Method, device and equipment for testing direct-current resistance of battery

Abstract

The embodiment of the invention provides a direct current resistance test method and device of a battery and test equipment. The method comprises the following steps: pretreating a battery monomer subjected to formation treatment so as to enable the battery monomer to be in a stable state; before the capacity test is carried out on the single battery, the direct current resistance test is carried out on the preprocessed single battery. According to the method, the device and the test equipment provided by the embodiment of the invention, the accurate direct-current resistance value can be obtained, and meanwhile, the mass production takt is not influenced.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of batteries, and in particular, to a method, device, and testing equipment for measuring the direct current resistance of a battery. Background Art

[0002] The conventional measurement of the direct current resistance (DCR) of a battery cell is carried out after the formation process, that is, after the capacity test. At this time, the battery cell needs to be left standing for a long time until it reaches a stable state before the DCR test is carried out. This test method is time-consuming and affects the production rhythm. Summary of the Invention

[0003] The embodiments of the present application provide a method, device, and testing equipment for measuring the direct current resistance of a battery, which can obtain an accurate direct current resistance value without affecting the mass production rhythm.

[0004] In a first aspect, a method for measuring the direct current resistance of a battery is provided. The method includes: preprocessing a battery cell that has undergone formation treatment to make the battery cell in a stable state; measuring the direct current resistance of the preprocessed battery cell before performing a capacity test on the battery cell.

[0005] By measuring the direct current resistance of the battery cell before performing the capacity test on the battery cell, compared with the solution of measuring the direct current resistance of the battery cell after the capacity test, the direct current resistance test value can be obtained without affecting the production rhythm, and the production capacity is improved. In addition, since the direct current resistance of the battery cell is measured when it is in a stable state after formation, the obtained direct current resistance data is accurate.

[0006] In a possible implementation, preprocessing a battery cell that has undergone formation treatment to make the battery cell in a stable state includes: measuring the self-discharge rate K value and / or aging test of the battery cell that has undergone formation treatment to make the voltage of the battery cell stable; measuring the direct current resistance of the battery cell in a stable state before performing a capacity test on the battery cell includes: measuring the direct current resistance of the battery cell after the self-discharge rate K value measurement and / or aging test before performing a capacity test on the battery cell.

[0007] Since the battery cell usually undergoes sufficient rest after the self-discharge rate K value and / or aging test of the battery cell, so that it has a stable voltage, which provides a stable initial voltage for the DC resistance test. Therefore, performing the DC resistance test after the self-discharge rate K value and / or aging test of the battery cell can obtain relatively accurate DC resistance data. In addition, since the DC resistance test is performed before the capacity test, the capacity test equipment can be directly used without additional equipment investment, which can save equipment costs and does not affect the mass production rhythm.

[0008] In a possible implementation manner, the method further includes: forming the battery cell to a first state of charge value; the performing the DC resistance test on the battery cell after the pre-treatment before the capacity test of the battery cell includes: performing the DC resistance test on the battery cell after the pre-treatment at the first state of charge value before the capacity test of the battery cell.

[0009] Performing the DC resistance test on the battery cell directly at the first state of charge value after formation before the capacity test can simplify the process of the DC resistance test.

[0010] In a possible implementation manner, the method further includes: converting a first DC resistance value obtained by performing the DC resistance test at the first state of charge value to a second DC resistance value at a second state of charge value, where the second state of charge value is in the state of charge interval at the end of charging, or the second state of charge value is in the state of charge interval at the end of discharging.

[0011] Since the uneven current distribution between battery cells usually occurs at the end of charging or at the end of discharging, therefore, by converting the first DC resistance value at the first state of charge value to the second DC resistance value at the second state of charge value at the end of charging or at the end of discharging, the influence of the DC resistance difference on the uneven current distribution between multiple battery cells can be reduced as much as possible. In addition, compared with the solution of directly adjusting the state of charge of the battery cell to the second state of charge value and then performing the DC resistance test, the test duration can be reduced and the mass production rhythm can be accelerated.

[0012] In a possible implementation manner, the performing the DC resistance test on the battery cell after the pre-treatment before the capacity test of the battery cell includes: adjusting the state of charge of the battery cell after the pre-treatment to the second state of charge value before the capacity test of the battery cell; performing the DC resistance test on the battery cell at the second state of charge value, where the second state of charge value is in the state of charge interval at the end of charging, or the second state of charge value is in the state of charge interval at the end of discharging.

[0013] By directly performing a DC resistance test on the battery cell at the second state of charge value at the charging end or the discharging end, the accuracy of obtaining the second DC resistance value can be improved.

[0014] In a possible implementation, performing a DC resistance test on the battery cell at the second state of charge value includes: performing a DC resistance test on the battery cell at the second state of charge value when the battery cell is left stationary for a preset time.

[0015] After the state of charge of the battery cell is adjusted to the second state of charge value at the charging end or the discharging end, the battery cell is allowed to stand for a long time before undergoing a DC resistance test. This allows the voltage of the battery cell to stabilize before the test, thereby further improving the accuracy of the second DC internal resistance value.

[0016] In a possible implementation, the method further includes: obtaining a third DC resistance value of the battery cell based on a DC resistance test performed on the battery cell; and grading the battery cell according to the third DC resistance value.

[0017] Grading battery cells according to their DC resistance values is beneficial for subsequently assembling multiple battery cells belonging to the same gear into an electrical box. This method has simple control steps, is easy to operate, and can also improve the consistency of DC resistance between battery cells.

[0018] In one possible implementation, obtaining a third DC resistance value of the battery cell based on a DC resistance test on the battery cell includes: obtaining a fourth DC resistance value of the battery cell by performing a DC resistance test on the battery cell; and performing temperature correction on the fourth DC resistance value to obtain a third DC resistance value.

[0019] In this embodiment, the fourth DC resistance value of the battery cell obtained through testing is temperature-corrected to obtain the third DC resistance value of the battery cell. The third DC resistance value of the battery cell can then be used as a basis for grading, thereby improving the consistency of the DC resistance between the battery cells.

[0020] In a second aspect, a DC resistance testing device for a battery is provided, which includes: a pretreatment unit for pretreatment of battery cells that have undergone formation treatment so that the battery cells are in a stable state; and a DC resistance testing unit for performing a DC resistance test on the pretreated battery cells before performing a capacity test on the battery cells.

[0021] In a possible implementation, the preprocessing unit is specifically configured to: perform a self-discharge rate K value test and / or an aging test on the battery cell that has undergone formation processing to stabilize the voltage of the battery cell; the DC resistance test unit is specifically configured to: before performing a capacity test on the battery cell, perform a DC resistance test on the battery cell after the self-discharge rate K value test and / or the aging test.

[0022] In a possible implementation, the device further includes: a formation unit for forming the battery cell to a first state of charge value; the DC resistance test unit is configured to: before performing a capacity test on the battery cell, at the first state of charge value, perform a DC resistance test on the battery cell after preprocessing.

[0023] In a possible implementation, the device further includes: a conversion unit for converting a first DC resistance value obtained by performing a DC resistance test at the first state of charge value to a second DC resistance value at a second state of charge value; wherein, the second state of charge value is in the state of charge interval at the end of charging, or the second state of charge value is in the state of charge interval at the end of discharging.

[0024] In a possible implementation, the DC resistance test unit is specifically configured to: before performing a capacity test on the battery cell, adjust the state of charge of the battery cell after preprocessing to the second state of charge value; at the second state of charge value, perform a DC resistance test on the battery cell; wherein, the second state of charge value is in the state of charge interval at the end of charging, or the second state of charge is in the state of charge interval at the end of discharging.

[0025] In a possible implementation, the DC resistance test unit is specifically configured to: when the battery cell is static for a preset duration, perform a DC resistance test on the battery cell at the second state of charge value.

[0026] In a possible implementation, the device further includes: an acquisition unit for obtaining a third DC resistance value of the battery cell based on the DC resistance test performed on the battery cell; a grading unit for grading the battery cell according to the third DC resistance value.

[0027] In a possible implementation, the acquisition unit is specifically configured to: obtain a fourth DC resistance value of the battery cell by performing a DC resistance test on the battery cell; perform temperature correction on the fourth DC resistance value to obtain the third DC resistance value.

[0028] In a third aspect, a test device for testing the DC resistance of a battery is provided, including a memory and a processor, the memory is used for storing instructions, and the processor is used for reading the instructions and executing the method in the first aspect and any one of the possible implementation manners of the first aspect according to the instructions.

[0029] In a fourth aspect, a chip is provided, including a processor configured to call and run a computer program from a memory, such that a device installed with the chip executes the method in the first aspect and any possible implementation manner of the first aspect.

[0030] In a fifth aspect, a computer program is provided, which causes a computer to execute the method in the first aspect and any possible implementation manner of the first aspect.

[0031] In a sixth aspect, a computer-readable storage medium is provided for storing a computer program, which causes a computer to execute the method in the first aspect and any possible implementation manner of the first aspect.

[0032] In a seventh aspect, a computer program product is provided, including computer program instructions, which cause a computer to execute the method in the first aspect and any possible implementation manner of the first aspect. Description of the Drawings

[0033] To more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on the drawings without creative efforts.

[0034] Figure 1 A schematic diagram showing an application scenario of the method for testing the DC resistance of a battery provided by an embodiment of the present application is shown.

[0035] Figure 2 A schematic block diagram showing the first method for testing the DC resistance of a battery according to an embodiment of the present application is shown.

[0036] Figure 3 A schematic block diagram showing the second method for testing the DC resistance of a battery according to an embodiment of the present application is shown.

[0037] Figure 4 A schematic block diagram showing the third method for testing the DC resistance of a battery according to an embodiment of the present application is shown.

[0038] Figure 5 A schematic block diagram showing the fourth method for testing the DC resistance of a battery according to an embodiment of the present application is shown.

[0039] Figure 6 A schematic block diagram showing the fifth method for testing the DC resistance of a battery according to an embodiment of the present application is shown.

[0040] Figure 7Schematic block diagram showing the sixth method for testing the DC resistance of a battery according to an embodiment of the present application.

[0041] Figure 8 Schematic block diagram showing the seventh method for testing the DC resistance of a battery according to an embodiment of the present application.

[0042] Figure 9 Schematic block diagram showing the eighth method for testing the DC resistance of a battery according to an embodiment of the present application.

[0043] Figure 10 Schematic flowchart showing the method for testing the DC resistance of a battery according to an embodiment of the present application.

[0044] Figure 11 Schematic block diagram showing the device for testing the DC resistance of a battery according to an embodiment of the present application.

[0045] Figure 12 Another schematic block diagram showing the device for testing the DC resistance of a battery according to an embodiment of the present application.

[0046] Figure 13 Schematic block diagram showing the test equipment for testing the DC resistance of a battery according to an embodiment of the present application. Detailed implementation manners

[0047] The following further describes in detail the implementation manners of the present application in conjunction with the accompanying drawings and embodiments. The detailed description and the accompanying drawings of the following embodiments are used to exemplarily illustrate the principle of the present application, but cannot be used to limit the scope of the present application, that is, the present application is not limited to the described embodiments.

[0048] In the description of the present application, it should be noted that unless otherwise specified, the meaning of "a plurality of" is two or more; the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "inner", "outer", etc. is 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 to the present application. In addition, terms such as "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. "Vertical" is not strictly vertical, but within the allowable error range. "Parallel" is not strictly parallel, but within the allowable error range.

[0049] The orientation terms used in the following description are all the directions shown in the figures, and do not limit the specific structure of the present application. In the description of the present application, it should also be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0050] The term "and / or" in the present application is merely a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent three situations: A exists, both A and B exist, and B exists. In addition, the character " / " in the present application generally represents an "or" relationship between the associated objects before and after.

[0051] Unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as those commonly understood by those skilled in the technical field to which the present application belongs; the terms used in the description of the present application in the specification are only for the purpose of describing specific embodiments, and are not intended to limit the present application; the terms "including" and "having" and any variations thereof in the description, claims and drawings of the present application are intended to cover non-exclusive inclusion. The terms "first", "second", etc. in the description, claims or drawings of the present application are used to distinguish different objects, rather than to describe a specific order or primary-secondary relationship.

[0052] Referring to "embodiment" in the present application means that the specific features, structures or characteristics described in combination with the embodiment can be included in at least one embodiment of the present application. The appearance of this phrase at various positions in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described in the present application can be combined with other embodiments.

[0053] A battery refers to a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery is a battery cell. For another example, the battery is an electrical box formed by connecting multiple battery cells in series, parallel or in a hybrid connection. For another example, the battery is an electrical cabinet, which can also be called a battery cluster, formed by connecting multiple electrical boxes in series. For another example, the battery can also be a container formed by connecting multiple battery clusters or electrical cabinets in parallel.

[0054] Optionally, the battery in the embodiments of the present application can be a lithium-ion battery, a lithium metal battery, a lead-acid battery, a nickel-cadmium battery, a nickel-metal hydride battery, a lithium-sulfur battery, a lithium-air battery or a sodium-ion battery, etc. The embodiments of the present application do not make specific limitations on this.

[0055] The direct current resistance (DCR) test of a conventional battery cell is carried out after the grading process. That is, after the capacity test, the battery cell needs to be left standing for a long time until it reaches a stable state before the DCR test is carried out. This test process is time-consuming and affects the production rhythm.

[0056] In view of this, the embodiments of the present application provide a DCR test method for a battery. By performing a DCR test on a battery cell that has reached a stable state after formation treatment before performing a capacity test on the battery cell, it is possible to make use of the capacity test equipment without additional equipment investment. At the same time, the measured DCR data is accurate, and it does not waste the mass production rhythm, improving the production capacity.

[0057] Figure 1 The figure shows a schematic diagram of an application scenario of the DCR test method for the battery provided by the embodiments of the present application. For example, the DCR values of battery cells obtained through DCR tests can be assembled step by step into a container. As Figure 1 shown, the battery cell is the smallest unit. An electrical box is assembled from L battery cells in series and / or parallel, where L is a positive integer greater than 1. An electrical cabinet is assembled from P electrical boxes in series and / or parallel, where P is a positive integer greater than 1. A container is assembled from Q electrical cabinets in parallel, where Q is a positive integer greater than 1.

[0058] It should be understood that the battery product assembled from battery cells in the embodiments of the present application can ultimately be an electrical box, an electrical cabinet, or a container.

[0059] It should also be understood that the technical solutions in the embodiments of the present application can be applied not only to energy storage batteries but also to power batteries.

[0060] Figure 2 The figure shows a schematic block diagram of the DCR test method 100 for the battery provided by the embodiments of the present application. Optionally, this method 100 can be executed by a test device in the battery automated production and assembly process. For example, this method 100 can be executed by a Manufacturing Execution System (MES). This method 100 may include some or all of the following content.

[0061] S110, perform pre-treatment on the battery cell that has undergone formation treatment to make the battery cell reach a stable state.

[0062] S120, perform a direct current resistance test on the pre-treated battery cell before performing a capacity test on the battery cell.

[0063] The direct current resistance (DCR) refers to the resistance that the current encounters when flowing through the inside of the battery during operation, including the ohmic internal resistance and the polarization internal resistance. The ohmic internal resistance is mainly determined by the total conductivity of the battery, while the polarization internal resistance is mainly determined by the solid-phase diffusion coefficient of lithium ions in the electrode active material. During the test, ensure that the battery is fully stationary and the voltage is at a stable value. Connect the battery to the test instrument, then inject a small current into the battery through the test instrument to charge or discharge the battery for a short time. Calculate the DCR of the battery based on the measured voltage drop and the applied current.

[0064] Generally, after the production of a single battery cell, formation treatment will be carried out first to form a passivation film, that is, a solid electrolyte interphase (SEI) film, at the solid-phase interface between the electrode material and the electrolyte. This SEI film avoids the damage to the electrode material, thereby improving the cycle performance and lifespan. Specifically, the formation treatment of the battery can include several or all of the following steps: 1. Pre-charge: First, perform a small-current pre-charge on the single battery cell to activate the electrolyte and the positive and negative active materials inside the single battery cell; 2. Fast charge: After the pre-charge, perform a large-current fast charge to rapidly increase the power inside the single battery cell to reach the expected capacity. During the first charging process, the positive and negative active materials will chemically react with the electrolyte to form an SEI film and gradually stabilize the chemical reaction inside the single battery cell.

[0065] Generally, after some pre-treatments on the single battery cell, a capacity test will be carried out first, and then the DCR test will be carried out. Specifically, after the capacity test, let the single battery cell stand fully until it reaches a stable state, then perform a short-time charge or discharge, and then let the single battery cell stand fully again. Calculate the DCR based on the voltage drop measured after the two standstills and the current applied to the single battery cell, and then complete the DCR test.

[0066] And after the formation of the single battery cell and before the capacity test, a series of pre-treatments are usually carried out on the single battery cell. For example, an aging test or a self-discharge rate K value test is carried out on the single battery cell, etc. Since the single battery cell can usually be in a stable state after a series of pre-treatments, there are conditions for performing the DCR test on the single battery cell from after the pre-treatment until before the capacity test.

[0067] Therefore, in the embodiment of the present application, by performing a direct current resistance test on the single battery cell before the capacity test, compared with the scheme of performing a direct current resistance test on the single battery cell after the capacity test, the direct current resistance test value can be obtained without wasting the production rhythm, improving the production capacity. In addition, since the direct current resistance test is carried out on the single battery cell in a stable state after its formation, the obtained direct current resistance data is accurate.

[0068] Optionally, as Figure 3 shown, S110, that is, preprocessing the battery cells after formation treatment to make the battery cells in a stable state, includes: S111, testing the self-discharge rate K value and / or aging test of the battery cells after formation treatment to make the voltage of the battery cells stable; S120, that is, before performing the capacity test on the battery cells, performing a DC resistance test on the battery cells after preprocessing, includes: S121, before performing the capacity test on the battery cells, performing a DC resistance test on the battery cells after the self-discharge rate K value test and / or aging test.

[0069] The self-discharge rate K value can be understood as the voltage drop per unit time, usually expressed in mv / h, which is an index used to measure the self-discharge rate of the battery. Its magnitude is related to whether there are abnormal particles inside the battery cell causing micro-short circuit self-discharge, and it can be used to evaluate the performance and stability of the battery cell. By testing the self-discharge rate K value, the self-discharge rate of the battery cell can be within the set standard range, thereby ensuring that the battery cell can work normally and reliably. Optionally, the self-discharge rate K value can be tested at room temperature or at high temperature, and the self-discharge rate K value at different temperatures will be different, and it can be selected to be tested at different temperatures according to needs.

[0070] The aging test is a process that accelerates the internal chemical reaction process of the battery cell through charge and discharge cycles of the battery cell to make the battery in a stable state. The aging test can help detect faults in the initial or final stage of the battery cell, thereby improving the quality and stability of the battery cell. Usually, the aging test can be divided into two methods: room temperature aging and high temperature aging.

[0071] Usually, the self-discharge K value test will be carried out after high temperature aging. After high temperature aging, the side reactions inside the battery cell are completed and the inside of the battery cell is relatively stable. After sufficient time of room temperature rest after high temperature aging, the battery cell temperature and the internal state of the battery are relatively stable. Measuring the voltage drop within a certain time under a stable chemical state can reflect the magnitude of physical self-discharge. If the K value is large, it means that there are abnormal particles or other micro-short circuit points inside the battery cell causing the voltage drop.

[0072] After the formation treatment of the battery cell, the self-discharge rate K value test and / or aging test can be further performed on the battery cell. Since the battery cell will have a stable voltage after the self-discharge rate K value test and / or aging test of the battery cell, this provides a stable initial voltage for the DCR test. Therefore, performing the DCR test after the self-discharge rate K value test and / or aging test on the battery cell before the capacity test can not only obtain relatively accurate DCR data, but also directly use the capacity test equipment without additional equipment investment, saving costs, and can also reduce the test duration and improve production capacity.

[0073] Optionally, as Figure 4 shown, the method 100 further includes: S105, forming the battery cell to a first state of charge value; S120, that is, before performing the capacity test on the battery cell, performing a DC resistance test on the pre-treated battery cell, including: S122, before performing the capacity test on the battery cell, performing a DC resistance test on the pre-treated battery cell at the first state of charge value.

[0074] In other words, the battery cell is formed to a certain SOC, and the DCR test is performed on the battery cell at this SOC. For example, if the battery cell is formed to 21% SOC, that is, the first SOC value is 21%, the DCR test can be directly performed on the battery cell at this 21% SOC. For another example, if the battery cell is formed to 50% SOC, that is, the first SOC value is 50%, the DCR test can be directly performed on the battery cell at this 50% SOC. For another example, if the battery cell is formed to 90%, that is, the first SOC value is 90%, the DCR test can be directly performed on the battery cell at this 90% SOC.

[0075] In this embodiment, directly performing the DC resistance test on the battery cell at the first state of charge value after formation before the capacity test can simplify the process of the DC resistance test.

[0076] Continue to refer to Figure 4 , optionally, the method 100 further includes: S140, converting the first DC resistance value obtained by performing the DC resistance test at the first state of charge value to a second DC resistance value at a second state of charge value, where the second state of charge value is in the state of charge interval at the end of charging, or the second state of charge value is in the state of charge interval at the end of discharging.

[0077] Due to the requirements of high voltage and large capacity in existing energy storage systems, a large number of batteries need to be connected in series and parallel to form container products, and then energy exchange is carried out with the power grid through the PCS. Inevitably, battery packs are connected to the battery system in parallel. Due to the issues of battery consistency and aging degree, the DCR differences, temperature differences, and SOC (State of Charge) differences among parallel battery clusters at different times will inevitably lead to current differences among clusters, resulting in the occurrence of circulating current and uneven current, thereby affecting the capacity and power of the energy storage system.

[0078] It has been found through research that when the energy storage system is at the end of charging or discharging, the uneven current phenomenon is more obvious. Therefore, the DC resistance value of a battery cell obtained at a certain SOC value at the end of charging or discharging can be selected as the basis for subsequent assembly of battery products such as electric boxes, electric cabinets, or containers. Battery cells with similar DC internal resistances are grouped to form battery products, ensuring the consistency of the products and avoiding the occurrence of uneven current.

[0079] Under normal circumstances, when a battery cell is being charged, the SOC value changes from low to high. Specifically, when the battery cell is charged to a relatively high SOC value, the charging current gradually decreases until it reaches the trickle charging state. At this time, the voltage of the battery cell also gradually increases until it reaches the charging cut-off voltage. Therefore, the SOC value at the end of charging usually refers to a high SOC value. For example, the SOC range at the end of charging in the embodiments of the present application is at least [50%, 100%], that is, the second SOC value is at least greater than 50%. In some embodiments, the SOC range at the end of charging can be in the range of [75%, 95%]. The second SOC value can be 75%, 80%, 85%, 90%, or 95%.

[0080] Similarly, when a battery cell is being discharged, the SOC value changes from high to low. When the battery cell is discharged to a relatively low SOC value, the voltage of the battery cell also gradually decreases until it reaches the discharge cut-off voltage and the discharge process stops. Therefore, the SOC value at the end of discharge usually refers to a low SOC value. For example, the SOC range at the end of discharge in the embodiments of the present application is at least [0, 50%], that is, the second SOC value is at least less than 50%. In some embodiments, the SOC range at the end of discharge can be in the range of [10%, 25%]. The second SOC value can be 10%, 15%, 20%, 21%, or 25%.

[0081] In some embodiments, the test device may internally store a conversion coefficient between a first DCR value at a first SOC value and a second DCR value at a second SOC value. For example, when the first SOC value is 40% and the second SOC value is 90%, the test device internally stores a conversion coefficient for converting the DCR value at 40% SOC to the DCR value at 90% SOC. For another example, when the first SOC value is 40% and the second SOC value is 21%, the test device internally stores a conversion coefficient for converting the DCR value at 40% SOC to the DCR value at 21% SOC.

[0082] Optionally, the conversion coefficient stored internally in the test device may be obtained by fitting test data obtained from DCR tests on multiple battery cells at the first SOC value and the second SOC value respectively.

[0083] As mentioned above, when the energy storage system is at the end of charging or discharging, the current unbalance phenomenon is more obvious. Usually, the SOC value of the battery cell after formation may not be in the SOC range at the end of charging or the SOC range at the end of discharging. Therefore, using the DCR data obtained by directly performing a DCR test on the battery cell at the SOC value after formation as the basis for assembling the energy storage system cannot effectively suppress the current unbalance phenomenon. Therefore, the DCR value obtained at the first SOC value of the battery cell after formation can be converted into the DCR value at the second SOC value at the end of charging or discharging, which can greatly suppress the occurrence of the current unbalance phenomenon and improve the overall lifespan of the battery product.

[0084] It should be noted that the process of performing a DCR test on the battery cell at the first SOC value may refer to the process of calculating the DCR value after a short-time charge of the battery cell at the first SOC value, or may refer to the process of calculating the DCR value after a short-time discharge of the battery cell at the first SOC value. The embodiments of the present application do not limit this.

[0085] Optionally, as Figure 5 shown in S120, that is, before performing a capacity test on the battery cell, a direct current resistance test is performed on the pre-treated battery cell, including: S123, before performing a capacity test on the battery cell, adjusting the state of charge of the pre-treated battery cell to a second state of charge value; S124, performing a direct current resistance test on the battery cell at the second state of charge value, where the second state of charge value is in the state of charge range at the end of charging or the state of charge range at the end of discharging.

[0086] Similarly, when the energy storage system is at the end of charging or discharging, the current sharing phenomenon is more obvious. Usually, the SOC value of a battery cell after formation may not be in the SOC range at the end of charging or the SOC range at the end of discharging. Therefore, using the DCR data obtained by directly performing a DCR test on the battery cell at the SOC value after formation as the basis for assembling the energy storage system cannot effectively suppress the current sharing phenomenon. Therefore, charging or discharging the battery cell after formation to a second SOC value at the end of charging or the end of discharging and then performing a DCR test, using the DCR data obtained at the second SOC value as the basis for assembling the energy storage system cannot effectively suppress the current sharing phenomenon, and it improves the power output and overall lifespan of the battery product.

[0087] It should be understood that when the SOC value of the battery cell after formation is the second SOC value, that is, when the battery cell is directly formed to the second SOC value at the end of charging or the end of discharging, there is no need to adjust the SOC value of the battery cell again and directly perform a DCR test on the battery cell, nor is it necessary to convert the DCR value after the test, and the DCR value at the SOC value at the end of charging or the end of discharging can be directly obtained. At this time, the test process is directly simplified.

[0088] Optionally, as Figure 6 shown, S124, that is, performing a direct current resistance test on the battery cell at the second state of charge value, includes: S1241, performing a direct current resistance test on the battery cell at the second state of charge value when the battery cell is static for a preset duration.

[0089] In other words, after charging or discharging the battery cell to the second SOC value, stop charging or discharging the battery cell, and allow the battery cell to be fully static, and then perform a direct current resistance test on the battery cell, so that before the test, the voltage of the battery cell tends to be stable, thereby further improving the accuracy of the second DCR value.

[0090] Optionally, continue to refer to Figure 7 , the method 100 further includes: S160, obtaining a third direct current resistance value of the battery cell based on the direct current resistance test performed on the battery cell; S170, grading the battery cell according to the third direct current resistance value.

[0091] For example, three DCR preset ranges can be set, corresponding to S gear, T gear, and U gear in ascending order. After obtaining the third DCR value of the battery cell, it can first be determined whether the third DCR value of the battery cell is within the DCR preset range corresponding to S gear, that is, to determine whether the battery cell belongs to S gear. If it belongs, the battery cell can be marked as S gear or placed in a fixed position belonging to S gear; if not, it is then continued to determine whether the third DCR value of the battery cell is within the DCR preset range corresponding to T gear, that is, to determine whether the battery cell belongs to T gear. If it belongs, the battery cell can be marked as T gear or placed in a fixed position belonging to T gear; if not, it is then continued to determine whether the third DCR value of the battery cell is within the DCR preset range corresponding to U gear, that is, to determine whether the battery cell belongs to U gear. If it belongs, the battery cell can be marked as U gear or placed in a fixed position belonging to U gear; if not, the battery cell can be placed in the scrap area.

[0092] After grading each battery cell, when assembling the electrical box, the battery cells of the same grade can be assembled together. For example, every L battery cells among the battery cells of the same grade can be assembled into an electrical box, and the electrical box can also be marked with the same grade as the battery cell, so as to subsequently assemble the electrical boxes belonging to the same grade into an electrical cabinet. Similarly, the electrical cabinet can also be marked with the same grade as the electrical box, so as to subsequently assemble the electrical cabinets belonging to the same grade into a container. In this way, the consistency of DCR among electrical cabinets can be improved, and ultimately the service life of the container can be extended.

[0093] In this embodiment, grading the battery cells according to the DCR value of the battery cells is beneficial to subsequently assembling multiple battery cells of the same grade into an electrical box. This method has simple control steps, convenient operation, and can also improve the consistency of DCR among battery cells.

[0094] Optionally, as Figure 8 shown, S160, that is, based on the DCR test performed on the battery cell, obtaining the third DCR value of the battery cell, includes: S161, the fourth DCR value of the battery cell obtained by performing the DCR test on the battery cell; S162, performing temperature correction on the fourth DCR value to obtain the third DCR value of the battery cell.

[0095] Generally, the DCR value of a battery cell is related to temperature. The DCR values of battery cells obtained at different temperatures vary greatly and cannot reflect the true differences between battery cells. Therefore, it is necessary to eliminate the data influence brought by temperature. For example, the fourth DCR values of different battery cells obtained at different test temperatures can be corrected to the third DCR values at the same temperature, so that the differences in the third DCR values between all battery cells are not affected by temperature. This same temperature can be a reference temperature, such as 25 °C, or this same temperature can also be the current ambient temperature.

[0096] Similar to the above conversion coefficient, the DCR values of a batch of battery cells can be tested at different test temperatures, and the test temperature and DCR values are curve-fitted to form a relational expression between the DCR value and temperature. After obtaining the test temperature of the battery cell on the production line and the fourth DCR value obtained at this test temperature, and then combining the reference temperature or the current ambient temperature, the third DCR value of this battery cell can be calculated.

[0097] In this embodiment, the fourth DCR value of the battery cell obtained through testing is temperature-corrected to obtain the third DCR value of the battery cell. Furthermore, the third DCR value of this battery cell can be used as the basis for grading, improving the consistency of the DCR between battery cells.

[0098] Optionally, as Figure 9 shown in S162, that is, temperature-correcting the fourth DCR value to obtain the third DCR value of the battery cell, includes: S1621, according to the following formula, correcting the fourth DCR value obtained at the test temperature to the third DCR value at the reference temperature:

[0099] R1 = f(T0) / f(T1) * R2 (1).

[0100] Wherein, R1 is the third DCR value, R2 is the fourth DCR value, T0 is the reference temperature, T1 is the test temperature, and f(T0) and f(T1) are the values obtained by substituting the reference temperature and the test temperature into the mapping function between the DCR value and temperature, respectively.

[0101] As mentioned above, there is a certain correspondence or mapping function between the DCR value and temperature. This correspondence or mapping function can be obtained through curve fitting. For example, the DCR test values of all battery cells on the production line in the recent month and the corresponding test temperatures can be collected, and the DCR test values and test temperatures of all battery cells are curve-fitted to obtain the correspondence or mapping function between the DCR value and temperature.

[0102] In some embodiments, the mapping function between the DCR value and temperature is f(t) = dt 2+ et + f, where d, e, and f are constants, t represents temperature and is a variable, and this mapping function can be updated or corrected regularly according to actual needs.

[0103] After obtaining the test temperature T1, the fourth DCR value R2, and the reference temperature T0 of the battery cell, first, T1 and T0 can be respectively substituted into the mapping function of the DCR value and temperature. After obtaining f(T1) and f(T0), then substitute them into the above formula (1), and then the third DCR value R1 of the battery cell can be calculated.

[0104] In other embodiments, after obtaining the DCR value of the battery monomer, the DCR value of the battery monomer can be uploaded to at least one of the Manufacturing Execution System (MES), Battery Management System (BMS), cloud server, and local database to realize the binding between the identification of the battery monomer and the DCR value. Subsequently, when calculating the DCR value of the electrical box or even the electrical cabinet, the DCR value of each battery monomer can be traced, so that the DCR value of the electrical box or electrical cabinet can be calculated based on the DCR value of the battery monomer, without performing DCR tests on the electrical box or electrical cabinet, thereby saving test costs.

[0105] Next, it will be combined with Figure 10 The DCR test method 200 of the battery according to the embodiments of the present application will be described in detail. Specifically, the method 200 mainly includes the following parts or all of the content.

[0106] S201, perform formation processing on the battery monomer and charge the battery monomer to 21% SOC. For example, during the first charging of the battery monomer, lithium ions can escape from the positive electrode, pass through the electrolyte - separator - electrolyte, and then embed into the negative electrode. During this process, a passivation film, namely the SEI film, is formed on the solid - phase interface between the electrode material and the electrolyte.

[0107] S202, perform aging test on the battery monomer. Generally, high - temperature aging can accelerate the elimination of chemical self - discharge and internal polarization of the battery monomer, making the voltage more stable.

[0108] S203, perform self - discharge rate K value test on the battery monomer. For example, screen out battery monomers with abnormal physical self - discharge or internal physical short - circuit through Open Circuit Voltage (OCV) test.

[0109] S204, perform DCR test on the battery monomer. For example, perform short - time charging or discharging on the battery monomer to obtain the DCR value of the battery monomer at 21% SOC.

[0110] S205, convert the DCR value of the battery cell at 21% SOC to the DCR value of the battery cell at 90% SOC.

[0111] S206, perform a capacity test on the battery cell.

[0112] It should be understood that in various embodiments of the present application, the magnitudes of the serial numbers of the above processes do not imply the order of execution. The order of execution of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present application. For example, S202 can be executed after S203.

[0113] The method for testing the DC resistance of the battery in the embodiments of the present application has been described in detail above. Next, in combination with Figure 11 and Figure 12 the DC resistance test device of the battery in the embodiments of the present application will be described in detail. The technical features described in the method embodiments are applicable to the following device embodiments.

[0114] Figure 11 FIG. shows a schematic block diagram of the DC resistance test device 300 of the battery in the embodiments of the present application. As Figure 11 shown, the device 300 includes the following parts or all of the content.

[0115] A pretreatment unit 310, configured to perform pretreatment on the battery cell that has undergone formation treatment so that the battery cell is in a stable state;

[0116] A DC resistance test unit 320, configured to perform a DC resistance test on the pretreated battery cell before performing a capacity test on the battery cell.

[0117] In a possible embodiment, the pretreatment unit 310 is specifically configured to: test the self-discharge rate K value and / or perform an aging test on the battery cell that has undergone formation treatment so that the voltage of the battery cell is stable; the DC resistance test unit 320 is specifically configured to: perform a DC resistance test on the battery cell after the self-discharge rate K value test and / or aging test before performing a capacity test on the battery cell.

[0118] In a possible embodiment, as Figure 12 shown, the device 300 further includes: a formation unit 330, configured to form the battery cell to a first state of charge value; the DC resistance test unit 320 is specifically configured to: perform a DC resistance test on the pretreated battery cell at the first state of charge value before performing a capacity test on the battery cell.

[0119] Continue to refer to Figure 12The device 300 also includes: a conversion unit 340, which is used to convert a first DC resistance value obtained by performing a DC resistance test at a first state of charge value into a second DC resistance value at a second state of charge value, wherein the second state of charge value is located in the state of charge range at the charging end, or the second state of charge value is located in the state of charge range at the discharging end.

[0120] In a possible embodiment, the DC resistance testing unit 320 is specifically used to: adjust the state of charge of the battery cell after pre-processing to a second state of charge value before performing a capacity test on the battery cell; and perform a DC resistance test on the battery cell at the second state of charge value; wherein the second state of charge value is located in the state of charge range at the charging end, or the second state of charge is located in the state of charge range at the discharging end.

[0121] In a possible embodiment, the DC resistance testing unit 320 is specifically configured to perform a DC resistance test on the battery cell at the second state of charge value when the battery cell is left stationary for a preset time period.

[0122] Continue to see Figure 12 The device 300 further includes: an acquisition unit 350 for obtaining a third DC resistance value of the battery cell based on a DC resistance test performed on the battery cell; and a grading unit 360 for grading the battery cell according to the third DC resistance value.

[0123] In a possible embodiment, the acquiring unit 350 is specifically configured to: obtain a fourth DC resistance value of the battery cell by performing a DC resistance test on the battery cell; and perform temperature correction on the sixth DC resistance value to obtain a third DC resistance value.

[0124] In a possible embodiment, the acquisition unit 350 is specifically used to correct the fourth DC resistance value obtained at the test temperature to the third DC resistance value at the reference temperature according to the following formula: R1=f(T0) / f(T1)*R2, wherein R1 is the third DC resistance value, R2 is the fourth DC resistance value, T0 is the reference temperature, T1 is the test temperature, and f(T0) and f(T1) are the values obtained by substituting the reference temperature and the test temperature into the mapping function of the DC resistance value and the temperature, respectively.

[0125] It should be understood that each of the above modules in the device 300 is used to implement Figures 2 to 10 For the sake of brevity, the corresponding processes in each method are not repeated here.

[0126] Figure 13 FIG. 4 is a schematic block diagram of a test device 400 for testing the DC resistance of a battery according to an embodiment of the present application. Figure 13As shown, the test device 400 includes a processor 410 and a memory 420. Among them, the memory 420 is used to store instructions, and the processor 410 is used to read the instructions and execute the methods of various embodiments of the present application based on the instructions.

[0127] Among them, the memory 420 can be a separate device independent of the processor 410, or can be integrated in the processor 410.

[0128] Optionally, as Figure 13 shown, the test device 400 may further include a transceiver 430, and the processor 410 can control the transceiver 430 to communicate with other devices. Specifically, it can send information or data to other devices, or receive information or data sent by other devices.

[0129] It should be understood that the processor in the embodiments of the present application may be an integrated circuit chip with signal processing capabilities. In the implementation process, each step of the above method embodiments can be completed by the integrated logic circuit in the hardware of the processor or instructions in software form. The above-mentioned processor can be a general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components. It can implement or execute the various methods, steps and logic block diagrams disclosed in the embodiments of the present application. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor, etc. The steps of the method disclosed in combination with the embodiments of the present application can be directly embodied as being executed and completed by the hardware decoding processor, or completed by the combination of the hardware and software modules in the decoding processor. The software module can be located in a mature storage medium in the art such as random access memory, flash memory, read-only memory, programmable read-only memory or electrically erasable programmable memory, register, etc. This storage medium is located in the memory, and the processor reads the information in the memory and combines its hardware to complete the steps of the above method.

[0130] It can be understood that the memory in the embodiments of the present application can be a volatile memory or a non-volatile memory, or can include both volatile and non-volatile memories. Among them, the non-volatile memory can be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory can be a random access memory (RAM), which is used as an external cache. By way of example but not limitation, many forms of RAM are available, such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchlink dynamic random access memory (SLDRAM), and direct rambus random access memory (DR RAM). It should be noted that the memory of the systems and methods described herein is intended to include but not be limited to these and any other suitable types of memory.

[0131] The embodiments of the present application further provide a computer-readable storage medium for storing a computer program.

[0132] Optionally, the computer-readable storage medium can be applied to the test device for the DC resistance test of the battery in the embodiments of the present application, and the computer program causes the computer to execute the corresponding processes implemented by the test device in the various methods of the embodiments of the present application. For the sake of brevity, it will not be described in detail here.

[0133] The embodiments of the present application further provide a computer program product including computer program instructions.

[0134] Optionally, the computer program product can be applied to the test device for the DC resistance test of the battery in the embodiments of the present application, and the computer program instructions cause the computer to execute the corresponding processes implemented by the test device in the various methods of the embodiments of the present application. For the sake of brevity, it will not be described in detail here.

[0135] The embodiments of the present application further provide a computer program.

[0136] Optionally, the computer program can be applied to the test equipment for the DC resistance test of the battery in the embodiments of the present application. When the computer program runs on a computer, it causes the computer to execute the corresponding processes implemented by the test equipment in the various methods of the embodiments of the present application. For the sake of brevity, it will not be elaborated here.

[0137] In several embodiments provided in the present application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed mutual coupling, direct coupling, or communication connection can be through some interfaces. The indirect coupling or communication connection of the devices or units can be in an electrical, mechanical, or other form.

[0138] The units described as separate components may or may not be physically separated. The components displayed as units may or may not be physical units, that is, they can be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0139] In addition, in each embodiment of the present application, the functional units can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit.

[0140] If the function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art, or a part of this technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions to cause a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of the present application. The aforementioned storage medium includes: various media such as USB flash drives, mobile hard disks, ROM, RAM, magnetic disks, or optical discs that can store program codes.

[0141] The above is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can easily think of changes or substitutions, which should all be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for testing the DC resistance of a battery, characterized in that, Including: Preprocessing the battery cells that have undergone formation to make the battery cells in a stable state; Before performing a capacity test on the battery cells, performing a DC resistance test on the battery cells after the preprocessing.

2. The method according to claim 1, wherein The preprocessing the battery cells that have undergone formation to make the battery cells in a stable state includes: Performing a self-discharge rate K value test and / or an aging test on the battery cells that have undergone formation to stabilize the voltage of the battery cells; The performing a DC resistance test on the battery cells after the preprocessing before performing a capacity test on the battery cells includes: Before performing a capacity test on the battery cells, performing a DC resistance test on the battery cells after the self-discharge rate K value test and / or the aging test.

3. The method according to claim 1 or 2, characterized in that, The method further includes: Forming the battery cells to a first state of charge value; The performing a DC resistance test on the battery cells after the preprocessing before performing a capacity test on the battery cells includes: Before performing a capacity test on the battery cells, at the first state of charge value, performing a DC resistance test on the battery cells after the preprocessing.

4. The method according to claim 3, wherein The method further includes: Converting a first DC resistance value obtained by performing a DC resistance test at the first state of charge value to a second DC resistance value at a second state of charge value; Wherein, the second state of charge value is in the state of charge interval at the end of charging, or the second state of charge value is in the state of charge interval at the end of discharging.

5. The method according to claim 1 or 2, characterized in that, The performing a DC resistance test on the battery cells after the preprocessing before performing a capacity test on the battery cells includes: Before performing a capacity test on the battery cells, adjusting the state of charge of the battery cells after the preprocessing to the second state of charge value; At the second state of charge value, performing a DC resistance test on the battery cells; Wherein, the second state of charge value is in the state of charge interval at the end of charging, or the second state of charge is in the state of charge interval at the end of discharging.

6. The method according to claim 5, wherein The performing a DC resistance test on the battery cells at the second state of charge value includes: When the battery cells are static for a preset duration, performing a DC resistance test on the battery cells at the second state of charge value.

7. The method according to any one of claims 1 to 6, characterized in that, The method further includes: Based on the DC resistance test performed on the battery cells, obtaining a third DC resistance value of the battery cells; According to the third DC resistance value, grading the battery cells.

8. The method according to claim 7, characterized in that, The obtaining a third DC resistance value of the battery cells based on the DC resistance test performed on the battery cells includes: A fourth DC resistance value of the battery cells obtained by performing a DC resistance test on the battery cells; Performing temperature correction on the fourth DC resistance value to obtain the third DC resistance value.

9. A DC resistance testing device for a battery, characterized in that, Including: A preprocessing unit for preprocessing the battery cells that have undergone formation to make the battery cells in a stable state; A DC resistance test unit is used to perform a DC resistance test on the battery cell after the pre-treatment before performing a capacity test on the battery cell.

10. The device according to claim 9, characterized in that, The pre-treatment unit is specifically configured to: Perform a self-discharge rate K value test and / or an aging test on the battery cell that has undergone formation treatment to stabilize the voltage of the battery cell; The DC resistance test unit is specifically configured to: Before performing a capacity test on the battery cell, perform a DC resistance test on the battery cell after the self-discharge rate K value test and / or the aging test.

11. The device according to claim 9 or 10, characterized in that, The device further includes: A formation unit for forming the battery cell to a first state of charge value; The DC resistance test unit is configured to: Before performing a capacity test on the battery cell, perform a DC resistance test on the battery cell after the pre-treatment at the first state of charge value.

12. The device according to claim 11, characterized in that, The device further includes: A conversion unit for converting a first DC resistance value obtained by performing a DC resistance test at the first state of charge value into a second DC resistance value at a second state of charge value; Wherein, the second state of charge value is in the state of charge interval at the end of charging, or the second state of charge value is in the state of charge interval at the end of discharging.

13. The device according to claim 9 or 10, characterized in that, The DC resistance test unit is specifically configured to: Before performing a capacity test on the battery cell, adjust the state of charge of the battery cell after the pre-treatment to the second state of charge value; Perform a DC resistance test on the battery cell at the second state of charge value; Wherein, the second state of charge value is in the state of charge interval at the end of charging, or the second state of charge is in the state of charge interval at the end of discharging.

14. The device according to claim 13, characterized in that, The DC resistance test unit is specifically configured to: When the battery cell is static for a preset duration, perform a DC resistance test on the battery cell at the second state of charge value.

15. The device according to any one of claims 9 to 14, characterized in that, The device further includes: An acquisition unit for obtaining a third DC resistance value of the battery cell based on the DC resistance test performed on the battery cell; A grading unit for grading the battery cell according to the third DC resistance value.

16. The device according to claim 15, wherein The acquisition unit is specifically configured to: A fourth DC resistance value of the battery cell obtained by performing a DC resistance test on the battery cell; Perform temperature correction on the fourth DC resistance value to obtain the third DC resistance value.

17. A test device for measuring the DC resistance of a battery, characterized in that, Includes: A memory for storing instructions; A processor for reading the instructions and executing the method according to any one of claims 1 to 8 based on the instructions.

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