Battery capacity detection method and device, terminal and storage medium

Abstract

The invention discloses a battery capacity detection method and device, a terminal and a storage medium. The battery capacity detection method comprises the following steps: obtaining thermodynamic discharge data of a reference battery monomer and dynamic discharge data of a to-be-detected battery monomer; wherein the reference battery monomer and the to-be-tested battery monomer belong to the same battery design of the same battery system; obtaining capacity compensation data based on the thermodynamic discharge data and the dynamic discharge data; and correcting the dynamic capacity data of the to-be-measured battery monomer by using the capacity compensation data to obtain the thermodynamic capacity data of the to-be-measured battery monomer. In this way, the detection period of the battery capacity can be shortened, and the detection accuracy of the battery capacity is improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a method for detecting battery capacity, a device for detecting battery capacity, a terminal, and a computer-readable storage medium. Background Technology

[0002] With the development of battery technology, battery devices are being applied in more and more fields, such as automotive power and energy storage, gradually replacing traditional fossil fuels. As the battery market rises, the long-life performance of battery devices has attracted much attention; however, the testing cycle for individual battery cells is long, especially for those used in energy storage. It is impractical to detect the long-life parameters of individual battery cells through full-life-cycle testing. Related technologies predict the lifespan of individual battery cells by testing a small amount of cycle data and extrapolating or modeling this data. However, this method of prediction through extrapolation or modeling of a small amount of cycle data is highly dependent on the quality and length of the test data. Data of substandard quality or length will introduce significant errors in the prediction, resulting in low accuracy of the detected battery capacity. Summary of the Invention

[0003] In view of the above problems, the battery capacity detection method, battery capacity detection device, terminal and computer-readable storage medium provided in this application can shorten the battery capacity detection cycle and improve the accuracy of battery capacity detection.

[0004] To address the aforementioned problems, this application provides a method for detecting battery capacity. The method includes: acquiring thermodynamic discharge data of a reference battery cell and kinetic discharge data of a battery cell under test; wherein the reference battery cell and the battery cell under test belong to the same battery system and the same battery design; acquiring capacity compensation data based on the thermodynamic discharge data and the kinetic discharge data; and correcting the kinetic capacity data of the battery cell under test using the capacity compensation data to obtain the thermodynamic capacity data of the battery cell under test. In this way, only the thermodynamic discharge data of one battery cell under the same battery design and the kinetic discharge data of the battery under test need to be acquired to obtain the thermodynamic capacity data of the battery under test. Since the acquisition cycle of thermodynamic discharge data is much longer than that of kinetic discharge data, but its reliability is high, and this embodiment does not require acquiring the thermodynamic discharge data of the battery under test, this embodiment can shorten the battery capacity detection cycle and obtain highly reliable thermodynamic capacity data, thereby improving the accuracy of battery capacity detection.

[0005] In some embodiments, the thermodynamic discharge data includes: the open-circuit voltage and first discharge capacity of the reference battery cell; the kinetic discharge data includes: the discharge termination voltage and second discharge capacity of the battery cell under test; obtaining capacity compensation data based on the thermodynamic discharge data and the kinetic discharge data includes: obtaining a first relationship based on the open-circuit voltage and the first discharge capacity, wherein the first relationship is the relationship between the remaining capacity and the open-circuit voltage of the reference battery cell; and obtaining the remaining capacity corresponding to the discharge termination voltage as capacity compensation data based on the first relationship. Open-circuit voltage and discharge capacity are important data related to battery capacity in a battery cell and are easily obtained. This embodiment uses these two data to determine the first relationship and obtains the remaining capacity corresponding to the discharge termination voltage of the battery cell under test as capacity compensation data based on this first relationship. Therefore, the remaining capacity corresponding to the discharge termination voltage can characterize the unreleased battery capacity of the battery cell under test after discharge due to factors such as polarization, thereby accurately obtaining the capacity compensation data of the battery cell under test.

[0006] In some embodiments, the first relationship includes a functional relationship. Obtaining the first relationship between the remaining capacity and open-circuit voltage of the reference battery cell based on the open-circuit voltage and the first discharge capacity includes: obtaining a first curve based on the open-circuit voltage and the first discharge capacity, where the first curve is a relationship curve between the open-circuit voltage and discharge capacity of the reference battery cell; converting the first curve into a second curve, where the second curve is a relationship curve between the open-circuit voltage and remaining capacity of the reference battery cell; and obtaining the functional relationship based on the second curve. This embodiment converts the first curve into a relationship curve between the open-circuit voltage and remaining capacity of the reference battery, so that the remaining capacity of the battery cell under test can be directly obtained based on this relationship curve. Furthermore, this embodiment obtains the corresponding functional relationship based on fitting the second curve, that is, regularizing the second curve. This not only facilitates the storage and subsequent use of the functional relationship but also removes the limitations imposed by the open-circuit voltage and discharge capacity on the functional relationship in the second curve, because the remaining capacity and open-circuit voltage of battery cells with different capacities differ. Therefore, this embodiment can improve the detection efficiency and accuracy of the battery capacity of the battery cell under test.

[0007] In some embodiments, converting the first curve into a second curve, where the second curve is the relationship between the open-circuit voltage and remaining capacity of the reference battery cell, includes: obtaining a third curve corresponding to the end-of-discharge stage of the reference battery cell from the first curve based on the discharge termination voltage; and converting the third curve into a second curve, where the second curve is the relationship between the open-circuit voltage and remaining capacity of the reference battery cell at the end-of-discharge stage. In dynamic discharge, i.e., high-rate discharge, the battery capacity is usually not fully discharged at the end-of-discharge stage, leading to data fluctuations and poor reliability. Therefore, to simplify detection and improve detection efficiency, this embodiment can obtain only the curve between the open-circuit voltage and discharge capacity corresponding to the end-of-discharge stage of the reference battery cell, i.e., the third curve.

[0008] In some embodiments, the second curve includes a first sub-curve and a second sub-curve. The first curve is converted into the second curve. The first sub-curve is the relationship curve between the open-circuit voltage of the reference battery cell and the percentage of its remaining capacity. The second sub-curve is the relationship curve between the open-circuit voltage of the reference battery and the absolute value of its remaining capacity. This embodiment can use different remaining capacity data to obtain the first curve and the first relationship for the same battery design in different battery systems, which can improve the accuracy of capacity detection of battery cells in various battery systems.

[0009] In some embodiments, the detection method further includes: acquiring at least a second curve corresponding to one discharge cycle of the reference battery cell as a third sub-curve, and a second curve corresponding to N discharge cycles as a fourth sub-curve; comparing at least the third sub-curve and the fourth sub-curve to obtain a comparison result; acquiring capacity compensation data based on the thermodynamic discharge data and the kinetic discharge data includes: in response to the comparison result being a match, acquiring capacity compensation data for one discharge cycle of the battery cell under test based on the thermodynamic discharge data of the reference battery cell and the kinetic discharge data; correcting the kinetic capacity data of the battery cell under test using the capacity compensation data to obtain the thermodynamic capacity data of the battery cell under test includes: correcting the kinetic capacity data of the battery cell under test using the capacity compensation data for one discharge cycle to obtain at least the thermodynamic capacity data of the battery cell under test for one discharge cycle. This embodiment only acquires the thermodynamic discharge data of the reference battery cell for one discharge cycle, which can shorten the detection cycle of the thermodynamic discharge data of the reference battery cell, thereby improving the detection efficiency of battery capacity.

[0010] In some embodiments, the capacity compensation data includes first capacity compensation data and second capacity compensation data. Obtaining the capacity compensation data based on the thermodynamic discharge data and the kinetic discharge data includes: in response to a mismatch in the comparison result, obtaining first capacity compensation data for at least one discharge cycle and second capacity compensation data for the Nth discharge cycle based on the thermodynamic discharge data of the reference battery cell after at least one discharge cycle, the thermodynamic discharge data after N discharge cycles, and the kinetic discharge data; correcting the kinetic capacity data of the battery cell under test using the capacity compensation data to obtain the thermodynamic capacity data of the battery cell under test includes: correcting the kinetic capacity data of the battery cell under test for one to (N-1) discharge cycles using the first capacity compensation data, and correcting the kinetic capacity data of the battery cell under test for N discharge cycles and beyond using the second capacity compensation data; wherein N is a natural number greater than 1. This embodiment only obtains the thermodynamic discharge data of the reference battery cell after multiple discharge cycles, and uses the capacity compensation data corresponding to each multiple discharge cycle to correct the kinetic capacity data of the battery cell under test, which can improve the reliability of the thermodynamic capacity data of the battery cell under test.

[0011] In some embodiments, obtaining the discharge end voltage includes: after the discharge is completed, allowing the battery cell under test to stand for a preset time, and obtaining the voltage after the preset time as the discharge end voltage. This embodiment uses the standing voltage as the discharge end voltage, which can improve the detection efficiency of battery capacity.

[0012] In some embodiments, obtaining the discharge termination voltage includes: after discharge, allowing the battery under test to rest for a preset time, and obtaining the voltage after the preset time as the resting voltage; fitting the resting voltage using a relaxation formula to obtain the discharge termination voltage. If improved accuracy of the discharge termination voltage is required or a shorter resting time is needed, a relaxation formula can be used to fit the resting voltage, and the fitted relaxation voltage can be used as the discharge termination voltage. Therefore, this embodiment can improve the measurement accuracy of the discharge termination voltage and shorten the resting time, thus improving the accuracy and efficiency of battery capacity detection.

[0013] To address the aforementioned problems, this application provides a battery capacity testing device, comprising: a testing module for acquiring thermodynamic discharge data of a reference battery cell and kinetic discharge data of a battery cell under test; wherein the reference battery cell and the battery cell under test belong to the same battery system and the same battery design; an analysis module for acquiring capacity compensation data based on the thermodynamic discharge data and the kinetic discharge data; and a correction module for correcting the kinetic capacity data of the battery cell under test using the capacity compensation data to obtain the thermodynamic capacity data of the battery cell under test.

[0014] To address the aforementioned problems, this application provides a terminal comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the processor executes program data to implement the aforementioned battery capacity detection method.

[0015] To address the aforementioned problems, this application provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the aforementioned battery capacity detection method.

[0016] Unlike existing technologies, this application obtains the thermodynamic discharge data of a single battery cell within the same battery system (i.e., a reference battery cell), and uses this thermodynamic discharge data, along with the kinetic discharge data of other battery cells under test within the same battery design, to obtain capacity compensation data for the battery cell under test. Finally, this capacity compensation data is used to correct the kinetic discharge data of the battery cell under test, yielding the thermodynamic capacity data of the battery cell under test. In this way, only the thermodynamic discharge data of a single battery cell within the same battery system and the same battery design, along with the kinetic discharge data of the battery under test, are needed to obtain the thermodynamic capacity data of the battery under test. Since the acquisition cycle of thermodynamic discharge data is much longer than that of kinetic discharge data, but its reliability is high, and this application does not require the acquisition of the thermodynamic discharge data of the battery under test, this application can shorten the battery capacity testing cycle and obtain highly reliable thermodynamic capacity data, thereby improving the accuracy of battery capacity testing. Attached Figure Description

[0017] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0018] Figure 1 This is a schematic flowchart of an embodiment of the battery capacity detection method provided in this application;

[0019] Figure 2 This is a schematic diagram of an embodiment of the curve showing the relationship between the open-circuit voltage and discharge capacity of a single battery cell under thermodynamic equilibrium conditions provided in this application;

[0020] Figure 3 This is a schematic diagram of an embodiment of the curve showing the relationship between the absolute value of the open-circuit voltage and the remaining capacity of a single battery cell under thermodynamic equilibrium conditions provided in this application.

[0021] Figure 4This is a schematic diagram of an embodiment of the curve showing the relationship between the open-circuit voltage and the percentage of remaining capacity of a single battery cell under thermodynamic equilibrium conditions provided in this application.

[0022] Figure 5 This is a schematic diagram of an embodiment of the modified thermodynamic capacity versus discharge cycle number curve provided in this application;

[0023] Figure 6 This is a schematic diagram of an embodiment of the relationship between resting voltage and discharge cycle number provided in this application;

[0024] Figure 7 This is a schematic flowchart of another embodiment of the battery capacity detection method provided in this application;

[0025] Figure 8 This is a schematic diagram of an embodiment of the battery capacity detection device provided in this application;

[0026] Figure 9 This is a schematic diagram of the structure of an embodiment of the terminal provided in this application;

[0027] Figure 10 This is a schematic diagram of an embodiment of the computer-readable storage medium provided in this application.

[0028] Reference numerals: Detection module 81; Analysis module 82; Correction module 83; Memory 91; Processor 92; Computer-readable storage medium 100; Program instructions 101. Detailed Implementation

[0029] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0031] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0032] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0033] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0034] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0035] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0036] Battery capacity is a crucial indicator of battery performance, representing the amount of electricity a battery can release under specific conditions (such as discharge rate, temperature, and cutoff voltage). The kinetic capacity of a single battery cell typically refers to its ability to store and release energy during rapid charging and discharging at high rates. The thermodynamic capacity of a single battery cell refers to its storage capacity in a thermodynamic equilibrium state; it is usually related to the cell's energy density, i.e., how much electrical energy a cell can store when fully charged. Kinetic capacity is generally limited by the cell's internal resistance and polarization effects, while thermodynamic capacity is limited by the chemical properties and structure of the battery materials.

[0037] With the development of battery technology, battery devices are being applied in more and more fields, such as automotive power and energy storage, gradually replacing traditional fossil fuels. With the rise of the battery market, the long life performance of battery cells has attracted much attention; however, the testing cycle of battery cells is long, especially for battery cells used in energy storage, and it is not realistic to test the long life parameters of battery cells through the entire life cycle.

[0038] In related technologies, the lifespan of a single battery cell is predicted by testing a small amount of cyclic data and then extrapolating or modeling that data. However, this method of prediction by extrapolating or modeling a small amount of cyclic data is obtained through low-rate testing, which is time-consuming and costly. The test data is also short, and this method is highly dependent on the quality and length of the test data. Data that is not of good quality or length will cause a large error in the prediction, resulting in low accuracy of the detected battery capacity.

[0039] In related technologies, battery parameter testing schemes cannot simultaneously ensure test quality, i.e., reliability and length: high-quality data, such as thermodynamic data, often have long test cycles and short data lengths; while data with sufficient length, such as kinetic data from normal or high-rate cycling, often have poor quality due to polarization or environmental influences.

[0040] Based on the above considerations, this application proposes a method that can correct low-reliability kinetic capacity data into high-reliability thermodynamic capacity data, thereby obtaining more accurate battery capacity without long-term testing.

[0041] Specifically, the thermodynamic discharge data of a single battery cell within the same battery system and design (i.e., a reference battery cell) is obtained. This thermodynamic discharge data, along with the kinetic discharge data of other battery cells under test within the same battery system and design, is then used to obtain capacity compensation data for the battery cell under test. Finally, this capacity compensation data is used to correct the kinetic discharge data of the battery cell under test, yielding the thermodynamic capacity data of the battery cell under test. In this method, only the thermodynamic discharge data of a single battery cell within the same battery design and the kinetic discharge data of the battery under test are needed to obtain the thermodynamic capacity data of the battery under test. While the acquisition cycle for thermodynamic discharge data is much longer than that for kinetic discharge data, it offers higher reliability. This application eliminates the need to acquire the thermodynamic discharge data of the battery under test, thus shortening the battery capacity testing cycle and obtaining highly reliable thermodynamic capacity data, thereby improving the accuracy of battery capacity testing.

[0042] Please refer to Figure 1 , Figure 1 This is a flowchart illustrating an embodiment of the battery capacity detection method provided in this application.

[0043] This embodiment provides a method for detecting battery capacity, which includes the following steps:

[0044] Step S11: Obtain the thermodynamic discharge data of the reference battery cell and the kinetic discharge data of the battery cell under test; wherein the reference battery cell and the battery cell under test belong to the same battery system and the same battery design.

[0045] In this context, "same battery design" refers to the chemical composition and design parameters of a single battery cell, primarily including the materials and quantities of the positive electrode, negative electrode, and electrolyte. Different battery designs determine variations in the performance, cost, and safety of individual battery cells. For example, a reference battery cell and a test battery cell may both belong to the LFP system 280Ah design; the same battery system and design can be used to assemble different types of batteries, such as LFP system 280Ah designs for pouch cells and hard-case cells.

[0046] Among them, the kinetic discharge data of a single battery cell refers to the performance parameters of the battery cell during rapid discharge at high rates. The thermodynamic discharge data of a single battery cell refers to the performance parameters of the battery cell during discharge under thermodynamic equilibrium conditions.

[0047] Step S12: Obtain capacity compensation data based on thermodynamic discharge data and kinetic discharge data.

[0048] Step S13: Use capacity compensation data to correct the kinetic capacity data of the cell under test to obtain the thermodynamic capacity data of the cell under test.

[0049] Kinetic capacity is typically limited by the internal resistance and polarization effects of a single battery cell. Furthermore, kinetic capacity data is generally tested at relatively high rates, where polarization is usually significant and greatly influenced by factors such as ambient temperature and the material's diffusion capacity. This results in large fluctuations in test results, often failing to reflect the true charge-discharge cycle life of a battery cell. In contrast, thermodynamic capacity data eliminates the interference of kinetic polarization, thus more accurately reflecting the actual charge-discharge capacity and lifespan of a battery cell. Therefore, the thermodynamic capacity data obtained in this embodiment is more accurate.

[0050] This embodiment acquires the thermodynamic discharge data of a single battery cell under the same battery design, i.e., a reference battery cell. Using this thermodynamic discharge data and the kinetic discharge data of other battery cells under test under the same battery design, it obtains the capacity compensation data of the battery cell under test. Finally, it uses this capacity compensation data to correct the kinetic discharge data of the battery cell under test, thus obtaining the thermodynamic capacity data of the battery cell under test. In this way, only the thermodynamic discharge data of a single battery cell under the same battery design and system, and the kinetic discharge data of the battery under test are needed to obtain the thermodynamic capacity data of the battery under test. Since the acquisition cycle of thermodynamic discharge data is much longer than that of kinetic discharge data, but its reliability is high, and this embodiment does not require the acquisition of the thermodynamic discharge data of the battery under test, this embodiment can shorten the battery capacity detection cycle and obtain highly reliable thermodynamic capacity data, thereby improving the accuracy of battery capacity detection.

[0051] In some embodiments, the thermodynamic discharge data of the reference battery cell includes: the open-circuit voltage (OCV) and the first discharge capacity of the reference battery cell, and the kinetic discharge data of the battery cell under test includes: the discharge termination voltage and the second discharge capacity of the battery cell under test. The step of obtaining capacity compensation data based on the thermodynamic discharge data and the kinetic discharge data in S12 specifically includes the following implementation methods:

[0052] A first relationship is obtained based on the open-circuit voltage and the first discharge capacity. The first relationship is the relationship between the remaining capacity of the reference battery cell and the open-circuit voltage. The remaining capacity corresponding to the discharge end voltage is obtained based on the first relationship as capacity compensation data.

[0053] In actual measurement, a voltmeter can be connected at the open circuit point, and the voltmeter reading is the open circuit voltage. A reference battery cell can be discharged to obtain the discharge capacity during the discharge process as the first discharge capacity. Multiple sets of open circuit voltages and the first discharge capacity are obtained, and a first relationship is derived based on these multiple sets of data. The discharge termination voltage refers to the open circuit voltage at which the battery cell's capacity remains unchanged or nearly unchanged within a preset resting time.

[0054] Open-circuit voltage and discharge capacity are important data related to battery capacity in a single battery cell and are easy to obtain. In this embodiment, the first relationship is determined by these two data and the remaining capacity corresponding to the discharge end voltage of the battery cell under test is obtained as capacity compensation data based on the first relationship. Therefore, the remaining capacity corresponding to the discharge end voltage can characterize the unreleased battery capacity of the battery cell under test after discharge due to factors such as polarization, thereby accurately obtaining the capacity compensation data of the battery cell under test.

[0055] In some embodiments, the first relationship includes a functional relationship, and the step of obtaining the first relationship between the remaining capacity and open-circuit voltage of the reference battery cell based on the open-circuit voltage and the first discharge capacity specifically includes the following implementation methods:

[0056] A first curve is obtained based on the open-circuit voltage and the first discharge capacity. The first curve is the relationship curve between the open-circuit voltage and the discharge capacity of the reference battery cell. The first curve is converted into a second curve, which is the relationship curve between the open-circuit voltage and the remaining capacity of the reference battery cell. The functional relationship is obtained based on the second curve.

[0057] The first curve is obtained based on multiple sets of open-circuit voltages and the first discharge capacity of a reference battery cell, such as... Figure 2 As shown, Figure 2 The horizontal axis represents the discharge capacity. Figure 2 The vertical axis represents the open-circuit voltage. Under thermodynamic equilibrium, cyclically discharging a reference battery cell can yield multiple sets of open-circuit voltages and the first discharge capacity for at least one discharge cycle. This embodiment converts the first curve into a curve showing the relationship between the open-circuit voltage and remaining capacity of the reference battery. This allows for direct acquisition of the remaining capacity of the battery cell under test based on this curve. Furthermore, this embodiment uses a second curve for fitting to obtain the corresponding functional relationship, thus regularizing the second curve. This not only facilitates the storage and subsequent use of the functional relationship but also removes the limitations imposed by the open-circuit voltage and discharge capacity on the functional relationship, as the remaining capacity and open-circuit voltage of battery cells with different capacities vary. Therefore, this embodiment improves the detection efficiency and accuracy of the battery capacity of the battery cell under test.

[0058] In some embodiments, the step of converting the first curve into a second curve, wherein the second curve is the relationship curve between the open-circuit voltage and the remaining capacity of a reference battery cell, specifically includes the following implementation methods:

[0059] Based on the discharge termination voltage, obtain the third curve corresponding to the discharge end stage of the reference battery cell from the first curve; convert the third curve into the second curve, which is the relationship curve between the open circuit voltage and the remaining capacity of the reference battery cell at the discharge end stage.

[0060] The starting point of the discharge end stage is determined by the discharge end voltage of the battery under test, so that the third curve corresponding to the discharge end stage of the reference battery cell can be extracted from the first curve.

[0061] For example, such as Figure 2 and Figure 3 As shown, Figure 3 The horizontal axis represents the open-circuit potential. Figure 3 The vertical axis represents the remaining capacity; Figure 3 The third curve is shown. Further analysis can be performed... Figure 3 Fitting the shown relationship curve yields the functional relationship: y = 71.156x 3 -563.96x 2 +1499.9x-1338.4.

[0062] When discharging at high rates (kinetic state), if the potential falls between 2.6 and 3.2V after the high-rate discharge ends and the device is left to stand, there will be a corresponding capacity that has not been fully released due to factors such as polarization. This portion of the capacity is corrected to the kinetic capacity data, thus obtaining high-quality kinetic capacity data.

[0063] During dynamic discharge, i.e., high-rate discharge, the battery capacity is often not fully discharged at the end of the discharge phase, leading to data fluctuations and poor reliability. Therefore, to simplify the detection and improve detection efficiency, this embodiment can obtain only the curve between the open-circuit voltage and discharge capacity corresponding to the end of the discharge phase of the reference battery cell, i.e., the third curve.

[0064] In some embodiments, the second curve includes a first sub-curve and a second sub-curve, wherein the first sub-curve is a curve showing the relationship between the open-circuit voltage of a reference battery cell and the percentage of its remaining capacity, such as... Figure 4 As shown, where, Figure 4 The functional relationship corresponding to the curve in the middle is: y = 0.2473x 3 -1.964x 2 +5.2338x-4.679, this relationship curve is the curve after one discharge cycle; the second sub-curve is the relationship curve between the open-circuit voltage of the reference battery and the absolute value of the remaining capacity, such as... Figure 3 As shown.

[0065] Similarly, the relationship between percentage correction and absolute value correction is independent of the magnitude of the attenuation. How to choose between them should refer to the aforementioned assumptions.

[0066] In fact, for LFP cells, the degradation is mainly driven by the loss of active lithium, while the loss of the negative electrode is relatively small. Therefore, the results of absolute value correction and percentage correction are similar for LFP.

[0067] When the battery capacity decays to a value greater than or equal to a preset value, the relationship curve between the thermodynamic capacity and the open-circuit voltage after the preset value is considered for correction.

[0068] The description of the two methods of absolute value correction and percentage correction for remaining capacity in this passage is not quite correct. The relationship between the two should be as follows:

[0069] In some embodiments, if the negative electrode of a battery cell does not age during the battery aging process, and the capacity decay is mainly caused by the aging of the positive electrode or the loss of active lithium, the second curve can be achieved using the second sub-curve for such a battery design. If the negative electrode also ages during the battery cell aging process, but its aging does not change the shape of the first curve (i.e., the curve describing the relationship between the thermodynamic capacity of the negative electrode and the open-circuit voltage), but only the curve is scaled proportionally, the second curve can be achieved using the first sub-curve for such a battery design. For example, in the LFP system cell shown in the embodiment, the aging process mainly involves the loss of active lithium, and the loss of the negative electrode is relatively small. Therefore, both curve correction methods can ultimately correct the results to be basically the same.

[0070] This embodiment can use different remaining capacity data to obtain the first curve and the first relationship for different battery designs, which can improve the accuracy of capacity detection of individual cells in each battery system.

[0071] In some embodiments, the detection method further includes: acquiring at least a second curve corresponding to one cycle of discharge of a reference battery cell as a third sub-curve, and a second curve corresponding to N cycles of discharge as a fourth sub-curve; comparing at least the third sub-curve and the fourth sub-curve to obtain a comparison result; the step of obtaining capacity compensation data based on thermodynamic discharge data and kinetic discharge data specifically includes the following implementation: in response to a matching comparison result, obtaining capacity compensation data for one cycle of discharge of the battery cell under test based on the thermodynamic discharge data and kinetic discharge data of the reference battery cell; the step of correcting the kinetic capacity data of the battery cell under test using the capacity compensation data to obtain the thermodynamic capacity data of the battery cell under test specifically includes the following implementation: correcting the kinetic capacity data of the battery cell under test using the capacity compensation data after one cycle of discharge, to obtain at least the thermodynamic capacity data of the battery cell under test after one cycle of discharge.

[0072] For example, lithium iron phosphate batteries have relatively small capacity decay values, and the relationship curve between open circuit voltage and discharge capacity after one discharge cycle is very similar to the relationship curve after multiple discharge cycles. Therefore, it is possible to obtain only the thermodynamic discharge data and capacity compensation data of the reference battery cell after one discharge cycle, and use the capacity compensation data to correct at least the kinetic capacity data of the battery cell under test after one discharge cycle.

[0073] This embodiment only acquires the thermodynamic discharge data of a reference battery cell after one discharge cycle, which can shorten the detection cycle of the thermodynamic discharge data of the reference battery cell and thus improve the detection efficiency of battery capacity.

[0074] In some embodiments, the capacity compensation data includes first capacity compensation data and second capacity compensation data. The step of obtaining capacity compensation data based on thermodynamic discharge data and kinetic discharge data specifically includes the following implementation: In response to a mismatch in the comparison result, first capacity compensation data for at least one discharge cycle and second capacity compensation data for the Nth discharge cycle are obtained based on thermodynamic discharge data and N discharge cycles of the reference battery cell, and kinetic discharge data. The step of correcting the kinetic capacity data of the battery cell under test using the capacity compensation data to obtain the thermodynamic capacity data of the battery cell under test specifically includes the following implementation: the first capacity compensation data is used to correct the kinetic capacity data of the battery cell under test for one to (N-1) discharge cycles, and the second capacity compensation data is used to correct the kinetic capacity data of the battery cell under test for N discharge cycles and beyond. Figure 5 As shown; where N is a natural number greater than 1.

[0075] For example, the capacity decay of ternary nickel-cobalt-manganese batteries is relatively large. The relationship curve between open circuit voltage and discharge capacity after one discharge cycle is very different from the relationship curve after multiple discharge cycles. It is possible to obtain at least one discharge cycle and thermodynamic discharge data and first capacity compensation data of a reference battery cell, as well as thermodynamic discharge data and second capacity compensation data after N discharge cycles. The first capacity compensation data is used to correct the kinetic capacity data of the battery cell under test after one to (N-1) discharge cycles, and the second capacity compensation data is used to correct the kinetic capacity data of the battery cell under test after N discharge cycles.

[0076] In this embodiment, only the thermodynamic discharge data of the reference battery cell after multiple discharge cycles are obtained. The kinetic capacity data of the battery cell under test after multiple discharge cycles are corrected by using the capacity compensation data corresponding to the multiple discharge cycles, which can improve the reliability of the thermodynamic capacity data of the battery cell under test.

[0077] The first curve is not static; it gradually changes as the battery cells age. It's generally acceptable to use the first curve from one discharge cycle of the same battery system and design to correct the kinetic capacity data of the tested battery cell. However, when the battery cell is severely aged, the first curve from one discharge cycle no longer matches the first curve from the aged state. In this case, the first curve after aging needs to be used to correct the kinetic capacity of the aged battery cell. The first curve, the specific number of discharge cycles, and the corresponding correction strategy can all be obtained based on the thermodynamic data of a reference battery cell. This correction strategy can be directly used to correct the kinetic capacity data of the tested battery cell after multiple discharge cycles under the same battery system and design.

[0078] For example, such as Figure 2The thermodynamic OCV curves of a reference cell for LFP battery design at the 1st, 100th, and 200th discharge cycles are provided. Figure 3 The relationship between the absolute value of the remaining capacity and the OCV is obtained by fitting the first curve at the 1st, 100th, and 300th discharge cycles, which is the second sub-curve. Figure 4 The first curves for the 1st, 100th, and 300th discharge cycles are provided to fit the relationship between the percentage of remaining capacity and OCV, i.e., the first sub-curve. For LFP battery design, the negative electrode decay is very small in the first 300 cycles, so the fitting results of these three curves are very similar, i.e., multiple second curves match. Therefore, the first curve of the 1st cycle can be used to correct the dynamic capacity data of all cycles of the battery cell under test.

[0079] Furthermore, since the negative electrode of the LFP battery cell has less degradation, the effects of the first and second sub-curve corrections for capacity are similar, with very small errors. Therefore, both methods are acceptable for LFP battery design.

[0080] However, in some other battery designs, the negative electrode degradation is too large. Assuming that the loss of negative electrode material is significant in the Nth cycle, the second curve in the Nth cycle will deviate from the second curve in the previous cycles. That is, multiple second curves are mismatched. In this case, it is necessary to use the second curve of the Nth cycle of the reference battery to correct the dynamic capacity data of the Nth cycle and thereafter of the battery under test.

[0081] like Figure 5 As shown, after correction, a sufficiently long length of thermodynamic cycle data can be obtained (before correction, there were only a dozen or so thermodynamic capacity points). Compared with obtaining capacity data of this length through testing, the time can be greatly shortened, while being almost unaffected by polarization.

[0082] like Figure 6 As shown, the function of the extracted settling voltage in the kinetic cycle is to substitute the settling voltage after each kinetic discharge cycle into the functional relationship. This allows us to determine how much capacity remains unreleased due to polarization and other factors after each kinetic discharge to that potential. Compensating for this unreleased capacity with the corresponding kinetic capacity at that cycle number yields the final value. Figure 5 Complete data on thermodynamic capacity and discharge cycle number.

[0083] In some embodiments, the step of obtaining the discharge end voltage of the battery cell under test specifically includes the following implementation: after discharge, the battery cell under test is left to stand for a preset time, and the voltage after the preset time is obtained, that is, the standing voltage is the discharge end voltage, such as... Figure 6 As shown.

[0084] The preset duration can be 5 minutes, 7 minutes, 9 minutes, etc. For example, after the battery cell under test has discharged, the voltage after standing for 5 minutes is close to the actual open circuit potential, so the voltage after standing can be directly substituted into the above functional relationship.

[0085] This embodiment uses the static voltage as the discharge termination voltage, which can improve the detection efficiency of battery capacity.

[0086] In some embodiments, the step of obtaining the discharge end voltage of the battery cell under test specifically includes the following implementation: after the discharge is completed, the battery under test is left to stand for a preset time, and the voltage after the preset time is obtained as the standing voltage; the standing voltage is fitted using the relaxation formula to obtain the discharge end voltage.

[0087] To improve the accuracy of the discharge termination voltage or to utilize a shorter resting time, a relaxation formula can be used to fit the resting voltage, and the fitted relaxation voltage can be used as the discharge termination voltage. Therefore, this embodiment can improve the measurement accuracy of the discharge termination voltage and shorten the resting time, thereby improving the accuracy and efficiency of battery capacity detection.

[0088] In some embodiments, such as Figure 7 As shown, the battery capacity testing process mainly includes: 1) a preparation stage and 2) a capacity correction stage. In the preparation stage, the relationship between the open-circuit voltage and discharge capacity of the battery cells in the battery system / design is first obtained. This relationship is acquired through the thermodynamic discharge data of the battery cell. Then, this relationship is converted into the relationship between the remaining capacity and the open-circuit voltage, and a functional relationship between the remaining capacity and the open-circuit voltage is obtained through fitting. This functional relationship is used to correct the dynamic capacity data of other battery cells in the same battery system and design. The preparation stage does not need to be repeated for multiple battery cells under test. Given this functional relationship, capacity correction can be performed. In the capacity correction stage, the cycle data of the battery cell under test during the discharge process is first obtained, i.e., the kinetic discharge data. Then, the resting voltage after each discharge cycle is obtained from the cycle data, i.e., the discharge end voltage, and the kinetic capacity data of each discharge cycle is obtained from the cycle data. Then, the discharge end voltage is substituted into the functional relationship to obtain the corresponding remaining capacity. This remaining capacity represents how much capacity the battery cell under test still has not been discharged. Finally, the remaining capacity of the corresponding number of cycles is corrected to the kinetic capacity data of the corresponding number of cycles. Specifically, the sum of the remaining capacity and the kinetic capacity data is obtained as the thermodynamic capacity data of the battery under test, thus obtaining the high-reliability thermodynamic capacity data of the battery under test.

[0089] This application further proposes a battery capacity detection device. In some embodiments, such as Figure 8As shown, the battery capacity detection device includes: a detection module 81, an analysis module 82, and a correction module 83; wherein, the detection module 81 is used to acquire the thermodynamic discharge data of a reference battery cell and the kinetic discharge data of the battery cell under test; wherein, the reference battery cell and the battery cell under test belong to the same battery system and the same battery design; the analysis module 82 is used to acquire capacity compensation data based on the thermodynamic discharge data and the kinetic discharge data; the correction module 83 is used to correct the kinetic capacity data of the battery cell under test using the capacity compensation data to obtain the thermodynamic capacity data of the battery cell under test.

[0090] This embodiment only requires obtaining the thermodynamic discharge data of a single cell within the same battery system and battery design, as well as the kinetic discharge data of the battery under test, to obtain the thermodynamic capacity data of the battery under test. Since the acquisition cycle for thermodynamic discharge data is much longer than that for kinetic discharge data, but its reliability is high, and this application does not require obtaining the thermodynamic discharge data of the battery under test, this application can shorten the battery capacity testing cycle and obtain highly reliable thermodynamic capacity data, thereby improving the accuracy of battery capacity testing.

[0091] The working principle of the battery capacity testing device can be found in the embodiments of the above testing method.

[0092] This application further proposes a battery capacity detection device. In some embodiments, such as Figure 9 As shown, the terminal includes a memory 91 and a processor 92 coupled to each other. The processor 92 is used to execute program instructions stored in the memory 91 to implement the steps of any of the above-described battery capacity detection method embodiments. In a specific implementation scenario, the terminal may include, but is not limited to, a microcomputer or a server. In addition, the terminal may also include, but is not limited to, mobile devices such as laptops and tablets.

[0093] Specifically, processor 92 controls itself and memory 91 to implement the steps of any of the battery capacity detection method embodiments described above. Processor 92 can also be referred to as a CPU (Central Processing Unit). Processor 92 may be an integrated circuit chip with signal processing capabilities. Processor 92 can also be a general-purpose processor, digital signal processor (DSP), application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. A general-purpose processor can be a microprocessor or any conventional processor. Furthermore, processor 92 can be implemented using integrated circuit chips.

[0094] This embodiment only requires obtaining the thermodynamic discharge data of a single cell within the same battery system and battery design, as well as the kinetic discharge data of the battery under test, to obtain the thermodynamic capacity data of the battery under test. Since the acquisition cycle for thermodynamic discharge data is much longer than that for kinetic discharge data, but its reliability is high, and this application does not require obtaining the thermodynamic discharge data of the battery under test, this application can shorten the battery capacity testing cycle and obtain highly reliable thermodynamic capacity data, thereby improving the accuracy of battery capacity testing.

[0095] This application further proposes a battery capacity detection device. In some embodiments, such as Figure 10 As shown, the computer-readable storage medium 100 stores program instructions 101 that can be executed by a processor. The program instructions 101 are used to implement the steps of any of the above-described embodiments of the battery capacity detection method.

[0096] This embodiment only requires obtaining the thermodynamic discharge data of a single cell within the same battery system and battery design, as well as the kinetic discharge data of the battery under test, to obtain the thermodynamic capacity data of the battery under test. Since the acquisition cycle for thermodynamic discharge data is much longer than that for kinetic discharge data, but its reliability is high, and this application does not require obtaining the thermodynamic discharge data of the battery under test, this application can shorten the battery capacity testing cycle and obtain highly reliable thermodynamic capacity data, thereby improving the accuracy of battery capacity testing.

[0097] In some embodiments, the functions or modules of the apparatus provided in this disclosure can be used to perform the methods described in the above method embodiments. The specific implementation can be referred to the description of the above method embodiments, and for the sake of brevity, it will not be repeated here.

[0098] The description of the various embodiments above tends to emphasize the differences between the various embodiments. The similarities or similarities between them can be referred to, and for the sake of brevity, they will not be repeated here.

[0099] In the several embodiments provided in this application, it should be understood that the disclosed methods and apparatus can be implemented in other ways. For example, the apparatus implementations described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the mutual coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection of devices or units may be electrical, mechanical, or other forms.

[0100] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0101] If the integrated unit is implemented as 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 this application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) or processor to execute all or part of the steps of the methods of various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A method for detecting battery capacity, characterized in that, The detection method includes: Acquire thermodynamic discharge data of a reference battery cell and kinetic discharge data of a battery cell under test; wherein the reference battery cell and the battery cell under test belong to the same battery design within the same battery system; Capacity compensation data is obtained based on the thermodynamic discharge data and the kinetic discharge data; The kinetic capacity data of the battery cell under test is corrected using the capacity compensation data to obtain the thermodynamic capacity data of the battery cell under test.

2. The detection method according to claim 1, characterized in that, The thermodynamic discharge data includes the open-circuit voltage and first discharge capacity of the reference battery cell, and the kinetic discharge data includes the discharge termination voltage and second discharge capacity of the battery cell under test. Capacity compensation data is obtained based on the thermodynamic discharge data and the kinetic discharge data, including: A first relationship is obtained based on the open-circuit voltage and the first discharge capacity. The first relationship is the relationship between the remaining capacity of the reference battery cell and the open-circuit voltage. Based on the first relationship, the remaining capacity corresponding to the discharge end voltage is obtained as capacity compensation data.

3. The detection method according to claim 2, characterized in that, The first relationship includes a functional relationship. The step of obtaining the first relationship between the remaining capacity and open-circuit voltage of the reference battery cell based on the open-circuit voltage and the first discharge capacity includes: A first curve is obtained based on the open-circuit voltage and the first discharge capacity. The first curve is the relationship curve between the open-circuit voltage and the discharge capacity of the reference battery cell. The first curve is converted into a second curve, which is the relationship between the open-circuit voltage and the remaining capacity of the reference battery cell. The functional relationship is obtained based on the second curve.

4. The detection method according to claim 3, characterized in that, The step of converting the first curve into a second curve, wherein the second curve is the relationship curve between the open-circuit voltage and the remaining capacity of the reference battery cell, includes: Based on the discharge end voltage, obtain the third curve corresponding to the discharge end stage of the reference battery cell from the first curve; The third curve is converted into a second curve, which is the relationship between the open-circuit voltage and the remaining capacity of the reference battery cell at the end of the discharge stage.

5. The detection method according to claim 3 or 4, characterized in that, The second curve includes a first sub-curve and a second sub-curve. The first sub-curve is the relationship curve between the open-circuit voltage of the reference battery cell and the percentage of its remaining capacity. The second sub-curve is the relationship curve between the open-circuit voltage of the reference battery and the absolute value of its remaining capacity.

6. The detection method according to any one of claims 3 to 5, characterized in that, The detection method further includes: At least the second curve corresponding to one discharge cycle of the reference battery cell is obtained as the third sub-curve, and the second curve corresponding to N discharge cycles is obtained as the fourth sub-curve; The comparison results are obtained by comparing at least the third sub-curve and the fourth sub-curve. The process of obtaining capacity compensation data based on the thermodynamic discharge data and the kinetic discharge data includes: If the comparison result is a match, the capacity compensation data of the battery cell under test for one discharge cycle is obtained based on the thermodynamic discharge data of the reference battery cell for one discharge cycle and the kinetic discharge data. The step of correcting the kinetic capacity data of the battery cell under test using the capacity compensation data to obtain the thermodynamic capacity data of the battery cell under test includes: The kinetic capacity data of the battery cell under test is corrected using the capacity compensation data from one discharge cycle, so as to obtain at least the thermodynamic capacity data of the battery cell under test after one discharge cycle.

7. The detection method according to any one of claims 1 to 6, characterized in that, The capacity compensation data includes first capacity compensation data and second capacity compensation data. The process of obtaining capacity compensation data based on the thermodynamic discharge data and the kinetic discharge data includes: In response to the comparison result being a mismatch, the first capacity compensation data and the second capacity compensation data for the test battery cell after at least one discharge cycle are obtained based on the thermodynamic discharge data of the reference battery cell after at least one discharge cycle, the thermodynamic discharge data after N discharge cycles, and the kinetic discharge data. The step of correcting the kinetic capacity data of the battery cell under test using the capacity compensation data to obtain the thermodynamic capacity data of the battery cell under test includes: The first capacity compensation data is used to correct the kinetic capacity data of the battery cell under test after one to (N-1) discharge cycles, and the second capacity compensation data is used to correct the kinetic capacity data of the battery cell under test after N discharge cycles. Wherein, N is a natural number greater than 1.

8. The detection method according to any one of claims 2 to 7, characterized in that, Obtaining the discharge termination voltage includes: After the discharge is completed, the battery cell under test is left to stand for a preset time, and the voltage after the preset time is obtained as the discharge end voltage.

9. The detection method according to any one of claims 2 to 7, characterized in that, Obtaining the discharge termination voltage includes: After the discharge is completed, the battery under test is left to stand for a preset time, and the voltage after the preset time is obtained as the standing voltage. The discharge termination voltage is obtained by fitting the resting voltage using the relaxation formula.

10. A battery capacity detection device, characterized in that, The battery capacity detection device includes: The detection module is used to acquire thermodynamic discharge data of a reference battery cell and kinetic discharge data of a battery cell under test; wherein the reference battery cell and the battery cell under test belong to the same battery design of the same battery system. The analysis module is used to obtain capacity compensation data based on the thermodynamic discharge data and the kinetic discharge data; The correction module is used to correct the kinetic capacity data of the battery cell under test using the capacity compensation data, so as to obtain the thermodynamic capacity data of the battery cell under test.

11. A terminal, characterized in that, The terminal includes a memory, a processor, and a computer program stored in the memory and running on the processor, the processor being used to execute program data to implement the battery capacity detection method as described in any one of claims 1 to 9.

12. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the battery capacity detection method as described in any one of claims 1 to 9.

Images