Testing method, apparatus and device for improving the estimation precision of state of charge of power battery

Abstract

A testing method, apparatus and device for improving the estimation precision of the state of charge of a power battery, relating to the technical field of power batteries. The method comprises: discharging a power battery to a first state of charge at a constant current, and charging the power battery to a second state of charge at a stepped constant current; under a variable temperature working condition, discharging the power battery after resting to a third state of charge; on the basis of the third state of charge and a fourth state of charge, performing a charge and discharge cycle test on the power battery; discharging the power battery to the first state of charge; on the basis of a state-of-charge ampere-hour integral value obtained by a charge and discharge device and a state-of-charge BMS value obtained by a power battery management system, determining a state-of-charge relative error (S50); and determining a state-of-charge evaluation result to improve the estimation precision of the state of charge of the power battery management system.

Description

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

[0001] The present application claims priority to Chinese Patent Application No. 202410982060.1, filed on July 22, 2024, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0002] The present application relates to the technical field of power batteries, in particular to a test method, device and equipment for improving estimation accuracy of state of charge of power batteries. BACKGROUND

[0003] A power battery management system (BMS) ensures the safe and efficient operation of the battery, and is crucial to improving the overall performance, safety and cycle life of an electric vehicle. The estimation of the state of charge (SOC) of the battery by the BMS is an important part of power battery management, which can provide accurate battery usage information for the driver or operator, understand the remaining capacity of the battery, and provide basic data for the charge and discharge management, thermal management and health management of the battery. Due to the complex structure of the battery and the numerous factors affecting the state of charge of the battery, there is currently less research on the test method for estimating the state of charge of the power battery management system, and the calculation method for estimating the state of charge of the power battery management system is complex and has insufficient accuracy.

[0004] The above content is only used to assist in understanding the technical solutions of the present application and does not represent an acknowledgement that the above content is prior art.

[0005] SUMMARY

[0006] The main purpose of the present application is to provide a test method, device and equipment for improving the estimation accuracy of the state of charge of power batteries, which aims to solve the technical problem of complex calculation method and insufficient accuracy of the state of charge estimation of the power battery management system in the prior art.

[0007] To achieve the above purpose, the present application provides a test method for improving the estimation accuracy of the state of charge of power batteries, which is applied to a test system for improving the estimation accuracy of the state of charge of power batteries. The test system for improving the estimation accuracy of the state of charge of power batteries at least includes a variable temperature box, a power battery management system and a charge and discharge device. The power battery is placed in the variable temperature box. The power battery management system and the charge and discharge device are respectively connected to the power battery. The charge and discharge device is used for charge and discharge test of the power battery and records the state of charge ampere-hour integral value of the power battery in the charge and discharge test. The power battery management system is used for obtaining the state of charge BMS value of the power battery in the charge and discharge test. The test method for improving the estimation accuracy of the state of charge of power batteries includes:

[0008] After the variable temperature oven is set to the constant temperature mode and the temperature is adjusted to the room temperature, the power battery is discharged to a first state of charge at a constant current and is charged to a second state of charge at a constant current in steps to complete full discharge and full charge;

[0009] The variable temperature oven is set to a temperature dynamic cycle mode, and a temperature cycle test is performed, and the power battery completed with standing is discharged to a third state of charge;

[0010] Based on the third state of charge and the fourth state of charge, the power battery is subjected to a charge-discharge cycle test 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;

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

[0012] Based on the state of charge relative error, a state of charge evaluation result is determined to improve the state of charge estimation accuracy of the power battery management system.

[0013] In an embodiment, after the variable temperature oven is set to the constant temperature mode and the temperature is adjusted to the room temperature, the power battery is discharged to a first state of charge at a constant current and is charged to a second state of charge at a constant current in steps to complete full discharge and full charge, and the steps include:

[0014] After the variable temperature oven is set to the constant temperature mode and the temperature is adjusted to the room temperature, the power battery is discharged to a first state of charge at a constant current based on a first preset discharge rate to complete full discharge;

[0015] After full discharge is completed, the power battery is charged to a second state of charge at a constant current in steps based on a preset step current to complete full charge.

[0016] In an embodiment, the variable temperature oven is set to a temperature dynamic cycle mode, and a temperature cycle test is performed, and the power battery completed with standing is discharged to a third state of charge, and the steps include:

[0017] The variable temperature oven is set to a temperature dynamic cycle mode, and a temperature cycle test is performed, and the power battery is subjected to standing treatment based on a first standing time;

[0018] After standing is completed, the power battery in the second state of charge is discharged to the third state of charge based on a second preset discharge rate.

[0019] In an embodiment, based on the third state of charge and the fourth state of charge, the power battery is subjected to a charge-discharge cycle test under a preset cycle condition, and the steps include:

[0020] discharge the power battery to a fourth state of charge based on a third preset discharge rate, and perform a standing treatment on the power battery based on a second standing time under a preset cycle condition;

[0021] charge the power battery to a third state of charge based on a fast charging strategy, and perform a standing treatment on the power battery based on a third standing time;

[0022] update the cycle number, and repeat the above steps until the cycle number meets a preset cycle number.

[0023] In an embodiment, the step of discharging the power battery to the first state of charge to complete full discharge after the charge-discharge cycle test is completed includes:

[0024] 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; and perform a standing treatment on the power battery based on a fourth standing time after the variable temperature box is set to a constant temperature mode and the temperature is adjusted to room temperature;

[0025] discharge the power battery to the first state of charge based on a fifth preset discharge rate after the standing is completed to complete full discharge.

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

[0027] obtaining a temperature correction factor, a rate correction factor, and charge-discharge current data, charge-discharge time data, and state of charge data recorded by the charge-discharge equipment in the charge-discharge test;

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

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

[0030] obtaining a state of charge BMS value obtained by the power battery management system, and taking a difference between the state of charge ampere-hour integral value and the state of charge BMS value as a state of charge relative error.

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

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

[0033] obtain the 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;

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

[0035] 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-discharge current data, the battery rated capacity, the battery peak charge-discharge current, the battery temperature correction coefficient, the ambient temperature correction coefficient, the charge-discharge current correction coefficient, and the third corresponding relationship.

[0036] In an embodiment, the state of charge relative error includes a state of charge relative error of the charge-discharge cycle test and a state of charge relative error of the overall charge-discharge test.

[0037] Based on the state of charge relative error, the step of determining the state of charge evaluation result to improve the state of charge estimation accuracy of the power battery management system includes:

[0038] When the state of charge relative error of the charge-discharge cycle test is greater than the preset error threshold, the state of charge evaluation result of the charge-discharge cycle test is determined to be that the accuracy does not meet the 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.

[0039] When the state of charge relative error of the overall charge-discharge test is greater than the preset error threshold, the state of charge evaluation result of the overall charge-discharge test is determined to be that the accuracy does not meet the 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 application also provides a test device for improving the state of charge estimation accuracy of a power battery, which comprises:

[0041] The test module is configured to discharge the power battery at a constant current to a first state of charge and charge the power battery at a constant current to a second state of charge in a step-by-step manner 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 configured to set the variable temperature box to a temperature dynamic cycle mode, perform a temperature cycle test, and discharge the power battery at rest to a third state of charge.

[0043] The test module is further configured to perform 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 the first state of charge after the charge-discharge cycle test is completed, so as to complete full discharge;

[0045] The evaluation module is configured to determine a state of charge relative error based on the state of charge ampere-hour integral value of the charge-discharge equipment in the charge-discharge test and the state of charge BMS value obtained by the power battery management system;

[0046] 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.

[0047] In addition, to achieve the above object, the application further provides a test device for improving the state of charge estimation accuracy of a power battery, which comprises a memory, a processor and a computer program stored in the memory and executable on the processor, and the computer program is configured to implement the steps of the test method for improving the state of charge estimation accuracy of a power battery.

[0048] In addition, to achieve the above object, the application further provides a storage medium, which is a computer readable storage medium, and the storage medium stores a computer program, and the computer program is executed by a processor to implement the steps of the test method for improving the state of charge estimation accuracy of a power battery.

[0049] In addition, to achieve the above object, the application further provides a computer program product, which comprises a computer program, and the computer program is executed by a processor to implement the steps of the test method for improving the state of charge estimation accuracy of a power battery.

[0050] The application provides a test method for improving the estimation accuracy of the state of charge of a power battery, 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 to a first state of charge at a constant current, and is charged to a second state of charge at a constant current in steps, so as 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 after standing is discharged to a third state of charge; based on the third state of charge and the fourth state of charge, the power battery is subjected to a charge-discharge cycle test under a preset cycle condition; after the charge-discharge cycle test is completed, the power battery is discharged to the first state of charge, so as to complete full discharge; based on the state of charge relative error of the state of charge of the charge-discharge equipment in the charge-discharge test and the state of charge BMS value obtained by the power battery management system, the state of charge evaluation result is determined, so as to improve the state of charge estimation accuracy of the power battery management system. The application uses the state of charge ampere-hour integral value obtained by the charge-discharge equipment based on the ampere-hour integral method to determine the state of charge relative error under the variable temperature condition, determines the state of charge evaluation result based on the design threshold of the state of charge relative error, and performs real-time SOC correction, so as to improve the state of charge estimation accuracy of the power battery management system. The test method is simple and convenient, easy to operate, effectively saves the development cost, and solves the technical problems of complex calculation method and insufficient precision of the state of charge estimation of the power battery management system. BRIEF DESCRIPTION OF DRAWINGS

[0051] The drawings incorporated into the specification and constituting a part of the specification show embodiments consistent with the application and, together with the specification, serve to explain the principles of the application.

[0052] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, those drawings can also provide other drawings based on the drawings without creative labor for those skilled in the art.

[0053] Fig. 1 is a structural schematic diagram of a test system for improving the estimation accuracy of the state of charge of a power battery involved in the test method for improving the estimation accuracy of the state of charge of a power battery according to the application;

[0054] Fig. 2 is a detailed structural schematic diagram of the test system for improving the estimation accuracy of the state of charge of a power battery involved in the test method for improving the estimation accuracy of the state of charge of a power battery according to the application;

[0055] Fig. 3 is a flow schematic diagram of embodiment one of the test method for improving the estimation accuracy of the state of charge of a power battery according to the application;

[0056] Fig. 4 is a schematic diagram of stepwise constant current charging provided by the test method for improving the estimation accuracy of the state of charge of a power battery according to embodiment one of the application;

[0057] FIG. 5 is a flowchart of a second embodiment of the test method for improving the estimation accuracy of the state of charge of the power battery according to the present application;

[0058] FIG. 6 is a flowchart of the test method for improving the estimation accuracy of the state of charge of the power battery according to the second embodiment of the present application;

[0059] FIG. 7 is a block diagram of the test device for improving the estimation accuracy of the state of charge of the power battery according to the present application;

[0060] FIG. 8 is a device structure diagram of the hardware operating environment involved in the test method for improving the estimation accuracy of the state of charge of the power battery according to the present application.

[0061] The implementation, functional features and advantages of the present application will be further described with reference to the accompanying drawings. DETAILED DESCRIPTION

[0062] It should be understood that the specific embodiments described herein are merely intended 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 solutions of the present application, the following will be described in detail with reference to the accompanying drawings and specific embodiments.

[0064] The main solution of the present application is as follows: after setting the variable temperature box to the constant temperature mode and adjusting the temperature to room temperature, the power battery is discharged at a constant current to a first state of charge, and is charged at a constant current in steps to a second state of charge, so as to complete full discharge and full charge; the variable temperature box is set to the temperature dynamic cycle mode, and the temperature cycle test is performed, and the power battery after standing is discharged to a third state of charge; based on the third state of charge and the fourth state of charge, the power battery is subjected to charge-discharge cycle test under a preset cycle condition; after the charge-discharge cycle test is completed, the power battery is discharged to the first state of charge, so as to complete full discharge; based on the state of charge relative error of the state of charge of the charge-discharge equipment in the charge-discharge test and the state of charge BMS value obtained by the power battery management system, the state of charge evaluation result is determined, so as to improve the state of charge estimation accuracy of the power battery management system.

[0065] At present, there is less research on the test method for the state of charge estimation of the power battery management system, and the calculation method of the state of charge estimation of the power battery management system is complex and has insufficient accuracy.

[0066] The application provides a solution. For variable temperature conditions, the state of charge relative error is determined by using the state of charge ampere-hour integral value obtained by the charging and discharging equipment based on the ampere-hour integral method, the state of charge evaluation result is determined based on the design threshold of the state of charge relative error, and the SOC is corrected in real time, so as 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 saves the development cost, and solves the technical problems of complex calculation method and insufficient precision of the state of charge estimation of the power battery management system.

[0067] The embodiment is applied to a test system for improving the state of charge estimation accuracy of a power battery. Referring to FIG. 1, the test system for improving the state of charge estimation accuracy of a power battery at least includes a variable temperature box 1, a power battery management system (BMS) 2, a charging and discharging equipment 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 equipment 3 are respectively connected to the power battery 4 through the CAN bus 5.

[0068] The BMS can generally realize functions such as online monitoring of battery state, SOC estimation, analysis of battery health state and implementation of necessary thermal management, so as to ensure safe operation of the battery pack and prolong the cycle life of the battery. For example, the BMS can collect the terminal voltage and temperature of each battery in the power battery pack of an electric vehicle, the charging and discharging current and the total voltage of the battery pack in real time, and prevent overcharging or overdischarging of the battery; the BMS can balance the charging and discharging of the single batteries in the power battery pack, so that each battery 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 voltage of the single battery is too high / low, whether the temperature rise of the battery is too fast, whether the insulation is faulty, whether the current is too high, whether the consistency of the battery is analyzed, whether the battery pack is faulty and whether the communication is faulty, etc.

[0069] In the embodiment, the charging and discharging equipment 3 is used for charging and discharging test of the power battery 4 and recording the state of charge ampere-hour integral value of the power battery 4 in the charging and discharging test, and the power battery management system 2 is used for obtaining the state of charge BMS value of the power battery 4 in the charging and discharging test. The state of charge ampere-hour integral value can be generally determined according to the data recorded by the charging and discharging equipment 3, and the state of charge BMS value is the SOC value estimated by the power battery management system 2, and there is a certain error between the state of charge ampere-hour integral value and the state of charge BMS value. The CAN bus 5 is used for connecting the power battery management system 2 and the power battery 4, and also used for connecting the charging and discharging equipment 3 and the power battery 4, so as to realize 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 temperature dynamic cycle mode.

[0070] In an embodiment, referring to FIG. 2, the test system for improving the estimation accuracy of the state of charge of the power battery can further include an oscilloscope, a power supply, a multimeter, a debugging bench, a CAN bus, a bus monitoring device, a notebook computer, and the like, which are not specifically limited in the embodiment. The CAN bus is used to connect the BMS battery management system and the notebook computer, and is used for data transmission between the BMS and the notebook computer, so as to obtain the SOC value estimated by the BMS. The CAN bus is also used to connect the charging and discharging device and the power battery, so as to obtain the state of charge ampere-hour integral value of the power battery.

[0071] The embodiment of the present application provides a test method for improving the estimation accuracy of the state of charge of the power battery. Referring to FIG. 3, FIG. 3 is a flowchart of a first embodiment of the test method for improving the estimation accuracy of the state of charge of the power battery.

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

[0073] In step S10, after the variable temperature box is set to the constant temperature mode and the temperature is adjusted to the room temperature, the power battery is discharged at a constant current to a first state of charge, and is charged at a constant current to a second state of charge in steps, so as to complete full discharge and full charge.

[0074] In the embodiment, the entire charging and discharging test includes 11 stages. Different stages usually need to perform different charging and discharging operations, and the charging and discharging operations can be realized by the charging and discharging device.

[0075] In addition, in the embodiment, under the variable temperature condition, the test method is used to obtain the state of charge BMS value and the state of charge ampere-hour integral value of the power battery management system, determine the state of charge evaluation result, and thus real-time correct the SOC, so as to improve the estimation accuracy of the state of charge of the power battery management system.

[0076] In a feasible implementation manner, step S10 can include steps S101-S102.

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

[0078] Generally, 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] The variable temperature box is set to a constant temperature mode, and the temperature is adjusted to room temperature, usually 25 DEG C. The first stage is a preparation stage, and the power battery needs to be fully discharged. In this embodiment, a constant current discharge mode is used. The first preset discharge rate is the discharge rate used in the first stage. In this embodiment, a lower discharge rate is selected, for example, 1 / 3C, that is, the size of the discharge current is 1 / 3 of the rated capacity of the battery. Other appropriate 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] In the first stage, the power battery is discharged at a discharge rate of 1 / 3C to SOC=0. In this process, since a low discharge rate is used, the polarization of the electrode is small, and the active material can be fully utilized, which is beneficial to the discharge process and can completely release the battery capacity, which is beneficial to the use safety and cycle life of the power battery.

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

[0082] After the full discharge is completed, the second stage is entered, and the second stage to the eleventh stage is a test stage. The second stage needs to fully charge the power battery, and in this embodiment, a step constant current charging mode is used. The preset step current is a step current used in the second stage charging process, which can be set according to actual needs, and this is not specifically limited. In this embodiment, the second state of charge is SOC equal to 100%, that is, a full charge state.

[0083] In addition, a plurality of preset step currents are usually set in the step constant current charging, and reference is made to FIG. 4. It is assumed that 7 preset step currents are set, which are I1, I2, I3, I4, I5, I6 and I7 respectively. The whole step constant current charging process is as follows: charging according to I1 until the single battery reaches the charging cut-off voltage specified in the technical conditions; charging according to I2 until the single battery reaches the charging cut-off voltage specified in the technical conditions; charging according to I3 until the single battery reaches the charging cut-off voltage specified in the technical conditions; charging according to I4 until the single battery reaches the charging cut-off voltage specified in the technical conditions; charging according to I5 until the single battery reaches the charging cut-off voltage specified in the technical conditions; charging according to I6 until the single battery reaches the charging cut-off voltage specified in the technical conditions; and charging according to I7 until the single battery reaches the charging cut-off voltage specified in the technical conditions. At this time, the battery system is in a full charge state. In this embodiment, I1>I2>I3>I4>I5>I6>I7, and exemplarily, I1=1 / 3C, I2=1 / 6C, I3=1 / 10C, I4=1 / 15C, I5=1 / 20C, I6=1 / 25C and I7=1 / 30C. The step charging mode with low rate and small current can weaken the polarization of the battery (including concentration polarization, electrochemical polarization and ohmic polarization), reduce the internal resistance of the battery, ensure that the active material can be fully utilized, ensure that the battery reaches the full charge state, prevent overcharging of the battery, balance the charging of the single battery in the power battery pack, and ensure that each battery cell reaches a balanced state, ensures the consistency of the battery, and ensures the safety performance and cycle life of the battery. In addition, considering that too small a charging current may not be able to charge the battery cell, the charging rate should be reasonably set, and the number of step currents should be reasonably set considering the time cost, which is not limited in this embodiment.

[0084] In the second stage, the power battery is step constant current charged according to the preset step current to SOC=100%.

[0085] In the first stage to the second stage, the variable temperature box is set to a constant temperature mode, and the temperature is adjusted to room temperature, which can be set to 25℃ or other values according to actual needs, which is not limited in this embodiment.

[0086] In step S20, the variable temperature box is set to a temperature dynamic cycle mode, and a temperature cycle test is performed. The power battery after the static treatment is discharged to a third state of charge.

[0087] In an available embodiment, step S20 can include steps S201-S202.

[0088] In step S201, the variable temperature box is set to a temperature dynamic cycle mode, and a temperature cycle test is performed. The power battery is statically treated based on the first static time.

[0089] After the completion of the full charging of the second stage, the third stage is entered, which requires static treatment of the power battery under a variable temperature condition. Therefore, the variable temperature box is set to a temperature dynamic cycle mode, i.e., a variable temperature condition, which generally needs to cover the normal working temperature range of the power battery. The temperature cycle test is a kind of simulation of the working environment of the power battery under different temperature conditions, which can comprehensively test the key performance indicators such as the electrochemical performance, thermal stability and mechanical stability of the power battery under different temperature conditions.

[0090] The temperature dynamic cycle mode needs to set an initial temperature, a linear temperature change rate, a minimum temperature and a maximum temperature. The initial temperature is the temperature of the variable temperature box at the initial moment of the temperature cycle test. The temperature dynamic cycle mode takes the initial temperature as the starting point, cools down to the minimum temperature at the linear temperature change rate, then warms up to the maximum temperature at the linear temperature change rate, and then cools down to the minimum temperature at the linear temperature change rate, and so on. For example, the normal working temperature range of the power battery is-20℃-45℃, the initial temperature can be set to 25℃, which is the temperature of the variable temperature box in the first stage when the variable temperature box is in the constant temperature mode, the linear temperature change rate is 5℃ / h, the minimum temperature is-20℃, and the maximum temperature is 45℃. The process of the temperature cycle test is to start from 25℃, cool down to-20℃ at a rate of 5℃ / h, then warm up to 45℃ at a rate of 5℃ / h, and then cool down to-20℃ at a rate of 5℃ / h, and so on. The temperature cycle test can be flexibly adjusted according to actual needs, and no specific limitation is made.

[0091] In addition, after the completion of the full charging, the third stage is entered, which requires static treatment of the power battery. The first static time is the time required for the static treatment of the third stage, which is usually greater than or equal to 30 minutes.

[0092] In the third stage, the BMS power supply is disconnected within 1 min after the battery is fully charged, the variable temperature box is set to the temperature dynamic cycle mode at the same time, and the BMS power supply is connected after static for more than 30 min. The BMS data and the charge-discharge equipment data during the static time are recorded, the SOC is adjusted to 100%, then the BMS power supply is disconnected within 1 min, and the static treatment is performed. The static treatment can eliminate the polarization of the electrode, and the correction operation of adjusting the SOC to 100% can be completed during the static treatment.

[0093] The BMS data and the charge-discharge equipment data can include the temperature of the battery, the charge-discharge current, the charge-discharge time, the true value of the state of charge, the BMS value of the state of charge, etc.

[0094] In step S202, after the completion of the static treatment, the power battery of the second state of charge is discharged to the third state of charge based on a second preset discharge rate.

[0095] After the third stage of standing is completed, the fourth stage is entered, and the power battery needs to be discharged in the fourth stage. The second preset discharge rate is the discharge rate used in the fourth stage. In this embodiment, a lower discharge rate is selected, for example, 1 / 3C, and other appropriate low discharge rates can also be selected, and no specific limitation is made in this regard. In this embodiment, the third state of charge is SOC equal to 80%.

[0096] 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. In step S30, based on the third state of charge and the fourth state of charge, the power battery is subjected to charge-discharge cycle test under the preset cycle condition;

[0097] The preset cycle condition is NEDC / WLTC condition, wherein NEDC (New European Driving Cycle) is a European endurance test standard, and WLTC (Worldwide Harmonized Light Vehicles Test Cycle) is a new type of cycle test standard developed by the United Nations.

[0098] In addition, after the fourth stage is completed, the fifth stage to the eighth stage are entered, and in this embodiment, the fifth stage to the eighth stage are subjected to charge-discharge cycle test, that is, the charge-discharge operation of the fifth stage to the eighth stage needs to be performed multiple times according to the set cycle number.

[0099] In a feasible implementation manner, step S30 can include steps S301-S303:

[0100] In step S301, under the preset cycle condition, the power battery is discharged to the fourth state of charge based on the third preset discharge rate, and the power battery is subjected to standing treatment based on the second standing time;

[0101] The fifth stage needs to discharge the power battery. The third preset discharge rate is the discharge rate used in the fifth stage. In this embodiment, a lower discharge rate is selected, for example, 1 / 3C. Since the actual capacity of the battery is closely related to the discharge current, when the discharge current is large, the polarization of the electrode is enhanced, the polarization internal resistance is increased, the discharge voltage is quickly reduced, and the energy efficiency of the battery is reduced, thereby resulting in a lower actual discharge capacity. Therefore, in the NEDC / WLTC cycle condition, a low-rate discharge current of 1 / 3C is used, the discharge voltage is slowly reduced, which is beneficial to the discharge process of the battery, and other appropriate low discharge rates can also be selected. The discharge rate can be flexibly adjusted according to the actual situation (battery characteristics, battery materials, specifications, etc.), and no specific limitation is made in this regard. At the same time, the time cost needs to be considered to determine the discharge rate, and the relationship between the discharge time, SOC and the discharge rate satisfies:

[0102] In the formula, the initial SOC is the SOC value before discharging, the target SOC refers to the target SOC value after discharging, σ is the discharging current ratio, and T is the discharging time (unit: h). For example, if the initial SOC = 80%, the target SOC = 30%, and the discharging current ratio σ = 1 / 3, the discharging time is 1.5 h. In this embodiment, the fourth state of charge is SOC equal to 30%.

[0103] In addition, the sixth stage requires static treatment of the power battery, and the second static time is the time required for the static treatment of the sixth stage. The second static time usually needs to be greater than or equal to 30 minutes. The purpose of the static treatment is to eliminate the polarization of the electrode, and the battery SOC correction operation can be performed during the static treatment.

[0104] In the fifth stage to the sixth stage, the power battery is discharged to SOC = 30% under the NEDC / WLTC working condition at a discharging current ratio of 1 / 3 C. The BMS data and the charging and discharging equipment data during the discharging process are recorded. The BMS power supply is disconnected within 1 min, and the static treatment is performed for more than half an hour.

[0105] In step S302, the power battery is charged to the third state of charge based on the fast charging strategy, and the power battery is subjected to static treatment based on the third static time.

[0106] After the static treatment of the sixth stage is completed, the seventh stage is entered, and the power battery needs to be charged to SOC = 80%. The fast charging strategy is the way of fast charging, for example, 3C high-rate charging, 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.

[0107] In the seventh stage, the BMS power supply is turned on, the BMS data and the charging and discharging equipment data during the static time are recorded, the power battery is charged to SOC = 80% by the fast charging strategy, and the BMS data and the charging and discharging equipment data during the charging process are recorded. In addition, the eighth stage requires static treatment of the power battery, and the third static time is the time required for the static treatment of the eighth stage. The third static time usually needs to be greater than or equal to 30 minutes.

[0108] In the eighth stage, the BMS power supply is disconnected, and the static treatment is performed for more than half an hour. The BMS power supply is connected within 1 min, and the BMS data and the charging and discharging equipment data during the static time are recorded.

[0109] In step S303, the cycle number is updated, and the above steps are repeatedly executed until the cycle number meets the preset cycle number.

[0110] After each round of the fifth stage to the eighth stage of the charge and discharge operation, the cycle number +1. The preset cycle number is the set number of cycles required, for example: 10 times, when the cycle number reaches 10 times, the charge and discharge cycle test is completed, and when the cycle number does not reach 10 times, the next round of charge and discharge operation is continued.

[0111] Step S40, after the charge and discharge cycle test is completed, the power battery is discharged to the first state of charge to complete the full discharge; in an available embodiment, step S40 can include steps S401-S403:

[0112] Step S401, after the charge and discharge cycle test is completed, the power battery is discharged to the discharge cut-off voltage based on the fourth preset discharge rate;

[0113] After the charge and discharge cycle test is completed, enter the ninth stage, the fourth preset discharge rate is the discharge rate used in the ninth stage, and a lower discharge rate is selected in this embodiment, for example: 1 / 3C, or other appropriate low discharge rate, which is not specifically limited.

[0114] In the ninth stage, the BMS power supply is turned on, and the power battery is discharged to the discharge cut-off voltage at a discharge rate of 1 / 3C under NEDC / WLTC working conditions. Since the variable temperature box is in a temperature dynamic cycle mode in this stage, the activity of the electrode active material is low at subzero low temperature, which is not conducive to ion diffusion, the polarization of the battery is large, which causes the polarization resistance to increase, resulting in the phenomenon of frozen end capacity of the battery, so that part of the battery capacity cannot be normally released. Therefore, at subzero low temperature, a lower discharge rate can be used, for example, from 1 / 3C to 1 / 10C, which is beneficial to the battery discharge process and improves the discharge efficiency of the power battery.

[0115] According to different types and different discharge conditions of the power battery, the capacity and service life of the battery are different, and the set discharge cut-off voltage is also different, so the discharge cut-off voltage in this embodiment can be flexibly adjusted according to the actual situation, which is not specifically limited.

[0116] 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 static treatment based on the fourth static time;

[0117] Next, enter the tenth stage, the temperature of the variable temperature box needs to be set to room temperature (usually 25℃), and the power battery is subjected to a static treatment. The fourth static time is the time required for the static treatment in the tenth stage, and the fourth static time usually needs to be greater than or equal to 8 hours, so that the temperature of the power battery and the ambient temperature of the variable temperature box reach a balanced state (the temperature difference between the power battery and the room temperature is not greater than 2℃), on the other hand, the static treatment can eliminate the polarization of the power battery.

[0118] In the tenth stage, the temperature of the variable temperature box is set to 25°C, the BMS power supply is disconnected within 1 min, and the power battery is left to stand for more than 8 hours.

[0119] In step S403, after the standing is completed, the power battery is discharged to a first state of charge based on a fifth preset discharge rate, so as to complete full discharge.

[0120] After the standing in the tenth stage is completed, the eleventh stage is entered. In order to ensure full discharge of the power battery, the eleventh stage needs to continue discharging. The fifth preset discharge rate is the discharge rate used in the twelfth stage. In order to avoid the situation that the SOC is 0 in advance but the lower limit of the voltage is not triggered, a low-rate current should be discharged to reduce the polarization of the battery, which is conducive to the discharging process of the battery and the completion of full discharge. Therefore, a lower discharge rate is selected in this embodiment, for example, 0.05C. Other appropriate low discharge rates can also be selected, and no specific limitation is made in this regard.

[0121] In the eleventh stage, the BMS power supply is connected, and the power battery is discharged to SOC=0 at a discharge rate of 0.05C. The BMS data and the charge-discharge equipment data in the discharging process are recorded.

[0122] In step S50, the state of charge relative error is determined based on the state of charge ampere-hour integral value recorded by the charge-discharge equipment in the charge-discharge test and the state of charge BMS value obtained by the power battery management system.

[0123] The state of charge relative error is the error between the state of charge ampere-hour integral value recorded by the charge-discharge equipment in the charge-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 state of charge estimation of the BMS, the state of charge relative error usually cannot exceed a certain value.

[0124] In step S60, the state of charge evaluation result is determined based on the state of charge relative error, so as to improve the state of charge estimation accuracy of the power battery management system.

[0125] The state of charge evaluation result is the condition of evaluating the state of charge estimation accuracy of the power battery management system. There are usually two conditions: the accuracy meets the requirements and the accuracy does not meet the requirements. The state of charge relative error includes the state of charge relative error in the charge-discharge cycle test and the state of charge relative error in the overall charge-discharge test, wherein the overall charge-discharge test refers to the entire charge-discharge test process. Based on the state of charge relative error in the charge-discharge cycle test, the state of charge evaluation result in the charge-discharge cycle test can be determined in this embodiment. Based on the state of charge relative error in the overall charge-discharge test, the state of charge evaluation result in the overall charge-discharge test can be determined in this embodiment.

[0126] In a feasible implementation, when the state of charge relative error of the charge-discharge cycle test is greater than the preset error threshold, it is determined that the state of charge evaluation result of the charge-discharge cycle test is that the accuracy does not meet the requirement, 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.

[0127] The preset error threshold is the design threshold of the state of charge relative error, that is, the state of charge relative error needs to be less than or equal to the preset error threshold. For different battery types, material systems, battery designs, manufacturing processes, and specific test conditions, the preset error threshold is different, which can be flexibly adjusted according to the specific situation to ensure the performance and safety of the battery, and no specific limitation is made, and exemplarily, the preset error threshold of the ternary lithium type power battery is set to 3%, and the preset error threshold of the lithium iron phosphate type power battery is set to 5%.

[0128] The state of charge relative error of the charge-discharge cycle test is greater than the preset error threshold, which indicates that the state of charge evaluation result of the charge-discharge cycle test is that the accuracy does not meet the requirement, and at this time, the SOC of the power battery management system needs to be corrected, and the correction event is recorded for debugging analysis, so as to improve the state of charge estimation accuracy of the power battery management system. The correction can be performed during the static period. The state of charge relative error of the charge-discharge cycle test is less than or equal to the preset error threshold, which indicates that the state of charge evaluation result of the charge-discharge cycle test is that the accuracy meets the requirement.

[0129] In a feasible implementation, when the state of charge relative error of the charge-discharge cycle test is greater than the preset error threshold, it is determined that the state of charge evaluation result of the charge-discharge cycle test is that the accuracy does not meet the requirement, 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.

[0130] The state of charge relative error of the charge-discharge cycle test is greater than the preset error threshold, which indicates that the state of charge evaluation result of the charge-discharge cycle test is that the accuracy does not meet the requirement, and at this time, the SOC of the power battery management system needs to be corrected, and the correction event is recorded for debugging analysis, so as to improve the state of charge estimation accuracy of the power battery management system. The correction can be performed during the static period. The state of charge relative error of the charge-discharge cycle test is less than or equal to the preset error threshold, which indicates that the state of charge evaluation result of the charge-discharge cycle test is that the accuracy meets the requirement.

[0131] The embodiment provides a test method for improving the estimation accuracy of the state of charge 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 at a constant current to a first state of charge, and is charged at a constant current to a second state of charge in steps, so as 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. The power battery after static placement is discharged to a third state of charge. Based on the third state of charge and a fourth state of charge, the power battery is subjected to a charge-discharge cycle test under a preset cycle condition. After the charge-discharge cycle test is completed, the power battery is discharged to the first state of charge, so as to complete full discharge. Based on the state of charge relative error of the state of charge of the charge-discharge equipment in the charge-discharge test and the state of charge BMS value obtained by the power battery management system, the state of charge evaluation result is determined, so as to improve the state of charge estimation accuracy of the power battery management system. For the variable temperature condition, the state of charge relative error is determined by using the state of charge ampere-hour integral value obtained by the charge-discharge equipment based on the ampere-hour integral method, the state of charge evaluation result is determined based on the design threshold of the state of charge relative error, the SOC is corrected in real time, so as to improve the state of charge estimation accuracy of the power battery management system. The test method is simple and convenient, easy to operate, and effectively saves the development cost.

[0132] Based on the first embodiment of the application, in the second embodiment of the application, the same or similar contents as the above-mentioned first embodiment can be referred to the above introduction, and the subsequent will not be repeated. On this basis, please refer to FIG. 5, the step S50 can include steps S501-S504:

[0133] In step S501, the temperature correction factor, the rate correction factor, and the charge-discharge current data, the charge-discharge time data and the state of charge data recorded by the charge-discharge equipment in the charge-discharge test are obtained.

[0134] Since the present embodiment is directed to variable temperature working conditions, the influence of temperature on performance parameters including battery internal resistance (polarization internal resistance, ohmic internal resistance), chemical reaction rate, electrode active material, etc. needs to be considered, for example: 1) In low temperature working conditions, the activity of electrode active material is low, which is not conducive to ion diffusion, the polarization of the battery is large, which causes the polarization internal resistance to increase, resulting in the phenomenon of freezing of the end capacity of the battery, so that part of the battery capacity cannot be normally released; 2) In high temperature working conditions, the rate of internal chemical reaction of the battery is accelerated, which causes the battery to age faster, thereby shortening the cycle life of the battery; 3) In large current discharge, the polarization of the electrode is large, the internal resistance of the battery increases, the discharge voltage drops quickly, the energy efficiency of the battery is reduced, and the actual capacity discharged is low. Correspondingly, under low rate discharge conditions, the discharge voltage drops slowly, which is conducive to the charging and discharging process of the battery; 4) In large current charging, as the charging current increases, the negative electrode potential gradually decreases. For lithium batteries, when the negative electrode potential is lower than the lithium precipitation potential, there is a risk of lithium precipitation, which is easy to form lithium dendrites, pierce the separator and cause short circuit, and there is a safety risk. Therefore, the actual discharge rate of the battery is affected by factors such as environmental temperature and discharge current, i.e. the capacity utilization rate of the battery may change at different temperatures and discharge currents, therefore, the present embodiment sets a rate correction factor and a temperature correction factor.

[0135] The rate correction factor includes a discharge rate correction factor and a charging rate correction factor.

[0136] In a feasible implementation, the step of determining the rate correction factor and the temperature correction factor includes steps S5011-S5014:

[0137] In step S5011, a second correspondence relationship between the battery temperature data, the temperature of the variable temperature box, the battery working temperature threshold, the battery characteristic correction parameter and the temperature correction factor is obtained;

[0138] The second correspondence relationship between the battery temperature data, the temperature of the variable temperature box, the battery working temperature threshold, the battery characteristic correction parameter and the temperature correction factor, i.e. the calculation relationship of the temperature correction factor, is as follows:

[0139] In the formula, T f is the temperature correction factor, T cell is the temperature of the power battery at a certain moment (which can be determined according to the battery temperature data), T0 is the temperature of the variable temperature box, T maxis the maximum temperature for the battery to work safely, i.e. the battery working temperature threshold, a and b are battery characteristic correction parameters, which are coefficients determined according to the battery characteristics and experimental data, the process of determining the coefficients a and b usually involves battery performance testing and data analysis, which is usually related to the capacity decay, aging characteristics of the battery and the influence of temperature on the performance of the battery, and the numerical values may vary due to factors such as battery type, manufacturing process, usage conditions, etc., which are not specifically limited.

[0140] In step S5012, a temperature correction factor is obtained based on the battery temperature data, the temperature of the variable temperature box, the battery working temperature threshold, the battery characteristic correction parameters and the second corresponding relationship.

[0141] The battery temperature data, the temperature of the variable temperature box, the battery working temperature threshold and the battery characteristic correction parameters are substituted into the above-mentioned second corresponding relationship to calculate the corresponding temperature correction factor.

[0142] In step S5013, a third corresponding relationship between the battery temperature data, the temperature of the variable temperature box, the battery working temperature threshold, the charge and discharge current data, the rated capacity of the battery, the peak charge and discharge current of the battery, the battery temperature correction coefficient, the ambient temperature correction coefficient, the charge and discharge current correction coefficient and the rate correction factor is obtained.

[0143] The third corresponding relationship between the battery temperature data, the temperature of the variable temperature box, the battery working temperature threshold, the charge and discharge current data, the rated capacity of the battery, the peak charge and discharge current of the battery, the battery temperature correction coefficient, the ambient temperature correction coefficient, the charge and discharge current correction coefficient and the rate correction factor is the calculation relationship of the rate correction factor, which is shown as follows:

[0144] In the formula, D f is the rate correction factor, T cell is the temperature of the battery at a certain moment (which can be determined according to the battery temperature data), T0 is the temperature of the variable temperature box, T max is the battery working temperature threshold, I(t) is 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, I reted is the peak charge and discharge current of the battery, C tetedThe battery rated capacity is c1, the ambient temperature correction coefficient is c2, the battery temperature correction coefficient is c3, c1, c2 and c3 are coefficients that need to be determined according to the 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, so as to determine the influence 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 under different discharge currents is measured, and the relationship between the discharge current and the battery capacity is analyzed, so as to determine the charge-discharge current correction coefficient c3, wherein the battery working temperature threshold, the battery rated capacity, the battery peak charge-discharge current are closely related to the battery characteristics, material type and the like, and need to be determined according to the actual situation.

[0145] In step S5014, based on the battery temperature data, the temperature of the variable temperature box, the battery working temperature threshold, the charge-discharge current data, the battery rated capacity, the battery peak charge-discharge current, the battery temperature correction coefficient, the ambient temperature correction coefficient, the charge-discharge current correction coefficient and the third corresponding relationship, the rate correction factor is obtained.

[0146] The rate actually refers to the current value output by the battery discharging its rated capacity within a specified time, which is equal to the multiple of the battery rated capacity in numerical value. The rate includes the charge rate and the discharge rate. The battery peak charging current is equal to the product of the maximum charging rate of the battery and the battery rated capacity, and the battery peak discharging current is equal to the product of the maximum discharging rate of the battery and the battery rated capacity.

[0147] When calculating the charge rate correction factor, the charge current data, the charge time data and the battery peak charging current are used. Correspondingly, when calculating the discharge rate correction factor, the discharge current data, the discharge time data and the battery peak discharging current are used. The battery temperature data, the temperature of the variable temperature box, the battery working temperature threshold, the charge-discharge current data, the battery rated capacity, the battery peak charge-discharge current, the battery temperature correction coefficient, the ambient temperature correction coefficient, the charge-discharge current correction coefficient are substituted into the third corresponding relationship to calculate the corresponding rate correction factor.

[0148] In step S502, the first corresponding relationship between the temperature correction factor, the rate correction factor, the charge-discharge current data, the charge-discharge time data, the state of charge data, the battery rated capacity and the state of charge ampere-hour integral value is obtained.

[0149] The first corresponding relationship between the temperature correction factor, the rate correction factor, the charge-discharge current data, the charge-discharge time data, the state of charge data and the state of charge ampere-hour integral value is the calculation relationship of the state of charge ampere-hour integral value, which is as follows:

[0150] In the formula, I(t) is the current of the power battery at time t, i.e. the charge and discharge current data, a positive value indicates charging and a negative value indicates discharging, SOC0 is the initial state of charge of the power battery (which can be determined according to the state of charge data), 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.

[0151] Step S503, 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 rated capacity of the battery and the first corresponding relationship, the state of charge ampere-hour integral value is obtained;

[0152] 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 rated capacity of the battery are substituted into the above-mentioned first corresponding relationship, and the corresponding state of charge ampere-hour integral value is calculated.

[0153] Step S504, obtaining the 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 the state of charge relative error.

[0154] The difference between the state of charge ampere-hour integral value and the state of charge BMS value is the state of charge relative error, as shown below: DEV Rel = SOC t -SOC BSM

[0155] In the formula, DEV Rel represents the state of charge relative error, SOC BSM represents the state of charge BMS value, SOC t represents the state of charge ampere-hour integral value.

[0156] Exemplarily, assuming that the overall charge and discharge test is t1-t6, t0=t1 and t=t6, at this time the state of charge relative error is:

[0157] Exemplarily, assuming that the charge and discharge cycle test is t2-t4, t0=t2 and t=t4, at this time the state of charge relative error is:

[0158] The embodiment provides a test method for improving the estimation accuracy of the state of charge of a power battery, for a variable-temperature working condition, a state of charge ampere-hour integral value obtained by a charging and discharging device based on an ampere-hour integral method is used to determine a state of charge relative error, a state of charge evaluation result is determined based on a design threshold of the state of charge relative error, and real-time SOC correction is performed, so that the estimation accuracy of the state of charge of the power battery management system is improved, and the test method is simple, convenient and easy to operate, and development cost is effectively saved.

[0159] Exemplarily, in order to facilitate understanding of the implementation process of the test method for improving the estimation accuracy of the state of charge of the power battery obtained after the above-mentioned embodiment two, reference is made to FIG. 6, which provides a brief flowchart of the test method for improving the estimation accuracy of the state of charge of the power battery, and specifically:

[0160] (1) Preparation stage: 0-t0 stage, place the power battery in a variable temperature box at 25 DEG C room temperature, and perform constant current discharge at a discharge rate of 1 / 3 C to SOC = 0, and at this time, t0 is recorded;

[0161] (2) t0-t1 stage of the test stage: a step constant current charging method is used to complete full charging, and SOC = 100%, and at this time, t1 is recorded;

[0162] (3) t1-t2 stage of the test stage: at t1, the BMS power supply is disconnected within 1 min after full charging of the battery, and the temperature of the variable temperature box is set to a variable temperature working condition (for example, decreasing to-20 DEG C at a rate of 5 DEG C / hour, and then increasing to 45 DEG C at a rate of 5 DEG C / hour after decreasing to-20 DEG C, and repeating the cycle), the power battery is placed for more than 30 min, the BMS power supply is connected, 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 min, and the battery is placed, and at this time, t2 is recorded;

[0163] (4) t2-t3 stage of the test stage: at t2, the BMS power supply is connected, and the full-charged power battery is discharged at a discharge rate of 1 / 3 C to SOC = 80%, and at this time, t3 is recorded;

[0164] (5) t3-t5 stage of the test stage: NEDC / WLTC working condition is run, and the battery is discharged at a discharge rate of 1 / 3 C to SOC = 30%, and t4 is recorded, BMS data and charging and discharging device data during the discharging process are recorded, the BMS power supply is disconnected within 1 min, and the battery is placed for more than half an hour, and at this time, t5 is recorded;

[0165] (6) t5-t7 stage of the test stage: at t5, the BMS power supply is turned on, the data during the standing time is recorded, the power battery is charged to SOC=80% in the fast charging mode, the BMS data and the charge-discharge equipment data during the charging process are recorded, at this time, t6 is recorded, the BMS power supply is turned off within 1 min, and the power battery is standing for half an hour, at this time, t7 is recorded, the BMS power supply is turned on, and the BMS data and the charge-discharge equipment data during the standing time are recorded;

[0166] (7) The steps of 5-6 are repeated, and the cycle is continued for 9 times, and after 10 cycles in total, the BMS data and the charge-discharge equipment data are recorded;

[0167] (8) The state of charge relative error is flexibly selected according to the actual situation, and the state of charge relative error can be used to determine whether the state of charge estimation accuracy of the power battery management system in the cycle test process meets the requirements, so as to perform real-time SOC correction;

[0168] (9) t7-t8 stage of the test stage: at t7, the BMS power supply is turned on, and the power battery is discharged to the discharge cut-off voltage under the NEDC / WLTC working condition at the discharge rate of 1 / 3C, at this time, t8 is recorded;

[0169] (10) t8-t9 stage of the test stage: at t8, the BMS power supply is turned off, the variable temperature box is set to the constant temperature mode, the temperature is set to the room temperature of 25℃, the BMS power supply is turned off within 1 min, and the power battery is standing for more than 8h, at this time, t9 is recorded;

[0170] (11) t9-t10 stage of the test stage: the BMS power supply is turned on, the power battery is discharged to SOC=0 at the discharge rate of 0.05C, and the BMS data and the charge-discharge equipment data during the discharging process are recorded, at this time, t10 is recorded;

[0171] (12) The state of charge relative error is calculated, and the state of charge relative error can be used to determine whether the state of charge estimation accuracy of the power battery management system in the entire test process meets the requirements, so as to perform real-time SOC correction.

[0172] The application also provides a test device for improving the state of charge estimation accuracy of a power battery, please refer to FIG. 7, the test device for improving the state of charge estimation accuracy of the power battery comprises:

[0173] The test module 10 is used to discharge the power battery to a first state of charge at a constant current and charge the power battery to a second state of charge at a constant current in steps after the variable temperature box is set to the constant temperature mode and the temperature is adjusted to the room temperature, so as to complete the full discharge and full charge;

[0174] The test module 10 is further configured to set the variable temperature box to a temperature dynamic cycle mode, perform a temperature cycle test, and discharge the power battery at the third state of charge to a first state of charge to complete full discharge.

[0175] The test 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 a fourth state of charge.

[0176] The test module 10 is further configured to discharge the power battery to the first state of charge to complete full discharge after the charge-discharge cycle test is completed.

[0177] The evaluation module 20 is configured to determine a state of charge relative error based on a state of charge ampere-hour integral value of the charge-discharge equipment in the charge-discharge test and a state of charge BMS value obtained by the power battery management system.

[0178] 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.

[0179] In an embodiment, the test module 10 is further configured to discharge the power battery to the first state of charge to complete full discharge 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.

[0180] After the full discharge is completed, the power battery is charged to a second state of charge based on a preset step current to complete full charge.

[0181] In an embodiment, the test module 10 is further configured to set the variable temperature box to a temperature dynamic cycle mode, perform a temperature cycle test, and perform a standing treatment on the power battery based on a first standing time.

[0182] After the standing is completed, the power battery at the second state of charge is discharged to a third state of charge based on a second preset discharge rate.

[0183] In an embodiment, the test 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 standing treatment on the power battery based on a second standing time.

[0184] The power battery is charged to the third state of charge based on a fast charging strategy, and a standing treatment is performed on the power battery based on a third standing time.

[0185] The cycle number is updated, and the above steps are repeatedly executed until the cycle number meets a preset cycle number.

[0186] In an embodiment, the test module 10 is further configured to discharge the power battery to a discharge cutoff voltage based on a fourth preset discharge rate after the charge-discharge cycle test is completed.

[0187] After the variable temperature box is set to the constant temperature mode and the temperature is adjusted to the room temperature, the power battery is subjected to a standing treatment based on a fourth standing time;

[0188] After the standing is completed, the power battery is discharged to a first state of charge based on a fifth preset discharge rate, so as to complete full discharge.

[0189] In an embodiment, the evaluation module 20 is further configured to acquire a temperature correction factor, a rate correction factor, and charge-discharge current data, charge-discharge time data, and state of charge data recorded by a charge-discharge device in the charge-discharge test;

[0190] The evaluation module 20 is further configured to acquire a first correspondence relationship between the temperature correction factor, the rate correction factor, the charge-discharge current data, the charge-discharge time data, the state of charge data, a rated capacity of the battery, and a state of charge ampere-hour integral value;

[0191] The evaluation module 20 is further configured to obtain the state of charge ampere-hour integral value based on the temperature correction factor, the rate correction factor, the charge-discharge current data, the charge-discharge time data, the state of charge data, the rated capacity of the battery, and the first correspondence relationship;

[0192] The evaluation module 20 is further configured to acquire a state of charge BMS value obtained by a power battery management system, and take a difference between the state of charge ampere-hour integral value and the state of charge BMS value as a state of charge relative error.

[0193] In an embodiment, the evaluation module 20 is further configured to acquire a second correspondence relationship between battery temperature data, a temperature of the variable temperature box, a battery operating temperature threshold, a battery characteristic correction parameter, and the temperature correction factor;

[0194] The evaluation module 20 is further configured to obtain the 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 correspondence relationship;

[0195] The evaluation module 20 is further configured to acquire a third correspondence relationship between the battery temperature data, the temperature of the variable temperature box, the battery operating temperature threshold, the charge-discharge current data, the rated capacity of the battery, a peak charge-discharge current of the battery, a battery temperature correction coefficient, an ambient temperature correction coefficient, a charge-discharge current correction coefficient, and the rate correction factor;

[0196] The evaluation module 20 is further configured to 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-discharge current data, the rated capacity of the battery, the peak charge-discharge current of the battery, the battery temperature correction coefficient, the ambient temperature correction coefficient, the charge-discharge current correction coefficient, and the third correspondence relationship.

[0197] In an embodiment, the evaluation module 20 is further configured to determine that the state of charge evaluation result of the charge-discharge cycle test is that the accuracy does not meet the requirement when the state of charge relative error of the charge-discharge cycle test is greater than the preset error threshold, and correct the state of charge of the power battery management system to improve the state of charge estimation accuracy of the power battery management system.

[0198] In an embodiment, the evaluation module 20 is further configured to determine that the state of charge evaluation result of the charge-discharge cycle test is that the accuracy does not meet the requirement when the state of charge relative error of the charge-discharge cycle test is greater than the preset error threshold, and correct the state of charge of the power battery management system to improve the state of charge estimation accuracy of the power battery management system.

[0199] The test device for improving the state of charge estimation accuracy of the power battery provided in the present application adopts the test method for improving the state of charge estimation accuracy of the power battery in the above embodiments, and can solve the technical problem of complex calculation method and insufficient accuracy of the state of charge estimation of the power battery management system. Compared with the prior art, the test device for improving the state of charge estimation accuracy of the power battery provided in the present application has the same beneficial effects as the test method for improving the state of charge estimation accuracy of the power battery provided in the above embodiments, and the other technical features of the test device for improving the state of charge estimation accuracy of the power battery are the same as the features disclosed in the above embodiment method, which will not be described here.

[0200] The test device for improving the state of charge estimation accuracy of the power battery provided in the present application adopts the test method for improving the state of charge estimation accuracy of the power battery in the above embodiments, and can solve the technical problem of complex calculation method and insufficient accuracy of the state of charge estimation of the power battery management system. Compared with the prior art, the test device for improving the state of charge estimation accuracy of the power battery provided in the present application has the same beneficial effects as the test method for improving the state of charge estimation accuracy of the power battery provided in the above embodiments, and the other technical features of the test device for improving the state of charge estimation accuracy of the power battery are the same as the features disclosed in the above embodiment method, which will not be described here.

[0201] As shown in FIG. 8, the test device for improving the estimation accuracy of the state of charge of a power battery can include a processing device 1001 (e.g., a central processing unit, a graphics processing unit, etc.) that can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM) 1002 or a program loaded from a storage device 1003 into a random access memory (RAM) 1004. In the RAM 1004, various programs and data required for the operation of the test device for improving the estimation accuracy of the state of charge of a power battery are also stored. The processing device 1001, the ROM 1002, and the RAM 1004 are connected to each other through a bus 1005. An input / output (I / O) interface 1006 is also connected to the bus. Generally, the following systems can be connected to the I / O interface 1006: an input device 1007 including, for example, a touch screen, a touch pad, a keyboard, a mouse, an image sensor, a microphone, an accelerometer, a gyroscope, etc.; an output device 1008 including, for example, a liquid crystal display (LCD), a speaker, a vibrator, etc.; the storage device 1003 including, for example, a magnetic tape, a hard disk, etc.; and a communication device 1009. The communication device 1009 can allow the test device for improving the estimation accuracy of the state of charge of a power battery to communicate with other devices wirelessly or by wire to exchange data. Although the test device for improving the estimation accuracy of the state of charge of a power battery having various systems is shown in the figure, it should be understood that all the systems shown are not required to be implemented or possessed. More or fewer systems can be alternatively implemented or possessed.

[0202] According to embodiments of the present disclosure, the processes described above with reference to the flowcharts can be implemented as a computer software program. For example, embodiments of the present disclosure include a computer program product comprising a computer program carrying out the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network by a communication device, or installed from the storage device 1003, or installed from the ROM 1002. When the computer program is executed by the processing device 1001, the above-mentioned functions defined in the methods of the embodiments of the present disclosure are performed.

[0203] The test device for improving the estimation accuracy of the state of charge of the power battery provided in the application adopts the test method for improving the estimation accuracy of the state of charge of the power battery in the above embodiment, and can solve the technical problems that the calculation method of the state of charge estimation of the power battery management system is complex and the precision is insufficient. Compared with the prior art, the beneficial effects of the test device for improving the estimation accuracy of the state of charge of the power battery provided in the application are the same as those of the test method for improving the estimation accuracy of the state of charge of the power battery provided in the above embodiment, and other technical features in the test device for improving the estimation accuracy of the state of charge of the power battery are the same as those disclosed in the above embodiment method, which will not be repeated here.

[0204] The application provides a computer-readable storage medium having computer-readable program instructions (i.e., a computer program) stored thereon for executing the test method for improving the estimation accuracy of the state of charge of the power battery in the above embodiment.

[0205] The computer readable storage medium provided in the application may be, for example, a U disk, but is not limited to an electric, magnetic, optical, electromagnetic, infrared, or semiconductor system, system, or device, or any combination of the above. More specific examples of the computer readable storage medium may include, but are not limited to, an electric connection with one or more conductive 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 of the above. In the present embodiment, the computer readable storage medium may be any tangible medium containing or storing 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 can be transmitted by any suitable medium, including but not limited to: electric wire, optical cable, RF (Radio Frequency), etc., or any suitable combination of the above. The above computer readable storage medium carries one or more programs, which, when executed by the test device for improving the estimation accuracy of the state of charge of the power battery, cause the test device for improving the estimation accuracy of the state of charge of the power battery to: after the variable temperature box is set to the 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 charge it at a constant current to a second state of charge in steps to complete full discharge and full charge; set the variable temperature box to the temperature dynamic cycle mode, perform temperature cycle test, and discharge the power battery after standing to a third state of charge; based on the third state of charge and the fourth state of charge, perform charge and discharge cycle test on the power battery under a preset cycle condition; after the charge and discharge cycle test is completed, discharge the power battery to the first state of charge to complete full discharge; based on the state of charge Ah integration 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, determine the state of charge relative error; based on the state of charge relative error, determine the state of charge evaluation result, so as to improve the estimation accuracy of the state of charge of the power battery management system.

[0206] Computer program code for carrying out operations of the present application can be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code can 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. In the latter scenario, the remote computer can be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection can be made to an external computer (for example, through the Internet using an Internet Service Provider).

[0207] The flow diagrams and the block diagrams in the drawings are meant as possible implementations of systems, methods, and computer program products according to the embodiments of the application. It should be noted that each block in the flow diagram and the block diagram, and a combination of blocks in the flow diagram and the block diagram can be implemented by a variety of means, such as hardware, software, and / or firmware. In this regard, the flow diagrams and the block diagrams in the drawings illustrate the possible functionality of the various embodiments and a combination of the various embodiments of the present application. Of course, the actual received functionality can vary from device to device. Also, the functionality as described in the flow diagrams and the block diagrams can not be executed in the order shown in the drawings. Also, well-known structures have not been described in order to not obscure the subject matter of the present application.

[0208] The readable storage medium provided by the application is a computer readable storage medium, and the computer readable storage medium stores computer readable program instructions (i.e. computer program) for executing the test method for improving the estimation accuracy of the state of charge of the power battery. Compared with the prior art, the computer readable storage medium provided by the application has the same beneficial effects as the test method for improving the estimation accuracy of the state of charge of the power battery provided by the above-mentioned embodiments, and details are not repeated here.

[0209] The application also provides a computer program product, comprising a computer program, which, when executed by a processor, implements the steps of the test method for improving the estimation accuracy of the state of charge of the power battery as described above.

[0210] The computer program product provided by the application can solve the technical problems of complex calculation method and insufficient precision of the state of charge estimation of the power battery management system. Compared with the prior art, the computer program product provided by the application has the same beneficial effects as the test method for improving the estimation accuracy of the state of charge of the power battery provided by the above-mentioned embodiments, and details are not repeated here.

[0211] The above merely describes some embodiments of the present application, and does not limit the patent scope of the present application. Any equivalent structural transformation, direct / indirect application in other related technical fields, or the like, made based on the technical concept of the present application, using the content of the present application specification and drawings, is included in the patent protection scope of the present application.

Claims

1. A test method for improving the estimation accuracy of the state of charge of a power battery, wherein, The application is applied to a test system for estimating the accuracy of the state of charge of a power battery, and the test system for estimating the accuracy of the state of charge of the power battery comprises 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, the power battery management system and the charging and discharging device are connected to the power battery respectively, the charging and discharging device is used for charging and discharging test of the power battery and recording the state of charge ampere-hour integral value of the power battery in the charging and discharging test, and the power battery management system is used for obtaining the state of charge BMS value of the power battery in the charging and discharging test, and the test method for improving the state of charge estimation accuracy of the power battery comprises: 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 to a first state of charge at a constant current, and is charged to a second state of charge at a constant current in steps 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 after static placement is discharged to a third state of charge; Based on the third state of charge and the fourth state of charge, the power battery is subjected to a charging and discharging cycle test under a preset cycle condition; After the charging and discharging 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 charging and discharging device in the charging and discharging test and the state of charge BMS value obtained by the power battery management system, a state of charge relative error is determined; Based on the state of charge relative error, a state of charge evaluation result is determined to improve the state of charge estimation accuracy of the power battery management system.

2. The method of claim 1, wherein, The step of setting the variable temperature box to a constant temperature mode and adjusting the temperature to room temperature, discharging the power battery to a first state of charge at a constant current, and charging the power battery to a second state of charge at a constant current in steps to complete full discharge and full charge comprises: After the temperature of the variable temperature box is adjusted to room temperature, the power battery is discharged to a first state of charge at a first preset discharge rate to complete full discharge; After full discharge is completed, the power battery is charged to a second state of charge at a preset step current to complete full charge.

3. The method of claim 1, 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 static placement to a third state of charge comprises: The variable temperature box is set to a temperature dynamic cycle mode, a temperature cycle test is performed, and the power battery is subjected to static placement treatment based on a first static placement time; After static placement is completed, the power battery in the second state of charge is discharged to the third state of charge based on a second preset discharge rate.

4. The method of claim 1, wherein, The step of performing a charging and discharging cycle test on the power battery based on the third state of charge and the fourth state of charge under a preset cycle condition comprises: Under a preset cycle condition, the power battery is discharged to the fourth state of charge based on a third preset discharge rate, and the power battery is subjected to static placement treatment based on a second static placement time; The power battery is charged to the third state of charge based on a fast charging strategy, and the power battery is subjected to static placement treatment based on a third static placement time; The updating of the cycle number is repeated until the cycle number meets a preset cycle number.

5. The method of claim 1, wherein, The discharging the power battery to the first state of charge to complete full discharge after the completion of the charge-discharge cycle test comprises: After the completion of the charge-discharge cycle test, the power battery is discharged 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, the power battery is subjected to a standing treatment based on a fourth standing time; After the standing is completed, the power battery is discharged to the first state of charge to complete full discharge based on a fifth preset discharge rate.

6. The method of claim 1, wherein, The step of determining a state of charge relative error based on a state of charge ampere-hour integral value of a charge-discharge device in a charge-discharge test and a state of charge BMS value obtained by a power battery management system comprises: obtaining a temperature correction factor, a rate correction factor, and charge-discharge current data, charge-discharge time data, and state of charge data recorded by the charge-discharge device in the charge-discharge test; obtaining a first correspondence relationship between the temperature correction factor, the rate correction factor, the charge-discharge current data, the charge-discharge time data, the state of charge data, a battery rated capacity, and the 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-discharge current data, the charge-discharge time data, the state of charge data, the battery rated capacity, and the first correspondence relationship; obtaining a state of charge BMS value obtained by the power battery management system, and taking a difference between the state of charge ampere-hour integral value and the state of charge BMS value as the state of charge relative error.

7. The method of claim 6, wherein, The method further comprises: obtaining a second correspondence relationship between battery temperature data, a temperature of the variable temperature box, a battery working temperature threshold, a battery characteristic correction parameter, and a temperature correction factor; obtaining the temperature correction factor based on the battery temperature data, the temperature of the variable temperature box, the battery working temperature threshold, the battery characteristic correction parameter, and the second correspondence relationship; obtaining a third correspondence relationship between the battery temperature data, the temperature of the variable temperature box, the battery working temperature threshold, charge-discharge current data, the battery rated capacity, a battery peak charge-discharge current, a battery temperature correction coefficient, an environmental temperature correction coefficient, a charge-discharge current correction coefficient, and a rate correction factor; obtaining the rate correction factor based on the battery temperature data, the temperature of the variable temperature box, the battery working temperature threshold, the charge-discharge current data, the battery rated capacity, the battery peak charge-discharge current, the battery temperature correction coefficient, the environmental temperature correction coefficient, the charge-discharge current correction coefficient, and the third correspondence relationship.

8. The method of any one of claims 1 to 7, wherein, The state of charge relative error comprises a state of charge relative error of a charge-discharge cycle test and a state of charge relative error of a charge-discharge overall test; The step of determining a state of charge evaluation result based on the state of charge relative error to improve a state of charge estimation accuracy of a power battery management system comprises: When the state of charge relative error of the charging and discharging cycle test is greater than the preset error threshold, it is determined that the state of charge evaluation result of the charging and discharging cycle test is that the accuracy does not meet the requirement, 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. When the state of charge relative error of the charging and discharging cycle test is greater than the preset error threshold, it is determined that the state of charge evaluation result of the charging and discharging cycle test is that the accuracy does not meet the requirement, 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.

9. A test device for improving the estimation accuracy of the state of charge of a power battery, wherein, The device comprises: The test module is configured to discharge the power battery to a first state of charge at a constant current and charge the power battery to a second state of charge at a constant current in steps to complete full discharge and full charge after the variable temperature box is set to a constant temperature mode and the temperature is adjusted to room temperature; The test module is further configured to set the variable temperature box to a temperature dynamic cycle mode, perform temperature cycle test, and discharge the power battery to a third state of charge after static placement; The test module is further configured to perform charging and discharging cycle test on the power battery under a preset cycle condition based on the third state of charge and a fourth state of charge; The test module is further configured to discharge the power battery to the first state of charge after the charging and discharging cycle test is completed to complete full discharge; The evaluation module is configured to determine a state of charge relative error based on the state of charge ampere-hour integral value of the charging and discharging equipment in the charging and discharging 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 to improve the state of charge estimation accuracy of the power battery management system.

10. A test device for improving the estimation accuracy of the state of charge of a power battery, wherein, The device comprises a memory, a processor, and a computer program stored on the memory and executable on the processor, and the computer program is configured to implement the steps of the test method for improving the state of charge estimation accuracy of the power battery according to any one of claims 1 to 8.

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