pack voltage of each battery in an electric vehicle's power battery pack in real time to prevent the battery from overcharging or over-discharging; the BMS can balance the charge and discharge of the individual cells in the power battery pack so that each cell in the battery pack reaches a balanced and consistent state; the BMS can analyze whether the SOC is too high, whether the battery temperature is too high / low, whether the individual cell voltage is too high / low, whether the battery temperature rises too quickly, whether the insulation is faulty, whether there is overcurrent, battery consistency analysis, whether there is a battery pack fault, and whether there is a communication fault.

[0069] In this embodiment, the charging and discharging device 3 is used to perform charge and discharge tests on the power battery 4 and record the state-of-charge (SOC) ampere-hour integral value of the power battery 4 during the charge and discharge tests. The power battery management system 2 is used to obtain the SOC (Soc) value of the power battery 4 during the charge and discharge tests. The SOC ampere-hour integral value can generally be determined based on the data recorded by the charging and discharging device 3. The SOC (Soc) value estimated by the power battery management system 2 generally has a certain error compared to the SOC ampere-hour integral value. The CAN bus 5 is used to connect the power battery management system 2 with the power battery 4, and is also used to connect the charging and discharging device 3 with the power battery 4 to enable data sharing and transmission. The variable temperature box can adjust the temperature according to different needs and can be set to a constant temperature mode or a dynamic temperature cycle mode.

[0070] Further, refer to Figure 2The test system for improving the accuracy of power battery state-of-charge estimation may also include an oscilloscope, a power supply, a multimeter, a debugging bench, a CAN bus, a bus monitoring device, a laptop computer, etc., which are not specifically limited in this embodiment. The CAN bus is used to connect the BMS battery management system and the laptop computer, and is used for data transmission between the BMS and the laptop computer to obtain the SOC value estimated by the BMS. The CAN bus is also used to connect the charging and discharging equipment and the power battery to obtain the power battery's state-of-charge ampere-hour integrated value.

[0071] The present application embodiment provides a test method for improving the accuracy of power battery state of charge estimation, referring to Figure 3 , Figure 3 This is a flow chart of the first embodiment of the test method for improving the accuracy of power battery state of charge estimation in this application.

[0072] In this embodiment, the test method for improving the accuracy of power battery state of charge estimation includes steps S10 to S60:

[0073] Step S10, after the variable temperature box is set to a constant temperature mode and the temperature is adjusted to room temperature, the power battery is discharged at a constant current to a first state of charge, and then charged at a stepwise constant current to a second state of charge, thereby completing full discharge and full charge;

[0074] It should be noted that the entire charge and discharge test in this embodiment includes 11 stages. Different stages usually require different charge and discharge operations, which can be achieved through charge and discharge equipment.

[0075] In addition, it should be noted that this embodiment uses a test method under variable temperature conditions to obtain the state of charge (BMS) value and the state of charge (Ah) integral value of the power battery management system, determine the state of charge evaluation result, and thus perform SOC correction in real time to improve the state of charge estimation accuracy of the power battery management system.

[0076] In a feasible implementation, step S10 may include steps S101 to S102:

[0077] Step S101, after the variable temperature box is set to a constant temperature mode and the temperature is adjusted to room temperature, the power battery is discharged at a constant current to a first state of charge based on a first preset discharge rate to complete full discharge;

[0078] Generally speaking, less than or equal to 1 / 3C is a low discharge rate, greater than 1 / 3C and less than 3C is a medium discharge rate, and greater than or equal to 3C is a high discharge rate.

[0079] It should be noted that the variable temperature box is set to constant temperature mode and adjusted to room temperature, typically 25°C. The first stage is the preparation stage, during which the power battery needs to be fully discharged. This embodiment uses a constant current discharge method. The first preset discharge rate is the discharge rate used in the first stage. This embodiment selects a lower discharge rate, for example: 1 / 3C, that is, the discharge current is 1 / 3 of the rated capacity of the battery. Other suitable low discharge rates can also be selected, and this is not specifically limited. In this embodiment, the first state of charge is SOC equal to 0.

[0080] It can be understood that in the first stage, the power battery is discharged at a constant current to SOC=0 at a discharge rate of 1 / 3C. During this process, due to the use of a low discharge rate, the polarization of the electrode is small, and the active material can be fully utilized, which is beneficial to the discharge process and can fully release the battery capacity, which is beneficial to the safety of the power battery and the cycle life.

[0081] Step S102, after the full discharge is completed, the power battery is charged to a second state of charge based on a preset step current using a step constant current to complete the full charge;

[0082] It should be noted that after full discharge, the battery enters the second stage. Stages 2 to 11 are the testing stage. The second stage requires the battery to be fully charged. This embodiment uses a stepped constant current charging method. The preset stepped current is the stepped current used during the second stage of charging and can be set according to actual needs. This is not specifically limited. In this embodiment, the second state of charge is an SOC of 100%, i.e., a fully charged state.

[0083] In addition, it should be noted that when step constant current charging is used, a plurality of preset step currents are usually set in descending order. Figure 4Assuming that 7 preset step currents are set, namely I1, I2, I3, I4, I5, I6, and I7, the entire step constant current charging process is: charging according to I1 constant current until a single cell reaches the charging cut-off voltage specified in the technical conditions; charging according to I2 constant current until a single cell reaches the charging cut-off voltage specified in the technical conditions; charging according to I3 constant current until a single cell reaches the charging cut-off voltage specified in the technical conditions; charging according to I4 constant current until a single cell reaches the charging cut-off voltage specified in the technical conditions; charging according to I5 constant current until a single cell reaches the charging cut-off voltage specified in the technical conditions; charging according to I6 constant current until a single cell reaches the charging cut-off voltage specified in the technical conditions; charging according to I7 constant current until a single cell reaches the charging cut-off voltage specified in the technical conditions; at this time, the battery system is fully charged. Among them, I1>I2>I3>I4>I5>I6>I7 must be satisfied. For example, I1=1 / 3C, I2=1 / 6C, I3=1 / 10C, ​​I4=1 / 15C, I5=1 / 20C, I6=1 / 25C, I7=1 / 30C. Selecting a step-by-step, low-rate, low-current charging method can reduce the polarization effect of the battery (including concentration polarization, electrochemical polarization, and ohmic polarization).

[0084] Reduce the internal resistance of the battery, ensure that the active materials can be fully utilized, ensure that the battery reaches a fully charged state, and prevent the battery from overcharging, so that the single cells in the power battery pack are charged evenly, and each cell reaches a balanced and consistent state, ensuring battery consistency and ensuring the battery's safety performance and cycle life; in addition, considering that too small a charging current may not be able to charge the cell, the charging rate should be set reasonably. At the same time, the time cost needs to be comprehensively considered and the number of step currents should be reasonably set. There is no specific limit on this.

[0085] It can be understood that in the second stage, the power battery is charged with a step-by-step constant current according to a preset step-by-step current to SOC=100%.

[0086] It should be understood that the variable temperature box is set to constant temperature mode from the first stage to the second stage, and the temperature is adjusted to room temperature. The room temperature can usually be set to 25°C, and other values ​​can also be set according to actual needs. This embodiment does not make specific limitations on this.

[0087] Step S20, setting the variable temperature box to a temperature dynamic cycle mode, performing a temperature cycle test, and discharging the power battery after resting to a third state of charge;

[0088] In a feasible implementation, step S20 may include steps S201 to S202:

[0089] Step S201, setting the variable temperature box to a temperature dynamic cycle mode, performing a temperature cycle test, and performing a rest treatment on the power battery based on a first rest time;

[0090] It should be noted that after the second stage is fully charged, the third stage begins. In the third stage, the power battery needs to be left to stand under variable temperature conditions. Therefore, in this embodiment, the variable temperature box is set to a temperature dynamic cycle mode, which is a variable temperature condition. It usually needs to cover the normal operating temperature range of the power battery. The temperature cycle test is a method of simulating the working environment of the power battery under different temperature conditions, which can comprehensively test the key performance indicators of the power battery under different temperature conditions, such as electrochemical performance, thermal stability and mechanical stability.

[0091] It should be noted that the dynamic temperature cycling mode requires setting an initial temperature, a linear temperature ramp rate, a minimum temperature, and a maximum temperature. The initial temperature refers to the temperature of the variable temperature chamber at the beginning of the temperature cycling test. The dynamic temperature cycling mode starts at the initial temperature and cools down to the minimum temperature at a linear temperature ramp rate. Then, it increases to the maximum temperature at a linear temperature ramp rate. Then, it cools down to the minimum temperature at a linear temperature ramp rate, repeating the cycle. For example, if the normal operating temperature range of a power battery is -20°C to 45°C, the initial temperature can be set to 25°C, the temperature of the variable temperature chamber in the first stage in constant temperature mode can be used, the linear temperature ramp rate is 5°C / hour, the minimum temperature is -20°C, and the maximum temperature is 45°C. The temperature cycling test process then starts at 25°C, cools down to -20°C at a rate of 5°C / hour, then increases to 45°C at a rate of 5°C / hour, and cools down to -20°C at a rate of 5°C / hour, repeating the cycle. The temperature cycling test can be flexibly adjusted according to actual needs and is not specifically limited to this.

[0092] In addition, it should be noted that after full charging is completed, the third stage begins, and the power battery needs to be left to rest in the third stage. The first resting time is the duration of the third stage resting process, and the first resting time is usually greater than or equal to 30 minutes.

[0093] It is understood that in the third stage, the BMS power supply is disconnected within 1 minute after the battery is fully charged, and the variable temperature chamber is set to the temperature dynamic cycle mode. It is left to stand for more than 30 minutes. The BMS power supply is then connected, and the BMS data and charging and discharging device data during the standing time are recorded. The SOC is adjusted to 100%, and then the BMS power supply is disconnected within 1 minute and left to stand. The standing treatment can eliminate the polarization of the electrodes, and the correction operation of adjusting the SOC to 100% can be completed during the standing treatment.

[0094] It should be understood that the BMS data and charging and discharging equipment data may include the battery temperature, charging and discharging current, charging and discharging time, the actual state of charge value, the state of charge BMS value, etc.

[0095] Step S202 : After the resting state is completed, the power battery in the second state of charge is discharged to a third state of charge based on a second preset discharge rate.

[0096] It should be noted that after the third stage of rest is completed, the fourth stage begins, in which the power battery is discharged. The second preset discharge rate is the discharge rate used in the fourth stage. In this embodiment, a lower discharge rate, such as 1 / 3C, is selected. Other suitable low discharge rates may also be selected and are not specifically limited. In this embodiment, the third state of charge is an SOC of 80%.

[0097] It can be understood that in the fourth stage, the BMS power supply is turned on and the fully charged power battery is discharged to SOC=80% at a discharge rate of 1 / 3C.

[0098] Step S30, performing a charge-discharge cycle test on the power battery under a preset cycle condition based on the third state of charge and the fourth state of charge;

[0099] It should be noted that the preset cycle conditions are NEDC / WLTC conditions, among which NEDC (New European Driving Cycle) is a European endurance test standard, and WLTC (Worldwide Harmonized Light Vehicles Test Cycle) is a new cycle test standard developed by the United Nations.

[0100] In addition, it should be noted that after completing the fourth stage, the fifth to eighth stages are entered. In this embodiment, the fifth to eighth stages are subjected to charge and discharge cycle tests, that is, the charge and discharge operations of the fifth to eighth stages need to be performed multiple times according to the set number of cycles.

[0101] In a feasible implementation, step S30 may include steps S301 to S303:

[0102] Step S301: discharging the power battery to a fourth state of charge based on a third preset discharge rate under a preset cycle condition, and performing a rest treatment on the power battery based on a second rest time;

[0103] It should be noted that the power battery needs to be discharged in the fifth stage. The third preset discharge rate is the discharge rate used in the fifth stage. This embodiment selects a lower discharge rate, for example: 1 / 3C. Since the actual capacity of the battery is closely related to the discharge current, when the current is large, the polarization of the electrode is enhanced, the polarization internal resistance increases, the discharge voltage drops rapidly, and the energy efficiency of the battery is reduced, resulting in a lower actual released capacity. Therefore, this embodiment adopts a 1 / 3C low-rate discharge current during the NEDC / WLTC cycle condition, and the discharge voltage drops slowly, which is beneficial to the discharge process of the battery. Other suitable low discharge rates can also be selected, which can be flexibly adjusted according to actual conditions (battery characteristics, battery materials, specifications, etc.), and there is no specific limitation on this. At the same time, it is necessary to consider the time cost and determine the discharge rate. The relationship between the discharge time, SOC and discharge rate satisfies:

[0104]

[0105] Where, initial SOC is the SOC value before discharge, target SOC is the target SOC value after discharge, σ is the discharge rate, and T is the discharge time (hours). For example, if initial SOC = 80%, target SOC = 30%, and discharge current rate σ = 1 / 3, then the discharge time is 1.5 hours. In this embodiment, the fourth state of charge is an SOC equal to 30%.

[0106] Additionally, it should be noted that the sixth stage requires the power battery to undergo a resting treatment. The second resting time, which is the duration of the sixth stage resting treatment, is typically 30 minutes or longer. The purpose of the resting treatment is to eliminate electrode polarization and allow battery SOC correction operations to be performed during the resting period.

[0107] It can be understood that from the fifth to the sixth stage, the vehicle is operated under NEDC / WLTC conditions, the power battery is discharged to SOC = 30% at a discharge rate of 1 / 3C, the BMS data and charging and discharging equipment data during the discharge process are recorded, the BMS power supply is disconnected within 1 minute, and the vehicle is left to stand for more than half an hour.

[0108] Step S302: charging the power battery to a third state of charge based on a fast charging strategy, and performing a rest process on the power battery based on a third rest time;

[0109] It should be noted that after the sixth stage of rest is completed, the seventh stage begins, in which the power battery needs to be charged to SOC = 80%. The fast charging strategy refers to the fast charging method, such as 3C high-rate charging and Reflex fast charging method, which can be flexibly adjusted according to the actual situation (battery characteristics, battery materials, specifications, etc.) and is not specifically limited.

[0110] It can be understood that in the seventh stage, the BMS power supply is turned on, the BMS data and charging and discharging equipment data during the static time are recorded, the power battery is charged to SOC = 80% with a fast charging strategy, and the BMS data and charging and discharging equipment data during the charging process are recorded.

[0111] In addition, it should be noted that the power battery needs to be placed in a static state in the eighth stage. The third static state time is the duration of the static state in the eighth stage. The third static state time is usually greater than or equal to 30 minutes.

[0112] It can be understood that in the eighth stage, the BMS power supply is disconnected, left to stand for half an hour, and then the BMS power supply is connected within 1 minute, and the BMS data and charging and discharging equipment data during the standing time are recorded.

[0113] Step S303: Update the number of cycles and repeat the above steps until the number of cycles meets the preset number of cycles.

[0114] It is understood that each time a round of charge and discharge operations from the fifth to the eighth stage is completed, the number of cycles is increased by 1. The preset number of cycles is the number of cycles required, for example, 10 times. When the number of cycles reaches 10, the charge and discharge cycle test ends. If the number of cycles does not reach 10, the next round of charge and discharge operations will continue.

[0115] Step S40, after the charge-discharge cycle test is completed, discharging the power battery to the first state of charge to complete full discharge;

[0116] In a feasible implementation, step S40 may include steps S401 to S403:

[0117] Step S401: After the charge-discharge cycle test is completed, the power battery is discharged to a discharge cut-off voltage based on a fourth preset discharge rate;

[0118] It should be noted that after the charge and discharge cycle test is completed, the ninth stage is entered. The fourth preset discharge rate is the discharge rate used in the ninth stage. This embodiment selects a lower discharge rate, for example: 1 / 3C, and other suitable low discharge rates can also be selected. There is no specific limitation on this.

[0119] It is understandable that in the ninth stage, the BMS power supply is turned on, the battery is operated under NEDC / WLTC conditions, and the power battery is discharged to the discharge cut-off voltage at a discharge rate of 1 / 3C. Since the variable temperature box is in a temperature dynamic cycle mode during this stage, it is necessary to consider that when the power battery is at sub-zero temperatures, the activity of the electrode active material is low, which is not conducive to ion diffusion. The polarization effect of the battery is large, resulting in an increase in polarization internal resistance, causing the battery discharge end capacity to freeze, and thus part of the battery capacity cannot be released normally. Therefore, at sub-zero temperatures, a lower discharge rate can be used, for example, reducing it from 1 / 3C to 1 / 10C, ​​which is beneficial to the battery discharge process and improves the discharge efficiency of the power battery.

[0120] It should be understood that, depending on the different types of power batteries and different discharge conditions, the requirements for battery capacity and life are also different, and the discharge cut-off voltage set accordingly is also different. Therefore, the discharge cut-off voltage in this embodiment can be flexibly adjusted according to actual conditions and is not specifically limited to this.

[0121] Step S402, after the variable temperature box is set to a constant temperature mode and the temperature is adjusted to room temperature, the power battery is subjected to a rest treatment based on a fourth rest time;

[0122] It should be noted that the next step, the tenth stage, requires the temperature of the variable temperature box to be set to room temperature (usually 25°C) to allow the power battery to rest. The fourth resting time, which is the duration of the tenth stage resting treatment, is usually required to be greater than or equal to 8 hours to allow the power battery temperature to reach equilibrium with the ambient temperature of the variable temperature box (the temperature difference between the power battery temperature and room temperature is no more than 2°C). In addition, resting can eliminate polarization of the power battery.

[0123] It can be understood that in the tenth stage, the temperature of the variable temperature box is set to 25°C, the BMS power supply is disconnected within 1 minute, and the power battery is left to stand for more than 8 hours.

[0124] Step S403 : After the resting state is completed, the power battery is discharged to the first state of charge based on the fifth preset discharge rate to complete full discharge.

[0125] It should be noted that after the tenth stage of rest is completed, the eleventh stage begins. To ensure full discharge of the power battery, discharge must continue in the eleventh stage. The fifth preset discharge rate, i.e., the discharge rate used in the twelfth stage, should be used at a low current rate to avoid premature SOC reaching 0 without triggering the lower voltage limit. This reduces battery polarization, facilitates the battery discharge process, and completes full discharge. Therefore, this embodiment selects a lower discharge rate, for example, 0.05C. Other suitable low discharge rates may also be selected, and this is not specifically limited.

[0126] It can be understood that in the eleventh stage, the BMS power supply is connected, the power battery is discharged to SOC=0 at a discharge rate of 0.05C, and the BMS data and charging and discharging equipment data during the discharge process are recorded.

[0127] Step S50, determining a relative state of charge error based on the state of charge ampere-hour integral value of the charge and discharge device during the charge and discharge test and the state of charge BMS value obtained by the power battery management system;

[0128] It should be noted that the relative error of the state of charge is the error between the ampere-hour integral value of the state of charge recorded by the charging and discharging equipment during the charge and discharge test and the state of charge BMS value obtained by the power battery management system. It can be seen that in order to ensure the accuracy of the BMS state of charge estimation, the relative error of the state of charge usually cannot exceed a certain value.

[0129] Step S60 : determining a state of charge evaluation result based on the state of charge relative error to improve the state of charge estimation accuracy of the power battery management system.

[0130] It should be noted that the state of charge evaluation result, that is, the evaluation of the state of charge estimation accuracy of the power battery management system, usually has two situations: the accuracy meets the requirements and the accuracy does not meet the requirements. The relative error of the state of charge includes the relative error of the state of charge of the charge and discharge cycle test and the relative error of the state of charge of the overall charge and discharge test, wherein the overall charge and discharge test is the entire charge and discharge test process. Based on the relative error of the state of charge of the charge and discharge cycle test, this embodiment can determine the state of charge evaluation result in the charge and discharge cycle test, and based on the relative error of the state of charge of the overall charge and discharge test, this embodiment can determine the state of charge evaluation result in the overall charge and discharge test.

[0131] In a feasible implementation, when the relative error of the state of charge of the charge and discharge cycle test is greater than a preset error threshold, it is determined that the state of charge evaluation result of the charge and discharge cycle test does not meet the accuracy requirements, and the state of charge of the power battery management system is corrected to improve the state of charge estimation accuracy of the power battery management system.

[0132] It should be noted that the preset error threshold is the design threshold for the relative SOC error. In other words, the relative SOC error must be less than or equal to this preset error threshold. The preset error threshold varies depending on the battery type, material system, battery design, manufacturing process, and specific testing conditions. It can be flexibly adjusted according to specific circumstances to ensure battery performance and safety. This is not a specific limitation. By way of example, the preset error threshold for ternary lithium-ion power batteries is set at 3%, and the preset error threshold for lithium iron phosphate power batteries is set at 5%.

[0133] It is understandable that if the relative error of the state of charge of the charge-discharge cycle test is greater than the preset error threshold, it means that the state of charge evaluation result of the charge-discharge cycle test does not meet the accuracy requirements. At this time, it is necessary to correct the SOC of the power battery management system and record the correction event for debugging and analysis, so as to improve the state of charge estimation accuracy of the power battery management system. Among them, the correction can be performed during the static period. If the relative error of the state of charge of the charge-discharge cycle test is less than or equal to the preset error threshold, it means that the state of charge evaluation result of the charge-discharge cycle test meets the accuracy requirements.

[0134] In a feasible implementation, when the relative error of the state of charge of the overall charge and discharge test is greater than a preset error threshold, it is determined that the state of charge evaluation result of the overall charge and discharge test does not meet the accuracy requirements, and the state of charge of the power battery management system is corrected to improve the state of charge estimation accuracy of the power battery management system.

[0135] It is understandable that if the relative error of the state of charge of the overall charge and discharge test is greater than the preset error threshold, it means that the state of charge evaluation result of the overall charge and discharge test does not meet the accuracy requirements. At this time, it is necessary to correct the SOC of the power battery management system and record the correction event for debugging and analysis, so as to improve the state of charge estimation accuracy of the power battery management system. Among them, the correction can be performed during the static period. If the relative error of the state of charge of the overall charge and discharge test is less than or equal to the preset error threshold, it means that the state of charge evaluation result of the overall charge and discharge test meets the accuracy requirements.

[0136] This embodiment provides a test method for improving the accuracy of power battery state of charge estimation. After a variable temperature box is set to a constant temperature mode and the temperature is adjusted to room temperature, the power battery is discharged to a first state of charge with a constant current, and is charged to a second state of charge with a step-by-step constant current to complete full discharge and full charge. The variable temperature box is set to a temperature dynamic cycle mode to perform a temperature cycle test, and the power battery that has been stationary is discharged to a third state of charge. Based on the third state of charge and a fourth state of charge, a charge and discharge cycle test is performed on the power battery under preset cycle conditions. After the charge and discharge cycle test is completed, the power battery is discharged to the first state of charge to complete full discharge. The relative error of the state of charge is determined based on the ampere-hour integral value of the state of charge of the charging and discharging equipment in the charge and discharge test and the state of charge (BMS) value obtained by the power battery management system. Based on the relative error of the state of charge, a state of charge evaluation result is determined to improve the accuracy of the state of charge estimation of the power battery management system. For variable temperature conditions, the state of charge ampere-hour integral value obtained by the charging and discharging equipment based on the ampere-hour integral method is used to determine the relative error of the state of charge. Based on the design threshold of the relative error of the state of charge, the state of charge evaluation result is determined, and the SOC correction is performed in real time to improve the state of charge estimation accuracy of the power battery management system. The test method is simple, convenient, easy to operate, and effectively saves development costs.

[0137] Based on the first embodiment of the present application, in the second embodiment of the present application, the same or similar contents as those in the above embodiment 1 can be referred to the above introduction and will not be described in detail later. Figure 5 , step S50 may include steps S501 to S504:

[0138] Step S501, obtaining a temperature correction factor, a rate correction factor, and charge and discharge current data, charge and discharge time data, and state of charge data recorded by a charge and discharge device during a charge and discharge test;

[0139] It should be noted that, since this embodiment is aimed at variable temperature conditions, it is necessary to consider the influence of temperature on performance parameters including battery internal resistance (polarization internal resistance, ohmic internal resistance), chemical reaction rate, electrode active material, etc. For example: 1) Under low temperature conditions, the activity of the electrode active material is low, and the polarization effect of the battery is large, resulting in an increase in polarization internal resistance, which leads to the phenomenon of freezing of the battery discharge end capacity, so that part of the battery capacity cannot be released normally; 2) Under high temperature conditions, the rate of chemical reaction inside the battery is accelerated, resulting in accelerated battery aging, thereby shortening the cycle life of the battery; 3) When discharging with a large current, the polarization effect of the battery increases, the battery internal resistance increases, the discharge voltage drops rapidly, and the actual released capacity is low. Correspondingly, under low-rate discharge conditions, the discharge voltage drops slowly, which is conducive to the battery charging process; 4) When charging with a large current, as the charging current increases, the negative electrode potential gradually decreases. For lithium batteries, when the negative electrode potential is lower than the lithium plating potential, there is a risk of lithium plating, which is easy to form lithium dendrites, pierce the diaphragm and cause a short circuit, posing a safety risk. Therefore, it is necessary to consider that the actual charge and discharge rate of the battery is affected by factors such as ambient temperature and charge and discharge current. That is, the battery capacity utilization rate may change with different temperatures and charge and discharge currents. Therefore, this embodiment sets a rate correction factor and a temperature correction factor.

[0140] It can be understood that the rate correction factor includes a discharge rate correction factor and a charge rate correction factor.

[0141] In a feasible implementation, the step of determining the rate correction factor and the temperature correction factor includes steps S5011 to S5014:

[0142] Step S5011, obtaining a second correspondence between battery temperature data, the temperature of the variable temperature box, the battery operating temperature threshold, the battery characteristic correction parameter, and the temperature correction factor;

[0143] It should be noted that the second correspondence between the battery temperature data, the temperature of the variable temperature box, the battery operating temperature threshold, the battery characteristic correction parameter, and the temperature correction factor, i.e., the calculation formula of the temperature correction factor, is as follows:

[0144]

[0145] Where, T f is the temperature correction factor, T cell is the temperature of the power battery at a certain moment (can be determined based on the battery temperature data), T0 is the temperature of the variable temperature box, T max The maximum temperature at which the battery can operate safely is also known as the battery operating temperature threshold. a and b are battery characteristic correction parameters, which are coefficients that need to be determined based on battery characteristics and experimental data. The process of determining coefficients a and b usually involves battery performance testing and data analysis, and is usually related to the battery's capacity attenuation, aging characteristics, and the impact of temperature on battery performance. The values ​​may vary depending on factors such as battery type, manufacturing process, and usage conditions, and are not specifically limited to this.

[0146] Step S5012, obtaining a temperature correction factor based on the battery temperature data, the temperature of the variable temperature box, the battery operating temperature threshold, the battery characteristic correction parameter, and the second corresponding relationship;

[0147] It is understandable that the battery temperature data, the temperature of the variable temperature box, the battery operating temperature threshold, and the battery characteristic correction parameter are substituted into the above second corresponding relationship to calculate the corresponding temperature correction factor.

[0148] Step S5013, obtaining battery temperature data, temperature of the variable temperature box, battery operating temperature threshold, charge and discharge current data, battery rated capacity, battery peak charge and discharge current, battery temperature correction coefficient, ambient temperature correction coefficient, and a third correspondence between the charge and discharge current correction coefficient and the rate correction factor;

[0149] It should be noted that the third correspondence between the battery temperature data, the temperature of the variable temperature box, the battery operating temperature threshold, the charge and discharge current data, the battery rated capacity, the battery peak charge and discharge current, the battery temperature correction coefficient, the ambient temperature correction coefficient, the charge and discharge current correction coefficient, and the rate correction factor, i.e., the calculation formula of the rate correction factor, is as follows:

[0150]

[0151] Where D f is the rate correction factor, T cell is the temperature of the battery pack at a certain moment (can be determined based on the battery temperature data), T0 is the temperature of the variable temperature box, T max is the battery operating temperature threshold, I(t) is the discharge current data in the charge and discharge current data, which is a function of the charge and discharge time. A positive value indicates that the battery is charging, and a negative value indicates that the battery is discharging. reted is the peak charge and discharge current of the battery, C tetedis the battery rated capacity, c1 is the ambient temperature correction coefficient, c2 is the battery temperature correction coefficient, and c3 is the charge and discharge current correction coefficient. c1, c2, and c3 are coefficients that need to be determined based on battery characteristics and experimental data. For example, the discharge capacity of the power battery is measured at different temperatures and compared with the capacity at the reference temperature to obtain the impact of temperature on the battery capacity and determine the ambient temperature correction coefficient c1 and the battery temperature correction coefficient c2; the battery discharge capacity is measured at different discharge currents, and the relationship between the discharge current and the battery capacity is analyzed to determine the charge and discharge current correction coefficient c3. Among them, the battery operating temperature threshold, battery rated capacity, and battery peak charge and discharge current are closely related to battery characteristics, material type, etc., and need to be determined based on actual conditions.

[0152] Step S5014: Obtain a rate correction factor based on the battery temperature data, the temperature of the variable temperature box, the battery operating temperature threshold, the charge and discharge current data, the battery rated capacity, the battery peak charge and discharge current, the battery temperature correction coefficient, the ambient temperature correction coefficient, the charge and discharge current correction coefficient, and the third corresponding relationship.

[0153] It should be noted that the rate actually refers to the current value output by the battery when it discharges its rated capacity within a specified time. It is numerically equal to a multiple of the battery's rated capacity. The battery's peak charge current is equal to the product of the battery's maximum charge rate and the battery's rated capacity. The battery's peak discharge current is equal to the product of the battery's maximum discharge rate and the battery's rated capacity.

[0154] It is understood that the discharge rate correction factor is calculated using the discharge current data, discharge time data, and battery peak discharge current. Similarly, the charge rate correction factor is calculated using the charge current data, charge time data, and battery peak charge current.

[0155] In addition, it can be understood that the battery temperature data, the temperature of the variable temperature box, the battery operating temperature threshold, the charge and discharge current data, the battery rated capacity, the battery peak charge and discharge current, the battery temperature correction coefficient, the ambient temperature correction coefficient, and the charge and discharge current correction coefficient are substituted into the above third corresponding relationship to calculate the corresponding rate correction factor.

[0156] Step S502, obtaining a first correspondence between a temperature correction factor, a rate correction factor, charge and discharge current data, charge and discharge time data, state of charge data, a battery rated capacity, and an ampere-hour integral value of the state of charge;

[0157] It should be noted that the first correspondence between the temperature correction factor, the rate correction factor, the charge and discharge current data, the charge and discharge time data, the state of charge data, and the state of charge ampere-hour integral value, that is, the calculation formula for the state of charge ampere-hour integral value, is as follows:

[0158]

[0159] Where I(t) is the current of the power battery at time t, i.e., the charge and discharge current data, SOC0 is the initial state of charge of the power battery (which can be determined based on the state of charge data), and C rated is the rated capacity of the battery, t0 is the initial time, t is the current time, T f is the temperature correction factor, D f is the rate correction factor.

[0160] Step S503, obtaining a state-of-charge ampere-hour integral value based on the temperature correction factor, the rate correction factor, the charge and discharge current data, the charge and discharge time data, the state-of-charge data, the battery rated capacity, and the first corresponding relationship;

[0161] It is understandable that the temperature correction factor, rate correction factor, charge and discharge current data, charge and discharge time data, state of charge data, and battery rated capacity are substituted into the above first corresponding relationship to calculate the corresponding state of charge ampere-hour integral value.

[0162] Step S504 , obtaining a state of charge (BMS) value obtained by the power battery management system, and taking the difference between the state of charge ampere-hour integral value and the state of charge BMS value as a relative error of the state of charge.

[0163] It can be understood that the difference between the SOC ampere-hour integral value and the SOC BMS value is the SOC relative error, as shown below:

[0164] DEV Rel =SOC t -SOC BSM

[0165] Where DEV Rel Indicates the relative error of the state of charge, SOC BSM Indicates the state of charge BMS value, SOC t Indicates the ampere-hour integral value of the state of charge.

[0166] For example, assuming that the overall charge and discharge test is from t1 to t6, then t0 = t1, t = t6, the relative error of the state of charge at this time is:

[0167]

[0168] For example, assuming that the charge-discharge cycle test is from t2 to t4, then t0 = t2, t = t4, the relative error of the state of charge at this time is:

[0169]

[0170] This embodiment provides a test method for improving the accuracy of power battery state of charge estimation. For variable temperature conditions, the state of charge ampere-hour integral value obtained by the charging and discharging equipment based on the ampere-hour integration method is used to determine the relative error of the state of charge. Based on the designed threshold of the relative error of the state of charge, the state of charge evaluation result is determined, and the SOC correction is performed in real time to improve the state of charge estimation accuracy of the power battery management system. The test method is simple, convenient, easy to operate, and effectively saves development costs.

[0171] For example, in order to help understand the implementation process of the test method for improving the estimation accuracy of the state of charge of the power battery obtained by combining this embodiment with the above-mentioned embodiment 2, please refer to Figure 6 , Figure 6 A brief flow chart of a test method for improving the accuracy of power battery state of charge estimation is provided. Specifically:

[0172] (1) Preparation stage: From 0 to t0, the power battery is placed in a variable temperature box at room temperature of 25°C and discharged at a constant current of 1 / 3C until SOC = 0, which is recorded as t0;

[0173] (2) During the test phase, from t0 to t1, a step-by-step constant current charging method is used to complete full charging, with SOC = 100%, which is recorded as t1.

[0174] (3) t1~t2 stage of the test phase: at t1, the BMS power supply is disconnected within 1 minute after the battery is fully charged, and the temperature of the variable temperature box is simultaneously set to the variable temperature condition (for example, it drops to -20°C at 5°C / hour, and then rises to 45°C at a rate of 5°C / hour after dropping to -20°C, and repeats the cycle). The power battery is left to stand for more than 30 minutes, and the BMS power supply is connected. The BMS data and charging and discharging equipment data during the standing time are recorded, and the SOC is adjusted to 100%. Then, the BMS power supply is disconnected within 1 minute and left to stand. This time is recorded as t2;

[0175] (4) t2-t3 of the test phase: At t2, the BMS power supply is turned on, and the fully charged power battery is discharged at a 1 / 3C discharge rate to SOC = 80%, which is recorded as t3;

[0176] (5) During the test phase, the vehicle is operated under NEDC / WLTC conditions and discharged at a 1 / 3C discharge rate until the SOC reaches 30%, which is recorded as t4. The BMS data and charging and discharging equipment data during the discharge process are recorded. The BMS power supply is disconnected within 1 minute and the vehicle is left to stand for more than half an hour, which is recorded as t5.

[0177] (6) t5 to t7 of the test phase: At t5, the BMS power supply is connected, and the data during the rest period is recorded. The power battery is charged to SOC = 80% in a fast charging mode. The BMS data and the charging and discharging equipment data during the charging process are recorded. This time is recorded as t6. The BMS power supply is disconnected within 1 minute and the battery is left to rest for half an hour. This time is recorded as t7. The BMS power supply is connected, and the BMS data and the charging and discharging equipment data during the rest period are recorded.

[0178] (7) Repeat steps 5 to 6 for 9 cycles, and after a total of 10 cycles, record the BMS data and charging and discharging equipment data;

[0179] (8) Flexibly choose whether to calculate the relative error of the state of charge according to the actual situation. The relative error of the state of charge can be used to determine whether the state of charge estimation accuracy of the power battery management system meets the requirements during the cycle test, so as to perform real-time SOC correction;

[0180] (9) t7-t8 of the test phase: At t7, the BMS power supply is turned on, the system is operated under NEDC / WLTC conditions, and the power battery is discharged to the discharge cut-off voltage at a discharge rate of 1 / 3C, which is recorded as t8;

[0181] (10) T8~T9 of the test phase: At t8, the BMS power supply is disconnected, and the variable temperature box is set to the constant temperature mode at the same time, and the temperature is set to room temperature of 25℃. The BMS power supply is disconnected within 1 minute, and the power battery is left to stand for more than 8 hours. This time is recorded as t9;

[0182] (11) During the test phase, t9 to t10: Connect the BMS power supply and discharge the power battery to SOC = 0 at a discharge rate of 0.05C. Record the BMS data and charging and discharging equipment data during the discharge process. This time is recorded as t10.

[0183] (12) Calculate the relative error of the state of charge. The relative error of the state of charge can be used to determine whether the state of charge estimation accuracy of the power battery management system meets the requirements during the entire test process, so as to perform real-time SOC correction.

[0184] This application also provides a test device to improve the accuracy of power battery state of charge estimation, please refer to Figure 7 , the test device for improving the accuracy of power battery state of charge estimation includes:

[0185] The test module 10 is used to discharge the power battery to a first state of charge using a constant current, and then charge the power battery to a second state of charge using a stepwise constant current, after the variable temperature box is set to a constant temperature mode and the temperature is adjusted to room temperature, to complete full discharge and full charge;

[0186] The test module 10 is further used to set the variable temperature box to a temperature dynamic cycle mode, perform a temperature cycle test, and discharge the power battery after standing to a third state of charge;

[0187] The testing module 10 is further configured to perform a charge-discharge cycle test on the power battery under a preset cycle condition based on the third state of charge and the fourth state of charge;

[0188] The testing module 10 is further configured to discharge the power battery to a first state of charge after the charge-discharge cycle test is completed, so as to achieve full discharge;

[0189] An evaluation module 20 is configured to determine a relative error in the state of charge based on the ampere-hour integral value of the state of charge of the charging and discharging device during the charge and discharge test and the state of charge BMS value obtained by the power battery management system;

[0190] The evaluation module 20 is further configured to determine a state of charge evaluation result based on the state of charge relative error, so as to improve the state of charge estimation accuracy of the power battery management system.

[0191] In one embodiment, the test module 10 is further configured to discharge the power battery at a constant current to a first state of charge based on a first preset discharge rate after the variable temperature box is set to a constant temperature mode and the temperature is adjusted to room temperature, so as to complete full discharge;

[0192] After the full discharge is completed, the power battery is charged to the second state of charge based on the preset step current to complete the full charge.

[0193] In one embodiment, the testing module 10 is further configured to set the variable temperature box to a temperature dynamic cycle mode to perform a temperature cycle test, and perform a rest treatment on the power battery based on the first rest time;

[0194] After the resting is completed, the power battery in the second state of charge is discharged to a third state of charge based on a second preset discharge rate.

[0195] In one embodiment, the testing module 10 is further configured to discharge the power battery to a fourth state of charge based on a third preset discharge rate under a preset cycle condition, and perform a rest treatment on the power battery based on a second rest time;

[0196] charging the power battery to a third state of charge based on a fast charging strategy, and performing a rest process on the power battery based on a third rest time;

[0197] Update the number of cycles and repeat the above steps until the number of cycles meets the preset number of cycles.

[0198] In one embodiment, the testing module 10 is further configured to discharge the power battery to a discharge cut-off voltage based on a fourth preset discharge rate after the charge-discharge cycle test is completed;

[0199] After the variable temperature box is set to a constant temperature mode and the temperature is adjusted to room temperature, the power battery is subjected to a rest treatment based on a fourth rest time;

[0200] After the resting is completed, the power battery is discharged to the first state of charge based on the fifth preset discharge rate to complete full discharge.

[0201] In one embodiment, the evaluation module 20 is further configured to obtain a temperature correction factor, a rate correction factor, and charge and discharge current data, charge and discharge time data, and state of charge data recorded by the charge and discharge device during the charge and discharge test;

[0202] Obtaining a first correspondence between a temperature correction factor, a rate correction factor, charge and discharge current data, charge and discharge time data, state of charge data, and a battery rated capacity and a state of charge ampere-hour integral value;

[0203] Obtaining a state-of-charge ampere-hour integral value based on the temperature correction factor, the rate correction factor, the charge and discharge current data, the charge and discharge time data, the state-of-charge data, the battery rated capacity, and the first corresponding relationship;

[0204] The state of charge (BMS) value obtained by the power battery management system is obtained, and the difference between the state of charge ampere-hour integral value and the state of charge BMS value is used as the state of charge relative error.

[0205] In one embodiment, the evaluation module 20 is further configured to obtain a second correspondence between the battery temperature data, the temperature of the variable temperature box, the battery operating temperature threshold, the battery characteristic correction parameter, and the temperature correction factor;

[0206] Obtaining a temperature correction factor based on battery temperature data, the temperature of the variable temperature box, a battery operating temperature threshold, a battery characteristic correction parameter, and a second corresponding relationship;

[0207] Obtain battery temperature data, temperature of the variable temperature box, battery operating temperature threshold, charge and discharge current data, battery rated capacity, battery peak charge and discharge current, battery temperature correction coefficient, ambient temperature correction coefficient, and the third correspondence between the charge and discharge current correction coefficient and the rate correction factor;

[0208] The rate correction factor is obtained based on the battery temperature data, the temperature of the variable temperature box, the battery operating temperature threshold, the charge and discharge current data, the battery rated capacity, the battery peak charge and discharge current, the battery temperature correction coefficient, the ambient temperature correction coefficient, the charge and discharge current correction coefficient and the third corresponding relationship.

[0209] In one embodiment, the evaluation module 20 is further configured to, when the relative error of the state of charge of the charge-discharge cycle test is greater than a preset error threshold, determine that the state of charge evaluation result of the charge-discharge cycle test does not meet the accuracy requirement, and perform state of charge correction on the power battery management system to improve the state of charge estimation accuracy of the power battery management system;

[0210] When the relative error of the state of charge of the overall charge and discharge test is greater than the preset error threshold, it is determined that the state of charge evaluation result of the overall charge and discharge test does not meet the accuracy requirements, and the state of charge of the power battery management system is corrected to improve the state of charge estimation accuracy of the power battery management system.

[0211] The test device for improving the accuracy of power battery state-of-charge estimation provided in this application utilizes the test method for improving the accuracy of power battery state-of-charge estimation in the above-mentioned embodiments, thereby resolving the technical issues of complex and inaccurate calculation methods for state-of-charge estimation in power battery management systems. Compared to the prior art, the beneficial effects of the test device for improving the accuracy of power battery state-of-charge estimation provided in this application are the same as those of the test method for improving the accuracy of power battery state-of-charge estimation provided in the above-mentioned embodiments. The other technical features of the test device for improving the accuracy of power battery state-of-charge estimation are the same as those disclosed in the above-mentioned embodiments and are not further elaborated here.

[0212] The present application provides a test device for improving the accuracy of power battery state of charge estimation. The test device for improving the accuracy of power battery state of charge estimation includes: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions that can be executed by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the test method for improving the accuracy of power battery state of charge estimation in the above-mentioned embodiment one.

[0213] Reference below Figure 8 , which shows a schematic structural diagram of a test device suitable for implementing the embodiment of the present application to improve the accuracy of power battery state of charge estimation. The test device for improving the accuracy of power battery state of charge estimation in the embodiment of the present application can include, but is not limited to, mobile terminals such as mobile phones, laptop computers, digital broadcast receivers, personal digital assistants, tablet computers, portable multimedia players, in-vehicle terminals (such as in-vehicle navigation terminals), and fixed terminals such as digital TVs and desktop computers. Figure 8 The test equipment shown for improving the accuracy of power battery state of charge estimation is merely an example and should not limit the functions and scope of use of the embodiments of the present application.

[0214] like Figure 8As shown, the test equipment for improving the accuracy of power battery state of charge estimation may include a processing device 1001 (such as a central processing unit, a graphics processing unit, etc.), which can perform various appropriate actions and processes according to the program stored in the read-only memory (ROM: Read Only Memory) 1002 or the program loaded from the storage device 1003 to the random access memory (RAM: Random Access Memory) 1004. Various programs and data required for the operation of the test equipment for improving the accuracy of power battery state of charge estimation are also stored in RAM1004. The processing device 1001, ROM1002 and RAM1004 are connected to each other via a bus 1005. The input / output (I / O) interface 1006 is also connected to the bus. Typically, the following systems can be connected to the I / O interface 1006: input devices 1007 including, for example, a touch screen, touchpad, keyboard, mouse, image sensor, microphone, accelerometer, gyroscope, etc.; output devices 1008 including, for example, a liquid crystal display (LCD), speaker, vibrator, etc.; storage devices 1003 including, for example, a magnetic tape, hard disk, etc.; and communication devices 1009. The communication device 1009 can allow the test device for improving the accuracy of power battery state of charge estimation to communicate wirelessly or wired with other devices to exchange data. Although the figure shows a test device for improving the accuracy of power battery state of charge estimation with various systems, it should be understood that it is not required to implement or have all the systems shown. More or fewer systems can be implemented or have instead.

[0215] In particular, according to the embodiments disclosed in the present application, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, the embodiments disclosed in the present application include a computer program product comprising a computer program carried on a computer-readable medium, the computer program comprising program code for executing the method shown in the flowchart. In such an embodiment, the computer program can be downloaded and installed from a network via a communication device, or installed from a storage device 1003, or installed from a ROM 1002. When the computer program is executed by the processing device 1001, the above-mentioned functions defined in the method of the embodiment disclosed in the present application are executed.

[0216] The test equipment for improving the accuracy of power battery state-of-charge estimation provided in this application utilizes the test method for improving the accuracy of power battery state-of-charge estimation in the above-mentioned embodiment, thereby resolving the technical issues of complex and inaccurate calculation methods for state-of-charge estimation in power battery management systems. Compared to the prior art, the beneficial effects of the test equipment for improving the accuracy of power battery state-of-charge estimation provided in this application are the same as those of the test method for improving the accuracy of power battery state-of-charge estimation provided in the above-mentioned embodiment. The other technical features of the test equipment for improving the accuracy of power battery state-of-charge estimation are the same as those disclosed in the method of the above-mentioned embodiment and are not further elaborated here.

[0217] The present application provides a computer-readable storage medium having computer-readable program instructions (i.e., a computer program) stored thereon, and the computer-readable program instructions are used to execute the test method for improving the accuracy of power battery state of charge estimation in the above-mentioned embodiment.

[0218] The computer-readable storage medium provided in this application may be, for example, a USB flash drive, but is not limited to electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, systems or devices, or any combination thereof. More specific examples of computer-readable storage media may include, but are not limited to: an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof. In this embodiment, the computer-readable storage medium may be any tangible medium that contains or stores a program that can be used by or in conjunction with an instruction execution system, system or device. The program code contained on the computer-readable storage medium may be transmitted using any appropriate medium, including but not limited to: wires, optical cables, RF (Radio Frequency), etc., or any suitable combination thereof.

[0219] The computer-readable storage medium carries one or more programs. When the one or more programs are executed by a test device for improving the accuracy of power battery state of charge estimation, the test device for improving the accuracy of power battery state of charge estimation: after the variable temperature box is set to a constant temperature mode and the temperature is adjusted to room temperature, the power battery is discharged with a constant current to a first state of charge, and is charged with a stepwise constant current to a second state of charge to complete full discharge and full charge; the variable temperature box is set to a temperature dynamic cycle mode, a temperature cycle test is performed, and the power battery that has been stationary is discharged to a third state of charge; based on the third state of charge and the fourth state of charge, a charge and discharge cycle test is performed on the power battery under preset cycle conditions; after the charge and discharge cycle test is completed, the power battery is discharged to the first state of charge to complete full discharge; based on the state of charge ampere-hour integral value of the charge and discharge device in the charge and discharge test and the state of charge BMS value obtained by the power battery management system, a relative error of the state of charge is determined; based on the relative error of the state of charge, a state of charge evaluation result is determined to improve the accuracy of state of charge estimation of the power battery management system.

[0220] Computer program code for carrying out the operations of the present application may be written in one or more programming languages, or a combination thereof, including object-oriented programming languages ​​such as Java, Smalltalk, C++, and conventional procedural programming languages ​​such as "C" or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer, or entirely on the remote computer or server.

[0221] The flow chart and block diagram in the accompanying drawings illustrate the possible architecture, function and operation of the system, method and computer program product according to various embodiments of the present application. In this regard, each box in the flow chart or block diagram can represent a module, program segment or a part of code, and the part of this module, program segment or code comprises one or more executable instructions for realizing the logical function of regulation. It should also be noted that in some as an alternative implementation, the function marked in the box can also occur in a different order than that marked in the accompanying drawings.

[0222] The computer-readable storage medium provided in this application is a computer-readable storage medium that stores computer-readable program instructions (i.e., a computer program) for executing the aforementioned test method for improving the accuracy of power battery state-of-charge estimation. This computer-readable storage medium can address the technical issues of complex and inaccurate calculation methods for state-of-charge estimation in power battery management systems. Compared to the prior art, the beneficial effects of the computer-readable storage medium provided in this application are the same as those of the test method for improving the accuracy of power battery state-of-charge estimation provided in the aforementioned embodiments, and are not further elaborated here.

[0223] The present application also provides a computer program product, including a computer program, which, when executed by a processor, implements the steps of the above-mentioned test method for improving the accuracy of power battery state of charge estimation.

[0224] The computer program product provided in this application can address the technical issues of complex and inaccurate calculation methods for state-of-charge estimation in power battery management systems. Compared to the prior art, the beneficial effects of the computer program product provided in this application are similar to those of the test method for improving the accuracy of power battery state-of-charge estimation provided in the aforementioned embodiments, and are not further elaborated here.

[0225] The above are only some embodiments of the present application and are not intended to limit the patent scope of the present application. All equivalent structural transformations made using the contents of the present application specification and drawings under the technical concept of the present application, or direct / indirect application in other related technical fields are included in the patent protection scope of the present application.

Claims

1. A test method for improving the accuracy of power battery state of charge estimation, characterized in that: A test system for power battery state of charge estimation accuracy, the test system comprising at least a variable temperature box, a power battery management system, and a charge-discharge device. The power battery is placed in the variable temperature box, the power battery management system and the charge-discharge device are respectively connected to the power battery, the charge-discharge device is used to perform charge and discharge tests on the power battery and record the ampere-hour integral value of the power battery's state of charge during the charge and discharge tests, and the power battery management system is used to obtain the state of charge (BMS) value of the power battery during the charge and discharge tests. After the variable temperature box is set to a constant temperature mode and the temperature is adjusted to room temperature, a temperature correction factor, a rate correction factor, and charge and discharge current data, charge and discharge time data, and state of charge data recorded by the charge and discharge device during the charge and discharge test are obtained; Obtaining a first correspondence between a temperature correction factor, a rate correction factor, charge and discharge current data, charge and discharge time data, state of charge data, and a battery rated capacity and a state of charge ampere-hour integral value; Obtaining the state-of-charge ampere-hour integral value based on the temperature correction factor, the rate correction factor, the charge and discharge current data, the charge and discharge time data, the state-of-charge data, the battery rated capacity, and the first corresponding relationship; The difference between the state-of-charge ampere-hour integral value and the state-of-charge BMS value is used as the state-of-charge relative error; Determining a state of charge evaluation result based on the state of charge relative error to improve the state of charge estimation accuracy of the power battery management system; wherein a second correspondence between battery temperature data, the temperature of the variable temperature box, the battery operating temperature threshold, a battery characteristic correction parameter, and a temperature correction factor is obtained; and the temperature correction factor is obtained based on the battery temperature data, the temperature of the variable temperature box, the battery operating temperature threshold, the battery characteristic correction parameter, and the second correspondence; Obtain battery temperature data, the temperature of the variable temperature box, the battery operating temperature threshold, charge and discharge current data, the battery rated capacity, the battery peak charge and discharge current, the battery temperature correction coefficient, the ambient temperature correction coefficient, the charge and discharge current correction coefficient, and a third correspondence between the rate correction factor; and obtain the rate correction factor based on the battery temperature data, the temperature of the variable temperature box, the battery operating temperature threshold, the charge and discharge current data, the battery rated capacity, the battery peak charge and discharge current, the battery temperature correction coefficient, the ambient temperature correction coefficient, the charge and discharge current correction coefficient, and the third correspondence.

2. The method according to claim 1, wherein After the step of setting the variable temperature box to a constant temperature mode and adjusting the temperature to room temperature, the step further includes: Discharging the power battery to a first state of charge using a constant current, and charging the power battery to a second state of charge using a stepwise constant current, thereby completing full discharge and full charge; Setting the variable temperature box to a temperature dynamic cycle mode, performing a temperature cycle test, and discharging the power battery after standing to a third state of charge; Based on the third state of charge and the fourth state of charge, performing a charge-discharge cycle test on the power battery under a preset cycle condition; After the charge-discharge cycle test is completed, the power battery is discharged to the first state of charge to complete full discharge.

3. The method according to claim 2, wherein The steps of discharging the power battery at a constant current to a first state of charge and charging it at a stepwise constant current to a second state of charge to complete full discharge and full charge include: Based on a first preset discharge rate, the power battery is discharged at a constant current to a first state of charge to complete full discharge; After the full discharge is completed, the power battery is charged to a second state of charge using a step constant current based on a preset step current to complete the full charge.

4. The method according to claim 2, wherein The step of setting the variable temperature box to a temperature dynamic cycle mode, performing a temperature cycle test, and discharging the power battery after standing to the third state of charge includes: Setting the variable temperature box to a temperature dynamic cycle mode, performing a temperature cycle test, and performing a rest treatment on the power battery based on a first rest time; After the resting is completed, the power battery in the second state of charge is discharged to the third state of charge based on the second preset discharge rate.

5. The method according to claim 2, wherein The step of performing a charge-discharge cycle test on the power battery under a preset cycle condition based on the third state of charge and the fourth state of charge includes: Under a preset cycle condition, discharging the power battery to the fourth state of charge based on a third preset discharge rate, and performing a rest treatment on the power battery based on a second rest time; charging the power battery to the third state of charge based on a fast charging strategy, and performing a rest process on the power battery based on a third rest time; Update the number of cycles and repeat the above steps until the number of cycles meets the preset number of cycles.

6. The method according to claim 2, wherein After the charge-discharge cycle test is completed, the step of discharging the power battery to the first state of charge to complete full discharge includes: After the charge-discharge cycle test is completed, discharging the power battery to a discharge cut-off voltage based on a fourth preset discharge rate; After the variable temperature box is set to a constant temperature mode and the temperature is adjusted to room temperature, performing a rest treatment on the power battery based on a fourth rest time; After the standing state is completed, the power battery is discharged to the first state of charge based on a fifth preset discharge rate to complete full discharge.

7. The method according to any one of claims 1 to 6, characterized in that The state of charge relative error includes the state of charge relative error of the charge-discharge cycle test and the state of charge relative error of the overall charge-discharge test; The step of determining a state of charge evaluation result based on the state of charge relative error to improve the state of charge estimation accuracy of the power battery management system includes: When the relative error of the state of charge of the charge-discharge cycle test is greater than a preset error threshold, determining that the state of charge evaluation result of the charge-discharge cycle test does not meet the accuracy requirement, and performing state of charge correction on the power battery management system to improve the state of charge estimation accuracy of the power battery management system; When the relative error of the state of charge of the overall charge and discharge test is greater than a preset error threshold, it is determined that the state of charge evaluation result of the overall charge and discharge test does not meet the accuracy requirements, and the state of charge of the power battery management system is corrected to improve the state of charge estimation accuracy of the power battery management system.

8. A test device for improving the accuracy of power battery state of charge estimation, characterized in that: The device applies the test method for improving the accuracy of power battery state of charge estimation according to any one of claims 1 to 7, and the device includes: a test module, configured to, after the variable temperature box is set to a constant temperature mode and the temperature is adjusted to room temperature, discharge the power battery at a constant current to a first state of charge, and perform stepwise constant current charging to a second state of charge, so as to complete full discharge and full charge; The test module is further configured to set the variable temperature box to a dynamic temperature cycle mode, perform a temperature cycle test, and discharge the power battery after rest to a third state of charge; The testing module is further configured to perform a charge-discharge cycle test on the power battery under a preset cycle condition based on the third state of charge and the fourth state of charge; The testing module is further configured to discharge the power battery to the first state of charge after the charge-discharge cycle test is completed, so as to achieve full discharge; An evaluation module is used to determine the relative error of the state of charge based on the ampere-hour integral value of the state of charge of the charging and discharging equipment during the charge and discharge test and the state of charge BMS value obtained by the power battery management system; The evaluation module is further configured to determine a state of charge evaluation result based on the state of charge relative error, so as to improve the state of charge estimation accuracy of the power battery management system.

9. A test device for improving the accuracy of power battery state of charge estimation, characterized in that: The device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the computer program is configured to implement the steps of the test method for improving the accuracy of power battery state of charge estimation as described in any one of claims 1 to 7.

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