Battery lithium precipitation detection method, battery management system and electric device

Abstract

The application discloses a battery lithium precipitation detection method, a battery management system and a power utilization device. The method comprises the following steps: extracting effective charging data according to vehicle historical charging data, setting a starting voltage V start and an ending voltage V end ; calculating dV / dQ=diffVtemp / dQ TempOut , dQ TempOut =dQ Temp [K], dQ Temp represents instantaneous charging capacity, K represents the distance between the actual voltage V Temp and the starting voltage V start , and diffVtemp represents a voltage interval; calculating the outlying degree of the voltage VTemp corresponding to the dV / dQ peak value of each cell when the voltage of each cell is charged from V start to V start +ΔV1; calculating the outlying degree of the voltage VTemp corresponding to the dV / dQ peak value of each cell when the voltage of each cell is charged from V end -ΔV2 to V end ; calculating the ratio of the number of times that the outlying degree is greater than a preset threshold to the total number of charges; if the total number of charges is greater than or equal to a preset number of times and the ratio is greater than or equal to a preset percentage, a battery pack lithium precipitation early warning is reported.

Description

Technical Field

[0001] This application relates to the field of battery management system technology, specifically to battery lithium plating detection methods, battery management systems, and power-consuming devices. Background Technology

[0002] Ternary lithium batteries have higher energy density than lithium iron phosphate batteries, but they also pose higher safety risks. Developing algorithms to perform safety assessments and tests on ternary lithium batteries to reduce consumer risks has become a key research focus for new energy companies. Lithium plating is an unavoidable phenomenon during the use of power batteries. With increased usage time and frequency, the degree of lithium plating in power batteries becomes increasingly severe. When impurities are introduced during battery production or defects such as torn tabs, crushed electrodes, or folded electrodes caused by process problems, the rate of lithium plating will be greatly accelerated. Lithium plating has a significant impact on the safety of power batteries. Generally, mild lithium plating affects battery capacity and reduces user experience; severe plating can penetrate the separator, causing a short circuit and potentially leading to thermal runaway, endangering the personal safety and property of customers. Existing lithium plating detection technologies assess the degree of lithium plating by observing changes in internal resistance and capacity after plating, but charging efficiency is also an important parameter characterizing whether lithium plating has occurred. Summary of the Invention

[0003] This application provides a battery lithium plating detection method, a battery management system, and an electrical device, which can solve the problem that the fast lithium plating speed of existing ternary lithium batteries affects the safety and capacity of power batteries and even leads to battery short circuits.

[0004] This application provides a battery lithium plating detection method, including the following steps: extracting valid charging data based on historical vehicle charging data, and setting the charging voltage corresponding to 20% of the battery cell as the starting voltage V. start The charging voltage corresponding to 70% of the battery cell is the final charging voltage V. end The calculation of dV / dQ during the charging process of each cell satisfies: dV / dQ=diffVtemp / dQ TempOut , where dQ TempOut Satisfy: dQ TempOut =dQ Temp [K],dQ Temp K represents the instantaneous charging capacity, and K represents the actual voltage (V). Temp With the starting voltage V start The distance between them, diffVtemp represents the voltage interval; calculate the distance between each cell from V start Charge to V start The outlier of the voltage VTemp corresponding to the peak value of dV / dQ of +ΔV1 is calculated, and the outlier of each cell from V is calculated. end -ΔV2 charged to V endThe outlier of the voltage VTemp corresponding to the peak value of dV / dQ is calculated; the ratio of the number of outliers COUNT that are greater than a preset threshold to the total number of charges is calculated; if the total number of charges is greater than or equal to the preset number of charges and the ratio is greater than or equal to the preset percentage, a lithium plating warning for the battery cell is reported.

[0005] In some embodiments, when a cell exhibits multiple dV / dQ peak values, the voltage VTemp corresponding to the first dV / dQ peak value is selected.

[0006] In some embodiments, the outlier degree satisfies: Outer(i) = abs((VTemp_mean - VTemp[i]) / VTemp_std), where Outer(i) represents the outlier degree of the i-th cell, VTemp_mean represents the mean of the peak values ​​of all cells, VTemp[i] represents the peak value of the i-th cell, and VTemp_std represents the standard deviation of all cells.

[0007] In some embodiments, ΔV1 is 0.1V; ΔV2 is 0.05V; the preset threshold is 4σ; the preset number of times is 10; and the preset percentage is 60%.

[0008] In some embodiments, based on the valid charging data, charging processes that start with SOC ≤ 20% and end with SOC ≥ 70% are filtered, along with charging count number j. The charging count number j is then iterated to obtain the occurrence count COUNT or the total number of charges.

[0009] In some embodiments, K satisfies: K = (V Temp -V start ) / diffVtemp+1, where, diffVtemp=dV, divides each charging voltage into a data segment with multiple voltage intervals dV0, dV0=0.01V.

[0010] In some embodiments, the instantaneous charge capacity dQ is calculated. Temp Satisfy: dQ Temp =Δt*I, where Δt is the time difference between the two messages, the unit of Δt is hours, and I is the absolute value of the current, the unit of I is amperes.

[0011] In some embodiments, dQ is selected based on the calculated dV / dQ of each cell. TempOut Abnormal data in the data and with dV / dQ = 0.

[0012] This application also provides a battery management system, including a memory and a processor, wherein the memory stores a computer program that can run on the processor, and the processor executes the computer program to implement the detection method described in any of the above claims.

[0013] This application also provides an electrical device, including the battery management system described above.

[0014] The beneficial effect of this application is that the battery lithium plating detection method, by dividing a complete charging process into two segments, calculates the lithium plating level of each cell from V... start Charge to V start The outlier of the voltage VTemp corresponding to the peak value of dV / dQ of +ΔV1 is calculated, and the outlier of each cell from V is calculated. end -ΔV2 charged to V end The outlier of the peak dV / dQ corresponding to the voltage VTemp can be detected online to determine whether lithium plating has occurred in the battery, which may affect driving safety. This solves the problem of traditional destructive testing methods for disassembling batteries and laboratory testing methods for identifying lithium plating under extreme conditions. It detects whether lithium plating has occurred by detecting the inconsistency of battery charging efficiency during the charging process, and has high accuracy in lithium plating detection. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic flowchart of the battery lithium plating detection method provided in the embodiments of this application;

[0017] Figure 2 This is a schematic diagram showing the peak dV / dQ voltage VTemp corresponding to each cell in the embodiments of this application. Detailed Implementation

[0018] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. In addition, it should be understood that the specific embodiments described herein are only for illustration and explanation of this application and are not intended to limit this application. In this application, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in actual use or operation, specifically the drawing directions in the accompanying drawings; while "inner" and "outer" refer to the outline of the device. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features.

[0019] In the embodiments of this application, reference is made to Figure 1 The lithium plating detection method for batteries described in this application includes the following steps:

[0020] Step 1: Extract valid charging data from the vehicle's historical charging data, and set the charging voltage corresponding to 20% battery cell charge as the starting voltage V. start The charging voltage corresponding to 70% of the battery cell is the final charging voltage V. end ;

[0021] In step 1, the extracted vehicle historical charging data is cleaned to obtain valid charging data. Charging processes with a starting SOC ≤ 20% and a ending SOC ≥ 70% are filtered out, and charging data that do not meet the above charging process are deleted; the charging number j is obtained.

[0022] In step 1, the battery OCV curve is selected based on the average temperature of the effective charging data. Based on the battery OCV curve, the voltage corresponding to 20% of the cell and the voltage corresponding to 70% SOC of the cell are found through the OCV table.

[0023] In step 1, the vehicle's historical charging data includes: time, current, voltage, SOC, temperature, and charging status. The vehicle's historical charging data is collected through the vehicle's BMS.

[0024] Step 2: Calculate the dV / dQ during the charging process of each cell to ensure that:

[0025] dV / dQ=diffVtemp / dQ TempOut ,

[0026] Among them, dQ TempOutsatisfy:

[0027] dQ TempOut =dQ Temp [K],

[0028] dQ Temp K represents the instantaneous charging capacity, and K represents the actual voltage (V). Temp With the starting voltage V start The distance between them, diffVtemp, represents the voltage interval;

[0029] In step 2, the instantaneous charge capacity dQ is... Temp This refers to the capacity difference generated during each charge, used to calculate the instantaneous charging capacity dQ. Temp satisfy:

[0030] dQ Temp =Δt*I,

[0031] Where Δt is the time difference between the two messages, and the unit of Δt is hours; I is the absolute value of the current, and the unit of I is amperes; and if the current of one message is 0, the current of the other message is taken; if the current of both messages is not 0, the average value of the currents of the two messages is taken.

[0032] In step 2, K satisfies:

[0033] K = (V Temp -V start ) / diffVtemp+1,

[0034] Where, diffVtemp = dV0, it should be noted that for each charging process, the charging voltage is divided into a segment of data with multiple voltage intervals dV0.

[0035] In the embodiments of this application, dV0 = 0.01V.

[0036] Step 3: Calculate the voltage of each cell from V start Charge to V start The outlier of the voltage VTemp corresponding to the peak value of dV / dQ of +ΔV1 is calculated for each cell from V end -ΔV2 charged to V end The outlier of the peak dV / dQ corresponds to the voltage VTemp;

[0037] In step 3, the outlier degree satisfies:

[0038] Outler(i)=abs((VTemp_mean-VTemp[i]) / VTemp_std),

[0039] Where Outer(i) represents the outlier degree of the i-th cell, VTemp_mean represents the mean of the peak values ​​of all cells, VTemp[i] represents the peak value of the i-th cell, and VTemp_std represents the standard deviation of all cells;

[0040] In step 3, it is necessary to define that, for the dV / dQ of each cell calculated in step 2, the starting point voltage V set in step 1 is... start End voltage V end However, V generally does not occur during actual charging. start Recharge to V end Therefore, in step 2, the calculated dQTempOut will contain many abnormal data. So, for each charge, when dQTempOut is abnormal, we use the dV / dQ of each cell to be equal to 0 as a limit, and retain the other dV / dQ values.

[0041] In step 3, in some embodiments, ΔV1 equals 0.1V.

[0042] In step 3, in some embodiments, ΔV2 is equal to 0.05V.

[0043] In step 3, in some other embodiments, the dV / dQ peak value of the cell is not limited to one. That is, when a cell has multiple dV / dQ peak values, the voltage VTemp corresponding to the first dV / dQ peak value is selected, and the outlier of the voltage VTemp corresponding to the first dV / dQ peak value is calculated.

[0044] like Figure 2 As shown, in this embodiment of the application, a complete charging process is divided into two segments, and the outlier of the voltage corresponding to the peak dV / dQ of each cell in each charging segment is calculated.

[0045] Step 4: Calculate the ratio of the number of outliers (COUNT) with an outlier degree greater than the preset threshold to the total number of charges. If the total number of charges is greater than or equal to the preset number of outliers and the ratio is greater than or equal to the preset percentage, report a lithium plating warning for the battery pack.

[0046] In step 4, the total number of charging times is obtained by iterating through the charging number j. In some embodiments, the preset threshold is equal to 4σ; the preset number of times is equal to 10; and the preset percentage is equal to 60%. If the total number of charging times is greater than or equal to 10 and the percentage is greater than or equal to 60%, a lithium plating warning for the battery cell is reported; otherwise, no alarm is triggered.

[0047] This application also provides a battery management system, including a memory and a processor, wherein the memory stores a computer program that can run on the processor, and the processor executes the computer program to implement the detection method described in any of the above claims.

[0048] This application also provides an electrical device, including the battery management system described above.

[0049] The battery lithium plating detection method, battery management system, and power device provided in this application include: the battery lithium plating detection method comprising: dividing a complete charging process into two segments, calculating the lithium plating level of each cell from V... start Charge to V start The outlier of the voltage VTemp corresponding to the peak value of dV / dQ of +ΔV1 is calculated, and the outlier of each cell from V is calculated. end -ΔV2 charged to V end The outlier of the peak dV / dQ corresponds to the voltage VTemp. By calculating the ratio of the number of outliers exceeding a preset threshold to the total number of charges, a lithium plating warning is issued when the total number of charges is greater than or equal to a preset number of outliers and the ratio is greater than or equal to a preset percentage. Therefore, this battery lithium plating detection method can detect whether the battery has lithium plating that affects driving safety online. It solves the problems of traditional destructive battery disassembly testing methods and laboratory testing methods for identifying lithium plating under extreme conditions. It detects lithium plating by detecting inconsistencies in battery charging efficiency during the charging process, resulting in high accuracy in lithium plating detection. The method provided by this invention uses a cloud-based big data system to detect whether the battery has lithium plating that affects driving safety online, solving the problems of traditional destructive battery disassembly testing methods and laboratory testing methods for identifying lithium plating under extreme conditions. It detects lithium plating by detecting inconsistencies in battery charging efficiency during the charging process, resulting in high accuracy in lithium plating detection.

[0050] The battery lithium plating detection method, battery management system, and power device provided in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for detecting lithium plating in batteries, characterized in that, Including the following steps: Extract valid charging data based on the vehicle's historical charging data, and set the charging voltage corresponding to 20% of the battery cell as the starting voltage V. start The charging voltage corresponding to 70% of the battery cell is the final charging voltage V. end ; The calculation of dV / dQ during the charging process of each cell satisfies: dV / dQ=diffVtemp / dQ TempOut , Among them, dQ TempOut Satisfy: dQ TempOut =dQ Temp [K],dQ Temp K represents the instantaneous charging capacity, and K represents the actual voltage (V). Temp and the starting voltage V start The distance, diffVtemp, represents the voltage interval; K satisfies: K=(V Temp -V start ) / diffVtemp+1, Where, diffVtemp=dV0, the charging voltage is divided into a data segment with multiple voltage intervals dV0, where dV0=0.01V; The charging process is divided into two segments, and the values ​​of each cell from V are calculated. start Charge to V start The outlier of the voltage VTemp corresponding to the peak dV / dQ of +ΔV1 is calculated, and the outlier of the voltage VTemp corresponding to the peak dV / dQ of each cell charged from Vend-ΔV2 to Vend is calculated; the outlier satisfies: Outler(i)=abs((VTemp_mean-VTemp[i]) / VTemp_std), Where Outer(i) represents the outlier degree of the i-th cell, VTemp_mean represents the mean of the peak values ​​of all cells, VTemp[i] represents the peak value of the i-th cell, and VTemp_std represents the standard deviation of all cells; Calculate the ratio of the number of outliers (COUNT) with an outlier degree greater than a preset threshold to the total number of charges. If the total number of charges is greater than or equal to a preset number of outliers and the ratio is greater than or equal to a preset percentage, report a lithium plating warning for the battery cell.

2. The battery lithium plating detection method according to claim 1, characterized in that, When a cell exhibits multiple dV / dQ peak values, the voltage VTemp corresponding to the first dV / dQ peak value is selected.

3. The battery lithium plating detection method according to claim 1, characterized in that, ΔV1 is 0.1V; ΔV2 is 0.05V; the preset threshold is 4σ; the preset number of times is 10; and the preset percentage is 60%.

4. The battery lithium plating detection method according to claim 1, characterized in that, Based on the valid charging data, the charging processes and charging counts that started charging with a SOC ≤ 20% and ended charging with a SOC ≥ 70% are selected. j Iterate through the charging times number j To obtain the occurrence count COUNT or the total number of charges.

5. The battery lithium plating detection method according to claim 1, characterized in that, Calculate the instantaneous charge capacity dQ Temp satisfy: dQ Temp = Δt * I , in, Δt The time difference between the two messages Δt The unit is hours. I The absolute value of the current. I The unit is ampere.

6. The battery lithium plating detection method according to claim 1, characterized in that, Based on the calculated dV / dQ of each cell, select the dQ TempOut Abnormal data in the data and with dV / dQ=0.

7. A battery management system, characterized in that, The device includes a memory and a processor, wherein the memory stores a computer program that can run on the processor, and the processor executes the computer program to implement the detection method according to any one of claims 1 to 6.

8. An electrical device, characterized in that, Includes the battery management system as described in claim 7.

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