A method for testing battery DC resistance, electronic device and readable storage medium

Abstract

The embodiment of the present application relates to the field of battery testing technology, and discloses a method for testing the DC resistance of a battery, an electronic device, and a readable storage medium. Based on the similar changing trend of the first DC resistance cycle curve and the second DC resistance cycle curve, a first parameter factor and a second parameter factor are determined according to the first DC resistance corresponding to the i-th cycle, the first DC resistance corresponding to the j-th cycle, the second DC resistance corresponding to the i-th cycle, and the second DC resistance corresponding to the j-th cycle. The first parameter factor and the second parameter factor are applied to the linear transformation relationship between the first DC resistance cycle curve and the third DC resistance cycle curve to determine the third DC resistance cycle curve. Thus, the DC resistance of the battery throughout its life at different discharge rates can be accurately obtained while reducing the number of DC resistance tests.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of battery testing technology, and in particular to a method for testing the direct current resistance of a battery, an electronic device, and a readable storage medium. Background Art

[0002] Battery DC resistance is one of the most important battery characteristics and a key indicator for evaluating battery performance. It can be used to assess battery health, estimate battery life, and perform other key battery operating parameters, such as system state of charge (SOC) and power output / input capabilities. It can also serve as a basis for assessing battery damage, malfunctions, and connection issues. Therefore, estimating battery DC resistance is essential.

[0003] The testing principle of DC resistance is to apply a large current (charging or discharging) to the battery for a short period of time. When the battery has not yet reached complete polarization, the DC resistance of the battery is calculated based on the voltage change of the battery before and after the current is applied and the applied current.

[0004] DC resistance testing is generally interspersed with cycle life testing to obtain the DC resistance of the battery throughout its life. However, DC resistance testing usually requires high-current equipment. That is, when switching from cycle life testing to DC resistance testing, it is necessary to switch equipment and reconnect lines, which affects the test cycle and accuracy, and also consumes a lot of manpower and material resources. Summary of the Invention

[0005] The embodiment of the present application provides a method for testing the DC resistance of a battery, which can accurately obtain the DC resistance of the battery throughout its life at different discharge rates while reducing the number of DC resistance tests.

[0006] In a first aspect, an embodiment of the present application provides a method for testing the DC resistance of a battery, comprising obtaining a first DC resistance cycle curve of the battery when a DC resistance test is performed at a first preset state of charge and a first discharge rate, wherein the cycle number is the number of cycles in a cycle life test; obtaining a second DC resistance corresponding to the i-th cycle number and a second DC resistance corresponding to the j-th cycle number when the DC resistance test is performed at a second preset state of charge and a second discharge rate, wherein the first DC resistance cycle curve and the second DC resistance cycle curve of the battery at the second preset state of charge and the second discharge rate show a similar change trend, i<j; determining a first parameter factor and a second parameter factor based on the first DC resistance corresponding to the i-th cycle number, the first DC resistance corresponding to the j-th cycle number, the second DC resistance corresponding to the i-th cycle number, and the second DC resistance corresponding to the j-th cycle number; and determining a third DC resistance cycle curve of the battery when the battery is at the first preset state of charge and a third discharge rate based on the first DC resistance cycle curve and the first parameter factor and the second parameter factor.

[0007] In the above embodiment of the present application, a battery DC resistance testing process is specifically described. During this testing process, based on the similar change trend of the first DC resistance cycle curve and the second DC resistance cycle curve of the battery at the second preset state of charge and the second discharge rate, that is, the first DC resistance at the first preset state of charge and the first discharge rate is proportional to the second DC resistance at the second preset state of charge and the second discharge rate, a first parameter factor and a second parameter factor can be determined based on the first DC resistance corresponding to the i-th cycle, the first DC resistance corresponding to the j-th cycle, the second DC resistance corresponding to the i-th cycle, and the second DC resistance corresponding to the j-th cycle. The first parameter factor and the second parameter factor are applied to the relationship between the first DC resistance at the first preset state of charge and the first discharge rate and the third DC resistance at the first preset state of charge and the third discharge rate. Therefore, based on the first DC resistance cycle curve and the first parameter factor and the second parameter factor, a third DC resistance cycle curve of the battery when the cycle life test is performed at the first preset state of charge and the third discharge rate can be determined. Therefore, there is no need to test the third DC resistance corresponding to each cycle number under the first preset state of charge and the third discharge rate, and the third DC resistance cycle curve can be obtained. The DC resistance of the battery throughout its life at different discharge rates can be accurately obtained while reducing the number of DC resistance tests.

[0008] In a possible implementation of the first aspect, the above-mentioned acquisition of a first DC resistance cycle curve when the battery is subjected to a DC resistance test at a first preset state of charge and a first discharge rate includes: for any target number of cycles in a cycle life test, obtaining the first DC resistance corresponding to the target number of cycles based on the first voltage of the battery after full charge and rest, the second voltage after discharging at the first discharge rate for a first preset time, and the first current of discharging at the first discharge rate, wherein the battery is in the first preset state of charge.

[0009] In the above-described embodiment of the present application, the first voltage after full charge and rest and the second voltage after discharge at the first discharge rate for the first preset time are obtained when the battery is not fully polarized. The first preset time may be an empirical value used by those skilled in the art, such as 10 seconds or 30 seconds. Thus, the first DC resistance is determined based on the first voltage, the second voltage, and the first current, ensuring that the first DC resistance is accurate.

[0010] In a possible implementation of the first aspect, obtaining a second DC resistance corresponding to the i-th cycle and a second DC resistance corresponding to the j-th cycle when the battery is subjected to a DC resistance test at a second preset state of charge and a second discharge rate includes: for the i-th cycle, obtaining the second DC resistance corresponding to the i-th cycle based on a third voltage of the battery after being fully charged and standing, a fourth voltage after being discharged at a second discharge rate for a first preset time, and a second current during discharge at the second discharge rate, wherein the battery is in the second preset state of charge; and for the j-th cycle, obtaining the second DC resistance corresponding to the j-th cycle based on a fifth voltage of the battery after being fully charged and standing, a sixth voltage after being discharged at the second discharge rate for a first preset time, and a third current during discharge at the second discharge rate, wherein the battery is in the second preset state of charge.

[0011] In the above-mentioned embodiment of the present application, the third voltage of the battery after being fully charged and standing still and the fourth voltage after being discharged at the second discharge rate for the first preset time are obtained when the battery has not reached complete polarization. The first preset time can be an empirical value of those skilled in the art, such as 10S or 30S. Thus, based on the third voltage, the fourth voltage and the second current, the second DC resistance corresponding to the i-th cycle number is determined, so that the second DC resistance corresponding to the i-th cycle number is accurate. Similarly, the fifth voltage of the battery after being fully charged and standing still and the sixth voltage after being discharged at the second discharge rate for the first preset time are obtained when the battery has not reached complete polarization. Thus, based on the fifth voltage, the sixth voltage and the third current, the second DC resistance corresponding to the j-th cycle number is determined, so that the second DC resistance corresponding to the j-th cycle number is accurate.

[0012] In a possible implementation manner of the first aspect, the i-th cycle number includes the cycle number corresponding to the initial life of the battery.

[0013] In the above embodiment of the present application, the i-th cycle number is in the initial life stage of the battery. For example, the i-th cycle number may be cycle number 1. A DC resistance test is performed at the second preset state of charge and the second discharge rate at the cycle number corresponding to the initial life stage to obtain a second DC resistance corresponding to the i-th cycle number. This makes the second DC resistance corresponding to the i-th cycle number more representative, thereby facilitating the calculation of more accurate first parameter factors and second parameter factors.

[0014] In a possible implementation manner of the first aspect, the jth cycle number includes the cycle number corresponding to the end of the battery life.

[0015] In the above embodiment of the present application, the jth cycle number is at the end-of-life stage of the battery. For example, the jth cycle number can be the number of cycles corresponding to when the state of charge decays to 80%, or the jth cycle number is the 2000th cycle number (where 2000 is a preset value). A DC resistance test is performed at the second preset state of charge and the second discharge rate at the cycle number corresponding to the end-of-life stage to obtain the second DC resistance corresponding to the jth cycle number. This makes the second DC resistance corresponding to the jth cycle number more representative, thereby facilitating the calculation of more accurate first parameter factors and second parameter factors.

[0016] In a possible implementation of the first aspect, determining the first parameter factor and the second parameter factor based on the first DC resistance corresponding to the i-th number of cycles, the first DC resistance corresponding to the j-th number of cycles, the second DC resistance corresponding to the i-th number of cycles, and the second DC resistance corresponding to the j-th number of cycles includes:

[0017] The first and second parameter factors are calculated as follows:

[0018]

[0019] b=k×DCR (1,i) -DCR (2,i) ;

[0020] Among them, DCR (1,i) is the first DC resistance corresponding to the i-th cycle number, DCR (1,j) is the first DC resistance corresponding to the jth cycle number; DCR (2,i) is the second DC resistance corresponding to the i-th cycle number, DCR (2,j) is the second DC resistance corresponding to the j-th cycle number, k is the first parameter factor, and b is the second parameter factor.

[0021] In the above embodiment of the present application, based on the similar change trend of the first DC resistance cycle curve and the second DC resistance cycle curve, that is, the first DC resistance at the first preset state of charge and the first discharge rate and the second DC resistance at the second preset state of charge and the second discharge rate have a certain linear mapping relationship. Therefore, in order to determine the first parameter factor k and the second parameter factor b that characterize the linear mapping relationship, the first DC resistance DCR corresponding to the i-th cycle number is found in the first DC resistance cycle curve. (1,i) The first DC resistance DCR corresponding to the jth cycle number (1,j) , thus, according to the first DC resistance DCR corresponding to the number of cycles i (1,i) , the first DC resistance DCR corresponding to the jth cycle number (1,j) , the second DC resistance DCR corresponding to the i-th cycle number (2,i) The second DC resistance DCR corresponding to the jth cycle number (2,j) , the first parameter factor k and the second parameter factor b can be calculated.

[0022] In a possible implementation of the first aspect, determining, based on the first DC resistance cycle curve and the first parameter factor and the second parameter factor, a third DC resistance cycle curve when the battery is subjected to a cycle life test at a first preset state of charge and a third discharge rate includes:

[0023] The third DC resistance cycle curve of the battery is calculated using the following formula when the battery is subjected to a cycle life test at the first preset state of charge and the third discharge rate:

[0024] DCR (3,x) =k×DCR (1.x) +b

[0025] Among them, DCR (3,x) The third DC resistance cycle curve, DCR (1,x) is the first DC resistance cycle curve, and x is the cycle number.

[0026] In the above embodiment of the present application, the linear mapping relationship between the first DC resistance cycle curve and the second DC resistance cycle curve is applied between the first DC resistance cycle curve and the third DC resistance cycle curve to obtain the above formula. Thus, the third DC resistance cycle curve is obtained, that is, the third DC resistance at the first preset state of charge and the third discharge rate does not need to be tested, only the first DC resistance cycle curve needs to be tested, and the third DC resistance cycle curve can be obtained by the above formula, thereby accurately obtaining the DC resistance of the battery at different discharge rates while reducing the number of DC resistance tests. In addition, for a battery including multiple cells, there will be connection resistance (physical impedance) between the cells, and the connection resistance is not affected by the discharge rate and state of charge. Thus, the mapping relationship between the first DC resistance cycle curve and the third DC resistance cycle curve is a linear mapping relationship, so that the connection resistance is not affected by the linear mapping relationship, that is, the linear mapping relationship is applied between the first DC resistance cycle curve and the third DC resistance cycle curve, so that the above formula can accurately predict the third DC resistance at the first preset state of charge and the third discharge rate.

[0027] In a possible implementation of the first aspect, the first discharge rate includes a lower limit of a discharge rate range when the battery is operating, and / or the third discharge rate includes an upper limit of a discharge rate range when the battery is operating.

[0028] In the above-mentioned embodiment of the present application, based on the different usage scenarios of the battery, the output power of the battery has a range. When the output power is large, the discharge rate of the battery is also large. When the output power is small, the discharge rate of the battery is also small. That is, in different usage scenarios, the discharge rate of the battery when working also has a range, such as the discharge rate range [1C, 4C]. The first discharge rate includes the lower limit of the discharge rate range when the battery is working, that is, the first DC resistance cycle curve of the battery when working at the lower limit of the discharge rate range is measured, and the third DC resistance cycle curve is predicted through the first DC resistance cycle curve. Optionally, the third discharge rate includes the upper limit of the discharge rate range when the battery is working, that is, the first DC resistance cycle curve corresponding to the lower limit of the discharge rate range can be used to predict the third DC resistance cycle curve corresponding to the upper limit of the discharge rate. There is no need to test the DC resistance corresponding to the upper limit of the discharge rate, which can reduce the number of tests and avoid battery loss due to high-rate discharge.

[0029] In a second aspect, an embodiment of the present application provides an electronic device comprising: a processor, and a memory communicatively connected to the processor, wherein the memory stores instructions executable by the processor, and the instructions are executed by the processor to enable the processor to execute the battery DC resistance testing method of the first aspect described above.

[0030] In a third aspect, an embodiment of the present application provides a readable storage medium, which stores a program or instruction. When the program or instruction is executed by a processor, the battery DC resistance testing method of the first aspect is implemented.

[0031] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] One or more embodiments are exemplarily illustrated by pictures in the corresponding drawings. These exemplifications do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings are represented as similar elements. Unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0033] Figure 1 A schematic diagram of battery testing according to some embodiments of the present application;

[0034] Figure 2 This is a flow chart of a method for testing the DC resistance of a battery according to some embodiments of the present application;

[0035] Figure 3 A schematic diagram of a DC resistance cycle curve according to some embodiments of the present application;

[0036] Figure 4 for Figure 2 A schematic diagram of a sub-process of step S21 in the method shown;

[0037] Figure 5 A schematic diagram of voltage drop in a DC resistance test in some embodiments of the present application;

[0038] Figure 6 for Figure 2 A schematic diagram of a sub-flow chart of step S22 in the method shown;

[0039] Figure 7 is a linear function of the correlation between the first DC resistance cycle number curve and the second DC resistance cycle number curve in some embodiments of the present application;

[0040] Figure 8 This is a schematic structural diagram of an electronic device according to some embodiments of the present application. DETAILED DESCRIPTION

[0041] The following embodiments of the technical solution of the present application will be described in detail with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only examples and are not intended to limit the scope of protection of the present application.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0043] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0044] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0045] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0046] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0047] In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0048] Currently, market developments indicate that power batteries are becoming increasingly widely used. They are not only used in energy storage systems such as hydropower, thermal, wind, and solar power plants, but are also widely used in electric vehicles like electric bicycles, electric motorcycles, and electric vehicles, as well as in military equipment and aerospace. As power battery applications continue to expand, market demand is also growing.

[0049] As the battery is used, its DC resistance continues to increase, which will affect the battery's charge and discharge performance, thereby affecting the battery's life and power behavior.

[0050] In order to test the DC resistance of the battery throughout its life, a DC resistance test is generally interspersed with the battery cycle life test. Among them, the battery cycle life test refers to the number of charge and discharge cycles that the battery can withstand before the state of charge (SOC) decays to a certain specified value (for example, before 80% SOC) under a certain charge and discharge system. One cycle is equivalent to one circle, including one full charge and one full discharge. The more charge and discharge circles the battery can perform before the state of charge decays to the specified value, the longer the battery life. Specifically, the cycle life test can be carried out with reference to existing national standards, industry standards or enterprise standards.

[0051] As the number of cycles increases, which is equivalent to the number of times the battery is used, the DC resistance will also increase. In order to understand the DC resistance at each stage of the battery's service life, DC resistance tests will be interspersed in the middle of the cycle life test, such as DC resistance tests at the 1st cycle, 100th cycle, 200th cycle, and 300th cycle. Figure 1 As shown, for battery 100, the cycle life test and DC resistance test utilize different test equipment. The cycle life test requires a low-current cycle life test device 200. Cycle life test device 200 records test data such as voltage U, current I, capacity, and temperature in real time while testing battery 100. The DC resistance test requires a high-current DC resistance test device 300. This requires switching equipment and reconnecting wiring when switching from the cycle life test to the DC resistance test, which is time-consuming and labor-intensive, and also affects test cycle time and accuracy.

[0052] Depending on the battery's usage scenario, the battery's output power has a range. For example, when the battery is used to power an electric vehicle, if the electric vehicle requires instant acceleration, the battery needs to output a higher power, that is, it needs to discharge at a higher discharge rate. If the electric vehicle does not require instant acceleration, the battery needs to output a lower power, that is, it needs to discharge at a lower discharge rate. Depending on the battery's usage scenario, the battery has a discharge rate range. For example, if battery #1 powers a small, slow-moving electric vehicle, the discharge rate range is [1C, 4C], while battery #2 powers a large, fast-moving electric vehicle, the discharge rate range is [2C, 8C]. To assess the battery's health in different usage scenarios, it is necessary to obtain DC resistance cycle curves at different discharge rates.

[0053] Based on the above considerations, in order to accurately obtain the DC resistance of the battery throughout its life at different discharge rates while reducing the number of DC resistance tests, that is, to accurately obtain the DC resistance cycle curve of the battery at different discharge rates, the inventors of this application have discovered through research that a correspondence between the DC resistance cycle curves at different discharge rates can be established. Thus, based on the DC resistance cycle curve at one discharge rate and the corresponding relationship, the DC resistance cycle curve at another discharge rate can be obtained, thereby reducing the number of DC resistance tests. It can be understood that the DC resistance cycle curve includes the number of cycles and the DC resistance corresponding to the number of cycles. The range of the cycle number reflects the entire life, for example, the range of the cycle number is [1,2000]. For example, when the correspondence between the DC resistance cycle curve at a discharge rate of 1C and the DC resistance cycle curves at discharge rates of 1C and 4C is known, if one wants to obtain the DC resistance DCR(4C, 100) corresponding to the 100th cycle at a discharge rate of 4C, one only needs to obtain the DC resistance DCR(1C, 100) corresponding to the 100th cycle at a discharge rate of 1C. Then, by mapping DCR(1C, 100) according to the correspondence, one can obtain DCR(4C, 100) without testing DCR(4C, 100). Thus, the number of DC resistance tests can be reduced, and the DC resistance of the battery throughout its life at different discharge rates can be obtained.

[0054] Specifically, in order to determine the correspondence between the DC resistance cycle curves under the aforementioned different discharge rates, first, a first DC resistance cycle curve of the battery when the DC resistance test is performed at a first preset state of charge and a first discharge rate can be obtained by testing. Then, a second DC resistance corresponding to the i-th cycle and a second DC resistance corresponding to the j-th cycle can be obtained by testing when the DC resistance test is performed at a second preset state of charge and a second discharge rate, where i<j.

[0055] Based on the similar change trend between the first DC resistance cycle curve and the second DC resistance cycle curve of the battery at the second preset state of charge and the second discharge rate, that is, the first DC resistance at the first preset state of charge and the first discharge rate is proportional to the second DC resistance at the second preset state of charge and the second discharge rate, the first parameter factor and the second parameter factor can be determined according to the first DC resistance corresponding to the i-th cycle, the first DC resistance corresponding to the j-th cycle, the second DC resistance corresponding to the i-th cycle, and the second DC resistance corresponding to the j-th cycle.

[0056] Finally, the first parameter factor and the second parameter factor are applied to the relationship between the first DC resistance at the first preset state of charge and the first discharge rate and the third DC resistance at the first preset state of charge and the third discharge rate. Thus, based on the first DC resistance cycle curve and the first parameter factor and the second parameter factor, the third DC resistance cycle curve of the battery at the first preset state of charge and the third discharge rate can be determined. Thus, without having to test the third DC resistance corresponding to each cycle at the first preset state of charge and the third discharge rate, the third DC resistance cycle curve can be obtained. This allows the DC resistance of the battery to be accurately obtained over its entire life at different discharge rates while reducing the number of DC resistance tests.

[0057] Since the method provided in the embodiment of the present application involves a cycle life test and a DC resistance test, for ease of understanding, the cycle life test and DC resistance test involved in the embodiment of the present application are first introduced.

[0058] (1) Cycle life test

[0059] The cycle life test should be conducted in an environment with a temperature of 25°C ± 5°C, a relative humidity of 15%-90%, and an atmospheric pressure of 86kPa-106kPa. The cycle life test can be conducted as follows:

[0060] a) Discharge at I1(A) until the preset discharge termination condition. For example, the discharge termination condition in the national standard includes the voltage dropping to 2.75V.

[0061] b) Leave to stand for not less than 30 minutes or under other specified static conditions;

[0062] c) Charge according to the following method: charge at a constant current of I1(A) to the specified charge termination voltage, then switch to constant voltage charging. Stop charging when the charge termination current drops to 0.05I1(A). Let the battery rest for 1 hour after charging.

[0063] d) Leave to stand for not less than 30 minutes or other specified static conditions.

[0064] e) Discharge at I1(A) to the specified discharge termination condition (e.g., discharge to 3V), and record the discharge capacity;

[0065] f) Cycle continuously for 500 times according to b) to e). If the discharge capacity is higher than 90% of the initial capacity, terminate the test; if the discharge capacity is lower than 90% of the initial capacity, continue to cycle for 500 times;

[0066] g) Measure the discharge capacity and discharge energy at room temperature.

[0067] It is understandable that the above-mentioned cycle life test steps are only an embodiment, and those skilled in the art may adjust the steps and parameters in the steps accordingly according to actual conditions, national standards, industry standards or enterprise standards.

[0068] (2) DC resistance test

[0069] DC resistance is measured by applying a DC signal to the battery to measure its internal resistance. It is typically calculated through the Hybrid Pulse Power Characterization (HPPC) test. Specifically, a 30s 1C discharge pulse is applied, followed by a 40s pause, and then a 10s 0.75C charge pulse is applied. The discharge internal resistance is the quotient of the discharge voltage drop and the discharge current, while the charge internal resistance is the quotient of the charge voltage rise and the charge current.

[0070] DC resistance testing usually requires high-current equipment, while cycle life testing requires low-current equipment. The two use different equipment.

[0071] According to some embodiments of this application, please refer to Figure 2 , Figure 2 A flowchart of a method for testing the DC resistance of a battery provided in an embodiment of the present application is provided. The method S20 may specifically include the following steps:

[0072] S21: Obtaining a first DC resistance cycle curve when the battery is subjected to a cycle life test at a first preset state of charge and a first discharge rate.

[0073] During the battery cycle life test, a DC resistance test is interspersed with a first preset state of charge and a first discharge rate to obtain a first DC resistance cycle curve. In some embodiments, the first preset state of charge can be 100% SOC and the first discharge rate can be 1C, that is, a DC resistance test is interspersed with 100% SOC and 1C. For example, a DC resistance test is performed every 50 cycles. That is, at the 1st cycle, 50th cycle, 100th cycle, 150th cycle, and 200th cycle, the battery is removed from the cycle life test equipment and connected to the DC resistance test equipment for a DC resistance test. The first DC resistance corresponding to each cycle is obtained, thereby obtaining a first DC resistance cycle curve.

[0074] It is understandable that if Figure 3 As shown, in the first DC resistance cycle number curve, the first coordinate axis (which may be the horizontal axis) represents the cycle number, and the second coordinate axis (which may be the vertical axis) represents the resistance value of the first DC resistor.

[0075] S22: Obtain a second DC resistance corresponding to the i-th cycle and a second DC resistance corresponding to the j-th cycle when the battery is subjected to a DC resistance test at a second preset state of charge and a second discharge rate, wherein a first DC resistance cycle curve and a second DC resistance cycle curve of the battery at the second preset state of charge and the second discharge rate show a similar change trend, i<j.

[0076] During the cycle life test of the battery, a DC resistance test at a second preset state of charge and a second discharge rate is performed alternately at the i-th cycle and the j-th cycle to obtain a second DC resistance corresponding to the i-th cycle and a second DC resistance corresponding to the j-th cycle. In some embodiments, the second preset state of charge may be 50% SOC and the second discharge rate may be 4C. That is, during the cycle life test at 50% SOC and 4C, the battery is removed from the cycle life test equipment at the i-th cycle and the j-th cycle, respectively, and connected to the DC resistance test equipment to perform a DC resistance test to obtain the second DC resistance corresponding to the i-th cycle and the second DC resistance corresponding to the j-th cycle at 50% SOC and 4C.

[0077] In this embodiment, the first DC resistance cycle curve and the second DC resistance cycle curve of the battery at the second preset state of charge and the second discharge rate show a similar change trend. It can be understood that if Figure 3 As shown, the inventors found that the first DC resistance cycle curve and the second DC resistance cycle curve showed similar trends in historical experimental data for multiple batteries. Therefore, when dealing with the battery in step S21, it is only necessary to perform DC resistance tests at the second preset state of charge and second discharge rate at the i-th cycle and the j-th cycle during the cycle life test to obtain the second DC resistance corresponding to the i-th cycle and the second DC resistance corresponding to the j-th cycle, without having to test every second DC resistance in the second DC resistance cycle curve.

[0078] Among them, the first DC resistance cycle curve and the second DC resistance cycle curve show a similar change trend, which means that the first DC resistance at the first preset state of charge and the first discharge rate is proportional to the second DC resistance at the second preset state of charge and the second discharge rate, that is, there is a linear transformation relationship between the first DC resistance cycle curve and the second DC resistance cycle curve. For example, by linearly transforming the first DC resistance cycle curve, the second DC resistance cycle curve can be obtained.

[0079] S23: Determine a first parameter factor and a second parameter factor according to the first DC resistance corresponding to the i-th cycle, the first DC resistance corresponding to the j-th cycle, the second DC resistance corresponding to the i-th cycle, and the second DC resistance corresponding to the j-th cycle.

[0080] In order to determine the linear transformation relationship between the first DC resistance cycle curve and the second DC resistance cycle curve, first, in the first DC resistance cycle, find the first DC resistance corresponding to the i-th cycle and the first DC resistance corresponding to the j-th cycle. Based on the similar change trend (linear transformation relationship) of the first DC resistance cycle curve and the second DC resistance cycle curve of the battery at the second preset state of charge and the second discharge rate, the first parameter factor and the second parameter factor can be determined according to the first DC resistance corresponding to the i-th cycle, the first DC resistance corresponding to the j-th cycle, the second DC resistance corresponding to the i-th cycle, and the second DC resistance corresponding to the j-th cycle. Specifically, the first DC resistance corresponding to the i-th cycle is linearly changed by using the first parameter factor and the second parameter factor to obtain the second DC resistance corresponding to the i-th cycle, and the first DC resistance corresponding to the j-th cycle is linearly changed by using the first parameter factor and the second parameter factor to obtain the second DC resistance corresponding to the j-th cycle.

[0081] S24: Determine, according to the first DC resistance cycle curve, the first parameter factor, and the second parameter factor, a third DC resistance cycle curve of the battery at a first preset state of charge and a third discharge rate.

[0082] Specifically, the first parameter factor and the second parameter factor are applied to the relationship between the first DC resistance at the first preset state of charge and the first discharge rate and the third DC resistance at the first preset state of charge and the third discharge rate. The third discharge rate can be 4C. That is, the first parameter factor and the second parameter factor are used as the linear change parameters between the first DC resistance cycle curve and the third DC resistance cycle curve. It can be understood that this is equivalent to assuming that the first parameter factor and the second parameter factor are applicable to the linear change between the first DC resistance cycle curve and the third DC resistance cycle curve. In historical experiments, the inventors conducted DC resistance tests on multiple batteries at the first preset state of charge and the third discharge rate and at the first preset state of charge and the first discharge rate, respectively, to obtain multiple sets of third DC resistance cycle curves and first DC resistance cycle curves. It was found that the linear transformation relationship between each set of third DC resistance cycle curves and the first DC resistance cycle curves all conformed to the corresponding first parameter factor and second parameter factor (the linear transformation relationship between the first DC resistance cycle curve and the second DC resistance cycle curve).

[0083] Thus, for the battery in step S21, a third DC resistance cycle curve can be determined based on the first DC resistance cycle curve and the first and second parameter factors when the battery is subjected to a cycle life test at the first preset state of charge and the third discharge rate. That is, the third DC resistance cycle curve can be obtained without having to test the third DC resistance corresponding to each number of cycles at the first preset state of charge and the third discharge rate. This allows the DC resistance of the battery to be accurately determined over its entire life at different discharge rates while reducing the number of DC resistance tests.

[0084] In the battery DC resistance testing process of this embodiment, based on the similar variation trend of the first DC resistance cycle curve and the second DC resistance cycle curve of the battery at the second preset state of charge and the second discharge rate, that is, the first DC resistance at the first preset state of charge and the first discharge rate is proportional to the second DC resistance at the second preset state of charge and the second discharge rate, a first parameter factor and a second parameter factor can be determined based on the first DC resistance corresponding to the i-th cycle, the first DC resistance corresponding to the j-th cycle, the second DC resistance corresponding to the i-th cycle, and the second DC resistance corresponding to the j-th cycle. The first parameter factor and the second parameter factor are applied to the relationship between the first DC resistance at the first preset state of charge and the first discharge rate and the third DC resistance at the first preset state of charge and the third discharge rate. Thus, based on the first DC resistance cycle curve and the first parameter factor and the second parameter factor, a third DC resistance cycle curve of the battery when the cycle life test is performed at the first preset state of charge and the third discharge rate can be determined. Therefore, there is no need to test the third DC resistance corresponding to each cycle number under the first preset state of charge and the third discharge rate, and the third DC resistance cycle curve can be obtained. The DC resistance of the battery throughout its life at different discharge rates can be accurately obtained while reducing the number of DC resistance tests.

[0085] According to some embodiments of the present application, optionally, see Figure 4 , step S21 specifically includes:

[0086] S211: For any target number of cycles in the cycle life test, obtain a first DC resistance corresponding to the target number of cycles based on the first voltage of the battery after full charge and rest, the second voltage of the battery after discharging at the first discharge rate for a first preset time, and the first current of discharging at the first discharge rate, wherein the battery is in a first preset state of charge.

[0087] In this embodiment, the battery is in a first preset state of charge. For example, if the first preset state of charge is 100% SOC, the state of charge of the battery is 100% SOC. It is understood that the state of charge of the battery can be adjusted by a charger or discharger.

[0088] Based on the fact that DC resistance test will be interspersed in the cycle life test, for any target number of cycles in the cycle life test, after the target number of cycles is fully charged, the battery is transferred and the DC resistance test is performed. It can be understood that the full charge here refers to the full charge during the cyclic charge and discharge process, for example, step c) in the aforementioned "(1) Cycle Life Test" achieves full charge, and step d) is a static step. Therefore, the first voltage can be a voltage after step d). In some embodiments, such as Figure 5 As shown, the first voltage may be the last voltage during the static process.

[0089] Then, the battery is transferred to a DC resistance test device for a DC resistance test, specifically, a pulse discharge is performed at a first discharge rate, and after a first preset time, a second voltage is obtained. Figure 5 As shown, the first discharge rate may be 1C, and the first preset time may be 30S, that is, after the battery is discharged at 1C for 30S, the voltage obtained at this moment is the second voltage.

[0090] During the discharge process, a first current of the battery discharged at a first discharge rate is obtained, so that a first DC resistance R1 corresponding to a target number of cycles can be obtained according to the first voltage U1, the second voltage U2 and the first current I1.

[0091] R1=(U1-U2) / I1

[0092] In the above-described embodiment of the present application, the first voltage after full charge and rest and the second voltage after discharge at the first discharge rate for the first preset time are obtained when the battery is not fully polarized. The first preset time may be an empirical value used by those skilled in the art, such as 10 seconds or 30 seconds. Thus, the first DC resistance is determined based on the first voltage, the second voltage, and the first current, ensuring that the first DC resistance is accurate.

[0093] According to some embodiments of the present application, optionally, see Figure 6 , step S22 specifically includes:

[0094] S221: For the i-th cycle, obtaining a second DC resistance corresponding to the i-th cycle based on a third voltage of the battery after being fully charged and allowed to rest, a fourth voltage after being discharged at a second discharge rate for a first preset time, and a second current during discharge at the second discharge rate, wherein the battery is in a second preset state of charge;

[0095] S222: For the j-th cycle, obtain a second DC resistance corresponding to the j-th cycle based on a fifth voltage of the battery after being fully charged and rested, a sixth voltage after being discharged at the second discharge rate for a first preset time, and a third current when discharged at the second discharge rate, wherein the battery is in a second preset state of charge.

[0096] In this embodiment, the battery is at a second predetermined state of charge. For example, if the second predetermined state of charge is 50% SOC, the battery's state of charge is 50%. It is understood that after the battery is removed from the cycle life test equipment, the state of charge can be adjusted to 50% SOC using a charger and discharger.

[0097] Since a DC resistance test is interspersed in the cycle life test, for the i-th cycle, after the i-th cycle is fully charged, the battery is transferred and the DC resistance test is performed. It can be understood that the full charge here refers to the full charge during the cyclic charge and discharge process. For example, step c) in the aforementioned "(1) Cycle Life Test" achieves full charge, and step d) is a static step. Therefore, the third voltage can be a voltage after step d). In some embodiments, the third voltage can be the last voltage during the static process.

[0098] The battery is then transferred to a DC resistance tester for a DC resistance test. Specifically, pulse discharge is performed at a second discharge rate for a first preset time, and then a fourth voltage is obtained. The second discharge rate may be 4C, and the first preset time may be 30 seconds. That is, after the battery is discharged at 4C for 30 seconds, the voltage obtained at this moment is the fourth voltage.

[0099] During the discharge process, the second current of the battery discharged at the second discharge rate in the i-th cycle is obtained. Therefore, the second DC resistance R2 corresponding to the i-th cycle can be obtained according to the third voltage U3, the fourth voltage U4 and the first current I2.

[0100] R2=(U3-U4) / I2

[0101] Similarly, for the jth cycle, after the jth cycle is fully charged, the battery is transferred and the DC resistance test is performed. It is understood that the full charge here refers to a full charge during the cyclic charge and discharge process. For example, step c) in the aforementioned "(1) Cycle Life Test" achieves full charge, and step d) is a static step. Therefore, the fifth voltage can be a voltage after step d). In some embodiments, the fifth voltage can be the last voltage during the static process.

[0102] The battery is then transferred to a DC resistance tester for a DC resistance test. Specifically, pulse discharge is performed at a second discharge rate for a first preset time, and then a sixth voltage is obtained. The second discharge rate may be 4C, and the first preset time may be 30 seconds. That is, after the battery is discharged at 4C for 30 seconds, the voltage obtained at this moment is the sixth voltage.

[0103] During the discharge process, the third current of the battery discharged at the second discharge rate in the jth cycle is obtained. Therefore, the third DC resistance R3 corresponding to the jth cycle can be obtained according to the fifth voltage U5, the sixth voltage U6 and the third current I3.

[0104] R3=(U5-U6) / I3

[0105] In the above-mentioned embodiment of the present application, the third voltage of the battery after being fully charged and standing still and the fourth voltage after being discharged at the second discharge rate for the first preset time are obtained when the battery has not reached complete polarization. The first preset time can be an empirical value of those skilled in the art, such as 10S or 30S. Thus, based on the third voltage, the fourth voltage and the second current, the second DC resistance corresponding to the i-th cycle number is determined, so that the second DC resistance corresponding to the i-th cycle number is accurate. Similarly, the fifth voltage of the battery after being fully charged and standing still and the sixth voltage after being discharged at the second discharge rate for the first preset time are obtained when the battery has not reached complete polarization. Thus, based on the fifth voltage, the sixth voltage and the third current, the second DC resistance corresponding to the j-th cycle number is determined, so that the second DC resistance corresponding to the j-th cycle number is accurate.

[0106] According to some embodiments of the present application, optionally, the i-th cycle number includes the cycle number corresponding to the initial life of the battery.

[0107] Those skilled in the art will understand that the initial life of a battery refers to the battery's initial life (BOL). For example, the number of cycles corresponding to the initial life may be cycle 1. It is understood that cycle 1 corresponds to the first use of the battery, i.e., the initial life.

[0108] In the above embodiment of the present application, the i-th cycle number is in the initial life stage of the battery. For example, the i-th cycle number may be cycle number 1. A DC resistance test is performed at the second preset state of charge and the second discharge rate at the cycle number corresponding to the initial life stage to obtain a second DC resistance corresponding to the i-th cycle number. This makes the second DC resistance corresponding to the i-th cycle number more representative, thereby facilitating the calculation of more accurate first parameter factors and second parameter factors.

[0109] According to some embodiments of the present application, optionally, the jth cycle number includes the cycle number corresponding to the end of the battery's life.

[0110] It will be understood by those skilled in the art that the end of life of a battery refers to the end of life (EOL) of the battery. For example, the number of cycles corresponding to the end of life may be the maximum number of cycles, such as 2000. For another example, the number of cycles corresponding to the end of life may be the number of cycles corresponding to when the battery is aged (for example, the state of charge decays to 80%). It will be understood that the 2000th cycle, or the number of cycles corresponding to when the battery is aged (for example, the state of charge decays to 80%), is equivalent to the battery being in a state close to being scrapped after being used many times, that is, at the end of its life.

[0111] In the above embodiment of the present application, the jth cycle number is at the end-of-life stage of the battery. For example, the jth cycle number can be the number of cycles corresponding to when the state of charge decays to 80%, or the jth cycle number is the 2000th cycle number (where 2000 is a preset value). A DC resistance test is performed at the second preset state of charge and the second discharge rate at the cycle number corresponding to the end-of-life stage to obtain the second DC resistance corresponding to the jth cycle number. This makes the second DC resistance corresponding to the jth cycle number more representative, thereby facilitating the calculation of more accurate first parameter factors and second parameter factors.

[0112] According to some embodiments of the present application, optionally, the aforementioned step S23 specifically includes:

[0113] The first and second parameter factors are calculated as follows:

[0114]

[0115] b=k×DCR (1,i) -DCR (2,i) ;

[0116] Among them, DCR (1,i) is the first DC resistance corresponding to the i-th cycle number, DCR (1,j) is the first DC resistance corresponding to the jth cycle number; DCR (2,i) is the second DC resistance corresponding to the i-th cycle number, DCR (2,j) is the second DC resistance corresponding to the j-th cycle number, k is the first parameter factor, and b is the second parameter factor.

[0117] When the first DC resistance cycle curve and the second DC resistance cycle curve show a similar change trend (linear transformation relationship), the first DC resistance corresponding to the i-th cycle is linearly changed using the first parameter factor and the second parameter factor to obtain the second DC resistance corresponding to the i-th cycle, and the first DC resistance corresponding to the j-th cycle is linearly changed using the first parameter factor and the second parameter factor to obtain the second DC resistance corresponding to the j-th cycle. Therefore, in order to determine the first parameter factor k and the second parameter factor b that represent the linear mapping relationship, first, find the first DC resistance DCR corresponding to the i-th cycle in the first DC resistance cycle curve. (1,i) The first DC resistance DCR corresponding to the jth cycle number (1,j) , thus, according to the principle of finding the slope and intercept of a linear function at two points, the above formula is derived to calculate the first parameter factor and the second parameter factor. In some embodiments, as Figure 7 As shown, you can also Figure 3 A linear regression equation is established between the first DC resistance cycle curve and the second DC resistance cycle curve, and the equation is: Figure 7 The correlation linear function shown in the figure shows that the correlation between the two is 0.9962, indicating that the first DC resistance cycle curve and the second DC resistance cycle curve have the same changing trend. Figure 7 The slope of the linear function is the first parameter factor, and the intercept is the second parameter factor. The inventors of this application found in historical experimental data that the first parameter factor range is [0.5, 1.5], and the second parameter factor range is [-0.8, 0.8]. Among them, the historical experimental data here include the first DC resistance cycle curve and the second DC resistance cycle curve of various types of batteries. Statistics of various types of batteries show that multiple groups of first DC resistance cycle curves and second DC resistance cycle curves are correlated. The multiple first parameter factors and multiple second parameter factors obtained by the correlation linear function are statistically obtained. The first parameter factor range is [0.5, 1.5], and the second parameter factor range is [-0.8, 0.8].

[0118] In the above embodiment of the present application, based on the similar change trend of the first DC resistance cycle curve and the second DC resistance cycle curve, that is, the first DC resistance at the first preset state of charge and the first discharge rate and the second DC resistance at the second preset state of charge and the second discharge rate have a certain linear mapping relationship. Therefore, in order to determine the first parameter factor k and the second parameter factor b that characterize the linear mapping relationship, the first DC resistance DCR corresponding to the i-th cycle number is found in the first DC resistance cycle curve. (1,i) The first DC resistance DCR corresponding to the jth cycle number (1,j), thus, according to the first DC resistance DCR corresponding to the number of cycles i (1,i) , the first DC resistance DCR corresponding to the jth cycle number (1,j) , the second DC resistance DCR corresponding to the i-th cycle number (2,i) The second DC resistance DCR corresponding to the jth cycle number (2,j) , the first parameter factor k and the second parameter factor b can be calculated.

[0119] According to some embodiments of the present application, optionally, the aforementioned step S24 specifically includes:

[0120] The third DC resistance cycle curve of the battery is calculated using the following formula when the battery is subjected to a cycle life test at the first preset state of charge and the third discharge rate:

[0121] DCR (3,x) =k×DCR (1.x) +b

[0122] Among them, DCR (3,x) The third DC resistance cycle curve, DCR (1,x) is the first DC resistance cycle curve, and x is the cycle number.

[0123] It is understandable that, in historical experiments, the inventors conducted DC resistance tests on multiple batteries at the first preset state of charge and the third discharge rate, and at the first preset state of charge and the first discharge rate, respectively, to obtain multiple sets of third DC resistance cycle curves and first DC resistance cycle curves. It was found that the linear transformation relationship between each set of third DC resistance cycle curves and the first DC resistance cycle curves all met the corresponding first parameter factor and second parameter factor (the linear transformation relationship between the first DC resistance cycle curve and the second DC resistance cycle curve). Therefore, the linear transformation between the first DC resistance cycle curve and the second DC resistance cycle curve was applied to the first DC resistance cycle curve and the third DC resistance cycle curve, thereby obtaining the above formula. Thus, based on the known first DC resistance cycle curve, according to the above formula, the third DC resistance cycle curve can be obtained without testing each third DC resistance in the third DC resistance cycle curve.

[0124] In the above embodiment of the present application, the linear mapping relationship between the first DC resistance cycle curve and the second DC resistance cycle curve is applied between the first DC resistance cycle curve and the third DC resistance cycle curve to obtain the above formula. Thus, the third DC resistance cycle curve is obtained, that is, the third DC resistance at the first preset state of charge and the third discharge rate does not need to be tested, only the first DC resistance cycle curve needs to be tested, and the third DC resistance cycle curve can be obtained by the above formula, thereby accurately obtaining the DC resistance of the battery at different discharge rates while reducing the number of DC resistance tests. In addition, for a battery including multiple cells, there will be connection resistance (physical impedance) between the cells, and the connection resistance is not affected by the discharge rate and state of charge. Thus, the mapping relationship between the first DC resistance cycle curve and the third DC resistance cycle curve is a linear mapping relationship, so that the connection resistance is not affected by the linear mapping relationship, that is, the linear mapping relationship is applied between the first DC resistance cycle curve and the third DC resistance cycle curve, so that the above formula can accurately predict the third DC resistance at the first preset state of charge and the third discharge rate.

[0125] According to some embodiments of the present application, optionally, the first discharge rate includes a lower limit of a discharge rate range when the battery is operating, and / or the third discharge rate includes an upper limit of a discharge rate range when the battery is operating.

[0126] Depending on the battery's usage scenario, the battery's output power has a range. For example, when the battery is used to power an electric vehicle, if the electric vehicle needs instantaneous acceleration, the battery needs to output a higher power, that is, the battery needs to discharge at a higher discharge rate. If the electric vehicle does not need instantaneous acceleration, the battery needs to output a lower power, that is, the battery needs to discharge at a lower discharge rate. Depending on the battery's usage scenario, the battery has a discharge rate range when operating. For example, if battery 1# powers a small, slow-moving electric vehicle, the discharge rate range of battery 1# is [1C, 4C]. If battery 2# powers a large, fast-moving electric vehicle, the discharge rate range of battery 2# is [2C, 8C].

[0127] The first discharge rate includes the lower limit of the discharge rate range during battery operation. For example, the first discharge rate of battery 1# may be 1C, and the first discharge rate of battery 2# may be 2C. The third discharge rate includes the upper limit of the discharge rate range during battery operation. For example, the third discharge rate of battery 1# may be 4C, and the third discharge rate of battery 2# may be 8C.

[0128] In the above-mentioned embodiment of the present application, based on the different usage scenarios of the battery, the output power of the battery has a range. When the output power is large, the discharge rate of the battery is also large. When the output power is small, the discharge rate of the battery is also small. That is, in different usage scenarios, the discharge rate of the battery when working also has a range, such as the discharge rate range [1C, 4C]. The first discharge rate includes the lower limit of the discharge rate range when the battery is working, that is, the first DC resistance cycle curve of the battery when working at the lower limit of the discharge rate range is measured, and the third DC resistance cycle curve is predicted through the first DC resistance cycle curve. Optionally, the third discharge rate includes the upper limit of the discharge rate range when the battery is working, that is, the first DC resistance cycle curve corresponding to the lower limit of the discharge rate range can be used to predict the third DC resistance cycle curve corresponding to the upper limit of the discharge rate. There is no need to test the DC resistance corresponding to the upper limit of the discharge rate, which can reduce the number of tests and avoid battery loss due to high-rate discharge.

[0129] According to some embodiments of the present application, the present application provides a method for testing the DC resistance of a battery, comprising:

[0130] (1) Obtaining a first DC resistance cycle curve of the battery when the battery is subjected to a DC resistance test at a first preset state of charge and a first discharge rate, wherein the cycle number is the number of cycles in the cycle life test. Specifically, for any target cycle number in the cycle life test, the first DC resistance DCR corresponding to the target cycle number is obtained based on the first voltage U1 of the battery after full charge and rest, the second voltage U2 after discharging at the first discharge rate (e.g., 1C) for a first preset time (e.g., 10S), and the first current I1 when discharging at the first discharge rate. (1,x) , wherein the battery is in a first preset state of charge (eg, 100% SOC).

[0131] (2) For the i-th cycle, the second DC resistance DCR corresponding to the i-th cycle is obtained based on the third voltage U3 of the battery after full charge and rest, the fourth voltage U4 after discharging at the second discharge rate (4C) for the first preset time, and the second current I2 discharged at the second discharge rate. (2,i) , wherein the battery is in a second preset state of charge (50% SOC); for the jth cycle, the second DC resistance DCR corresponding to the jth cycle is obtained based on the fifth voltage U5 of the battery after full charge and rest, the sixth voltage U6 after discharging at the second discharge rate (4C) for the first preset time (10S), and the third current I3 when discharging at the second discharge rate (4C). (2,j)The inventors found in historical experimental data of multiple batteries that the first DC resistance cycle curve and the second DC resistance cycle curve of the battery at the second preset state of charge and the second discharge rate showed similar changing trends.

[0132] (3) The first DC resistance DCR corresponding to the number of cycles i (1,i) , the first DC resistance DCR corresponding to the jth cycle number (1,j) , the second DC resistance DCR corresponding to the i-th cycle number (2,i) The second DC resistance DCR corresponding to the jth cycle number (2,j) , determine the first parameter factor k and the second parameter factor b. Specifically, the first parameter factor and the second parameter factor are calculated according to the following formula:

[0133]

[0134] b=k×DCR (1,i) -DCR (2,i) ;

[0135] The i-th cycle number in (2) and (3) above includes the cycle number corresponding to the initial life of the battery, such as the first cycle number, and the j-th cycle number includes the cycle number corresponding to the end of the battery life, such as the cycle number when the state of charge of the battery decays to 80%. The first discharge rate includes the lower limit of the discharge rate range when the battery is in operation, and the third discharge rate includes the upper limit of the discharge rate range when the battery is in operation.

[0136] (4) Calculate the third DC resistance cycle curve of the battery when the battery is subjected to a cycle life test at the first preset state of charge and the third discharge rate according to the following formula:

[0137] DCR (3,x) =k×DCR (1.x) +b

[0138] Among them, DCR (3,x) The third DC resistance cycle curve, DCR (1,x) is the first DC resistance cycle curve, where x is the cycle number.

[0139] In historical experiments, the inventors conducted DC resistance tests on multiple batteries at a first preset state of charge and a third discharge rate, and at a first preset state of charge and a first discharge rate, respectively. Multiple sets of third DC resistance cycle curves and first DC resistance cycle curves were obtained. It was found that the linear transformation relationship between each set of third DC resistance cycle curves and first DC resistance cycle curves conformed to the corresponding first parameter factor and second parameter factor (the linear transformation relationship between the first DC resistance cycle curve and the second DC resistance cycle curve). Therefore, it was concluded that the first parameter factor and the second parameter factor are applicable to the linear change between the first DC resistance cycle curve and the third DC resistance cycle curve.

[0140] The inventors of this application have verified the formula in (4) above. Specifically, the third DC resistance (measured value) corresponding to the 200th and 400th cycles of a test battery at the first preset state of charge and the first discharge rate was compared with the third DC resistance (fitted value) corresponding to the 200th and 400th cycles calculated using the formula in (4). As shown in Table 1 below, the fitted values ​​obtained by fitting the formula in (4) above have a small error compared to the measured values, with the error being less than 2.5%.

[0141] Table 1 Verification results

[0142] DCR / mΩ Initial laps 200 laps 400 laps 596 laps Fitted values 2.79 3.33 3.85 4.25 Measured value 2.79 3.42 3.91 4.25 error / 2.5％ 1.6％ /

[0143] In this embodiment, based on the similar variation trend between the first DC resistance cycle curve and the second DC resistance cycle curve of the battery at the second preset state of charge and the second discharge rate, that is, the first DC resistance at the first preset state of charge and the first discharge rate is proportional to the second DC resistance at the second preset state of charge and the second discharge rate, a first parameter factor and a second parameter factor can be determined based on the first DC resistance corresponding to the i-th cycle, the first DC resistance corresponding to the j-th cycle, the second DC resistance corresponding to the i-th cycle, and the second DC resistance corresponding to the j-th cycle. The first parameter factor and the second parameter factor are applied to the relationship between the first DC resistance at the first preset state of charge and the first discharge rate and the third DC resistance at the first preset state of charge and the third discharge rate. Thus, based on the first DC resistance cycle curve and the first parameter factor and the second parameter factor, a third DC resistance cycle curve of the battery when the cycle life test is performed at the first preset state of charge and the third discharge rate can be determined. Therefore, there is no need to test the third DC resistance corresponding to each cycle number under the first preset state of charge and the third discharge rate, and the third DC resistance cycle curve can be obtained. The DC resistance of the battery throughout its life at different discharge rates can be accurately obtained while reducing the number of DC resistance tests.

[0144] According to some embodiments of this application, please refer to Figure 8 The present application also provides an electronic device 400, comprising: a processor 410, and a memory 420 communicatively connected to the processor 410, wherein the memory 420 stores instructions that can be executed by the processor 410, and the instructions are executed by the processor 410 to enable the processor 410 to perform the aforementioned battery DC resistance testing method.

[0145] Memory 420 may include read-only memory and random access memory, and provides instructions and data to the processor. A portion of memory 420 may also include non-volatile random access memory (NVRAM). Memory 420 stores operating instructions, executable modules, or data structures, or a subset or extended set thereof.

[0146] Processor 410 can be an integrated circuit chip with signal processing capabilities. During implementation, each step of the aforementioned training method can be completed by hardware integrated logic circuits or software instructions in processor 410. The aforementioned processor 410 can be a general-purpose processor, a digital signal processor (DSP), a microprocessor, or a microcontroller, and can further include an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic device, discrete gate or transistor logic device, or discrete hardware components. The processor can implement or execute the aforementioned battery DC resistance testing method.

[0147] According to some embodiments of the present application, the present application also provides a readable storage medium, which stores a program or instruction. When the program or instruction is executed by a processor, the various processes of the above-mentioned battery DC resistance testing method embodiment are implemented, and the same technical effect can be achieved. To avoid repetition, it will not be repeated here.

[0148] The readable storage medium includes a computer-readable storage medium, such as a computer read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0149] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Based on the concept of the present application, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present application as described above. For the sake of simplicity, they are not provided in detail. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for testing the DC resistance of a battery, characterized in that: include: Obtaining a first DC resistance cycle curve of the battery when a DC resistance test is performed at a first preset state of charge and a first discharge rate, where the cycle number is the number of cycles in a cycle life test; Obtaining a second DC resistance corresponding to an i-th cycle and a second DC resistance corresponding to a j-th cycle of the battery when a DC resistance test is performed at a second preset state of charge and a second discharge rate, wherein the first DC resistance cycle curve and the second DC resistance cycle curve of the battery at the second preset state of charge and the second discharge rate show a similar change trend, i<j; Determining a first parameter factor and a second parameter factor according to a first DC resistance corresponding to an i-th number of cycles, a first DC resistance corresponding to a j-th number of cycles, a second DC resistance corresponding to the i-th number of cycles, and a second DC resistance corresponding to the j-th number of cycles; A third DC resistance cycle curve of the battery under the first preset state of charge and a third discharge rate is determined according to the first DC resistance cycle curve, the first parameter factor, and the second parameter factor.

2. The testing method according to claim 1, wherein: The step of obtaining a first DC resistance cycle curve when the battery is subjected to a DC resistance test at a first preset state of charge and a first discharge rate includes: For any target number of cycles in the cycle life test, a first DC resistance corresponding to the target number of cycles is obtained based on a first voltage of the battery after full charge and rest, a second voltage of the battery after discharging at the first discharge rate for a first preset time, and a first current when discharging at the first discharge rate, wherein the battery is in the first preset state of charge.

3. The testing method according to claim 1, wherein: The obtaining of a second DC resistance corresponding to an i-th cycle and a second DC resistance corresponding to a j-th cycle of the battery when a DC resistance test is performed at a second preset state of charge and a second discharge rate includes: For the i-th cycle, obtaining a second DC resistance corresponding to the i-th cycle according to a third voltage of the battery after being fully charged and allowed to stand, a fourth voltage after being discharged at the second discharge rate for a first preset time, and a second current during discharge at the second discharge rate, wherein the battery is in the second preset state of charge; For the j-th cycle, a second DC resistance corresponding to the j-th cycle is obtained based on a fifth voltage of the battery after being fully charged and standing, a sixth voltage after being discharged at the second discharge rate for a first preset time, and a third current when discharged at the second discharge rate, wherein the battery is in the second preset state of charge.

4. The testing method according to any one of claims 1 to 3, characterized in that: The i-th cycle number includes the cycle number corresponding to the initial life of the battery.

5. The testing method according to claim 4, characterized in that: The jth number of cycles includes the number of cycles corresponding to the end of the battery life.

6. The testing method according to claim 1, wherein: The determining of the first parameter factor and the second parameter factor according to the first DC resistance corresponding to the i-th number of cycles, the first DC resistance corresponding to the j-th number of cycles, the second DC resistance corresponding to the i-th number of cycles, and the second DC resistance corresponding to the j-th number of cycles includes: The first parameter factor and the second parameter factor are calculated according to the following formula: ； b=k×DCR (1，i) -DCR (2，i) ; Among them, DCR (1，i) is the first DC resistance corresponding to the i-th cycle number, DCR (1，j) is the first DC resistance corresponding to the j-th cycle number; DCR (2，i) is the second DC resistance corresponding to the i-th cycle number, DCR (2，j) is the second DC resistance corresponding to the j-th cycle number, k is the first parameter factor, and b is the second parameter factor.

7. The testing method according to claim 6, characterized in that: The determining, based on the first DC resistance cycle curve and the first parameter factor and the second parameter factor, a third DC resistance cycle curve when the battery is subjected to a cycle life test at the first preset state of charge and a third discharge rate includes: The third DC resistance cycle curve of the battery is calculated according to the following formula when the battery is subjected to a cycle life test at the first preset state of charge and the third discharge rate: DCR (3，x) =k×DCR (1，x) +b Among them, DCR (3，x) The third DC resistance cycle curve, DCR (1，x) is the first DC resistance cycle curve, where x is the cycle number.

8. The testing method according to any one of claims 1-3 and 5-7, characterized in that: The first discharge rate includes a lower limit of a discharge rate range when the battery is in operation, and / or the third discharge rate includes an upper limit of a discharge rate range when the battery is in operation.

9. An electronic device, characterized in that: include: processor, and a memory communicatively connected to the processor, wherein: The memory stores instructions that can be executed by the processor, and the instructions are executed by the processor to enable the processor to perform the method according to any one of claims 1 to 8.

10. A readable storage medium, characterized in that: The readable storage medium stores a program or instruction, and when the program or instruction is executed by a processor, the method according to any one of claims 1 to 8 is implemented.

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