A method and system for evaluating power battery capacity attenuation

Abstract

The present invention relates to a method and system for evaluating power battery capacity degradation, belonging to the technical field of power batteries. The method comprises: obtaining uploaded data from the power battery of a vehicle to be evaluated; preprocessing the uploaded data to obtain a charging capacity evaluation data segment of the power battery; obtaining the initial full charge capacity and current full charge capacity of the power battery of the vehicle to be evaluated based on the charging capacity evaluation data segment; and evaluating the capacity degradation of the power battery of the vehicle to be evaluated based on the initial full charge capacity and the current full charge capacity to obtain an evaluation result. The power battery capacity degradation evaluation method of the present invention is highly operable, low-cost, and highly efficient.

Description

Technical Field

[0001] The present invention belongs to the technical field of power batteries, and in particular relates to a method and system for evaluating power battery capacity attenuation. Background Art

[0002] my country's new energy vehicle market has developed rapidly in recent years. In 2021, sales of new energy vehicles reached 3.52 million, accounting for approximately 13% of total vehicle sales, maintaining years of rapid growth. The number of new energy vehicles on the road has also increased annually, reaching nearly 8 million by the end of 2021. With the development of new energy vehicles, the safety, quality, and service life of key components have attracted increasing attention. As a core component of new energy vehicles, especially pure electric vehicles, power batteries have always been a focus of new energy vehicle development and research, and their condition assessment and fault detection have always been key. The capacity of a power battery reflects its energy storage capacity and is one of its most critical parameters, as well as an important indicator of battery life. Because power batteries are electrochemical systems, their capacity decreases over time during use. Therefore, assessing the capacity decay of on-board power batteries is of great significance. Furthermore, assessing power battery capacity decay has important applications in power battery recycling and cascade utilization.

[0003] Patent application number 202111137547.2 discloses a power battery capacity assessment method. By integrating power battery test data from new vehicles with vehicle networking operation data, two dynamic databases of complete SOC-OCV data corresponding to different temperature and operating conditions and new power battery capacity standard values ​​are established. The power battery capacity is assessed by finding the corresponding capacity for the current operating conditions of the target vehicle and comparing it with the standard data of the new power battery. This method relies on a large amount of experimental data to construct a complete SOC-OCV database, which limits its application in new energy vehicles.

[0004] Patent application number 201911328591.4 discloses a method for predicting power battery capacity degradation. This method trains a neural network model using historical vehicle usage data and charging characteristics to determine the relationship between the power battery's apparent capacity and charging characteristics. The method then predicts the future apparent capacity degradation of the power battery of the target vehicle based on the charging characteristics of the first vehicle with the greatest similarity to the target vehicle. This method relies on a large amount of data from the same power battery model to train the model, and the model's accuracy is affected by the input data. If the characteristics of the target vehicle differ significantly from those of other vehicles, accurate predictions will be impossible.

[0005] The main existing methods for evaluating capacity decay are experimental analysis and model analysis. The experimental analysis method requires testing the power battery under standard operating conditions. However, the operating conditions of on-board power batteries during actual use are complex and differ significantly from standard operating conditions, making it impossible to obtain the test capacity under standard operating conditions. Disassembling the on-board power battery from the vehicle for standard operating condition testing is not feasible, and is not only costly but also inefficient. The model analysis method requires high model accuracy and a large amount of offline data for model training and optimization iterations, which is computationally intensive and inefficient. Summary of the Invention

[0006] The main purpose of the present invention is to overcome the shortcomings and deficiencies of the existing technology and provide a method and system for evaluating the capacity attenuation of a power battery. By preprocessing the data uploaded by the power battery, the initial full charge capacity and current full charge capacity of the power battery are obtained, and then the capacity attenuation status of the power battery is evaluated. The method and system have strong operability, low cost and high evaluation efficiency.

[0007] According to one aspect of the present invention, a method for evaluating capacity decay of a power battery is provided, the method comprising the following steps:

[0008] S1: Obtain the power battery upload data of the vehicle to be evaluated;

[0009] S2: Preprocessing the uploaded data of the power battery to obtain a charging capacity evaluation data segment of the power battery;

[0010] S3: Obtaining the initial full charge capacity and the current full charge capacity of the power battery of the vehicle to be evaluated according to the charging capacity evaluation data segment;

[0011] S4: Evaluate the capacity attenuation condition of the power battery of the vehicle to be evaluated based on the initial full charge capacity and the current full charge capacity to obtain an evaluation result.

[0012] Preferably, the pre-processing of the power battery uploaded data to obtain the charging capacity evaluation data fragment of the power battery includes:

[0013] The preprocessing includes: data cleaning, data slicing and data screening; the data cleaning includes eliminating duplicate values, invalid values ​​and abnormal values; the data slicing includes extracting charging segments based on the charging status; the data screening includes extracting charging segments that meet preset conditions as charging capacity evaluation data segments based on the reporting time, charging status, SOC, total current, maximum and minimum temperatures.

[0014] Preferably, obtaining the initial full charge capacity and the current full charge capacity of the power battery of the vehicle to be evaluated according to the charging capacity evaluation data segment includes:

[0015] The full charge capacity of each charge capacity evaluation data segment is obtained by the following formula:

[0016]

[0017] Among them, C i is the full charge capacity of a single charging capacity evaluation data segment, T0 is the charging start time, T1 is the charging end time, I is the charging current, SOC T0 SOC is the starting SOC for charging. T1 End SOC for charging;

[0018] After obtaining the full charge capacity of each charging capacity evaluation data segment, if the difference between two adjacent full charge capacities is greater than a predetermined threshold, the latter full charge capacity value is discarded.

[0019] Preferably, obtaining the initial full charge capacity and the current full charge capacity of the power battery of the vehicle to be evaluated includes:

[0020] The initial full charge capacity is obtained by averaging the full charge capacities of multiple charging segments during the initial use of the vehicle.

[0021] The current full charge capacity is obtained by averaging the full charge capacities of multiple recent charging segments of the vehicle.

[0022] Preferably, the evaluating the capacity attenuation condition of the power battery of the vehicle to be evaluated based on the initial full charge capacity and the current full charge capacity to obtain the evaluation result includes:

[0023] The capacity attenuation rate of the power battery is calculated using the following formula:

[0024] Capacity decay rate = 1-current full charge capacity / initial full charge capacity.

[0025] According to another aspect of the present invention, the present invention further provides a system for evaluating capacity degradation of a power battery, the system comprising:

[0026] The first acquisition module is used to obtain the uploaded power battery data of the vehicle to be evaluated;

[0027] A data preprocessing module, configured to preprocess the data uploaded by the power battery to obtain a charging capacity evaluation data segment of the power battery;

[0028] A second acquisition module is configured to obtain an initial full charge capacity and a current full charge capacity of the power battery of the vehicle to be evaluated based on the charging capacity evaluation data segment;

[0029] The capacity evaluation module is used to evaluate the capacity attenuation condition of the power battery of the vehicle to be evaluated based on the initial full charge capacity and the current full charge capacity to obtain an evaluation result.

[0030] Preferably, the data preprocessing module preprocesses the power battery uploaded data to obtain the charging capacity evaluation data fragment of the power battery, including:

[0031] The preprocessing includes: data cleaning, data slicing and data screening; the data cleaning includes eliminating duplicate values, invalid values ​​and abnormal values; the data slicing includes extracting charging segments based on the charging status; the data screening includes extracting charging segments that meet preset conditions as charging capacity evaluation data segments based on the reporting time, charging status, SOC, total current, maximum and minimum temperatures.

[0032] Preferably, the second acquisition module obtains the initial full charge capacity and the current full charge capacity of the power battery of the vehicle to be evaluated according to the charging capacity evaluation data segment, including:

[0033] The full charge capacity of each charge capacity evaluation data segment is obtained by the following formula:

[0034]

[0035] Among them, C i is the full charge capacity of a single charging capacity evaluation data segment, T0 is the charging start time, T1 is the charging end time, I is the charging current, SOC T0 SOC is the starting SOC for charging. T1 End SOC for charging;

[0036] After obtaining the full charge capacity of each charging capacity evaluation data segment, if the difference between two adjacent full charge capacities is greater than a predetermined threshold, the latter full charge capacity value is discarded.

[0037] Preferably, the second acquisition module obtains the initial full charge capacity and the current full charge capacity of the power battery of the vehicle to be evaluated, including:

[0038] The initial full charge capacity is obtained by averaging the full charge capacities of multiple charging segments during the initial use of the vehicle.

[0039] The current full charge capacity is obtained by averaging the full charge capacities of multiple recent charging segments of the vehicle.

[0040] Preferably, the capacity evaluation module evaluates the capacity attenuation condition of the power battery of the vehicle to be evaluated based on the initial full charge capacity and the current full charge capacity, and obtains an evaluation result including:

[0041] The capacity attenuation rate of the power battery is calculated using the following formula:

[0042] Capacity decay rate = 1-current full charge capacity / initial full charge capacity.

[0043] Beneficial effect: Without relying on test and R&D data, and only using the national standard uploaded data of the vehicle power battery to be evaluated, the capacity decay of the power battery is efficiently quantitatively analyzed. There is no need for special processing or testing of the on-board power battery. The present invention obtains the initial full charge capacity and current full charge capacity of the power battery by pre-processing the uploaded power battery data, and then evaluates the capacity decay status of the power battery. It has strong operability, low cost and high evaluation efficiency.

[0044] The features and advantages of the present invention will become clear through the following detailed description of specific embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a flow chart of the method for evaluating the capacity decay of a power battery according to the present invention;

[0046] Figure 2 Schematic diagram of the power battery capacity decay evaluation system of the present invention. DETAILED DESCRIPTION

[0047] The following is a clear and complete description of the technical solutions in the embodiments of the present invention, in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts are within the scope of protection of the present invention.

[0048] Example 1

[0049] Figure 1 This is a flow chart of the method for evaluating the capacity decay of a power battery according to the present invention. Figure 1 As shown, the present invention provides a method for evaluating the capacity attenuation of a power battery, the method comprising the following steps:

[0050] S1: Obtain the power battery upload data of the vehicle to be evaluated.

[0051] Specifically, the format of the power battery uploaded data complies with national standards, including: reporting time, vehicle status, charging status, total current, SOC (State of Charge), maximum and minimum cell voltage, and maximum and minimum temperature. The above data fields are uploaded to the cloud in accordance with the GB / T 32960-2016 standard.

[0052] S2: Preprocessing the uploaded data of the power battery to obtain a charging capacity evaluation data segment of the power battery.

[0053] Specifically, the preprocessing includes: data cleaning, data slicing and data screening; the data cleaning includes eliminating duplicate values, invalid values ​​and abnormal values; the data slicing includes extracting charging segments according to the charging status; the data screening includes extracting charging segments that meet preset conditions as charging capacity evaluation data segments based on the reporting time, charging status, SOC, total current, maximum and minimum temperatures.

[0054] Furthermore, when removing duplicate values, the reissued data may be retained based on a flag indicating whether it is reissued data;

[0055] When eliminating invalid values, refer to the range definition in GB / T 32960.3-2016 to filter the data fields;

[0056] When removing outliers, different thresholds can be set based on the type of battery cells used in the vehicle being evaluated. Optionally, the maximum and minimum cell voltage ranges for ternary batteries are [2.7, 4.3], and for lithium iron phosphate batteries are [2.5, 3.65].

[0057] Data slicing includes extracting charging segments based on charging status; charging status can be divided into parking charging, driving charging, uncharged state, and charging completed; optionally, when the charging status is parking charging, it is identified as a charging segment, and the duration should be no less than 10 minutes;

[0058] Data screening includes extracting charging segments that meet preset conditions as charging capacity evaluation data segments based on dimensions such as reporting time, charging status, SOC, total current, maximum and minimum temperatures, where the preset conditions can be the same or similar conditions.

[0059] As a specific embodiment, data segments in which the charging state is slow charging, the maximum and minimum charging temperatures are between 20° C. and 30° C., the starting SOC of charging is less than 40%, and the ending SOC of charging is greater than 90% can be used as charging capacity evaluation data segments.

[0060] S3: According to the charging capacity evaluation data segment, obtain the initial full charge capacity and current full charge capacity of the power battery of the vehicle to be evaluated.

[0061] The specific steps include: 1. obtaining the charging capacity of each charging segment by current integration, 2. obtaining the charging ΔSOC of each charging segment by the difference between the charging end SOC and the charging start SOC, 3. dividing the charging capacity of each charging segment by the charging ΔSOC to obtain the full charging capacity of each charging segment, 4. taking the average of the full charging capacities of multiple charging segments in the initial stage of the vehicle to obtain the initial full charging capacity, and the multiple charging segments can be 5 to 10.

[0062] That is, the full charge capacity of each charging capacity evaluation data segment is obtained by the following formula:

[0063]

[0064] Among them, C i is the full charge capacity of a single charging capacity evaluation data segment, T0 is the charging start time, T1 is the charging end time, I is the charging current, SOC T0 SOC is the starting SOC for charging. T1 End SOC for charging;

[0065] After obtaining the full charge capacity of each charging capacity evaluation data segment, if the difference between two adjacent full charge capacities is greater than a predetermined threshold, the latter full charge capacity value is discarded.

[0066] Furthermore, since the actual power battery capacity cannot undergo sudden changes, after calculating the full charge capacity of each charging capacity evaluation data segment, if the difference between two adjacent full charge capacities is too large, the latter full charge capacity value should be discarded; optionally, the capacity difference threshold can be defined as 5%.

[0067] Preferably, obtaining the initial full charge capacity and the current full charge capacity of the power battery of the vehicle to be evaluated includes:

[0068] The initial full charge capacity is obtained by averaging the full charge capacities of multiple charging segments in the initial use of the vehicle; the current full charge capacity is obtained by averaging the full charge capacities of multiple charging segments in the recent period of the vehicle.

[0069] Specifically, the initial full charge capacity is obtained by averaging the full charge capacities of multiple charging segments in the early stage of vehicle use, and the number of charging segments can be 5 to 10. The current full charge capacity is obtained by averaging the full charge capacities of multiple charging segments in the recent period, and the number of charging segments can be 5 to 10.

[0070] S4: Evaluate the capacity attenuation condition of the power battery of the vehicle to be evaluated based on the initial full charge capacity and the current full charge capacity to obtain an evaluation result.

[0071] Specifically, the capacity decay rate of the power battery is calculated by the following formula: capacity decay rate = 1 - current full charge capacity / initial full charge capacity.

[0072] This embodiment does not rely on test and R&D data, but only uses the national standard uploaded data of the vehicle power battery to be evaluated to perform efficient quantitative analysis of the capacity decay of the power battery. There is no need for special processing or testing of the on-board power battery. The present invention obtains the initial full charge capacity and current full charge capacity of the power battery by preprocessing the uploaded power battery data, and then evaluates the capacity decay status of the power battery. It has strong operability, low cost and high evaluation efficiency.

[0073] Example 2

[0074] Figure 2 Schematic diagram of the power battery capacity attenuation evaluation system of the present invention. Figure 2 As shown, the present invention also provides a power battery capacity attenuation evaluation system, the system comprising:

[0075] The first acquisition module 201 is used to acquire the power battery uploaded data of the vehicle to be evaluated;

[0076] A data preprocessing module 202 is configured to preprocess the data uploaded by the power battery to obtain a charging capacity evaluation data segment of the power battery;

[0077] A second acquisition module 203 is configured to obtain an initial full charge capacity and a current full charge capacity of the power battery of the vehicle to be evaluated based on the charging capacity evaluation data segment;

[0078] The capacity evaluation module 204 is configured to evaluate the capacity attenuation of the power battery of the vehicle to be evaluated based on the initial full charge capacity and the current full charge capacity to obtain an evaluation result.

[0079] Preferably, the data preprocessing module 202 preprocesses the power battery uploaded data to obtain the charging capacity evaluation data fragment of the power battery, including:

[0080] The preprocessing includes: data cleaning, data slicing and data screening; the data cleaning includes eliminating duplicate values, invalid values ​​and abnormal values; the data slicing includes extracting charging segments based on the charging status; the data screening includes extracting charging segments that meet preset conditions as charging capacity evaluation data segments based on the reporting time, charging status, SOC, total current, maximum and minimum temperatures.

[0081] Preferably, the second acquisition module 203 obtains the initial full charge capacity and the current full charge capacity of the power battery of the vehicle to be evaluated according to the charging capacity evaluation data segment, including:

[0082] The full charge capacity of each charge capacity evaluation data segment is obtained by the following formula:

[0083]

[0084] Among them, C i is the full charge capacity of a single charging capacity evaluation data segment, T0 is the charging start time, T1 is the charging end time, I is the charging current, SOC T0 SOC is the starting SOC for charging. T1 End SOC for charging;

[0085] After obtaining the full charge capacity of each charging capacity evaluation data segment, if the difference between two adjacent full charge capacities is greater than a predetermined threshold, the latter full charge capacity value is discarded.

[0086] Preferably, the second acquisition module 203 obtains the initial full charge capacity and the current full charge capacity of the power battery of the vehicle to be evaluated, including:

[0087] The initial full charge capacity is obtained by averaging the full charge capacities of multiple charging segments during the initial use of the vehicle.

[0088] The current full charge capacity is obtained by averaging the full charge capacities of multiple recent charging segments of the vehicle.

[0089] Preferably, the capacity evaluation module 204 evaluates the capacity attenuation of the power battery of the vehicle to be evaluated based on the initial full charge capacity and the current full charge capacity, and obtains an evaluation result including:

[0090] The capacity attenuation rate of the power battery is calculated using the following formula:

[0091] Capacity decay rate = 1-current full charge capacity / initial full charge capacity.

[0092] The specific implementation process of the functions realized by each module in Example 2 of the present invention is the same as the implementation process of each method step in Example 1, and will not be repeated here.

[0093] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention description and drawings under the concept of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for evaluating power battery capacity attenuation, characterized in that: The method comprises the following steps: S1: Obtain the power battery upload data of the vehicle to be evaluated; S2: Preprocessing the uploaded data of the power battery to obtain a charging capacity evaluation data segment of the power battery; S3: Obtaining the initial full charge capacity and the current full charge capacity of the power battery of the vehicle to be evaluated according to the charging capacity evaluation data segment; S4: Evaluate the capacity attenuation of the power battery of the vehicle to be evaluated based on the initial full charge capacity and the current full charge capacity to obtain an evaluation result; Obtaining the initial full charge capacity and current full charge capacity of the power battery of the vehicle to be evaluated includes: The initial full charge capacity is obtained by averaging the full charge capacities of multiple charging segments during the initial use of the vehicle. The current full charge capacity is obtained by averaging the full charge capacities of multiple recent charging segments of the vehicle.

2. The method according to claim 1, characterized in that The pre-processing of the power battery uploaded data to obtain the charging capacity evaluation data fragment of the power battery includes: The preprocessing includes: data cleaning, data slicing and data screening; the data cleaning includes eliminating duplicate values, invalid values ​​and abnormal values; the data slicing includes extracting charging segments based on the charging status; the data screening includes extracting charging segments that meet preset conditions as charging capacity evaluation data segments based on the reporting time, charging status, SOC, total current, maximum and minimum temperatures.

3. The method according to claim 1, characterized in that Obtaining the initial full charge capacity and the current full charge capacity of the power battery of the vehicle to be evaluated according to the charging capacity evaluation data segment includes: The full charge capacity of each charge capacity evaluation data segment is obtained by the following formula: Among them, C i is the full charge capacity of a single charging capacity evaluation data segment, T0 is the charging start time, T1 is the charging end time, I is the charging current, SOC T0 SOC is the starting SOC for charging. T1 End SOC for charging; After obtaining the full charge capacity of each charging capacity evaluation segment, if the difference between two adjacent full charge capacities is greater than a predetermined threshold, the latter full charge capacity value is discarded.

4. The method according to claim 1, wherein The evaluating the capacity attenuation condition of the power battery of the vehicle to be evaluated based on the initial full charge capacity and the current full charge capacity, and obtaining the evaluation result includes: The capacity attenuation rate of the power battery is calculated using the following formula: Capacity decay rate = 1-current full charge capacity / initial full charge capacity.

5. A power battery capacity attenuation evaluation system, characterized in that: The system comprises: The first acquisition module is used to obtain the uploaded power battery data of the vehicle to be evaluated; A data preprocessing module, configured to preprocess the data uploaded by the power battery to obtain a charging capacity evaluation data segment of the power battery; A second acquisition module is configured to obtain an initial full charge capacity and a current full charge capacity of the power battery of the vehicle to be evaluated based on the charging capacity evaluation data segment; a capacity evaluation module, configured to evaluate the capacity attenuation of the power battery of the vehicle to be evaluated based on the initial full charge capacity and the current full charge capacity, and obtain an evaluation result; The second acquisition module obtains the initial full charge capacity and the current full charge capacity of the power battery of the vehicle to be evaluated, including: The initial full charge capacity is obtained by averaging the full charge capacities of multiple charging segments during the initial use of the vehicle. The current full charge capacity is obtained by averaging the full charge capacities of multiple recent charging segments of the vehicle.

6. The system according to claim 5, characterized in that The data preprocessing module preprocesses the power battery uploaded data to obtain the charging capacity evaluation data segment of the power battery, including: The preprocessing includes: data cleaning, data slicing and data screening; the data cleaning includes eliminating duplicate values, invalid values ​​and abnormal values; the data slicing includes extracting charging segments based on the charging status; the data screening includes extracting charging segments that meet preset conditions as charging capacity evaluation data segments based on the reporting time, charging status, SOC, total current, maximum and minimum temperatures.

7. The system according to claim 5, characterized in that The second acquisition module obtains the initial full charge capacity and the current full charge capacity of the power battery of the vehicle to be evaluated according to the charging capacity evaluation data segment, including: The full charge capacity of each charge capacity evaluation data segment is obtained by the following formula: Among them, C i is the full charge capacity of a single charging capacity evaluation data segment, T0 is the charging start time, T1 is the charging end time, I is the charging current, SOC T0 SOC is the starting SOC for charging. T1 End SOC for charging; After obtaining the full charge capacity of each charging capacity evaluation data segment, if the difference between two adjacent full charge capacities is greater than a predetermined threshold, the latter full charge capacity value is discarded.

8. The system according to claim 5, wherein: The capacity evaluation module evaluates the capacity attenuation of the power battery of the vehicle to be evaluated based on the initial full charge capacity and the current full charge capacity, and obtains an evaluation result including: The capacity attenuation rate of the power battery is calculated using the following formula: Capacity decay rate = 1-current full charge capacity / initial full charge capacity.

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