Leakage current detection method and detection system thereof

Abstract

The application discloses a leakage current detection method and a detection system thereof. The detection method comprises the following steps: connecting a standard battery and a battery to be detected in parallel; removing the connection between the standard battery and the battery to be detected when the voltage of the standard battery and the battery to be detected reaches balance; placing the battery to be detected for a preset first time; connecting an ammeter between the battery to be detected and the standard battery after the first time; and calculating the leakage current value of the battery to be detected according to the current reading of the ammeter and the self-discharge parameter of the standard battery. The method can quickly and accurately calculate the real leakage current of the battery to be detected through the standard battery with known self-discharge parameters. Accordingly, appropriate battery screening standards can be formulated, and false positives or false negatives can be avoided.

Description

Technical Field

[0001] This application relates to the field of battery self-discharge detection, specifically to a leakage current detection method and its detection system. Background Technology

[0002] Due to limitations in process scale, technological level, and cell voltage, current power battery energy storage systems used in large equipment such as electric vehicles are typically composed of multiple cells connected in series or parallel. To avoid the energy bottleneck effect, high consistency in self-discharge among the cells within the same power battery energy storage system is required.

[0003] Therefore, screening out cells with significantly excessive self-discharge rates from a large number of cells is a crucial step in the manufacturing process of power battery energy storage systems. Currently, the commonly used screening method is to detect the cell's K-value (i.e., the voltage drop of the cell per unit time). However, this method has drawbacks such as being time-consuming and cannot adequately meet the needs of screening for abnormal self-discharge. Summary of the Invention

[0004] In view of the above problems, this application provides a leakage current detection method and system, which can effectively overcome at least some of the defects of traditional detection methods.

[0005] Firstly, this application provides a leakage current detection method. The leakage current detection method includes: connecting a standard battery cell and a battery cell under test in parallel; disconnecting the standard battery cell and the battery cell under test when voltage equilibrium is achieved; allowing the battery cell under test to stand still for a preset first time; connecting an ammeter between the battery cell under test and the standard battery cell after the first time of standing still; and calculating the leakage current value of the battery cell under test based on the ammeter reading and the self-discharge parameters of the standard battery cell.

[0006] In the technical solution of this application embodiment, the specific leakage current of the cell under test can be quickly and accurately calculated using a standard cell with known self-discharge parameters. The calculated leakage current result is a true leakage current value, which can be used to formulate appropriate cell screening standards without easily causing erroneous screening results.

[0007] In some embodiments, the leakage current detection method further includes: determining that the standard cell and the cell under test have reached voltage balance after a preset second time interval between the parallel-connected standard cell and the cell under test. The above technical solution provides a method for determining whether the standard cell and the cell under test have reached voltage balance by connecting them in parallel for a certain period of time. This method of determining whether voltage balance has been achieved is easy to implement and simple to operate.

[0008] In some embodiments, the second time is 6 to 10 hours. The above technical solution provides an optimal voltage equalization time, which on the one hand ensures that the two cells achieve voltage equalization, and on the other hand avoids unnecessary voltage equalization time.

[0009] In some embodiments, the step of calculating the leakage current value of the cell under test based on the current reading of the ammeter and the self-discharge parameters of the standard cell specifically includes: calculating a first voltage value that the standard cell reduces after a first time using the self-discharge parameters; calculating a second voltage value that the cell under test reduces after a first time based on the current reading and the first voltage value; and calculating the leakage current value of the cell under test based on the second voltage value.

[0010] The technical solution of this application embodiment provides a method to calculate the true leakage current value of the cell under test by correspondingly converting the voltage change between the standard cell and the cell under test after a first time. This method of calculating the true leakage current value can reuse the self-discharge parameters of a standard cell and is easy to implement.

[0011] In some embodiments, the self-discharge parameters of the standard battery cell include: the leakage current value of the standard battery cell and the electrical energy contained in the standard battery cell within a unit voltage range. The above technical solution provides specific self-discharge parameters required to calculate the first voltage value. Such self-discharge parameters are easily obtained using existing detection methods.

[0012] In some embodiments, the first voltage value can be calculated using the following formula (1), the second voltage value can be calculated using the following formula (2), and the leakage current value of the cell under test can be calculated using the following formula (3):

[0013]

[0014] V2 = V1 + R × I read (2)

[0015]

[0016] Where V1 is the first voltage value, I leak1 Here, T represents the leakage current value of a standard battery cell, dq / dv represents the electrical energy contained within a unit voltage range, and V2 represents the second voltage value. read The reading is the current, where R is the internal resistance of the ammeter; I leak2 Let T be the leakage current value of the cell under test, T be the first time interval, and dq / dv be the electrical energy contained within a unit voltage range. The above technical solution provides specific calculation formulas for the first voltage value, the second voltage value, and the leakage current of the cell under test. These formulas allow for the rapid calculation of the actual leakage current of the cell under test.

[0017] In some embodiments, the leakage current detection method further includes: acquiring the OCV-SOC curve of a standard battery cell; determining, within the test voltage range, the electrical energy contained in the standard battery cell under test within a unit voltage range from the OCV-SOC curve; wherein the test voltage range is the voltage range in which the battery cell under test is located when it is at rest. The above technical solution provides a method for obtaining the required self-discharge parameters using the OCV-SOC curve. The OCV-SOC curve of the battery cell can be obtained using mature detection methods, facilitating quick and simple acquisition of the required self-discharge parameters.

[0018] In some embodiments, the standard cell and the cell under test are of the same type, and the leakage current value of the standard cell is 10-5000uA. The above technical solution provides specific conditions that the standard cell should meet. Using a cell of the same type that meets the above leakage current conditions as the standard cell helps improve the accuracy of leakage current detection.

[0019] In some embodiments, the aforementioned first time is 6-7 hours. The above technical solution provides an optimal detection time, which on the one hand ensures that a sufficient voltage difference can accumulate between the cell under test and the standard cell. On the other hand, it avoids unnecessary detection time, thus shortening the total time required for leakage current detection.

[0020] Secondly, this application provides a leakage current detection system. The leakage current detection system includes: a potential equalization device for connecting the cell under test and a standard cell in parallel to perform potential equalization; a cell resting device for disconnecting the connection between the cell under test and the standard cell after potential equalization, allowing the cell under test to rest; a current detection device for connecting an ammeter between the cell under test and the standard cell after the cell under test has rested; a storage device for recording self-discharge parameters determined by the test results of the standard cell; and a calculation device for calculating the leakage current value of the cell under test based on the ammeter reading and the self-discharge parameters.

[0021] In the technical solution of this application embodiment, the leakage current detection system can quickly and accurately calculate the specific leakage current of the cell under test using a standard cell with known self-discharge parameters. Since the leakage current detection result is the actual leakage current of the cell under test, more accurate cell screening standards can be formulated based on this, improving the accuracy of screening cells with abnormal self-discharge.

[0022] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, specific embodiments of this application are given below. Attached Figure Description

[0023] 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:

[0024] Figure 1 This is a schematic diagram of the leakage current detection system according to some embodiments of this application;

[0025] Figure 2 This is a flowchart of a leakage current detection method according to some embodiments of this application;

[0026] Figure 3 This is a flowchart of a leakage current detection method according to some other embodiments of this application;

[0027] Figure 4 This is a flowchart illustrating a method for calculating the leakage current of a battery cell under test according to some embodiments of this application, showing a method for calculating leakage current based on self-discharge parameters and current readings;

[0028] Figure 5 This is a flowchart illustrating a method for determining the electrical energy contained within a unit voltage range according to some embodiments of this application, showing a method for obtaining the electrical energy contained within a unit voltage range based on the OCV-SOC curve;

[0029] Figure 6 This is a functional block diagram of a leakage current calculation device according to some embodiments of this application;

[0030] Figure 7 This is a schematic diagram of an electronic device according to some embodiments of this application. Detailed Implementation

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0036] 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).

[0037] 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.

[0038] 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.

[0039] Currently, typical methods for screening battery cell self-discharge anomalies mainly rely on detecting the K-value, which measures whether the battery's voltage drop per unit time meets requirements. However, the voltage change caused by cell self-discharge is relatively weak, especially for large-capacity batteries. Therefore, this voltage drop-based self-discharge detection method suffers from problems such as long processing time.

[0040] In principle, cell self-discharge is caused by the spontaneous decrease in electronic voltage due to factors such as chemical side reactions and micro-short circuits within the cell. Therefore, the leakage current of the cell, compared to the voltage drop, is a more direct and accurate indicator of the magnitude of cell self-discharge.

[0041] The applicant notes that typical cell leakage current detection methods only detect relative current changes within the cell. Such relative current changes are difficult to use to formulate appropriate cell screening criteria. Screening criteria based on relative current changes can easily lead to both over-selection and under-selection of cells. Over-selection refers to screening criteria that are too strict, resulting in the incorrect exclusion of many cells whose self-discharge characteristics do not significantly deviate from normal values. Under-selection refers to screening criteria that are too lenient, resulting in the failure to correctly exclude cells whose self-discharge characteristics significantly deviate from normal values.

[0042] To address the challenge of establishing suitable cell screening criteria based on relative current changes, the applicant has proposed a technical solution for leakage current detection using standard cells. This solution uses standard cells with known self-discharge parameters as a benchmark to detect the leakage current of the cell under test. The detected leakage current is the true leakage current of the cell under test, rather than a relative current change. Therefore, suitable cell screening criteria can be established based on this, significantly reducing the risk of over- or under-selection of cells.

[0043] To fully illustrate the specific application scenarios of this application, the following description uses two identical battery cells as examples. Of course, those skilled in the art will understand that, based on the same principles and concepts, the leakage current detection system of this application can also be applied to the detection of other quantities and types of leakage current, thereby obtaining the true leakage current value of a specific battery cell.

[0044] Please see Figure 1 , Figure 1 This is a schematic diagram of the structure of a leakage current detection system according to some embodiments of this application. The leakage current detection system includes: a potential equalization device 110, a cell resting device 120, a current detection device 130, a storage device 140, and a computing device 150.

[0045] The potential equalization device 110 is used to achieve potential equalization between the standard cell S and the cell B under test. It can be implemented using wires or any other suitable type of electrical connection component, as long as it allows for parallel connection between multiple cells. For example, Figure 1 The connecting wires are shown.

[0046] A "standard cell" is a cell that has undergone one or more tests and whose self-discharge parameters are known. A "cell under test" is a cell that has not yet been tested and needs to be tested to determine its true leakage current value.

[0047] The cell settling device 120 is a device used to disconnect the standard cell and the cell under test B from each other and set them aside for a certain period of time to demonstrate their self-discharge characteristics. In this embodiment, the term "settling device" is used for convenience of description, but it can be implemented in any suitable way and is not limited to a physical device. For example, it can be a specific placement location or storage space, as long as it is large enough to accommodate the standard cell S and the cell under test B.

[0048] The current detection device 130 is used to obtain the magnitude of the current between the standard cell S and the cell B under test. Specifically, any suitable type of current detection instrument can be used, as long as it has sufficient current detection accuracy. In this embodiment, the term "ammeter" is used to refer to a detection device capable of displaying the magnitude of the current passing through its circuit.

[0049] In some embodiments, please refer to Figure 1 The current detection device 130 can be a device that electrically connects the negative terminals of the standard cell S and the cell B under test through a wire, and connects an ammeter A between the positive terminals of the standard cell S and the cell B under test.

[0050] Of course, the position of ammeter A can be adjusted according to actual needs to provide corresponding current readings, and is not limited to this. Figure 1 As shown.

[0051] Storage device 140 is a data storage device used to record data information. Specifically, it can be any suitable type of device capable of storing data information for a long time and being searchable and retrieved, such as a cloud database and a locally deployed storage device.

[0052] The self-discharge parameters of the standard cell S can be obtained by a series of self-discharge detection methods and can be pre-recorded in the storage device 140 in any suitable form for subsequent operation.

[0053] The computing device 150 refers to an electronic computing device with logic operation functions, including but not limited to servers or industrial computers. It can establish a communication connection with the ammeter A of the current detection device 130 and the storage device 140 through wired or wireless means, thereby receiving the current reading collected by the ammeter A and the self-discharge parameters recorded in the storage device 140, and calculating the actual leakage current of the cell B under test through a series of pre-set calculation steps.

[0054] Of course, for the sake of simplicity, in Figure 1 The above-described storage device 140 and computing device 150, which have different functions, are shown with different illustrations. However, those skilled in the art will understand that in other embodiments, the storage device 140 and computing device 150 can be integrated into the same device, and the implementation is not limited to this. Figure 1 As shown, for example, the self-discharge parameters of a standard battery cell S can be pre-stored in a computer's storage medium (such as flash memory).

[0055] During operation, the standard cell S and the cell under test B are connected in parallel via the potential equalization device 110 to achieve potential equalization. After potential equalization, when the voltages of the standard cell S and the cell under test B are consistent, the electrical connection between the two cells is removed via the cell resting device 120, and the cells are allowed to rest for a period of time. After the preset resting time has elapsed, an ammeter A is reconnected between the standard cell S and the cell under test via the current detection device 130 to detect the current flowing between the two cells. Finally, the calculation device 150 retrieves the self-discharge parameters determined by the test results of the standard cell S from the storage device 140, and calculates the actual leakage current value of the cell under test B based on the self-discharge parameters and the current reading of the ammeter A.

[0056] One advantage of this application's embodiments is that, based on the detected current flowing between the parallel-connected standard cell and the cell under test, and given the known self-discharge parameters of the standard cell, the true leakage current value of the cell under test can be calculated. This true leakage current value is beneficial for developing appropriate self-discharge anomaly screening criteria, avoiding over-detection and false detection.

[0057] Another advantage of this application embodiment is that the self-discharge parameters of the standard cell can be repeatedly applied to the leakage current detection of multiple cells under test, without having to retest in each test process, which effectively improves the testing efficiency.

[0058] According to some embodiments of this application, Figure 2 This is a flowchart illustrating a leakage current detection method according to some embodiments of this application. This leakage current detection method can be executed by the aforementioned leakage current detection system. Please refer to... Figure 2The leakage current detection method includes:

[0059] S201, Connect the standard cell and the cell under test in parallel.

[0060] "Cell under test" refers to an energy storage component that has been manufactured and requires leakage current testing to obtain its true leakage current value. It can be a single cell or a battery module composed of multiple cells. "Standard cell" refers to an energy storage component that has undergone a series of self-discharge related tests and whose self-discharge parameters are known.

[0061] The cell under test and the standard cell may have different self-discharge characteristics. By connecting them in parallel for a period of time, the voltage values ​​of the two cells can be made to be consistent due to the characteristics of the parallel connection.

[0062] S203. When the standard cell and the cell under test are connected in parallel and the voltage is balanced, disconnect the standard cell and the cell under test.

[0063] "Voltage equalization" refers to the voltage values ​​of multiple battery cells reaching a basic consistency. Battery cells that have achieved voltage equalization can be considered to have the same degree of self-discharge, which can serve as a starting point for comparing the self-discharge characteristics of two battery cells. "Removal" refers to disconnecting the electrical connection between the standard battery cell and the battery cell under test, so that the two will not affect each other.

[0064] S205, Set the battery cell under test to stand for a preset first time.

[0065] The "first time" setting is a time value set by technicians based on actual needs. In a static state, the cell under test and the standard cell will release their stored charge according to their respective self-discharge characteristics.

[0066] S207. Connect an ammeter between the cell to be tested and the standard cell after the first resting time.

[0067] As described above, during the resting process, due to the different self-discharge characteristics between the test cell and the standard cell, the amount of electricity released by them per unit time will also differ. This difference, after accumulating over time, will manifest as a voltage difference between the standard cell and the test cell. Therefore, the voltage difference can be obtained by connecting an ammeter between the standard cell and the test cell and observing the ammeter's current reading.

[0068] S209. Calculate the leakage current value of the cell under test based on the current reading of the ammeter and the self-discharge parameters of the standard cell.

[0069] Among them, "self-discharge parameters" are one or more parameter data related to the self-discharge characteristics of the battery cell, obtained by conducting self-discharge characteristic tests on standard battery cells in advance.

[0070] Therefore, by obtaining current readings that can represent the difference in self-discharge levels between the cell under test and the standard cell, the actual leakage current value of the cell under test can be calculated by combining the self-discharge parameters.

[0071] One advantage of this application is that the true leakage current of the cell under test can be quickly and accurately calculated using a standard cell with known self-discharge parameters. Cell screening criteria based on this true leakage current are more precise and less prone to erroneous screening results.

[0072] According to the embodiments of this application, optionally, please refer to... Figure 3 , Figure 3 This is a flowchart illustrating a leakage current detection method provided in other embodiments of this application. Besides... Figure 2 In addition to the steps shown, the leakage current detection method may further include the following after step S201:

[0073] S202. After a preset second time has elapsed between the standard cell and the cell under test connected in parallel, determine that the standard cell and the cell under test have reached voltage balance.

[0074] The preset second time is a time set by technicians based on the actual situation of the battery cell, such as capacity and type, and indicates the length of time that the standard battery cell and the battery cell under test need to be connected in parallel.

[0075] One of the advantages of this application's embodiments is that the detection method of determining whether voltage balance is achieved between the standard cell and the cell under test based on the parallel connection time between them is easy to implement and simple to operate, and can be well applied in actual testing.

[0076] In some embodiments, the second time can optionally be set to a value between 6 hours and 10 hours. On the one hand, as the parallel connection time between the standard cell and the cell under test continues to increase, the voltage values ​​between the two will become more consistent, achieving a higher degree of voltage balance. On the other hand, the longer the potential balancing operation takes, the longer the detection time consumed in detecting the leakage current of the cell under test will be, thus it is always desirable to shorten the required detection time as much as possible.

[0077] Therefore, in the process of realizing this application, it was surprisingly found that setting the second time to a value between 6 and 10 hours can well balance the above two needs, and can ensure voltage balance between the cell under test and the standard cell while shortening the detection time as much as possible, thus avoiding unnecessary parallel connection time.

[0078] According to some embodiments of this application, optionally, please refer to Figure 4 , Figure 4 A flowchart illustrating the method for calculating the leakage current value of a battery cell under test, provided in an embodiment of this application. Step S209 specifically includes:

[0079] S2091. Calculate the first voltage drop of the standard cell after the first time using the self-discharge parameters.

[0080] Given suitable self-discharge parameters, the voltage drop of a standard battery cell after being left to stand for a first time can be directly calculated. In this embodiment, the term "first voltage value" is used to represent the voltage drop of the standard battery cell after the first time of self-discharge due to the accumulated energy loss.

[0081] The specific self-discharge parameters used can be determined according to actual needs; it is sufficient to calculate the first voltage value.

[0082] In some embodiments, the self-discharge parameters may optionally include: the leakage current value of a standard cell and the electrical energy contained in a standard cell within a unit voltage range. These self-discharge parameters are commonly used and can be easily obtained using existing detection methods.

[0083] S2092. Based on the current reading and the first voltage value, calculate the second voltage value that the cell under test decreases after the first time.

[0084] Here, "current reading" represents the magnitude of the current flowing between the standard cell and the cell under test, from which the voltage difference between the two cells can be calculated. Knowing the first voltage value, the voltage drop of the cell under test after a first period of self-discharge can be calculated. In this embodiment, to distinguish it from the voltage drop of the standard cell, the term "second voltage value" is used.

[0085] S2093. Calculate the leakage current value of the cell under test based on the second voltage value.

[0086] As described above, the second voltage value is due to the energy lost by the battery cell under test during its self-discharge in the first time period. Therefore, given the second voltage value, the actual leakage current value of the battery cell under test can be calculated using an appropriate method.

[0087] One advantage of this application is that it provides a method to calculate the true leakage current value of the cell under test by correspondingly converting the voltage change between the standard cell and the cell under test after a first time. In this method of calculating the true leakage current value, the self-discharge parameters of the same standard cell can be reused in multiple different cells under test without needing to be tested again, which can well meet the needs of practical use.

[0088] Based on some embodiments of this application, the following uses the self-discharge parameters of a standard battery cell as examples, specifically the leakage current value of the standard battery cell and the electrical energy contained in the standard battery cell within a unit voltage range, to provide detailed calculation methods for the aforementioned first voltage value, second voltage value, and leakage current value, in order to fully illustrate... Figure 4 Steps S2091, S2092, and S2093 are shown.

[0089] First, the first voltage value can be calculated using the following formula (1):

[0090]

[0091] Where V1 is the first voltage value, I leak1 Here, dq / dv represents the leakage current value of a standard battery cell, T represents the first time, and dq / dv represents the electrical energy contained within a unit voltage range.

[0092] Secondly, based on the calculated first voltage value, the second voltage value can be calculated using the following formula (2):

[0093] V2 = V1 + R × I read (2)

[0094] Where V2 is the second voltage value, I read R is the current reading, and R is the internal resistance of the ammeter.

[0095] Finally, based on the calculated second voltage value, the leakage current value of the cell under test can be calculated using the following formula (3):

[0096]

[0097] Among them, I leak2 dq / dv represents the leakage current value of the cell under test, T represents the first time, and dq / dv represents the electrical energy contained within a unit voltage range.

[0098] One advantage of this application is that it provides specific calculation formulas for the first voltage value, the second voltage, and the leakage current of the cell under test, given the known leakage current value of a standard cell and the electrical energy contained within a unit voltage range. These formulas allow a computer or similar electronic computing platform to quickly calculate the actual leakage current of the cell under test.

[0099] It should be noted that, based on the principle of calculating the leakage current value of the battery cell under test disclosed in the embodiments of this application, those skilled in the art can also adjust, replace or delete one or more of the above calculation formulas according to different actual situations (such as different self-discharge parameters selected), and are not limited to the formulas described in the embodiments of this application.

[0100] According to some embodiments of this application, optionally, please refer to Figure 5 , Figure 5 A flowchart illustrating a method for obtaining the electrical energy contained in a standard battery cell within a unit voltage range, as provided in this application embodiment. The method specifically includes:

[0101] S501. Obtain the OCV-SOC curve of a standard battery cell.

[0102] Open circuit voltage (OCV) refers to the potential difference between the positive and negative terminals of a battery cell when it is in an open-circuit state and not being discharged. State of charge (SOC) is a parameter used to reflect the remaining capacity of a battery cell.

[0103] By plotting the test results obtained during the testing process on a coordinate system with OCV as the ordinate and SOC as the abscissa, a curve representing the correlation between the open-circuit voltage value and the electrical energy stored in the cell can be obtained. In this embodiment, for simplicity, such a curve is described as an "OCV-SOC curve". The specific test method for obtaining the OCV-SOC curve is well known to those skilled in the art and will not be elaborated here.

[0104] S502. Determine the test voltage range of the standard cell when it is at rest.

[0105] The "test voltage range" refers to the voltage range formed by the change in open-circuit voltage of the standard cell or the cell under test during the initial static period (i.e., step S205), from the start to the end of static state. This range can be easily determined using a voltmeter or similar voltage testing instrument.

[0106] S503. Obtain the electrical energy contained in the OCV-SOC curve within the unit voltage range of the test voltage range.

[0107] The electrical energy contained within a unit voltage range can be considered as the corresponding reduction in cell capacity when the open-circuit voltage of the cell drops by one unit voltage. This can be determined from the OCV-SOC curve, for example, by calculating the difference between the electrical energy stored in the cell corresponding to two voltage values ​​that differ by a specific voltage unit (e.g., 1 mV).

[0108] In a typical OCV-SOC curve, there are always significant differences in the slope of the curve across different voltage ranges. Therefore, it is necessary to select an appropriate voltage range so that the electrical energy contained within a unit voltage range meets the actual needs.

[0109] One advantage of this application is that it provides a method for obtaining the electrical energy contained within a unit voltage range using the OCV-SOC curve. The electrical energy contained within a unit voltage range obtained in this way can match the actual testing conditions of a standard battery cell, which helps improve the detection accuracy of the true leakage current of the battery cell under test.

[0110] In some embodiments, optionally, a battery cell of the same type as the battery cell under test is selected as a standard battery cell. Furthermore, the leakage current value of this standard battery cell is 10-5000uA.

[0111] The standard battery cell needs to be controlled within a suitable leakage current range. If the leakage current value required for the standard battery cell is too high, the difference between the tested cell and the standard cell may be too large, making it difficult to distinguish between them. Conversely, if the leakage current value of the standard battery cell is too low, it may cause similar problems because it cannot be effectively identified by an ammeter.

[0112] Therefore, in the process of realizing this application, it was surprisingly discovered that setting the leakage current value of the standard battery cell to 10-5000uA can effectively ensure the accuracy of leakage current detection.

[0113] In some embodiments, the aforementioned first time period can optionally be set to a value between 6 and 7 hours. On the one hand, as the resting time continues to increase, the differences accumulated between the standard cell and the cell under test due to their different self-discharge characteristics will become larger and larger, which is more conducive to improving the detection accuracy. On the other hand, the longer the resting time, the longer the detection time consumed in detecting the leakage current of the cell under test, so it is always desirable to shorten the required detection time as much as possible.

[0114] Therefore, in the process of realizing this application, it was surprisingly found that setting the first time to a value between 6 and 7 hours can well balance the above two needs, and can ensure that sufficient difference is accumulated between the cell under test and the standard cell while shortening the detection time as much as possible, so as to ensure the accuracy of leakage current detection.

[0115] The following provides several specific examples to fully illustrate the specific implementation of each step of the leakage current detection method in the embodiments of this application.

[0116] Example 1:

[0117] 1) Select a standard cell of the same type as the cell under test, which has been stored for 90 days. Using the constant voltage method and compensation current self-discharge leakage current test methods, the leakage current of the standard cell is measured to be 800uA. The non-polarized OCV-SOC curve of the standard cell is measured using the relevant non-polarized OCV-SOC method.

[0118] In the OCV-SOC curve, the electrical energy (i.e., dq / dv) contained in the standard cell within a unit voltage range of the test voltage range is determined to be 80mAh / mV.

[0119] 2) Connect the standard cell and the cell under test in parallel to perform potential equalization. After the standard cell and the cell under test are connected in parallel for 6 hours, remove the parallel connection between them and let them stand for 6 hours.

[0120] 3) After the resting period, connect an ammeter with an internal resistance of 0.2Ω between the standard cell and the cell under test for testing. The ammeter reading should be 50µA. The total circuit resistance at this point can be roughly represented by the ammeter's internal resistance.

[0121] 4) First, the voltage change of the standard cell after the first resting time is calculated by formula (1): 800uA*6h / 80mAh / mV=60uV.

[0122] Then, the voltage change of the cell under test after the first time of rest is calculated according to formula (2): 0.2Ω*50uA+60uV=70uV.

[0123] Finally, given the known voltage change, the actual leakage current of the cell under test is calculated using formula (3) as 70uV*80mAh / mV / 6h=933uA.

[0124] Example 2:

[0125] 1) Select a standard cell of the same type as the cell under test, which has been stored for 120 days. Using the constant voltage method and compensation current and other self-discharge leakage current test methods, the leakage current of the standard cell is measured to be 750uA. The non-polarized OCV-SOC curve of the standard cell is measured using the relevant non-polarized OCV-SOC method.

[0126] In the OCV-SOC curve, the electrical energy (i.e., dq / dv) contained in the standard cell within a unit voltage range of the test voltage range is determined to be 80mAh / mV.

[0127] 2) Connect the standard cell and the cell under test in parallel to perform potential equalization. After the standard cell and the cell under test are connected in parallel for 10 hours, remove the parallel connection between them and let them stand for 7 hours.

[0128] 3) After the settling period, connect an ammeter with an internal resistance of 0.2Ω between the standard cell and the cell under test for testing. The ammeter reading should be 50µA. The total circuit resistance at this point can be roughly represented by the ammeter's internal resistance.

[0129] 4) First, the voltage change of the standard cell after the first resting time is calculated using formula (1): 750uA*7h / 80mAh / mV=65.63uV.

[0130] Then, the voltage change of the cell under test after the first time of rest is calculated according to formula (2): 0.2Ω*100uA+65.63uV=85.63uV.

[0131] Finally, given the voltage change, the actual leakage current of the battery cell under test can be calculated using formula (3): 85.63uV*80mAh / mV / 7h=978.63uA.

[0132] One advantage of this application's embodiments is that by connecting it in parallel with a standard battery cell and allowing it to stand for a preset time, the true leakage current value of the battery cell under test can be quickly calculated using self-discharge parameters related to the self-discharge characteristics of the standard battery cell. Furthermore, the self-discharge parameters of the standard battery cell can be reused multiple times in the leakage current detection of similar battery cells under test, eliminating the need for tedious re-testing and thus shortening the detection time.

[0133] According to some embodiments of this application, please refer to Figure 6 , Figure 6 This is a leakage current calculation device according to an embodiment of the present application. The leakage current calculation device 600 includes: a first voltage value calculation module 610, a second voltage value calculation module 620, and a leakage current value calculation module 630.

[0134] The first voltage value calculation module 610 is used to calculate the first voltage drop of the standard cell after a first time using self-discharge parameters. The second voltage value calculation module 620 is used to calculate the second voltage drop of the cell under test after the first time based on the current reading and the first voltage value. The leakage current value calculation module 630 is used to calculate the leakage current value of the cell under test based on the second voltage value.

[0135] In operation, the first voltage value calculation module 610 calculates the first voltage value that a standard cell experiences after being left to stand for a period of time, based on self-discharge parameters recorded from a storage device. The second voltage value calculation module 620 acquires the first voltage value and the current reading from an ammeter, and accordingly calculates the second voltage value that the cell under test experiences after being left to stand for the same period of time. The leakage current value calculation module receives the second voltage value and converts it into the corresponding leakage current value.

[0136] One advantage of this application's embodiments is that the leakage current calculation device can quickly calculate the true leakage current value of the cell under test based on the self-discharge parameters of a standard cell. Furthermore, the self-discharge parameters of the pre-determined standard cell can be reused in cells of the same type under test.

[0137] According to some embodiments of this application, optionally, the self-discharge parameters of the standard battery cell recorded in the storage device may include: the leakage current value of the standard battery cell and the electrical energy contained in the standard battery cell within a unit voltage range. Correspondingly, the first voltage value calculation module 610 is specifically used to: calculate the first voltage value using formula (1), the second voltage value calculation module 620 is specifically used to: calculate the second voltage value using formula (2), and the leakage current value calculation module 630 is specifically used to: calculate the leakage current value of the battery cell under test using formula (3).

[0138] One of the advantages of this application is that it provides a specific calculation formula for gradually calculating and determining the leakage current value. The self-discharge parameters used are all typical test items that can be obtained through mature detection methods, which is convenient for practical application.

[0139] It should be noted that, in the embodiments of this application, the functional modules of the leakage current calculation device are divided according to the method steps to be performed. In some embodiments, one or more functional modules (such as the first voltage value calculation module, the second voltage value calculation module, and the leakage current value calculation module) of the leakage current calculation device in the embodiments of this application may be split into more functional modules as needed to perform the corresponding method steps. In other embodiments, one or more functional modules of the leakage current calculation device in the embodiments of this application may be integrated into fewer functional modules to perform the corresponding method steps.

[0140] According to some embodiments of this application, please refer to Figure 7 , Figure 7 This is a schematic diagram of the electronic device provided in an embodiment of this application. The electronic device can be any suitable type of electronic computing platform for implementing the above-described leakage current calculation device, and its specific implementation is not limited herein.

[0141] The electronic device may include: a processor 710, a communication interface 720, a memory 730, and a communication bus 740.

[0142] The processor 710, communication interface 720, and memory 730 communicate with each other via communication bus 740. Communication interface 720 is used for communication connections with other devices (e.g., an ammeter). The processor 710 calls program 750 to implement one or more functional modules of the leakage current calculation device in the above embodiments. Specifically, program 750 may include program code or computer operation instructions.

[0143] In this embodiment, depending on the type of hardware used, the processor 710 may be a central processing unit, other general-purpose processors, digital signal processors, application-specific integrated circuits, off-the-shelf programmable gate arrays or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc.

[0144] The memory 730 is used to store the program 750. The memory 730 may include high-speed RAM memory, and may also include non-volatile memory, such as at least one disk storage device.

[0145] This application also provides a computer-readable storage medium. This computer-readable storage medium can be a non-volatile computer-readable storage medium. This computer-readable storage medium stores a computer program.

[0146] When the computer program is executed by the processor, it implements one or more functional modules of the leakage current calculation device in the above embodiments. The complete computer program product is embodied on one or more computer-readable storage media (including but not limited to, disk storage, CD-ROM, optical storage, etc.) containing the computer program disclosed in the embodiments of this application.

[0147] 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 leakage current detection method, characterized in that, include: Connect the standard battery cell and the battery cell under test in parallel; When the standard battery cell and the battery cell under test reach voltage equilibrium in the parallel connection, the connection between the standard battery cell and the battery cell under test is removed. The cell under test is left to stand still for a preset first time; Connect an ammeter between the cell under test and the standard cell after the first settling time. The leakage current value of the cell under test is calculated based on the current reading of the ammeter and the self-discharge parameters of the standard cell. The step of calculating the leakage current value of the cell under test based on the current reading of the ammeter and the self-discharge parameters of the standard cell specifically includes: The self-discharge parameters are used to calculate the first voltage drop of the standard cell after the first time. Based on the current reading and the first voltage value, calculate the second voltage value that the cell under test decreases after the first time. Based on the second voltage value, the leakage current value of the battery cell under test is calculated.

2. The leakage current detection method according to claim 1, characterized in that, Also includes: When the standard cell and the cell under test connected in parallel have passed a preset second time, it is determined that the standard cell and the cell under test have reached voltage balance.

3. The leakage current detection method according to claim 2, characterized in that, The second time is 6 to 10 hours.

4. The leakage current detection method according to claim 1, characterized in that, The self-discharge parameters of the standard battery cell include: the leakage current value of the standard battery cell and the electrical energy contained in the standard battery cell within a unit voltage range.

5. The leakage current detection method according to claim 4, characterized in that, The first voltage value is calculated using the following formula: in, V 1 represents the first voltage value. The value represents the leakage current of a standard battery cell, and T represents the first time. It refers to the electrical energy contained within a unit voltage range; The second voltage value is calculated using the following formula: in, V 2 represents the second voltage value. The reading is the current, and R is the internal resistance of the ammeter. The leakage current value of the battery cell under test is calculated using the following formula: in, The value of the leakage current of the battery cell under test is given by T, where T is the first time. It refers to the electrical energy contained within a unit voltage range.

6. The leakage current detection method according to claim 1, characterized in that, Also includes: Obtain the OCV-SOC curve of the standard battery cell; Determine the test voltage range of the standard battery cell when it is at rest; The OCV-SOC curve is obtained as the electrical energy contained within a unit voltage range within the test voltage range.

7. The leakage current detection method according to any one of claims 1-6, characterized in that, The standard cell and the cell under test are of the same type; the leakage current value of the standard cell is 10-5000uA.

8. The leakage current detection method according to any one of claims 1-6, characterized in that, The first time is 6-7 hours.

9. A leakage current detection system, characterized in that, include: A potential equalization device is used to connect the cell under test and a standard cell in parallel to perform potential equalization. A cell settling device is used to disconnect the cell under test and the standard cell after potential equalization is completed, and to set the cell under test for a first time. A current detection device is used to connect an ammeter between the battery cell under test and the standard battery cell after the battery cell under test has been left to stand. A storage device for recording self-discharge parameters determined by the test results of the standard battery cell; A computing device is used to calculate the leakage current value of the battery cell under test based on the current reading of the ammeter and the self-discharge parameters. The computing device is specifically used to calculate, using the self-discharge parameters, the first voltage value that the standard cell drops after the first time. Based on the current reading and the first voltage value, calculate the second voltage value that the cell under test decreases after the first time. Based on the second voltage value, the leakage current value of the cell under test is calculated.

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