Method and device for testing direct current internal resistance of battery

Abstract

The invention discloses a battery DC internal resistance testing method and device, and relates to the technical field of battery management. The method comprises the following steps: acquiring a corresponding relation between real-time SOC and real-time voltage of battery charging / discharging under each preset rate; calculating the SOC at the end of battery charging / discharging under each preset SOC according to the corresponding preset SOC under each preset SOC, the preset test current and the preset test duration; fitting the corresponding relationship between the SOC at the end of charging / discharging of the battery under each preset SOC and the real-time SOC and the real-time voltage at the end of charging / discharging of the battery under each preset rate to obtain the corresponding relationship between the voltage at the end of charging / discharging of the battery under each preset SOC and the charging / discharging rate; and calculating the DC internal resistance of the battery under each preset SOC according to the corresponding relationship between the voltage and the charging / discharging rate when the charging / discharging of the battery under each preset SOC is finished, thereby realizing the DCR calculation under different temperatures and / or SOCs.

Description

Technical Field

[0001] The present application relates to the field of battery management technology, and in particular to a method and device for testing the DC internal resistance of a battery. Background Art

[0002] Direct Current Resistance (DCR) is a measure of the DC internal resistance of each battery cell in a battery or battery pack. It plays a key role in battery management systems and battery performance analysis, for example, analyzing the health degradation of a single cell or the entire battery pack.

[0003] The existing DCR test method mainly applies short-term high-current pulses for charging and discharging, and calculates DCR based on the instantaneous voltage drop and current value. However, this method has a large test volume, high cost, and cumbersome steps. Especially when the actual required DCR data volume is large, for example, when it is necessary to test DCR at different temperatures and different SOCs, if this method is used for testing, the test time and cost are relatively high. Summary of the invention

[0004] The embodiments of the present application provide a method and device for testing the DC internal resistance of a battery, so as to realize the calculation of the DC internal resistance of the battery at different temperatures and / or different SOCs, reduce the test amount, reduce the test time and cost, and improve the efficiency and flexibility of the calculation.

[0005] In order to solve the above technical problems, the embodiments of the present application disclose the following technical solutions:

[0006] In a first aspect, a method for testing a DC internal resistance of a battery is provided, comprising:

[0007] Get the initial charge / discharge voltage of the battery;

[0008] Setting multiple preset rates, performing charge / discharge tests on the battery at preset temperatures according to each preset rate, and obtaining battery charge / discharge test data at each preset rate;

[0009] According to the battery charge / discharge test data at each preset rate, the corresponding relationship between the real-time SOC and the real-time voltage of the battery charge / discharge at each preset rate is obtained;

[0010] Setting a plurality of preset SOCs, applying a preset test current corresponding to a preset test duration to the battery at each preset SOC, and calculating the SOC of the battery at the end of charge / discharge at each preset SOC according to the preset SOC, preset test current and preset test duration corresponding to each preset SOC;

[0011] Fitting the corresponding relationship between the SOC at the end of battery charge / discharge at each preset SOC and the real-time SOC and real-time voltage of the battery charge / discharge at each preset rate, to obtain the corresponding relationship between the voltage at the end of battery charge / discharge at each preset SOC and the charge / discharge rate;

[0012] The DC internal resistance of the battery at each preset SOC is calculated based on the corresponding relationship between the voltage and the charge / discharge rate at the end of the battery charge / discharge at each preset SOC, the preset test current corresponding to each preset SOC, and the initial charge / discharge voltage of the battery.

[0013] In combination with the first aspect, the method for testing the DC internal resistance of the battery further includes: obtaining the constant capacity of the battery;

[0014] The step of calculating the SOC at the end of battery charging / discharging at each preset SOC according to the preset SOC, the preset test current and the preset test duration corresponding to each preset SOC includes:

[0015] Calculate the battery charge / discharge SOC change at each preset SOC based on the battery fixed capacity, the preset test current and the preset test duration corresponding to each preset SOC;

[0016] The SOC at the end of battery charging / discharging at each preset SOC is calculated according to the battery charging / discharging SOC change at each preset SOC and the corresponding preset SOC.

[0017] In combination with the first aspect, the corresponding relationship between the voltage of the battery at the end of charging / discharging and the charging / discharging rate under each preset SOC is:

[0018] V=a*C+b

[0019] Where V is the voltage of the battery at the end of charge / discharge, C is the battery charge / discharge rate; a and b are coefficients;

[0020] The calculation formula of C is:

[0021] C=I / (Q0 / 1[h])

[0022] Where, I is the preset test current, 1[h] is the time of 1 hour, and Q0 is the fixed capacity of the battery.

[0023] In combination with the first aspect, the multiple preset SOC values ​​range from 10% to 30%.

[0024] In combination with the first aspect, the plurality of preset SOCs are: 10%, 15%, 20% and 30% respectively;

[0025] Among them, the corresponding relationship between the voltage and the charging rate at the end of battery charging at 10% is:

[0026] V1=0.092157*C1+3.246733;

[0027] Among them, the corresponding relationship between the voltage and the charging rate at the end of battery charging at 15% is:

[0028] V2=0.089865*C2+3.277186;

[0029] Among them, the corresponding relationship between the voltage and the charging rate at the end of battery charging at 20% is:

[0030] V3=0.086207*C3+3.307464;

[0031] Among them, the corresponding relationship between the voltage and the charging rate at the end of battery charging at 30% is:

[0032] V4=0.0842*C4+3.3296;

[0033] Among them, V1-V4 are the voltages at the end of battery charging at 10% SOC, 15% SOC, 20% SOC and 30% SOC respectively, and C1-C4 are the battery charging rates at 10% SOC, 15% SOC, 20% SOC and 30% SOC respectively.

[0034] In combination with the first aspect, the method for testing the DC internal resistance of the battery further includes: obtaining an actual charge / discharge rate of the battery;

[0035] The method calculates the DC internal resistance of the battery at each preset SOC according to the corresponding relationship between the voltage and the charge / discharge rate of the battery at the end of charge / discharge at each preset SOC, the preset test current corresponding to each preset SOC, and the initial charge / discharge voltage of the battery, including:

[0036] Determine the voltage of the battery at the end of charge / discharge at each preset SOC according to the corresponding relationship between the voltage of the battery at the end of charge / discharge at each preset SOC and the charge / discharge rate and the actual charge / discharge rate of the battery;

[0037] The DC internal resistance of the battery at each preset SOC is calculated according to the voltage of the battery at the end of charge / discharge at each preset SOC, the preset test current corresponding to each preset SOC, and the initial charge / discharge voltage of the battery.

[0038] In combination with the first aspect, the corresponding relationship between the real-time SOC and the real-time voltage of the battery at each preset rate is obtained according to the battery charge / discharge test data at each preset rate, including:

[0039] According to the battery charge / discharge test data at each preset rate, the charge / discharge capacity, real-time voltage and constant capacity of each SOC collection point at each preset rate are respectively extracted;

[0040] Calculate the real-time SOC of the battery charge / discharge at each preset rate according to the charge / discharge capacity and constant capacity of each SOC collection point at each preset rate;

[0041] The corresponding relationship between the real-time SOC and the real-time voltage of the battery at each preset charge / discharge rate is determined according to the real-time SOC and the real-time voltage of the battery at each preset charge / discharge rate.

[0042] In combination with the first aspect, the obtaining of the initial charge / discharge voltage of the battery includes:

[0043] The SOC-OCV test is performed on the battery at the preset temperature to obtain the initial charge / discharge voltage of the battery.

[0044] In combination with the first aspect, the value range of the multiple preset ratios is: 0.33C-2.5C.

[0045] In a second aspect, a battery DC internal resistance testing device is provided, comprising:

[0046] A first acquisition module, used to acquire an initial charge / discharge voltage of a battery;

[0047] The first test module is used to set a plurality of preset rates and perform charge / discharge tests on the battery at each preset rate at a preset temperature;

[0048] The second acquisition module is used to acquire battery charge / discharge test data at each preset rate;

[0049] A first corresponding relationship determination module, used to obtain the corresponding relationship between the real-time SOC and the real-time voltage of the battery at each preset rate of charge / discharge according to the battery charge / discharge test data at each preset rate;

[0050] The second test module is used to set a plurality of preset SOCs and apply a preset test current corresponding to a preset test time to the battery at each preset SOC;

[0051] A first calculation module, used to calculate the SOC at the end of battery charging / discharging at each preset SOC according to the preset SOC, preset test current and preset test duration corresponding to each preset SOC;

[0052] A second corresponding relationship determination module is used to fit the corresponding relationship between the SOC at the end of battery charge / discharge at each preset SOC and the real-time SOC and real-time voltage of the battery charge / discharge at each preset rate, so as to obtain the corresponding relationship between the voltage at the end of battery charge / discharge at each preset SOC and the charge / discharge rate;

[0053] The second calculation module is used to calculate the DC internal resistance of the battery at each preset SOC according to the corresponding relationship between the voltage and the charge / discharge rate of the battery at the end of charge / discharge at each preset SOC, the preset test current corresponding to each preset SOC, and the initial charge / discharge voltage of the battery.

[0054] One of the above technical solutions has the following advantages or beneficial effects:

[0055] Compared with the prior art, the present invention provides a method for testing the DC internal resistance of a battery, comprising: obtaining the initial charge / discharge voltage of the battery; setting a plurality of preset rates, performing charge / discharge tests on the battery at a preset temperature according to each preset rate, and obtaining the battery charge / discharge test data at each preset rate; obtaining the corresponding relationship between the real-time SOC and the real-time voltage of the battery charge / discharge at each preset rate according to the battery charge / discharge test data at each preset rate; setting a plurality of preset SOCs, applying a preset test current corresponding to a preset test time to the battery at each preset SOC, and obtaining the corresponding relationship between the real-time SOC and the real-time voltage of the battery charge / discharge at each preset rate according to the battery charge / discharge test data at each preset rate; and obtaining the corresponding relationship between the real-time SOC and the real-time voltage of the battery charge / discharge at each preset rate according to the battery charge / discharge test data at each preset rate. The test current and the preset test duration are set to calculate the SOC at the end of battery charge / discharge under each preset SOC; the SOC at the end of battery charge / discharge under each preset SOC is fitted with the corresponding relationship between the real-time SOC and the real-time voltage of the battery charge / discharge under each preset rate, and the corresponding relationship between the voltage at the end of battery charge / discharge under each preset SOC and the charge / discharge rate is obtained; according to the corresponding relationship between the voltage at the end of battery charge / discharge under each preset SOC and the charge / discharge rate, the preset test current corresponding to each preset SOC, and the initial charge / discharge voltage of the battery, the DC internal resistance of the battery under each preset SOC is calculated. The test method of battery DC internal resistance provided in the present application can realize the calculation of battery DC internal resistance under different temperatures and / or different SOCs, meet the DCR calculation requirements under different temperatures and / or different SOCs, and has a small amount of data testing, low test time and cost, and high calculation efficiency. And this method is not limited to the size of the test current and test time, has strong flexibility, and is suitable for scenarios with large amounts of DCR calculation data.

[0056] The battery DC internal resistance test device of the present application can realize the calculation of the battery DC internal resistance at different temperatures and / or different SOCs, meet the DCR calculation requirements at different temperatures and / or different SOCs, and has a small amount of data testing, low test time and cost, and high calculation efficiency. Moreover, the method is not limited to the size of the test current and test time, has strong flexibility, and is suitable for scenarios with large amounts of DCR calculation data. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0058] Figure 1 It is a flow chart of a method for testing the DC internal resistance of a battery provided in an embodiment of the present application;

[0059] Figure 2 It is a curve of charging voltage changing with SOC at different preset rates at 25°C provided in the embodiment of the present application;

[0060] Figure 3 It is the SOC-OCV curve under the 25°C charging test provided in the embodiment of the present application;

[0061] Figure 4 It is a curve of the change of different charging SOC voltage with the rate at 25°C provided in the embodiment of the present application;

[0062] Figure 5 A schematic diagram comparing the accuracy of the present application scheme and the traditional DCR test method provided in the embodiments of the present application;

[0063] Figure 6 It is a principle structural block diagram of a battery DC internal resistance testing device provided in an embodiment of the present application.

[0064] Reference numerals:

[0065] 10-first acquisition module; 20-first test module; 30-second acquisition module; 40-first correspondence determination module; 50-second test module; 60-first calculation module; 70-second correspondence determination module; 80-second calculation module; 100-battery DC internal resistance test device. DETAILED DESCRIPTION

[0066] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0067] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first" and "second" are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more features. In the description of the present application, "multiple" means two or more, and at least one means one, two or more, unless otherwise clearly and specifically defined.

[0068] Figure 1 This is a flow chart of a battery DC internal resistance test method provided in an embodiment of the present application. This method is suitable for implementing battery DCR testing in a battery management system, especially DCR testing in application scenarios with a large amount of DCR test data, and reducing the amount of test data, reducing test time and cost, and improving test efficiency. This method can be performed by a battery DC internal resistance test device, which can be implemented by software and / or hardware, and can be configured in a management system or processor of a battery management platform. Please refer to Figure 1 The test method of the DC internal resistance of the battery includes the following steps:

[0069] Step 110: Obtain the initial charge / discharge voltage of the battery.

[0070] Among them, the specific implementation method of obtaining the initial charge / discharge voltage of the battery can be: the initial charge / discharge voltage of the battery is obtained by performing an SOC-OCV test on the battery at a preset temperature. For example, the battery cell is subjected to a 25°C constant capacity and SOC-OCV test. Set 0.33C (C is the standard capacity of the battery cell) for constant current and constant voltage charging and 0.33C constant current discharge, and this charge / discharge capacity is the constant capacity Q0. Among them, the upper limit voltage and the lower limit voltage are the upper limit cut-off voltage E_max and the lower limit cut-off voltage E_min of the battery cell, respectively.

[0071] Among them, the SOC-OCV test includes a charging SOC-OCV test and a discharging SOC-OCV test. Exemplarily, taking the charging SOC-OCV test as an example, the specific test process is: first, stand at the required temperature (such as 25°C) for a certain time (generally 1-4h, the specific standing time can be set according to the actual situation, and no specific limitation is made here). Then, 0.33C discharges to the lower limit cut-off voltage E_min, and stands for a certain time (generally 1-4h, the specific standing time can be set according to the actual situation, and no specific limitation is made here). Secondly, 0.33C constant current charges for a certain time (generally 3.6-36min, which can be specifically formulated according to the SOC interval), and stands for a certain time (generally 1-4h, the specific standing time can be set according to the actual situation, and no specific limitation is made here). Finally, read the initial charging voltage V0, set the cyclic charging, until the total charging time is 180min (it can also be other values, which can be set according to the actual situation, and no specific limitation is made here). Thus, the SOC-OCV charging test data is obtained. Similarly, SOC-OCV discharge test data can be obtained according to the charging method.

[0072] Step 120 , setting a plurality of preset rates, performing charge / discharge tests on the battery at each preset rate at a preset temperature, and obtaining battery charge / discharge test data at each preset rate.

[0073] The preset temperature may be 25°C or the like, and the specific value may be set according to the actual situation, and no specific limitation is made here.

[0074] It should be noted that by setting the preset temperature as the required test temperature, the DCR test of the battery at different temperatures can be achieved. Therefore, the solution of the embodiment of the present application can be applicable to the application scenario of the DCR test of the battery at different temperatures.

[0075] The value range of the multiple preset magnifications is: 0.33 C-2.5 C. The specific preset magnifications can be set according to actual conditions and are not specifically limited here.

[0076] Exemplarily, multiple different preset rates are set to perform charge / discharge tests on the battery cells. Among them, when calculating the charging DCR, it is necessary to test the battery charging data of different preset rates, and when calculating the discharging DCR, it is necessary to test the battery discharging data of different preset rates. Exemplarily, taking the charging DCR as an example, the specific test process is: first, set multiple different preset rates to stand for a certain time (generally 1-4h, the specific standing time can be set according to the actual situation, and no specific limitation is made here) at the required temperature (i.e., the preset temperature, such as 25°C). Then, constant current charging is performed for different preset rates, and after reaching the upper limit cut-off voltage E_max or the negative electrode potential is lower than zero, stand at 25°C for a certain time (generally 0.5-4h, the specific standing time can be set according to the actual situation, and no specific limitation is made here). Secondly, 0.33C constant current discharge to the cut-off voltage, and collect data at a certain time interval (the time interval for collecting data is generally 1-120s) to obtain battery charging test data of different preset rates. Similarly, according to the charging test method, battery discharge test data of different preset discharge DCR rates can be obtained.

[0077] Step 130: Obtain the corresponding relationship between the real-time SOC and the real-time voltage of the battery at each preset rate of charge / discharge according to the battery charge / discharge test data at each preset rate.

[0078] In some embodiments, optionally, a specific implementation method for obtaining the correspondence between the real-time SOC and the real-time voltage of the battery charge / discharge at each preset rate based on the battery charge / discharge test data at each preset rate includes: extracting the charge / discharge capacity, real-time voltage and constant capacity of each SOC collection point at each preset rate according to the battery charge / discharge test data at each preset rate; calculating the corresponding real-time SOC of the battery charge / discharge at each preset rate according to the charge / discharge capacity and constant capacity of each SOC collection point at each preset rate; determining the correspondence between the real-time SOC and the real-time voltage of the battery charge / discharge at each preset rate according to the real-time SOC and the real-time voltage of the battery charge / discharge at each preset rate.

[0079] Among them, the settings of each SOC collection point under each preset ratio can be the same as the value of multiple preset SOCs, or can be other numbers and other proportions of SOCs. The specific settings can be made according to actual conditions and are not specifically limited here.

[0080] Among them, according to the battery charging test data under each preset rate, the charging capacity, charging real-time voltage and fixed capacity of each SOC collection point under each preset rate can be extracted. Similarly, according to the battery discharge test data under each preset rate, the discharge capacity, discharge real-time voltage and fixed capacity of each SOC collection point under each preset rate can be extracted. Among them, the fixed capacity under different preset rates is different, and the fixed capacity under the same preset rate is the same.

[0081] Among them, the real-time SOC of the battery charging at each preset rate can be calculated according to the charging capacity and fixed capacity of each SOC collection point at each preset rate. Similarly, the real-time SOC of the battery discharging at each preset rate can be calculated according to the discharge capacity and fixed capacity of each SOC collection point at each preset rate.

[0082] Among them, the corresponding relationship between the real-time SOC and the real-time voltage of the battery at each preset rate can be determined according to the real-time SOC and the real-time voltage of the battery at each preset rate, for example, the corresponding relationship curve between the real-time SOC and the real-time voltage of the battery at each preset rate. Similarly, the corresponding relationship between the real-time SOC and the real-time voltage of the battery at each preset rate can be determined according to the real-time SOC and the real-time voltage of the battery at each preset rate, for example, the corresponding relationship curve between the real-time SOC and the real-time voltage of the battery at each preset rate.

[0083] Figure 2 The curves of the charging voltage and SOC at different preset rates at 25°C provided in the embodiment of the present application are shown in Figure 1. For example, the six preset rates of 0.33C, 0.5C, 0.75C, 1C, 1.75C, and 2.5C are used as examples. For example, the corresponding relationship curves between the real-time SOC and the real-time voltage at each preset rate are shown in Figure 1. Figure 2 As shown. Among them, curve L1 is the corresponding relationship curve between the real-time SOC and the real-time voltage charged at a rate of 0.33C, curve L2 is the corresponding relationship curve between the real-time SOC and the real-time voltage charged at a rate of 0.5C, curve L3 is the corresponding relationship curve between the real-time SOC and the real-time voltage charged at a rate of 0.75C, curve L4 is the corresponding relationship curve between the real-time SOC and the real-time voltage charged at a rate of 1C, curve L5 is the corresponding relationship curve between the real-time SOC and the real-time voltage charged at a rate of 1.75C, and curve L6 is the corresponding relationship curve between the real-time SOC and the real-time voltage charged at a rate of 2.5C.

[0084] Step 140, set multiple preset SOCs, apply preset test currents corresponding to preset test durations to the battery at each preset SOC, and calculate the SOC of the battery at the end of charging / discharging at each preset SOC based on the preset SOC, preset test current, and preset test duration corresponding to each preset SOC.

[0085] The value range of the multiple preset SOCs is 10%-30%. The specific value can be set according to the actual situation and is not specifically limited here.

[0086] Among them, the preset test currents corresponding to different preset SOCs are different, and the preset test durations of the preset test currents corresponding to different preset SOCs are the same.

[0087] In some embodiments, optionally, a specific implementation method for calculating the SOC at the end of battery charge / discharge at each preset SOC according to the preset SOC, preset test current and preset test duration corresponding to each preset SOC includes: calculating the battery charge / discharge SOC change at each preset SOC according to the battery fixed capacity, and the preset test current and preset test duration corresponding to each preset SOC; calculating the battery SOC at the end of battery charge / discharge at each preset SOC according to the battery charge / discharge SOC change at each preset SOC and the corresponding preset SOC.

[0088] The calculation formula for calculating the battery charge / discharge SOC change at each preset SOC is as follows:

[0089] △SOC=It / Q0

[0090] Among them, △SOC is the battery charge / discharge SOC change under each preset SOC, I is the preset test current, t is the preset test time, and Q0 is the battery fixed capacity.

[0091] Specifically, the SOC at the end of the battery charging / discharging at each preset SOC can be calculated based on the sum of the battery charging / discharging SOC change at each preset SOC and the corresponding preset SOC. For example, taking the charging test as an example, assuming that the preset SOC is SOC0, and the corresponding battery charging SOC change at SOC0 is △SOC, then the SOC1 at the end of charging is: SOC0+It / Q0, thereby the SOC1 at the end of the battery charging can be obtained.

[0092] Step 150: Fit the SOC at the end of battery charge / discharge at each preset SOC to the corresponding relationship between the real-time SOC and the real-time voltage of the battery charge / discharge at each preset rate, to obtain the corresponding relationship between the voltage at the end of battery charge / discharge at each preset SOC and the charge / discharge rate.

[0093] Among them, the corresponding relationship between the SOC at the end of battery charge / discharge under each preset SOC and the real-time SOC and real-time voltage of the battery charge / discharge under each preset rate can be fitted by polynomials to obtain the corresponding relationship between the voltage at the end of battery charge / discharge under each preset SOC and the charge / discharge rate. For example, taking the battery charging test as an example, the corresponding relationship between the SOC at the end of battery charge under each preset SOC and the real-time SOC and real-time voltage of the battery charge under each preset rate can be fitted by polynomials to obtain the corresponding relationship between the voltage at the end of battery charge under each preset SOC and the charge rate. Similarly, according to the charging test method, the corresponding relationship between the voltage at the end of battery discharge under each preset SOC and the discharge rate can be obtained.

[0094] Step 160, calculating the DC internal resistance of the battery at each preset SOC according to the corresponding relationship between the voltage and the charge / discharge rate at the end of charge / discharge of the battery at each preset SOC, the preset test current corresponding to each preset SOC, and the initial charge / discharge voltage of the battery.

[0095] In some embodiments, optionally, a specific implementation method for calculating the DC internal resistance of the battery at each preset SOC based on the correspondence between the voltage of the battery at the end of charging / discharging and the charge / discharge rate at each preset SOC, the preset test current corresponding to each preset SOC, and the initial charge / discharge voltage of the battery includes: determining the voltage of the battery at the end of charging / discharging at each preset SOC based on the correspondence between the voltage of the battery at the end of charging / discharging and the charge / discharge rate at each preset SOC and the actual charge / discharge rate of the battery; calculating the DC internal resistance of the battery at each preset SOC based on the voltage of the battery at the end of charging / discharging at each preset SOC, the preset test current corresponding to each preset SOC, and the initial charge / discharge voltage of the battery.

[0096] The formula for calculating the DC internal resistance of the battery at each preset SOC according to the voltage of the battery at the end of charge / discharge at each preset SOC, the preset test current corresponding to each preset SOC, and the initial charge / discharge voltage of the battery is:

[0097] DCR=(V-OCV0) / I

[0098] Wherein, DCR is the DC internal resistance under the preset SOC, V is the voltage of the battery at the end of charge / discharge under the preset SOC, I is the preset test current corresponding to the preset SOC, and OCV0 is the initial charge / discharge voltage of the battery.

[0099] In the technical solution of this embodiment, the working principle of the battery DC internal resistance test method is as follows: Figure 1 First, obtain the initial charge / discharge voltage of the battery. Then, set multiple preset rates, perform charge / discharge tests on the battery at preset temperatures according to each preset rate, and obtain the battery charge / discharge test data at each preset rate. Secondly, obtain the corresponding relationship between the real-time SOC and the real-time voltage of the battery charge / discharge at each preset rate according to the battery charge / discharge test data at each preset rate. Secondly, set multiple preset SOCs, apply preset test currents corresponding to preset test durations to the battery at each preset SOC, and calculate the SOC of the battery at the end of charge / discharge at each preset SOC according to the preset SOC, preset test current and preset test duration corresponding to each preset SOC. Fit the SOC at the end of charge / discharge of the battery at each preset SOC with the corresponding relationship between the real-time SOC and the real-time voltage of the battery charge / discharge at each preset rate, and obtain the corresponding relationship between the voltage at the end of charge / discharge of the battery at each preset SOC and the charge / discharge rate. Finally, according to the corresponding relationship between the voltage and the charge / discharge rate at the end of the battery charge / discharge under each preset SOC, the preset test current corresponding to each preset SOC, and the initial charge / discharge voltage of the battery, the DC internal resistance of the battery under each preset SOC is calculated. It can be seen that this method uses the corresponding relationship between the SOC and voltage of the battery at different charge and discharge rates, and fits the SOC at the end of the charge and discharge of the battery under different preset SOCs in the DCR test to construct the mathematical relationship between the voltage at the end of the battery charge and discharge under each preset SOC and the battery charge and discharge rate, thereby realizing the DCR test of the battery under different temperatures and / or different SOCs (or different charge and discharge rates) of the battery under charge and discharge, which can meet the application occasions with a relatively large amount of DCR test data. Compared with the traditional DCR test method, it can reduce the experimental test data, reduce the test time and cost, and improve the test efficiency. And this method is not limited to the test current and test duration, and has strong flexibility.

[0100] In some embodiments, optionally, the corresponding relationship between the voltage of the battery at the end of charging / discharging at each preset SOC and the charging / discharging rate is:

[0101] V = a*C+b;

[0102] Where V is the voltage of the battery at the end of charge / discharge, C is the battery charge / discharge rate; a and b are coefficients;

[0103] The calculation formula of C is:

[0104] C = I / (Q0 / 1[h]);

[0105] Where, I is the preset test current, 1[h] is the time of 1 hour, and Q0 is the fixed capacity of the battery.

[0106] Exemplarily, in the embodiment of the present application, taking the charging test of battery cell A, and taking multiple preset SOCs of 10%, 15%, 20% and 30%, and multiple different preset rates of 0.33C, 0.5C, 0.75C, 1C, 1.75C and 2.5C as an example, the test process of the battery DC internal resistance is described, which specifically includes the following steps:

[0107] Step 1: Perform constant capacity and SOC-OCV tests on battery cell A at 25°C. Set 0.33C (C is the standard capacity of the cell) for constant current and constant voltage charging, and 0.33C for constant current discharge. The discharge capacity is 128.94Ah. The upper and lower voltage limits are the upper and lower cut-off voltages of the cell, 3.65V and 2V, respectively.

[0108] Figure 3 This is the SOC-OCV curve under the 25°C charging test provided in the embodiment of this application. The specific process of testing the charging SOC-OCV is: standing at 25°C for 3 hours, discharging at 0.33C to the lower limit cut-off voltage of 2V, standing for 3 hours, charging at 0.33C constant current for 9 minutes, standing for 3 hours, reading the voltage of 3.139V, setting the cycle charge until the total charging time is 180 minutes. Thus, the SOC-OCV charging data is obtained as follows Figure 3 shown.

[0109] Step 2: Set the six rates of 0.33C, 0.5C, 0.75C, 1C, 1.75C, and 2.5C to test the battery cells. The specific process of the charging test is: First, let it stand for 3 hours at 25°C. Then, use the above six rates to charge at constant current in turn, and the charging is cut off when the negative electrode potential reaches zero. Secondly, let it stand for 3 hours at 25°C, and discharge at a constant current of 0.33C to the cut-off voltage, and the data collection time interval is 30s. Finally, extract the charging test data at different rates.

[0110] Step 3: Process the charging test data of different rates obtained in the second step. The specific processing process is: taking the calculation of charging DCR as an example, respectively extract the charging capacity Q, battery voltage V and fixed capacity Q0 of each SOC collection point in the above six charging rate tests. Use the charging capacity and fixed capacity of each SOC collection point to calculate the SOC of the battery cell in the charging test, that is, SOC = Q / Q0. In this way, the SOC and voltage data of different charging rates can be obtained for backup, and the corresponding relationship curve between the SOC and voltage data of different charging rates can be obtained according to the SOC and voltage data of different charging rates, as shown in the figure. Figure 2 shown.

[0111] Step 4: Calculate DCR. Taking charging DCR as an example, the charging DCR is tested when the battery cell is at 10%, 15%, 20%, and 30% SOC. Accordingly, the preset test currents applied to the battery cell at 10%, 15%, 20%, and 30% SOC are 513.08A, 505.07A, 496.02A, and 468.03A, respectively, and the test time is 10s. According to the SOC-OCV charging data obtained in the first step, the voltages of the battery cell at 10%, 15%, 20%, and 30% SOC are 3.205V, 3.225V, 3.259V, and 3.293V, respectively.

[0112] In the charging test, the 10% SOC test obtained that the cell SOC change was △SOC0.1=513.08*10 / 3600 / 128.94=0.011053375. The cell SOC1 at the end of charging was 0.1+0.011053375=0.111053375. Similarly, the SOC1 at 15%, 20%, and 30% SOC were obtained respectively. The specific values ​​are shown in Table 1 below.

[0113] Table 1 Summary of SOC1 calculations at 10%, 15%, 20%, and 30% SOC

[0114] SOC0 I / A OCV0 △SOC SOC1 0.3 468.03 3.293 0.010082855 0.310082855 0.20 496.02 3.259 0.010685849 0.210685849 0.15 505.07 3.225 0.010880815 0.160880815 0.10 513.08 3.205 0.011053375 0.111053375

[0115] Then, according to the SOC1 value corresponding to each preset SOC, the rate and voltage corresponding to the SOC1 value corresponding to each preset SOC in the third step are extracted respectively, and fitting is performed to obtain the corresponding relationship between the voltage and the charge / discharge rate at the end of battery charge / discharge under each preset SOC.

[0116] Figure 4 This is the curve of the change of different charging SOC voltage with the rate at 25°C provided in the embodiment of this application. Figure 4The corresponding relationship curve between the voltage and the charging rate at the end of charging of a 10% SOC battery is shown as curve S1, the corresponding relationship curve between the voltage and the charging rate at the end of charging of a 15% SOC battery is shown as curve S2, the corresponding relationship curve between the voltage and the charging rate at the end of charging of a 20% SOC battery is shown as curve S3, and the corresponding relationship curve between the voltage and the charging rate at the end of charging of a 30% SOC battery is shown as curve S4.

[0117] For example, taking 10% SOC as an example, according to the value of SOC1 corresponding to 10% SOC, the rate and voltage corresponding to the value of SOC1 corresponding to 10% SOC in the third step can be extracted, and the mathematical relationship between the voltage at the end of battery charging at 10% SOC and the charge / discharge rate can be obtained by fitting:

[0118] V1=0.092157*C1+3.246733;

[0119] Among them, a is 0.092157 and b is 3.246733.

[0120] Among them, C = I / (Q0 / 1[h]) = 513.08 / 128.94 = 3.979215139, substituting it into V1 = 0.092157x3.979215139+3.246733 = 3.61344553V. Similarly, the voltages at 15%, 20%, and 30% SOC can be obtained as shown in Table 2, and the mathematical relationship between the voltage and the charging rate at the end of battery charging is as follows:

[0121] Among them, the corresponding relationship between the voltage and the charging rate at the end of battery charging at 15% is:

[0122] V2=0.089865*C2+3.277186;

[0123] Among them, the corresponding relationship between the voltage and the charging rate at the end of battery charging at 20% is:

[0124] V3=0.086207*C3+3.307464;

[0125] Among them, the corresponding relationship between the voltage and the charging rate at the end of battery charging at 30% is:

[0126] V4=0.0842*C4+3.3296;

[0127] Among them, V1-V4 are the voltages at the end of battery charging at 10% SOC, 15% SOC, 20% SOC and 30% SOC respectively, and C1-C4 are the battery charging rates at 10% SOC, 15% SOC, 20% SOC and 30% SOC respectively.

[0128] Table 2 Summary of voltage calculations at 10%, 15%, 20%, and 30% SOC

[0129] SOC C1-C4 a b V DCR / Ω 03 3.629827827 0.0842 3.3296 3.635231503 0.000731217 0.20 3.846905537 0.086207 3.307464 3.639094186 0.000766288 0.15 3.917093222 0.089865 3.277186 3.629195582 0.000800276 0.10 3.979215139 0.092157 3.246733 3.61344553 0.000796066

[0130] In summary, DCR measured at 10% SOC = (V-OCV0) / I = (3.61344553-3.205) / 513.08 = 0.000796066Ω. Similarly, DCR at 15%, 20%, and 30% SOC are obtained, and the values ​​are shown in Table 2.

[0131] Table 3 Summary of DCR accuracy at 10%, 15%, 20%, and 30% SOC

[0132] SOC DCR Calculation DCR measured value Accuracy 0.3 0.000731217 0.000723 0.9886 0.20 0.000766288 0.000716 0.9298 0.15 0.000800276 0.000731 0.9052 0.10 0.000796066 0.000759 0.9512

[0133] Finally, the accuracy of the battery DC internal resistance test method provided in this application is verified. For example, the accuracy of the 10% SOC test is verified as: 1-|(calculated value-measured value)| / measured value=1-|(0.000796066-0.000759)| / 0.000759=0.9512. Similarly, the DCR at 15%, 20%, and 30% SOC is obtained, and the values ​​are shown in Table 3.

[0134] The DCR calculated value is the value of the battery DCR calculated by the solution of the present application, and the DCR measured value is the value obtained by using the traditional DCR test method. Figure 5 This is a schematic diagram comparing the voltage at the end of the DCR test of the present application and the voltage value actually measured by the traditional DCR test method at different SOCs and the same rate provided in the embodiments of the present application. Figure 5, curves L11-L14 are curves obtained by the 10% SOC calculated voltage, 15% SOC calculated voltage, 20% SOC calculated voltage, and 30% SOC calculated voltage of this scheme, respectively, and curves L21-L24 are curves obtained by the 10% SOC test voltage, 15% SOC test voltage, 20% SOC test voltage, and 30% SOC test voltage obtained by the traditional DCR test method, respectively. Taking 10% SOC as an example, point A1 in curve L11 is the voltage of this scheme at the end of the DCR charging test of 10% SOC, and point A2 in curve L21 is the measured voltage of the traditional DCR test method. Substituting them into the DCR calculation formula, the DCR calculated value and the DCR measured value can be obtained, as well as the accuracy of DCR as shown in Table 3. The accuracy of this scheme at 10% SOC test is 0.9512. Taking 15% SOC as an example, point B1 in curve L12 is the voltage of this solution at the end of the DCR charging test at 15% SOC, and point B2 in curve L22 is the measured voltage of the traditional DCR test method. Substituting them into the DCR calculation formula can obtain the DCR calculated value and the DCR measured value, as well as the accuracy of DCR as shown in Table 3. The accuracy of this solution at 15% SOC test is 0.9052. Taking 20% ​​SOC as an example, point C1 in curve L13 is the voltage of this solution at the end of the DCR charging test at 20% SOC, and point C2 in curve L23 is the measured voltage of the traditional DCR test method. Substituting them into the DCR calculation formula can obtain the DCR calculated value and the DCR measured value, as well as the accuracy of DCR as shown in Table 3. The accuracy of this solution at 20% SOC test is 0.9298. Taking 30% SOC as an example, point D1 in curve L14 is the voltage of this solution at the end of the DCR charging test at 30% SOC, and point D2 in curve L24 is the measured voltage of the traditional DCR test method. Substituting them into the DCR calculation formula can obtain the DCR calculation value and the DCR measured value, as well as the accuracy of DCR as shown in Table 3. The accuracy of this solution at 30% SOC test is 0.9886. It can be seen that the accuracy of the battery DCR test method provided by this solution is relatively high, so this solution can be used for DCR test requirements of batteries at different temperatures and / or different SOCs.

[0135] Similarly, according to the above steps, the DCR test of different SOC under the discharge test can be obtained. Therefore, the solution of the present application can meet the DCR test requirements of the battery at different temperatures and / or different SOCs, can reduce the amount of test data, reduce test time and cost, improve test efficiency and flexibility, and is suitable for occasions with large DCR test requirements.

[0136] Figure 6 is a principle structure diagram of a battery DC internal resistance test device provided in an embodiment of the present application. Correspondingly, an embodiment of the present application also provides a battery DC internal resistance test device, please refer to Figure 6 The battery DC internal resistance test device 100 includes: a first acquisition module 10, used to acquire the initial charge / discharge voltage of the battery; a first test module 20, used to set a plurality of preset rates, and perform charge / discharge tests on the battery at a preset temperature according to each preset rate; a second acquisition module 30, used to acquire the battery charge / discharge test data at each preset rate; a first correspondence determination module 40, used to obtain the correspondence between the real-time SOC and the real-time voltage of the battery charge / discharge at each preset rate according to the battery charge / discharge test data at each preset rate; a second test module 50, used to set a plurality of preset SOCs, and apply a preset test current corresponding to the preset test time to the battery at each preset SOC; a first calculation module 60, used to calculate the corresponding relationship between the real-time SOC and the real-time voltage of the battery charge / discharge at each preset rate according to the battery charge / discharge test data at each preset rate; The SOC at the end of battery charge / discharge under each preset SOC is calculated according to the preset SOC, the preset test current and the preset test duration corresponding to the preset SOC; the second correspondence determination module 70 is used to fit the SOC at the end of battery charge / discharge under each preset SOC with the correspondence between the real-time SOC and the real-time voltage of the battery charge / discharge under each preset rate, so as to obtain the correspondence between the voltage at the end of battery charge / discharge under each preset SOC and the charge / discharge rate; the second calculation module 80 is used to calculate the DC internal resistance of the battery under each preset SOC according to the correspondence between the voltage at the end of battery charge / discharge under each preset SOC and the charge / discharge rate, the preset test current corresponding to each preset SOC, and the initial charge / discharge voltage of the battery.

[0137] The technical solution of the embodiment of the present application provides a battery DC internal resistance test device, which can realize the calculation of the battery DC internal resistance at different temperatures and / or different SOCs, meet the DCR calculation requirements at different temperatures and / or different SOCs, and has a small amount of data testing, low test time and cost, and high calculation efficiency. Moreover, the method is not limited to the size of the test current and test time, has strong flexibility, and is suitable for scenarios with large amounts of DCR calculation data.

[0138] In some embodiments, the battery DC internal resistance testing device further includes: a third acquisition module, used to obtain the battery fixed capacity.

[0139] The first calculation module is also used to: calculate the battery charge / discharge SOC change at each preset SOC according to the battery fixed capacity, and the corresponding preset test current and preset test duration at each preset SOC; calculate the SOC of the battery at the end of charge / discharge at each preset SOC according to the battery charge / discharge SOC change at each preset SOC and the corresponding preset SOC.

[0140] In some embodiments, the corresponding relationship between the voltage of the battery at the end of charging / discharging at each preset SOC and the charging / discharging rate is:

[0141] V=a*C+b

[0142] Where V is the voltage of the battery at the end of charge / discharge, C is the battery charge / discharge rate; a and b are coefficients;

[0143] The calculation formula of C is:

[0144] C=I / (Q0 / 1[h])

[0145] Where, I is the preset test current, 1[h] is the time of 1 hour, and Q0 is the fixed capacity of the battery.

[0146] In some embodiments, the value range of the plurality of preset SOCs is: 10%-30%.

[0147] In some embodiments, the plurality of preset SOCs are: 10%, 15%, 20% and 30% respectively;

[0148] Among them, the corresponding relationship between the voltage and the charging rate at the end of battery charging at 10% is:

[0149] V1=0.092157*C1+3.246733;

[0150] Among them, the corresponding relationship between the voltage and the charging rate at the end of battery charging at 15% is:

[0151] V2=0.089865*C2+3.277186;

[0152] Among them, the corresponding relationship between the voltage and the charging rate at the end of battery charging at 20% is:

[0153] V3=0.086207*C3+3.307464;

[0154] Among them, the corresponding relationship between the voltage and the charging rate at the end of battery charging at 30% is:

[0155] V4=0.0842*C4+3.3296;

[0156] Among them, V1-V4 are the voltages at the end of battery charging at 10% SOC, 15% SOC, 20% SOC and 30% SOC respectively, and C1-C4 are the battery charging rates at 10% SOC, 15% SOC, 20% SOC and 30% SOC respectively.

[0157] In some embodiments, the battery DC internal resistance testing device further includes: a fourth acquisition module, used to acquire the actual charge / discharge rate of the battery.

[0158] The second calculation module is also used to: determine the voltage of the battery at the end of charging / discharging at each preset SOC according to the corresponding relationship between the voltage of the battery at the end of charging / discharging at each preset SOC and the charge / discharge rate and the actual charge / discharge rate of the battery; calculate the DC internal resistance of the battery at each preset SOC according to the voltage of the battery at the end of charging / discharging at each preset SOC, the preset test current corresponding to each preset SOC, and the initial charge / discharge voltage of the battery.

[0159] In some embodiments, the first correspondence determination module is also used to: extract the charge / discharge capacity, real-time voltage and constant capacity of each SOC collection point at each preset rate according to the battery charge / discharge test data at each preset rate; calculate the corresponding real-time SOC of the battery charge / discharge at each preset rate according to the charge / discharge capacity and constant capacity of each SOC collection point at each preset rate; determine the correspondence between the real-time SOC and the real-time voltage of the battery charge / discharge at each preset rate according to the real-time SOC and real-time voltage of the battery charge / discharge at each preset rate.

[0160] In some embodiments, the first acquisition module is further used to: perform a SOC-OCV test on the battery at a preset temperature to obtain an initial charge / discharge voltage of the battery.

[0161] In some embodiments, the value range of the multiple preset magnifications is: 0.33C-2.5C.

[0162] The above is a detailed introduction to a method and device for testing the DC internal resistance of a battery provided in an embodiment of the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solution and its core idea of ​​the present application. Ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some of the technical features therein with equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for testing the DC internal resistance of a battery, characterized in that: include: Get the initial charge / discharge voltage of the battery; Setting multiple preset rates, performing charge / discharge tests on the battery at preset temperatures according to each preset rate, and obtaining battery charge / discharge test data at each preset rate; According to the battery charge / discharge test data at each preset rate, the corresponding relationship between the real-time SOC and the real-time voltage of the battery charge / discharge at each preset rate is obtained; Setting a plurality of preset SOCs, applying a preset test current corresponding to a preset test duration to the battery at each preset SOC, and calculating the SOC of the battery at the end of charge / discharge at each preset SOC according to the preset SOC, preset test current and preset test duration corresponding to each preset SOC; Fitting the corresponding relationship between the SOC at the end of battery charge / discharge at each preset SOC and the real-time SOC and real-time voltage of the battery charge / discharge at each preset rate, to obtain the corresponding relationship between the voltage at the end of battery charge / discharge at each preset SOC and the charge / discharge rate; The DC internal resistance of the battery at each preset SOC is calculated based on the corresponding relationship between the voltage and the charge / discharge rate at the end of the battery charge / discharge at each preset SOC, the preset test current corresponding to each preset SOC, and the initial charge / discharge voltage of the battery.

2. The method for testing the DC internal resistance of a battery according to claim 1, characterized in that: Also includes: Get the battery capacity; The step of calculating the SOC at the end of battery charging / discharging at each preset SOC according to the preset SOC, the preset test current and the preset test duration corresponding to each preset SOC includes: Calculate the battery charge / discharge SOC change at each preset SOC based on the battery fixed capacity, the preset test current and the preset test duration corresponding to each preset SOC; The SOC at the end of battery charging / discharging at each preset SOC is calculated according to the battery charging / discharging SOC change at each preset SOC and the corresponding preset SOC.

3. The method for testing the DC internal resistance of a battery according to claim 1, characterized in that: The corresponding relationship between the voltage of the battery at the end of charging / discharging and the charging / discharging rate under each preset SOC is: V=a*C+b Where V is the voltage of the battery at the end of charge / discharge, C is the battery charge / discharge rate; a and b are coefficients; The calculation formula of C is: C=I / (Q0 / 1[h]) Where, I is the preset test current, 1[h] is the time of 1 hour, and Q0 is the fixed capacity of the battery.

4. The method for testing the DC internal resistance of a battery according to claim 3, characterized in that: The value range of the multiple preset SOCs is: 10%-30%.

5. The method for testing the DC internal resistance of a battery according to claim 4, characterized in that: The multiple preset SOCs are: 10%, 15%, 20% and 30% respectively; Among them, the corresponding relationship between the voltage at the end of battery charging at 10% and the charging rate is: V1=0.092157*C1+3.246733; Among them, the corresponding relationship between the voltage and the charging rate at the end of battery charging at 15% is: V2=0.089865*C2+3.277186; Among them, the corresponding relationship between the voltage and the charging rate at the end of battery charging at 20% is: V3=0.086207*C3+3.307464; Among them, the corresponding relationship between the voltage and the charging rate at the end of battery charging at 30% is: V4=0.0842*C4+3.3296; Among them, V1-V4 are the voltages at the end of battery charging at 10% SOC, 15% SOC, 20% SOC and 30% SOC respectively, and C1-C4 are the battery charging rates at 10% SOC, 15% SOC, 20% SOC and 30% SOC respectively.

6. The method for testing the DC internal resistance of a battery according to claim 1, characterized in that: Also includes: Get the actual charge / discharge rate of the battery; The method calculates the DC internal resistance of the battery at each preset SOC according to the corresponding relationship between the voltage and the charge / discharge rate of the battery at the end of charge / discharge at each preset SOC, the preset test current corresponding to each preset SOC, and the initial charge / discharge voltage of the battery, including: Determine the voltage of the battery at the end of charge / discharge at each preset SOC according to the corresponding relationship between the voltage of the battery at the end of charge / discharge at each preset SOC and the charge / discharge rate and the actual charge / discharge rate of the battery; The DC internal resistance of the battery at each preset SOC is calculated according to the voltage of the battery at the end of charge / discharge at each preset SOC, the preset test current corresponding to each preset SOC, and the initial charge / discharge voltage of the battery.

7. The method for testing the DC internal resistance of a battery according to claim 1, characterized in that: The corresponding relationship between the real-time SOC and the real-time voltage of the battery at each preset rate is obtained according to the battery charge / discharge test data at each preset rate, including: According to the battery charge / discharge test data at each preset rate, the charge / discharge capacity, real-time voltage and constant capacity of each SOC collection point at each preset rate are respectively extracted; Calculate the real-time SOC of the battery charge / discharge at each preset rate according to the charge / discharge capacity and constant capacity of each SOC collection point at each preset rate; The corresponding relationship between the real-time SOC and the real-time voltage of the battery charging / discharging at each preset rate is determined according to the real-time SOC and the real-time voltage of the battery charging / discharging at each preset rate.

8. The method for testing the DC internal resistance of a battery according to claim 1, characterized in that: The obtaining of the initial charge / discharge voltage of the battery comprises: The SOC-OCV test is performed on the battery at the preset temperature to obtain the initial charge / discharge voltage of the battery.

9. The method for testing the DC internal resistance of a battery according to claim 1, characterized in that: The value range of the multiple preset magnifications is: 0.33C-2.5C.

10. A battery DC internal resistance testing device, characterized in that: include: A first acquisition module, used to acquire an initial charge / discharge voltage of a battery; The first test module is used to set a plurality of preset rates and perform charge / discharge tests on the battery at each preset rate at a preset temperature; The second acquisition module is used to acquire battery charge / discharge test data at each preset rate; A first corresponding relationship determination module, used to obtain the corresponding relationship between the real-time SOC and the real-time voltage of the battery at each preset rate of charge / discharge according to the battery charge / discharge test data at each preset rate; The second test module is used to set a plurality of preset SOCs and apply a preset test current corresponding to a preset test time to the battery at each preset SOC; A first calculation module, used to calculate the SOC at the end of battery charging / discharging at each preset SOC according to the preset SOC, preset test current and preset test duration corresponding to each preset SOC; A second corresponding relationship determination module is used to fit the corresponding relationship between the SOC at the end of battery charge / discharge at each preset SOC and the real-time SOC and real-time voltage of the battery charge / discharge at each preset rate, so as to obtain the corresponding relationship between the voltage at the end of battery charge / discharge at each preset SOC and the charge / discharge rate; The second calculation module is used to calculate the DC internal resistance of the battery at each preset SOC according to the corresponding relationship between the voltage and the charge / discharge rate of the battery at the end of charge / discharge at each preset SOC, the preset test current corresponding to each preset SOC, and the initial charge / discharge voltage of the battery.

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