A method for evaluating the health status of power batteries

Abstract

This invention provides a method for assessing the health status of a power battery. The method includes: calculating the state of harmonics (SOH) of a battery cell based on individual cell parameters, the change in battery cell capacity during charging, and the relationship curve between the battery's initial temperature and capacity coefficient; dividing the battery into intervals based on the average state of charge (SOC) at the end of charging, and calculating battery consistency parameters based on the SOC and voltage range thresholds of different intervals; and obtaining the power battery's health status based on the individual cell SOH and the battery consistency parameters. This invention can be widely applied to assessing the health status of power batteries in new energy electric vehicles, helping to promptly detect battery performance degradation, optimize battery management and maintenance strategies, extend battery life, and improve the reliability and safety of electric vehicles.

Description

Technical Field

[0001] This invention belongs to the field of battery health assessment, and specifically relates to a method for assessing the health status of a power battery. Background Technology

[0002] As the power source for electric vehicles, the demands and requirements for power batteries are becoming increasingly stringent. Lithium-ion batteries, due to their advantages such as high energy density, high power, high voltage platform, low self-discharge rate, and no memory effect, have become the mainstream power batteries for automobiles. However, with prolonged use, power batteries will naturally age, their performance will deteriorate, and their health status will decline. Therefore, accurate assessment of the health status of power batteries is particularly important. However, existing technologies have the following two shortcomings: they do not consider the influence between battery temperature and capacity, and they do not consider the impact of cell consistency on battery health status. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention proposes a novel method for assessing the health status of power batteries.

[0004] The technical solution of the present invention is as follows:

[0005] A method for assessing the health status of a power battery, the method comprising:

[0006] Calculate the battery cell parameters, the change in battery cell capacity during charging, and the battery initial temperature-capacity coefficient relationship curve. SOH ;

[0007] Based on the average battery level at the end of charging SOCIETY The values ​​are divided into intervals, and the battery cells within each interval are further classified. SOCIETY Battery consistency parameters are calculated using the voltage range threshold.

[0008] Based on battery cells SOH The health status of the power battery is calculated based on battery consistency parameters.

[0009] Furthermore, the calculation of battery cells based on individual battery cell parameters, changes in battery capacity during charging, and the battery initial temperature-capacity coefficient relationship curve... SOH Specifically:

[0010] Record the battery cell parameters at the start and end times of charging; the battery cell parameters include the maximum battery cell size. SOCIETY Value, minimum value of a single battery cell SOCIETY Values, maximum temperature of a single battery cell, and minimum temperature of a single battery cell;

[0011] The change in the capacity of a single battery cell during charging is calculated by integrating the charging current over time.

[0012] Based on the maximum value of the battery cell at the start and end times of charging. SOCIETY Value, minimum value of a single battery cell SOCIETY The value is calculated to obtain the battery cell's value. SOCIETY Change;

[0013] Based on the change in the capacity of individual battery cells and SOCIETY The change in quantity is used to calculate the usable capacity of a single battery cell;

[0014] The capacity coefficient is calculated by substituting the lowest temperature value of a single battery cell at the start of charging into the pre-established battery initial temperature-capacity coefficient relationship curve.

[0015] The battery cell is calculated based on the capacity factor. SOH .

[0016] Furthermore, the formula for calculating the change in battery cell capacity during the charging process is as follows:

[0017] ,

[0018] in, I For charging current, t For charging time, This represents the change in the capacity of a single battery cell during the charging process.

[0019] Furthermore, the formula for calculating the SOC change of the battery cell is as follows:

[0020] ,

[0021] in, SOCIETY ema The maximum value of a single battery cell at the end of charging. SOCIETY value, SOCIETY emi The minimum value of a single battery cell at the end of charging. SOCIETY value, SOCIETY bma The maximum value of a single battery cell at the start of charging. SOCIETY value, SOCIETY bmi The minimum value of a single battery cell at the start of charging. SOCIETY value.

[0022] Furthermore, the formula for calculating the usable capacity of the battery cell is as follows:

[0023] ,

[0024] in, C R This refers to the usable capacity of a single battery cell. This represents the change in the capacity of a single battery cell during charging. For battery cells SOCIETY Change.

[0025] Furthermore, the battery cell SOH The calculation formula is:

[0026] ,

[0027] in, C B The rated capacity of a single battery cell. C R This refers to the usable capacity of a single battery cell. σ is the capacity factor, and SOH is the state of health of a single battery cell.

[0028] Furthermore, the average battery charge at the end of charging... SOCIETY The values ​​are divided into intervals, and the battery cells within each interval are further classified. SOCIETY The specific process of calculating battery consistency parameters using the voltage range threshold is as follows:

[0029] Based on the average battery level at the end of charging SOCIETY Divide the value into three intervals and obtain SOCIETY Partitioning;

[0030] Each section is equipped with a single battery cell. SOCIETY The range threshold is based on the maximum value of a single battery cell at the end of charging. SOCIETY Value and minimum SOCIETY The difference in values ​​divided by the number of individual cells within the range SOCIETY The range threshold is used to obtain the battery cell. SOCIETY Consistency parameters;

[0031] according to SOCIETY Partitions, set different SOCIETY The threshold for the voltage range of individual cells within the interval is obtained by dividing the difference between the highest and lowest voltage of a single cell at the end of charging by the threshold for the voltage range of individual cells within the interval.

[0032] battery cells SOCIETY The battery consistency parameter is obtained by multiplying the consistency parameter of the individual cell voltage by the consistency parameter of the battery.

[0033] Furthermore, the battery cell SOCIETY The formula for calculating the consistency parameter is:

[0034] ,

[0035] in, SOCIETY i For the range of battery cells S OC Range threshold SOCIETY ema The maximum value of a single battery cell at the end of charging. SOCIETY value, SOCIETY emi The minimum value of a single battery cell at the end of charging. SOCIETY value.

[0036] Furthermore, the calculation formula for the battery cell voltage consistency parameter is as follows:

[0037] ,

[0038] in, V i This represents the threshold value for the voltage range of individual battery cells within the specified range. V emi This is the lowest voltage of a single battery cell. V ema This is the highest voltage of a single battery cell.

[0039] Furthermore, the formula for calculating the health status of the power battery is as follows:

[0040] ,

[0041] in, HI For the health status of the power battery, These are battery consistency parameters, and SOH represents the health status of a single battery cell.

[0042] Compared with the prior art, the present invention has the following advantages:

[0043] This invention takes into account the impact of battery temperature on capacity, improving the accuracy of battery SOH estimation. It also introduces battery consistency parameters, which better reflect the health status of the power battery system and improve the accuracy of battery health status assessment. Attached Figure Description

[0044] The accompanying drawings illustrate various embodiments generally by way of example rather than limitation, and are used, together with the specification and claims, to explain embodiments of the invention. Where appropriate, the same reference numerals are used in all drawings to refer to the same or similar parts. Such embodiments are illustrative and are not intended to be exhaustive or exclusive embodiments of the apparatus or method.

[0045] Figure 1 A schematic diagram of the method of the present invention is shown. Detailed Implementation

[0046] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0047] like Figure 1 As shown, this embodiment of the invention provides a method for assessing the health status of a power battery, specifically:

[0048] The method for estimating battery SOH during charging is as follows:

[0049] Record the maximum value of a single battery cell at the start of charging. SOCIETY value SOCIETY bma The smallest battery cell SOCIETY value SOCIETY bmi Maximum battery temperature T bma Minimum battery temperature T bmi Record the maximum value of a single battery cell at the end of charging. SOCIETY value SOCIETY ema The smallest battery cell SOCIETY value SOCIETY emi Maximum battery temperature T ema Minimum battery temperature T emi .

[0050] Change in battery capacity during charging Calculated by integrating the charging current over time, i.e.

[0051] ,

[0052] in, I For charging current, t For charging time, This represents the change in the capacity of a single battery cell during the charging process.

[0053] Available capacity of battery cell C R Measured by the change in capacity and the change in SOC during the charging process, i.e.

[0054] ,

[0055] in, C R This refers to the usable capacity of a single battery cell. This represents the change in the capacity of a single battery cell during charging. For battery cells SOCIETY Change.

[0056] here ΔSOC The end time and start time of charging SOCIETY Difference, i.e.

[0057] ,

[0058] Since low temperatures have a greater impact on battery capacity than high temperatures, the lowest battery temperature at the start of charging will be used as the starting point. T bmi The reference temperature for capacity is established in a laboratory environment. T-σ Relationship curve T For battery initial temperature, σ The capacity factor is T Charging capacity at temperature C T With rated capacity C B The ratio, i.e. σ=C T / C B .

[0059] The lowest battery temperature at the start of charging. T bmi Substitution T-σ Relationship curve calculation σ Then, the SOH of the battery is the ratio of its usable capacity to its rated capacity at this temperature, i.e.

[0060] ,

[0061] The battery consistency measurement method is as follows:

[0062] Based on the average battery level at the end of charging SOCIETY value SOCIETY avg Divide the space into three intervals by size, among which

[0063] ,

[0064] The first interval is SOCIETY avg Less than 40%, the second interval is SOCIETY avg The range is 40% to 70%, and the third range is... SOCIETY avg Greater than 70%. Each interval has individual battery cells. SOCIETY Compared with the voltage range threshold, the battery cell SOCIETY Consistency parameter ξ soc The maximum and minimum values ​​of a single battery cell at the end of charging. SOCIETY The difference is the same as that of a single battery cell. SOCIETY The ratio of the range threshold, i.e.

[0065] ,

[0066] in, SOCIETY i For the range of battery cells S OC Range threshold SOCIETY ema The maximum value of a single battery cell at the end of charging. SOCIETY value, SOCIETY emi The minimum value of a single battery cell at the end of charging. SOCIETY value.

[0067] Similarly, according to SOCIETY Partitions, set different SOCIETY The threshold for the voltage range of individual cells within the range, and the voltage consistency parameter ξ of individual cells. vol V is the highest voltage of a single battery cell at the end of charging. ema With the lowest voltage V of the single unit emi The ratio of the difference to the threshold voltage range of a single battery cell, i.e.

[0068] ,

[0069] in, V i This represents the threshold value for the voltage range of individual battery cells within the specified range. V emi This is the lowest voltage of a single battery cell. V ema This is the highest voltage of a single battery cell.

[0070] The battery consistency parameter ξ is the product of the cell SOC and the voltage consistency parameter, i.e. .

[0071] The health status of the power battery is determined by... HI Parameter evaluation, HI It is a battery SOH Comprehensive calculation with consistency, i.e.

[0072] ,

[0073] in, HI For the health status of the power battery, These are battery consistency parameters, and SOH represents the health status of a single battery cell.

[0074] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for assessing the health status of a power battery, characterized in that, The method includes: Calculate the battery cell parameters, the change in battery cell capacity during charging, and the battery initial temperature-capacity coefficient relationship curve. SOH ; The calculation of battery cells is based on individual battery parameters, changes in battery capacity during charging, and the battery initial temperature-capacity coefficient relationship curve. SOH Specifically: Record the battery cell parameters at the start and end times of charging; the battery cell parameters include the maximum battery cell size. SOC Value, minimum value of a single battery cell SOC Values, maximum temperature of a single battery cell, and minimum temperature of a single battery cell; The change in the capacity of a single battery cell during charging is calculated by integrating the charging current over time. Based on the maximum value of the battery cell at the start and end times of charging. SOC Value, minimum value of a single battery cell SOC The value is calculated to obtain the battery cell's value. SOC Change; Based on the change in the capacity of individual battery cells and SOC The change in quantity is used to calculate the usable capacity of a single battery cell; The capacity coefficient is calculated by substituting the lowest temperature value of a single battery cell at the start of charging into the pre-established battery initial temperature-capacity coefficient relationship curve. The battery cell is calculated based on the capacity factor. SOH ; Based on the average battery level at the end of charging SOC The values ​​are divided into intervals, and the battery cells within each interval are further classified. SOC Battery consistency parameters are calculated using the voltage range threshold. The average battery level at the end of charging SOC The values ​​are divided into intervals, and the battery cells within each interval are further classified. SOC The specific process of calculating battery consistency parameters using the voltage range threshold is as follows: Based on the average battery level at the end of charging SOC Divide the value into three intervals and obtain SOC Partitioning; Each section is equipped with a single battery cell. SOC The range threshold is based on the maximum value of a single battery cell at the end of charging. SOC Value and minimum SOC The difference in values ​​divided by the number of individual cells within the range SOC The range threshold is used to obtain the battery cell. SOC Consistency parameters; according to SOC Partitions, set different SOC The threshold for the voltage range of individual cells within the interval is obtained by dividing the difference between the highest and lowest voltage of a single cell at the end of charging by the threshold for the voltage range of individual cells within the interval. battery cells SOC The battery consistency parameter is obtained by multiplying the consistency parameter of the individual cell voltage by the consistency parameter of the battery. Based on battery cells SOH The health status of the power battery is calculated based on battery consistency parameters.

2. The method for assessing the health status of a power battery according to claim 1, characterized in that, The formula for calculating the change in the capacity of a single battery cell during the charging process is as follows: ， in, I For charging current, t For charging time, This represents the change in the capacity of a single battery cell during the charging process.

3. The method for assessing the health status of a power battery according to claim 1, characterized in that, The formula for calculating the SOC change of the battery cell is: ， in, SOC ema The maximum value of a single battery cell at the end of charging. SOC value, SOC emi The minimum value of a single battery cell at the end of charging. SOC value, SOC bma The maximum value of a single battery cell at the start of charging. SOC value, SOC bmi The minimum value of a single battery cell at the start of charging. SOC value.

4. The method for assessing the health status of a power battery according to claim 1, characterized in that, The formula for calculating the usable capacity of the battery cell is as follows: ， in, C R This refers to the usable capacity of a single battery cell. This represents the change in the capacity of a single battery cell during charging. For battery cells SOC Change.

5. The method for assessing the health status of a power battery according to claim 1, characterized in that, The battery cell SOH The calculation formula is: ， in, C B The rated capacity of a single battery cell. C R This refers to the usable capacity of a single battery cell. σ is the capacity factor, and SOH is the state of health of a single battery cell.

6. The method for assessing the health status of a power battery according to claim 1, characterized in that, The battery cell SOC The formula for calculating the consistency parameter is: ， in, SOC i For the range of battery cells S OC Range threshold SOC ema The maximum value of a single battery cell at the end of charging. SOC value, SOC emi The minimum value of a single battery cell at the end of charging. SOC value.

7. The method for assessing the health status of a power battery according to claim 1, characterized in that, The formula for calculating the battery cell voltage consistency parameter is as follows: ， in, V i This represents the threshold value for the voltage range of individual battery cells within the specified range. V emi This is the lowest voltage of a single battery cell. V ema This is the highest voltage of a single battery cell.

8. The method for assessing the health status of a power battery according to claim 1, characterized in that, The formula for calculating the health status of the power battery is as follows: ， in, HI For the health status of the power battery, These are battery consistency parameters, and SOH represents the health status of a single battery cell.

Images