Cell screening methods, apparatus, equipment, storage media and process products

Abstract

This application relates to a method, apparatus, device, storage medium, and program product for battery cell screening, specifically for new energy vehicles. The method, executed by a computer device, includes: acquiring a first open-circuit voltage corresponding to at least two battery cells; acquiring a second open-circuit voltage corresponding to at least two battery cells after the placement time of the at least two battery cells meets a second target time; acquiring self-discharge characteristic parameters of each of the at least two battery cells; constructing a normal distribution diagram of the self-discharge characteristic parameters of each of the at least two battery cells; acquiring a target standard deviation and an average self-discharge characteristic parameter based on the normal distribution diagram; and screening battery cells that meet the self-discharge consistency condition from the at least two battery cells based on the self-discharge characteristic parameters of each of the at least two battery cells, the target standard deviation, and the average self-discharge characteristic parameter. This method can improve the efficiency of battery cell screening.

Description

Technical Field

[0001] This application relates to the field of new energy vehicles, and in particular to a cell screening method, apparatus, equipment, storage medium, and program product. Background Technology

[0002] With the rapid development of new energy sources, lithium-ion batteries have become the mainstream power batteries, and the self-discharge rate of the battery cell is a key indicator affecting battery consistency.

[0003] In related technologies, testers can charge the battery cells to 10%-30% SOC (State of Charge), then let the charged cells stand for a period of time. Based on the discharge performance of the cells, they can screen out cells with large self-discharge and retain cells with good self-discharge performance.

[0004] However, the above method cannot guarantee the reliability of cell test data, and therefore cannot guarantee the accuracy of screening cell self-discharge characteristics. Summary of the Invention

[0005] This application provides a method, apparatus, device, storage medium, and program product for screening battery cells, which can improve the screening accuracy of battery cell discharge consistency. The technical solution is as follows:

[0006] On the one hand, a cell screening method is provided, the method comprising:

[0007] Obtain the first open-circuit voltage corresponding to at least two battery cells respectively; the first open-circuit voltage is obtained when at least two of the battery cells are charged with a specified current and placed for a first target duration;

[0008] After the placement time of at least two of the battery cells meets the second target time, the second open-circuit voltage corresponding to each of the at least two battery cells is obtained;

[0009] Obtain the self-discharge characteristic parameters of at least two of the battery cells; the self-discharge characteristic parameter is the ratio of a first difference between the first open-circuit voltage and the second open-circuit voltage to a second difference between the first target duration and the second target duration;

[0010] Construct normal distribution diagrams of the self-discharge characteristic parameters of at least two of the battery cells;

[0011] The target standard deviation and average self-discharge characteristic parameters are obtained based on the normal distribution plot.

[0012] Based on the self-discharge characteristic parameters, target standard deviation, and average self-discharge characteristic parameters of at least two cells, cells that meet the self-discharge consistency condition are selected from at least two cells; the self-discharge consistency condition includes: the self-discharge characteristic parameter of the cell does not exceed the sum of the average self-discharge characteristic parameter and three times the target standard deviation.

[0013] On the other hand, a battery cell screening device is provided, the device comprising:

[0014] The first open-circuit voltage acquisition module is used to acquire the first open-circuit voltage corresponding to at least two battery cells respectively; the first open-circuit voltage is the battery cell that has been charged with a specified current and placed for a first target duration.

[0015] The second open-circuit voltage acquisition module is used to acquire the second open-circuit voltage corresponding to at least two of the battery cells after the placement time of at least two of the battery cells meets the second target time.

[0016] The self-discharge characteristic parameter acquisition module is used to acquire the self-discharge characteristic parameters of at least two of the battery cells; the self-discharge characteristic parameter is the ratio of a first difference between the first open-circuit voltage and the second open-circuit voltage to a second difference between the first target duration and the second target duration.

[0017] A normal distribution plot construction module is used to construct normal distribution plots of the self-discharge characteristic parameters of at least two of the battery cells.

[0018] The target standard deviation and average self-discharge characteristic parameter acquisition module is used to acquire the target standard deviation and average self-discharge characteristic parameters based on the normal distribution plot.

[0019] The target cell acquisition module is used to select cells that meet the self-discharge consistency condition from at least two cells based on the self-discharge characteristic parameters, the target standard deviation, and the average self-discharge characteristic parameters of each of the at least two cells; the self-discharge consistency condition includes: the self-discharge characteristic parameter of the cell does not exceed the sum of the average self-discharge characteristic parameter and three times the target standard deviation.

[0020] In some embodiments, before obtaining the first open-circuit voltage corresponding to at least two cells, the device further includes:

[0021] A cell discharge module is used to discharge the internal voltage of at least two cells at a specified current.

[0022] In some embodiments, the specified current does not exceed 0.1C.

[0023] In some embodiments, the first target duration is any duration from 1 to 5 hours.

[0024] In some embodiments, the second target duration is any duration between 3 and 7 days.

[0025] In some embodiments, the second open-circuit voltage acquisition module is used to acquire the second open-circuit voltage corresponding to at least two of the battery cells after the duration of at least two of the battery cells being placed at a specified ambient temperature meets a second target duration; the specified ambient temperature is any temperature between 30 and 50 degrees Celsius.

[0026] In another aspect, a computer device is provided, the computer device comprising a processor and a memory, the memory storing at least one instruction, at least one program, code set or instruction set, the at least one instruction, the at least one program, the code set or instruction set being loaded and executed by the processor to implement the cell screening method as described above.

[0027] In another aspect, a computer-readable storage medium is provided, wherein at least one instruction, at least one program, code set, or instruction set is stored therein, wherein the at least one instruction, the at least one program, the code set, or the instruction set is loaded and executed by a processor to implement the cell screening method described above.

[0028] In another aspect, a computer program product is provided, comprising a computer program stored in a computer-readable storage medium. A processor of a computer device reads the computer program from the computer-readable storage medium and executes the computer program, causing the computer device to perform the cell screening method provided in the various alternative implementations described above.

[0029] The technical solution provided in this application may include the following beneficial effects:

[0030] In this embodiment, testers can obtain two open-circuit voltage values ​​and corresponding durations for placing at least two charged cells for different durations. A normal distribution diagram is constructed based on the open-circuit voltage values ​​and corresponding durations. Combining the normal distribution diagram with the self-discharge consistency condition, cells that do not meet the self-discharge consistency condition are eliminated from the cells to be screened. Since the normal distribution diagram combines multiple sets of test data, it is possible to intuitively observe the overall self-discharge performance distribution and extreme outliers (such as abnormal self-discharge rates) of the cells to be screened. Cells with defects can be identified through extreme outliers. Furthermore, screening based on the self-discharge consistency condition can more accurately and effectively screen out cells with poor self-discharge performance, retain cells with consistent self-discharge, and improve the accuracy of cell screening.

[0031] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0032] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0033] Figure 1 This is a schematic diagram of the test environment for a cell screening method according to an embodiment of this application;

[0034] Figure 2 This is a flowchart of a cell screening method provided in one embodiment of this application;

[0035] Figure 3 This is a flowchart of a cell screening method provided in one embodiment of this application;

[0036] Figure 4 This is a flowchart of a cell screening method provided in one embodiment of this application;

[0037] Figure 5 This is a block diagram of a cell screening device provided in an exemplary embodiment of this application;

[0038] Figure 6 This is a schematic diagram of the structure of a computer device provided in an exemplary embodiment of this application. Detailed Implementation

[0039] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0040] This application proposes a cell screening method. This method can screen cells that meet the self-discharge consistency condition by using the normal distribution diagrams of the self-discharge characteristic parameters of at least two cells, thus effectively improving the accuracy of cell screening. For ease of understanding, some concepts involved in this application are explained below.

[0041] 1) A battery cell is the core component inside a battery or battery pack, and it is the main part that stores electrical charge and generates current. It generally consists of a positive electrode, a negative electrode, and an electrolyte, with the positive and negative electrodes separated by the electrolyte. The structure and materials of a battery cell vary depending on the type of battery; for example, lithium-ion battery cells are typically composed of lithium-ion conductive materials.

[0042] 2) A lithium-ion battery is a rechargeable battery that achieves charge and discharge through the migration of lithium ions between the positive and negative electrodes. It is currently one of the most important energy sources widely used in portable electronic devices (such as mobile phones and laptops), power tools, electric vehicles, and energy storage systems. The working principle of a lithium-ion battery is based on the movement of lithium ions in the positive and negative electrode materials. During charging, lithium ions are released from the positive electrode (usually an oxide, such as lithium cobalt oxide), pass through the electrolyte, and move to the negative electrode (usually graphite). Simultaneously, the positive electrode absorbs electrons, while the negative electrode releases electrons. During discharging, lithium ions move from the negative electrode back to the positive electrode, while electrons flow in the external circuit, generating current to power the device.

[0043] 3) Lithium iron phosphate (LFP) batteries are a type of lithium-ion battery. The positive electrode material is lithium iron phosphate, while the negative electrode typically uses graphite. It is a relatively new lithium-ion battery technology, primarily used in applications requiring high safety, long lifespan, and high power output, such as electric vehicles, hybrid vehicles, power tools, and energy storage systems.

[0044] 4) Self-discharge refers to the phenomenon where a battery or battery cell discharges itself due to chemical reactions when it is not connected to an external load. Simply put, even when the battery is not in use, it will slowly lose the stored electrical energy. Self-discharge is caused by the characteristics of the chemical reactions inside the battery, which cause the stored charge in the battery to be gradually depleted, and eventually the battery will be completely discharged.

[0045] The self-discharge rate depends on the battery type and quality, as well as storage conditions. For example, lithium-ion batteries have a lower self-discharge rate than nickel-cadmium and nickel-metal hydride batteries, meaning they can remain charged for longer without fully discharging. However, even lithium-ion batteries will experience self-discharge and reduced capacity if left unused for extended periods or stored in high-temperature environments.

[0046] 5) SOC (State of Charge) refers to the ratio between the current amount of charge a battery stores and its maximum capacity to store. It is usually expressed as a percentage; for example, a battery with an SOC of 80% means it has been charged to 80% of its capacity. Accurate SOC is crucial for battery management and use. By monitoring SOC, the current usable capacity of the battery can be determined, preventing over-discharge or over-charging. Modern battery management systems typically use various sensors and algorithms to estimate or measure SOC to ensure stable and safe battery operation.

[0047] Figure 1 This is a schematic diagram of the test environment for a cell screening method according to one embodiment of this application. Figure 1 As shown, Figure 1 It includes at least two battery cells 100, a multimeter 101, a clock 102, a computer device 120, and a server 130 corresponding to the computer device 120, wherein the computer device 120 and the server 130 are connected via a wired / wireless network 140.

[0048] The device type of computer device 120 includes at least one of the following: smartphone, tablet computer, e-book reader, MP3 player, MP4 player, laptop computer, and desktop computer.

[0049] Optionally, the wireless network mentioned above is typically the Internet, but it can also be any network, including but not limited to any of the following:

[0050] 1) Controller Area Network (CAN): CAN is a common in-vehicle communication network used to connect various electronic control units within the vehicle, such as the engine control unit, braking system control unit, and air conditioning control unit. CAN bus offers high transmission speed and reliability, and is used to transmit real-time data and commands within the vehicle.

[0051] 2) Local Area Network (LAN): A local area network is a network used to connect various electronic devices and systems within a vehicle, such as multimedia systems, navigation systems, and in-vehicle entertainment systems. LANs are typically based on Ethernet technology, providing high-speed data transmission and multi-device connectivity.

[0052] 3) Wireless Local Area Network (WLAN): Wireless Local Area Network refers to the function of providing wireless network connectivity inside the vehicle, enabling the driver and passengers to connect to the Internet, download data, and use online services.

[0053] Among them, at least two of the above-mentioned cells 100 are cells to be screened and can be used to form a battery.

[0054] The multimeter 101 mentioned above is a tool used to measure the voltage and current of at least two battery cells 100. In this embodiment of the application, the multimeter 101 can also be any other tool that can measure voltage and current, such as a charge and discharge tester, an oscilloscope, and a power supply.

[0055] The aforementioned clock 102 is a tool for calculating the charging time, discharging time, and resting time of at least two battery cells 100. In this embodiment, the clock 102 can also be any other tool capable of calculating duration.

[0056] During the application process, multimeter 101 measures the first open-circuit voltage and the second open-circuit voltage of at least two battery cells 100, and clock 102 counts the first target duration and the second target duration of at least two battery cells 100; computer device 120 acquires the first open-circuit voltage, the second open-circuit voltage, the first target duration, and the second target duration, and constructs (or constructs through server 130) a normal distribution map of the self-discharge characteristic parameters of each of the at least two battery cells 100, and finally selects battery cells that meet the self-discharge consistency condition based on the normal distribution map.

[0057] Figure 2 This is a flowchart of a battery cell screening method provided in one embodiment of this application. The battery cell screening method described above can be performed by... Figure 1 The computer device 120 performs the following steps:

[0058] Step 210: Obtain the first open-circuit voltage corresponding to at least two cells respectively; the first open-circuit voltage is the voltage of at least two cells that have been charged with a specified current and placed for a first target duration.

[0059] Among them, the above-mentioned at least two cells can be a batch of cells to be screened for self-discharge consistency for use in assembling batteries. This batch of cells can be cells of the same model, the same material or the same state, and the number of cells can be multiple, for example, any number of more than 100.

[0060] In the embodiments of this application, the above-mentioned at least two battery cells are battery cells that are first discharged with a specified current, then left to stand for a period of time, then charged with a low current constant current for a specified duration, and finally left to stand.

[0061] For example, at least two of the aforementioned cells are first discharged at a current of 0 to 0.1C, meaning each cell discharges at a rate of 0 to 0.1 times its rated capacity. For instance, if a cell has a rated capacity of 1000mAh, then the 0-0.1C discharge current range is 0 to 100mA, meaning the maximum discharge current is 0.1 times the battery capacity. Then, the cells are left to rest for 3 to 12 hours. The specific resting time is determined based on the voltage fluctuation range of this batch of cells (i.e., the aforementioned at least two cells). The greater the voltage difference (i.e., voltage difference) among cells in the same batch, the longer the resting time. Next, at least two cells are charged at a current of 0 to 0.1C for 0 to 1 hour. The specific charging time is determined by the current and SOC inside the cell. The lower the SOC, the shorter the charging time; the higher the current, the shorter the charging time. Finally, the cells are left to rest for a period of time after charging, with the resting time meeting the first target duration.

[0062] In the embodiments of this application, each battery cell that has been charged by a specified current and placed for a first target duration can be measured with a voltage as a first open-circuit voltage. The open-circuit voltage refers to the voltage measured when the battery cell is not connected to a load. The open-circuit voltage can reflect the current charge state of the battery cell. The measuring tool can be a digital multimeter (e.g., a multimeter) or a dedicated battery tester.

[0063] In the embodiments of this application, the aforementioned first target duration is the resting time after at least two cells have been charged according to a specified current, without any connected load, that is, the resting time when the cells are not in use and not being charged.

[0064] It should be noted that the first target duration and the first open-circuit voltage in this embodiment can be configured by the tester. The tester can manually obtain the measurement data through a measuring tool and then input it into the computer device; or it can be directly tested and obtained by a computer device with voltage measurement / timing function.

[0065] Step 220: After at least two cells have been placed for a period of time that meets the second target duration, obtain the second open-circuit voltage corresponding to each of the at least two cells.

[0066] In this embodiment of the application, after the computer device measures and obtains the first open-circuit voltage of at least two battery cells, the tester can place at least two battery cells in the same or different temperature environment as when the first open-circuit voltage was measured, leave them for a specified time, and measure the second target time and the second open-circuit voltage corresponding to at least two battery cells.

[0067] In the embodiments of this application, the aforementioned second open-circuit voltage refers to the voltage measured when the cell is not connected to a load. The open-circuit voltage can reflect the current charge state of the cell. The measuring tool can be a digital multimeter (e.g., a multimeter) or a dedicated battery tester.

[0068] Step 230: Obtain the self-discharge characteristic parameters of at least two cells; the self-discharge characteristic parameter is the ratio of the first difference between the first open-circuit voltage and the second open-circuit voltage to the second difference between the first target duration and the second target duration.

[0069] Among them, the self-discharge characteristic parameters mentioned above are used to indicate the voltage change of the battery cell during the resting process. They are usually used to evaluate the self-discharge rate and stability of the battery cell. The smaller the self-discharge characteristic parameters, the lower the self-discharge rate of the battery cell, that is, the battery cell can maintain a higher charge state and stability when the device is at rest.

[0070] For example, assuming the first open-circuit voltage of a single battery cell is V0, the second open-circuit voltage is V1, the first target duration is T0, and the second target duration is T1, the self-discharge characteristic parameter K of the battery cell can be calculated according to formula (I), as follows:

[0071] Formula (I) is K = (V1 - V0) / (T1 - T0).

[0072] Step 240: Construct normal distribution plots of the self-discharge characteristic parameters of at least two cells.

[0073] The computer equipment organizes the calculated self-discharge characteristic parameters into a dataset, which includes the self-discharge characteristic parameters of at least two cells. Based on the dataset, data analysis tools or graphing software are used to draw a normal distribution graph. The normal distribution graph is based on the distribution shape of the self-discharge characteristic parameters, where the horizontal axis represents the value of the self-discharge characteristic parameters, and the vertical axis represents the probability density or frequency corresponding to the value of the self-discharge characteristic parameters in this batch of cells. The self-discharge characteristics of this batch of cells can be intuitively seen through the normal distribution graph.

[0074] Step 250: Obtain the target standard deviation and average self-discharge characteristic parameters based on the normal distribution plot.

[0075] In this embodiment of the application, the computer device can calculate the standard deviation based on the parameters in the normal distribution graph, use it as the target standard deviation, and calculate the average value of all self-discharge characteristic parameters in the normal distribution graph, use it as the average self-discharge characteristic parameter.

[0076] Step 260: Based on the self-discharge characteristic parameters, target standard deviation, and average self-discharge characteristic parameters of at least two cells, select cells that meet the self-discharge consistency condition from the at least two cells; the self-discharge consistency condition includes: the self-discharge characteristic parameters of the cell do not exceed the sum of the average self-discharge characteristic parameters and three times the target standard deviation.

[0077] In this embodiment, the sum of the average self-discharge characteristic parameter and three times the target standard deviation is calculated, and the self-discharge characteristic parameter in the normal distribution plot is obtained. The parameter is then compared with the calculated sum. If the self-discharge characteristic parameter in the normal distribution plot is greater than or equal to the sum, the cell corresponding to the self-discharge characteristic parameter is removed as a cell that does not meet the self-discharge consistency requirement. Cells with self-discharge characteristic parameters less than the sum are retained as cells that meet the self-discharge consistency requirement.

[0078] In this embodiment, testers can obtain two open-circuit voltage values ​​and corresponding durations for placing at least two charged cells for different durations. A normal distribution graph is constructed based on the open-circuit voltage values ​​and corresponding durations. Combining the normal distribution graph with the self-discharge consistency condition, cells that do not meet the self-discharge consistency condition are eliminated from the cells to be screened. The normal distribution graph, combined with multiple sets of test data, can intuitively observe the overall self-discharge performance distribution and extreme outliers (such as abnormal self-discharge rates) of the cells to be screened. Cells with defects can be identified through extreme outliers. Furthermore, screening based on the self-discharge consistency condition can more accurately and effectively screen out cells with poor self-discharge performance, retain cells with consistent self-discharge, and improve the accuracy of cell screening.

[0079] based on Figure 2 Please refer to Figure 3 , Figure 3 This is a flowchart of a cell screening method provided in one embodiment of this application. Before step 210, it further includes step 205:

[0080] Step 205: Discharge the internal voltage of at least two cells with a specified current.

[0081] In this embodiment of the application, the tester can find the rated current of each battery cell according to the technical specifications of each cell. The specified current can be a part of the rated current of the battery cell, generally not exceeding a specified multiple of the rated current, in order to ensure the safety and lifespan of the battery cell.

[0082] For example, if the rated current of the battery cell is 1C, then the specified current can be selected as a portion of 1C, such as 0.5C or 0.2C.

[0083] In this embodiment, discharging the battery cell with a specified current can effectively ensure the internal stability and safety of the battery cell during the discharge process. Furthermore, discharging the voltage inside the battery cell before screening its self-discharge performance can provide a good test condition, which is beneficial to the accuracy of the subsequent screening process.

[0084] In some embodiments, the specified current does not exceed 0.1C.

[0085] In the embodiments of this application, charging / discharging at least two cells with a specified current not exceeding 0.1C can quickly and accurately assess the actual capacity of the current, which helps to ensure the reliability of the cells in actual use.

[0086] In some embodiments, the first target duration is any duration from 1 to 5 hours.

[0087] In this embodiment of the application, placing at least two charged cells for a period of time can better detect the self-discharge of at least two cells. Measuring the voltage after at least two cells have self-discharged for a certain period of time can more accurately assess the self-discharge rate of at least two cells.

[0088] In some embodiments, the second target duration is any duration between 3 and 7 days.

[0089] In this embodiment of the application, after charging at least two cells, the voltage of the at least two cells is obtained after a second, longer period of time. This allows for the acquisition of voltages that are significantly different from those obtained during the first placement of the at least two cells, ensuring the validity of the data. Based on this data, the subsequent screening for the self-discharge consistency of the at least two cells is more accurate.

[0090] In some embodiments, step 220 above can also be implemented as obtaining the second open-circuit voltage corresponding to at least two cells after the duration of at least two cells being placed at a specified ambient temperature meets the second target duration; the specified ambient temperature is any temperature between 30 and 50 degrees Celsius.

[0091] In this embodiment, at least two battery cells are placed in a warm-up environment for a period of time at a stable ambient temperature to allow their internal temperatures to reach equilibrium with the ambient temperature. This eliminates voltage measurement errors caused by temperature changes, ensuring the accuracy and comparability of voltage measurement results for the at least two battery cells.

[0092] For example, based on Figure 2 as well as Figure 3 For a corresponding implementation example, taking the application in screening the self-discharge consistency of lithium iron phosphate battery cells as an example, please refer to... Figure 4 , Figure 4 This is a flowchart of screening the self-discharge consistency of lithium iron phosphate battery cells according to an embodiment of this application. The specific steps are as follows:

[0093] Step 410: Obtain the first open-circuit voltage corresponding to at least two lithium iron phosphate cells respectively; the first open-circuit voltage is the voltage at least two lithium iron phosphate cells that have been charged with a specified current and placed for a first target duration.

[0094] Step 420: After at least two lithium iron phosphate cells have been placed for a period of time that meets the second target duration, obtain the second open-circuit voltage corresponding to each of the at least two lithium iron phosphate cells.

[0095] Step 430: Obtain the self-discharge characteristic parameters of at least two lithium iron phosphate cells; the self-discharge characteristic parameter is the ratio of the first difference between the first open-circuit voltage and the second open-circuit voltage to the second difference between the first target duration and the second target duration.

[0096] Step 440: Construct normal distribution plots of the self-discharge characteristic parameters of at least two lithium iron phosphate cells.

[0097] Step 450: Obtain the target standard deviation and average self-discharge characteristic parameters based on the normal distribution plot.

[0098] Step 460: Based on the self-discharge characteristic parameters, target standard deviation, and average self-discharge characteristic parameters of at least two lithium iron phosphate cells, select lithium iron phosphate cells that meet the self-discharge consistency condition from the at least two lithium iron phosphate cells; the self-discharge consistency condition includes: the self-discharge characteristic parameters of the lithium iron phosphate cells do not exceed the sum of the average self-discharge characteristic parameters and three times the target standard deviation.

[0099] In some embodiments, step 420 above can be implemented as obtaining the second open-circuit voltage corresponding to at least two cells after the duration of at least two cells being placed at a specified ambient temperature meets the second target duration; the specified ambient temperature is any temperature between 30 and 50 degrees Celsius.

[0100] This application example provides a method for screening the self-discharge of lithium iron phosphate batteries. This method reduces polarization by charging with a small current, and achieves rapid and short cycles in the low SOC range through the confidence interval. The method is fast, effective, and energy-saving.

[0101] Another objective of this embodiment is to provide the above-mentioned method for evaluating battery self-discharge quickly and efficiently.

[0102] The primary objective of this embodiment is achieved through the following technical solution:

[0103] A method for screening the self-discharge of lithium iron phosphate batteries includes the following steps:

[0104] (1) Select a batch of lithium iron phosphate cells, discharge the cells with a small current, and let them stand for a period of time.

[0105] (2) Charge the battery cell with a low current constant for a period of time after it has been left to stand, and then let it stand for a period of time before testing the open circuit voltage V0.

[0106] (3) Place the battery cell at a specific ambient temperature and let it stand for a period of time to test the open circuit voltage V1.

[0107] (4) Calculate K1 = (V1 - V0) / (T1 - T0) using the method described above.

[0108] (5) Perform normal distribution data analysis on the series of K1 values ​​obtained above. K is recorded as the average value of this set of data. Calculate the standard deviation δ and remove outliers ≥ K+3δ.

[0109] Preferably, the batch of battery cells in step (1) consists of 100 or more battery cells.

[0110] Preferably, the small current in step (1) is 0-0.1C.

[0111] Preferably, the time period described in step (1) is 3-12 hours.

[0112] Preferably, the low current in step (2) is 0-0.1C.

[0113] Preferably, the charging time in step (2) is 0-1 hour.

[0114] Preferably, the standing time in step (2) is 1-5 hours.

[0115] Preferably, the specific ambient temperature in step (3) is 30-50℃.

[0116] Preferably, the resting period in step (3) is 3-7 days.

[0117] Another objective of this embodiment is achieved through the following technical solution:

[0118] By using low-current discharge and charging, the battery's charging time is reduced, ensuring effective capture of voltage sensitivity changes. At the same time, scientific and efficient data analysis greatly shortens the battery's static aging time and improves enterprise production efficiency.

[0119] Compared with the prior art, this embodiment has the following advantages and beneficial effects:

[0120] (1) The charging and discharging strategy of this embodiment is to use a smaller current to charge a smaller amount of electricity, which has the advantage of reducing enterprise energy consumption.

[0121] (2) The embodiment uses low SOC storage, which utilizes the high voltage change sensitivity of lithium iron phosphate batteries in the low SOC range, which has the characteristics of rapid anomaly identification and high efficiency.

[0122] (3) The embodiment utilizes the normal distribution characteristics of regular data to quickly identify batteries with abnormal data and poor consistency in a short period of time through data statistics. This method has broad application prospects in the field of new energy.

[0123] The following detailed description of this embodiment, with reference to specific implementation examples, is provided, but the implementation of this embodiment is not limited thereto.

[0124] (1) Select 500 pcs of lithium iron phosphate batteries and discharge the batteries completely using a constant current and constant voltage method. The specific discharge steps are as follows:

[0125] 1. Discharge to 2.5V with a 1C discharge current;

[0126] 2. Let stand for 30 minutes;

[0127] 3. Discharge to 2.0V with a discharge current of 0.05C;

[0128] 4. Let stand for 12 hours. After standing, perform an open-circuit voltage test on the battery cell and record it as V0.

[0129] (2) After the voltage test, the batch of cells were placed in a 45°C high-temperature environment for 5 days before the open circuit voltage V1 of the battery was tested.

[0130] (3) Calculate the K value for the 500pcs battery, K = (V1 - V0) / 5. Calculate the standard deviation δ of the obtained series of K values ​​using the normal distribution analysis method for regular data, and the average value is K. 平 Remove K≥K 平 An outlier of +3δ.

[0131] The results show that this method can effectively screen out batteries with poor consistency, with a screening cycle of only 7 days. It is efficient, simple, and highly operable. This embodiment is simple to operate, has obvious effects, and has strong application prospects.

[0132] Please refer to Figure 5 The diagram illustrates a block diagram of a battery cell screening device provided in an exemplary embodiment of this application. This battery cell screening device can be implemented as all or part of a computer device through hardware or a combination of hardware and software, to achieve the above-described... Figures 2 to 4 All or part of the steps in the illustrated embodiments.

[0133] like Figure 5 As shown, the battery cell screening device includes:

[0134] The first open-circuit voltage acquisition module 501 is used to acquire the first open-circuit voltage corresponding to at least two battery cells respectively; the first open-circuit voltage is the voltage of at least two battery cells that have been charged with a specified current and placed for a first target duration.

[0135] The second open-circuit voltage acquisition module 502 is used to acquire the second open-circuit voltage corresponding to at least two cells respectively after the placement time of at least two cells meets the second target time.

[0136] The self-discharge characteristic parameter acquisition module 503 is used to acquire the self-discharge characteristic parameters of at least two cells respectively; the self-discharge characteristic parameter is the ratio of the first difference between the first open circuit voltage and the second open circuit voltage to the second difference between the first target duration and the second target duration.

[0137] Normal distribution plot construction module 504 is used to construct normal distribution plots of the self-discharge characteristic parameters of at least two cells;

[0138] The target standard deviation and average self-discharge characteristic parameter acquisition module 505 is used to acquire the target standard deviation and average self-discharge characteristic parameters based on the normal distribution plot.

[0139] The target cell acquisition module 506 is used to select cells that meet the self-discharge consistency condition from at least two cells based on their respective self-discharge characteristic parameters, target standard deviation, and average self-discharge characteristic parameters. The self-discharge consistency condition includes: the self-discharge characteristic parameter of the cell does not exceed the sum of the average self-discharge characteristic parameter and three times the target standard deviation.

[0140] In some embodiments, before acquiring the first open-circuit voltage corresponding to at least two cells, the apparatus further includes:

[0141] A cell discharge module is used to discharge the internal voltage of at least two cells at a specified current.

[0142] In some embodiments, the specified current does not exceed 0.1C.

[0143] In some embodiments, the first target duration is any duration from 1 to 5 hours.

[0144] In some embodiments, the second target duration is any duration between 3 and 7 days.

[0145] In some embodiments, the second open-circuit voltage acquisition module 502 is used to acquire the second open-circuit voltage corresponding to at least two battery cells after the duration of at least two battery cells being placed at a specified ambient temperature meets a second target duration; the specified ambient temperature is any temperature between 30 and 50 degrees Celsius.

[0146] Please refer to Figure 6 , Figure 6 This is a schematic diagram of the structure of a computer device provided in an exemplary embodiment of this application. The computer device 600 includes a Central Processing Unit (CPU) 601, a system memory 604 including Random Access Memory (RAM) 602 and Read-Only Memory (ROM) 603, and a system bus 605 connecting the system memory 604 and the CPU 601. The computer device 600 also includes a Basic Input / Output System (I / O System) 606 that facilitates the transfer of information between various devices within the computer, and a mass storage device 607 for storing the operating system 613, application programs 614, and other program modules 615.

[0147] The basic input / output system 606 includes a display 608 for displaying information and an input device 609 for user input, such as a mouse or keyboard. Both the display 608 and the input device 609 are connected to the central processing unit 601 via an input / output controller 610 connected to the system bus 605. The basic input / output system 606 may also include the input / output controller 610 for receiving and processing input from multiple other devices such as a keyboard, mouse, or electronic stylus. Similarly, the input / output controller 610 also provides output to a display screen, printer, or other types of output devices.

[0148] The mass storage device 607 is connected to the central processing unit 601 via a mass storage controller (not shown) connected to the system bus 605. The mass storage device 607 and its associated computer-readable media provide non-volatile storage for the computer device 600. That is, the mass storage device 607 may include computer-readable media (not shown) such as a hard disk or a CD-ROM (Compact Disc Read-Only Memory) drive.

[0149] Without loss of generality, the computer-readable medium may include computer storage media and communication media. Computer storage media include volatile and non-volatile, removable and non-removable media implemented using any method or technology for storing information such as computer-readable instructions, data structures, program modules, or other data. Computer storage media include RAM (Random Access Memory), ROM (Read-Only Memory), EPROM (Erasable Programmable Read-Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), flash memory or other solid-state storage technologies, CD-ROM, DVD (Digital Video Disc) or other optical storage, magnetic tape cassettes, magnetic tape, disk storage, or other magnetic storage devices. Of course, those skilled in the art will recognize that the computer storage media are not limited to the above-mentioned types. The system memory 604 and the mass storage device 607 described above can be collectively referred to as memory.

[0150] Computer device 600 can be connected to the Internet or other network devices via network interface unit 611 connected to the system bus 605.

[0151] The memory also includes one or more programs, which are stored in the memory, and the central processing unit 601 implements these programs. Figures 2 to 4 All or some of the steps in the method shown.

[0152] In an exemplary embodiment, a chip is also provided, the chip including programmable logic circuitry and / or program instructions, which, when the chip is run on a computer device, are used to implement all or part of the steps of the methods shown in the above embodiments of this application.

[0153] In an exemplary embodiment, a computer program product is also provided, comprising computer instructions stored in a computer-readable storage medium. A processor of a computer device reads the computer instructions from the computer-readable storage medium and executes the computer instructions to implement all or part of the steps of the methods shown in the above embodiments of this application.

[0154] In an exemplary embodiment, a computer-readable storage medium is also provided, which stores a computer program that is loaded and executed by a processor to implement all or part of the steps of the methods shown in the above embodiments of this application.

[0155] Those skilled in the art will understand that all or part of the steps of the above embodiments can be implemented by hardware or by a program instructing related hardware. The program can be stored in a computer-readable storage medium, such as a read-only memory, a disk, or an optical disk.

[0156] Those skilled in the art will recognize that the functions described in the embodiments of this application in one or more of the above examples can be implemented using hardware, software, firmware, or any combination thereof. When implemented using software, these functions can be stored in a computer-readable medium or transmitted as one or more instructions or code on a computer-readable medium. Computer-readable media include computer storage media and communication media, wherein communication media include any medium that facilitates the transfer of a computer program from one place to another. Storage media can be any available medium that can be accessed by a general-purpose or special-purpose computer.

[0157] The above description is merely an optional embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for screening battery cells, characterized in that, The method includes: Discharge the internal voltage of at least two cells with a specified current; Obtain the first open-circuit voltage corresponding to at least two of the battery cells respectively; the first open-circuit voltage is obtained when at least two of the battery cells are charged with a specified current and placed for a first target duration. After the placement time of at least two of the battery cells meets the second target time, the second open-circuit voltage corresponding to each of the at least two battery cells is obtained; Obtain the self-discharge characteristic parameters of at least two of the battery cells; the self-discharge characteristic parameter is the ratio of a first difference between the first open-circuit voltage and the second open-circuit voltage to a second difference between the first target duration and the second target duration; Construct normal distribution diagrams of the self-discharge characteristic parameters of at least two of the battery cells; The target standard deviation and average self-discharge characteristic parameters are obtained based on the normal distribution plot. Based on the self-discharge characteristic parameters, target standard deviation, and average self-discharge characteristic parameters of at least two cells, cells that meet the self-discharge consistency condition are selected from at least two cells; the self-discharge consistency condition includes: the self-discharge characteristic parameter of the cell does not exceed the sum of the average self-discharge characteristic parameter and three times the target standard deviation.

2. The method according to claim 1, characterized in that, The specified current does not exceed 0.1C.

3. The method according to claim 1, characterized in that, The first target duration is any duration between 1 and 5 hours.

4. The method according to claim 1, characterized in that, The second target duration is any duration between 3 and 7 days.

5. The method according to claim 1, characterized in that, After at least two of the battery cells have been placed for the second target duration, obtaining the second open-circuit voltage corresponding to each of the at least two battery cells includes: After at least two of the battery cells have been placed at a specified ambient temperature for a duration that meets the second target duration, the second open-circuit voltage corresponding to each of the at least two battery cells is obtained; the specified ambient temperature is any temperature between 30 and 50 degrees Celsius.

6. A battery cell screening device, characterized in that, The device includes: A cell discharge module is used to discharge the internal voltage of at least two cells at a specified current. The first open-circuit voltage acquisition module is used to acquire the first open-circuit voltage corresponding to at least two of the battery cells respectively; the first open-circuit voltage is the battery cell that has been charged with a specified current and placed for a first target duration. The second open-circuit voltage acquisition module is used to acquire the second open-circuit voltage corresponding to at least two of the battery cells after the placement time of at least two of the battery cells meets the second target time. The self-discharge characteristic parameter acquisition module is used to acquire the self-discharge characteristic parameters of at least two of the battery cells; the self-discharge characteristic parameter is the ratio of a first difference between the first open-circuit voltage and the second open-circuit voltage to a second difference between the first target duration and the second target duration. A normal distribution plot construction module is used to construct normal distribution plots of the self-discharge characteristic parameters of at least two of the battery cells. The target standard deviation and average self-discharge characteristic parameter acquisition module is used to acquire the target standard deviation and average self-discharge characteristic parameters based on the normal distribution plot. The target cell acquisition module is used to select cells that meet the self-discharge consistency condition from at least two cells based on the self-discharge characteristic parameters, the target standard deviation, and the average self-discharge characteristic parameters of each of the at least two cells; the self-discharge consistency condition includes: the self-discharge characteristic parameter of the cell does not exceed the sum of the average self-discharge characteristic parameter and three times the target standard deviation.

7. A computer device, characterized in that, The computer device includes a processor and a memory, the memory storing at least one computer instruction, which is loaded and executed by the processor to implement the cell screening method as described in any one of claims 1 to 5.

8. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores at least one computer instruction, which is loaded and executed by a processor to implement the cell screening method as described in any one of claims 1 to 5.

9. A computer program product, characterized in that, The computer program product includes computer instructions stored in a computer-readable storage medium; the computer instructions are read and executed by a processor of a computer device to implement the cell screening method as described in any one of claims 1 to 5.

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