Power battery health state assessment method

Abstract

The invention provides a power battery health state assessment method. The method comprises the following steps: calculating SOH of a battery monomer based on battery monomer parameters, battery monomer capacity variation in a charging process and a battery initial temperature-capacity coefficient relation curve; intervals are divided according to the average SOC value of the battery at the charging end moment, and battery consistency parameters are obtained through calculation according to the SOC of the single batteries in different intervals and the voltage range threshold value; and obtaining the health state of the power battery based on the SOH of the single battery and the battery consistency parameter. The method can be widely applied to power battery health state evaluation of the new energy electric vehicle, and is beneficial to finding battery performance degradation in time, optimizing battery management and maintenance strategies, prolonging the service life of the battery and improving the reliability and safety of the electric vehicle.

Description

Technical Field

[0001] The present invention belongs to the field of battery health assessment, and in particular relates to a method for assessing the health status of a power battery. Background Art

[0002] As the power source of electric vehicles, the demand and requirements for power batteries are getting higher and higher. Lithium-ion batteries have become the mainstream automotive power batteries due to their advantages such as high energy density, high power, high voltage platform, low self-discharge rate and no memory effect. However, with long-term use, power batteries will naturally age, performance will deteriorate and decline, and the health level will decrease. Therefore, accurate assessment of the health status of power batteries is particularly important. However, the existing technology has the following two shortcomings: it does not consider the influence between battery temperature and capacity, and does not consider the influence of battery cell consistency on battery health. Summary of the invention

[0003] In view of the shortcomings of the prior art, the present invention proposes a new method for evaluating the health status of a power battery.

[0004] The technical solution of the present invention is as follows: A method for evaluating the health status of a power battery, the method comprising: Calculate the battery cell based on the battery cell parameters, the battery cell capacity change during charging and the battery initial temperature-capacity coefficient relationship curve SOH ; According to the battery average at the end of charging SOCIETY The value is divided into intervals, and the battery cells in different intervals are SOCIETY The battery consistency parameters are calculated with the voltage extreme difference threshold; Based on battery cells SOH Calculate the power battery health status based on the battery consistency parameters.

[0005] Furthermore, the battery cell parameters, the battery capacity change during charging and the battery initial temperature-capacity coefficient relationship curve are used to calculate the battery cell capacity. SOH Specifically: Record the battery cell parameters at the start and end of charging; the battery cell parameters include the maximum SOCIETY Value, battery cell minimum SOCIETY value, the maximum temperature value of the battery cell and the minimum temperature value of the battery cell; The change in battery cell capacity during the charging process is calculated by integrating the charging current over time; The maximum value of the battery cell based on the charging start and end time SOCIETY Value, battery cell minimum SOCIETY The value of the battery cell is calculated SOCIETY Amount of change; According to the change of battery cell capacity and SOCIETY The change amount is used to calculate the available capacity of the battery cell; By using the pre-established battery starting temperature-capacity coefficient relationship curve, the lowest temperature value of the battery cell at the start of charging is substituted into the curve to calculate the capacity coefficient; Calculate the battery cell based on the capacity coefficient SOH .

[0006] Furthermore, the calculation formula for the change in battery cell capacity during the charging process is: , in, I is the charging current, t For charging time, It is the change of battery cell capacity during charging process.

[0007] Furthermore, the calculation formula of the SOC change of the battery cell is: , in, SOCIETY ema The maximum value of the battery cell at the end of charging SOCIETY value, SOCIETY emi The minimum value of the battery cell at the end of charging SOCIETY value, SOCIETY bma The maximum value of the battery cell at the start of charging SOCIETY value, SOCIETY bmi The minimum value of the battery cell at the start of charging SOCIETY value.

[0008] Furthermore, the calculation formula for the available capacity of the battery cell is: , in, C R is the available capacity of the battery cell, is the change in battery cell capacity during charging. For battery cells SOCIETY Amount of change.

[0009] Furthermore, the battery cell SOH The calculation formula is: , in, C B is the rated capacity of the battery cell, C R is the available capacity of the battery cell, σ is the capacity factor, and SOH is the health status of the battery cell.

[0010] Further, the battery average at the end of charging SOCIETY The value is divided into intervals, and the battery cells in different intervals are SOCIETY The specific process of calculating the battery consistency parameters with the voltage extreme difference threshold is as follows: According to the battery average at the end of charging SOCIETY The value size is divided into three intervals, and we get SOCIETY Partitions; Each section is equipped with a battery cell SOCIETY The extreme value is based on the maximum value of the battery cell at the end of charging. SOCIETY Value and minimum SOCIETY The difference in values ​​divided by the battery cells in the interval SOCIETY Extreme value threshold, get battery cell SOCIETY consistency parameters; according to SOCIETY Partitions, different settings SOCIETY The battery cell voltage extreme difference threshold within the interval is obtained by dividing the difference between the battery cell maximum voltage and the battery cell minimum voltage at the end of charging by the battery cell voltage extreme difference threshold within the interval to obtain the battery cell voltage consistency parameter; The battery cell SOCIETY The consistency parameter is multiplied by the battery cell voltage consistency parameter to obtain the battery consistency parameter.

[0011] Furthermore, the battery cell SOCIETY The calculation formula of the consistency parameter is: , in, SOCIETY i For the interval battery cell S OC The extreme value threshold, SOCIETY ema The maximum value of the battery cell at the end of charging SOCIETY value, SOCIETY emi The minimum value of the battery cell at the end of charging SOCIETY value.

[0012] Furthermore, the calculation formula of the battery cell voltage consistency parameter is: , in, V i is the voltage extreme difference threshold of the battery cell in the interval, V emi is the minimum voltage of the battery cell, V emaIt is the maximum voltage of the battery cell.

[0013] Furthermore, the calculation formula of the power battery health status is: , in, HI Is the health status of the power battery, It is a battery consistency parameter, and SOH is the health status of the battery cell.

[0014] Compared with the prior art, the present invention has the following advantages: The present invention takes into account the influence of battery temperature on capacity, improves the accuracy of battery SOH estimation, and introduces battery consistency parameters, which can better reflect the health status of the power battery system and improve the accuracy of battery health status assessment. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings generally illustrate various embodiments by way of example and not limitation, and together with the description and claims, serve to illustrate the embodiments of the invention. Where appropriate, the same reference numerals are used throughout the 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 present apparatus or method.

[0016] Figure 1 A schematic diagram of the method of the present invention is shown. DETAILED DESCRIPTION

[0017] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0018] like Figure 1 As shown, an embodiment of the present invention provides a method for evaluating the health status of a power battery, specifically: The battery SOH estimation method during charging is as follows: Record the maximum value of the 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 the 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 .

[0019] Battery capacity change during charging By integrating the charging current over time, , in, I is the charging current, t For charging time, It is the change of battery cell capacity during charging process.

[0020] Available capacity of battery cells C R The capacity change and SOC change during the charging process are measured, that is, , in, C R is the available capacity of the battery cell, is the change in battery cell capacity during charging. For battery cells SOCIETY Amount of change.

[0021] here ΔSOC The charging end time and start time SOCIETY The difference, that is , Since low temperature has a greater impact on battery capacity than high temperature, the lowest battery temperature at the start of charging is T bmi As a reference temperature for capacity, a laboratory environment is established T-σ Relationship curve, T is the battery starting temperature, σ is the capacity factor, T Charge capacity at temperature C T With rated capacity C B The ratio of σ=C T / C B .

[0022] The lowest battery temperature at the start of charging T bmi Substitution T-σ Relationship curve calculation σ , then the battery SOH is the ratio of the available capacity to the rated capacity at this temperature, that is, , The battery consistency measurement method is as follows: According to the battery average at the end of charging SOCIETY value SOCIETY avg The size is divided into three intervals, among which , The first interval is SOCIETY avg Less than 40%, the second interval is SOCIETY avg 40%~70%, the third interval is SOCIETY avg More than 70%. Each interval is equipped with a battery cell SOCIETY and voltage extreme difference threshold, battery cell SOCIETY Consistency parameter ξ soc The maximum and minimum values ​​of the battery cells at the end of charging SOCIETY The difference is the same as the battery cell SOCIETY The ratio of the extreme value threshold, that is , in, SOCIETY i For the interval battery cell S OC The extreme value threshold, SOCIETY ema The maximum value of the battery cell at the end of charging SOCIETY value, SOCIETY emi The minimum value of the battery cell at the end of charging SOCIETY value.

[0023] Similarly, according to SOCIETY Partitions, different settings SOCIETY The voltage difference threshold of the battery cell within the interval, the battery cell voltage consistency parameter ξ vol The maximum voltage of the battery cell at the end of charging V ema With the lowest voltage of the monomer V emi The ratio of the difference to the extreme difference threshold of the battery cell voltage, that is, , in, V i is the voltage extreme difference threshold of the battery cell in the interval, V emi is the minimum voltage of the battery cell, V ema It is the maximum voltage of the battery cell.

[0024] The battery consistency parameter ξ is the product of the single cell SOC and the voltage consistency parameter, that is, .

[0025] The health status of the power battery is HI Parameter evaluation, HI It's the battery SOH The comprehensive calculation of consistency, that is , in, HI Is the health status of the power battery, It is a battery consistency parameter, and SOH is the health status of the battery cell.

[0026] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for evaluating the health status of a power battery, characterized in that: The method comprises: Calculate the battery cell based on the battery cell parameters, the change in battery cell capacity during charging, and the battery initial temperature-capacity coefficient relationship curve SOH ; The battery cell parameters, the battery capacity change during charging and the battery initial temperature-capacity coefficient relationship curve are used to calculate the battery cell SOH Specifically: Record the battery cell parameters at the start and end of charging; the battery cell parameters include the maximum SOC Value, battery cell minimum SOC value, the maximum temperature value of the battery cell and the minimum temperature value of the battery cell; The change in battery cell capacity during the charging process is calculated by integrating the charging current over time; The maximum value of the battery cell based on the charging start and end time SOC Value, battery cell minimum SOC The value of the battery cell is calculated SOC Amount of change; According to the change of battery cell capacity and SOC The change amount is used to calculate the available capacity of the battery cell; By using the pre-established battery starting temperature-capacity coefficient relationship curve, the lowest temperature value of the battery cell at the start of charging is substituted into the curve to calculate the capacity coefficient; Calculate the battery cell based on the capacity coefficient SOH ; According to the battery average at the end of charging SOC The value is divided into intervals, and the battery cells in different intervals are SOC The battery consistency parameters are calculated with the voltage extreme difference threshold; The average battery value at the end of charging SOC The value is divided into intervals, and the battery cells in different intervals are SOC The specific process of calculating the battery consistency parameters with the voltage extreme difference threshold is as follows: According to the battery average at the end of charging SOC The value size is divided into three intervals, and we get SOC Partitioning; Each section is equipped with a battery cell SOC The extreme value is based on the maximum value of the battery cell at the end of charging. SOC Value and minimum SOC The difference in values ​​divided by the battery cells in the interval SOC Extreme value threshold, get battery cell SOC consistency parameters; according to SOC Partitions, different settings SOC The battery cell voltage extreme difference threshold within the interval is obtained by dividing the difference between the battery cell maximum voltage and the battery cell minimum voltage at the end of charging by the battery cell voltage extreme difference threshold within the interval to obtain the battery cell voltage consistency parameter; The battery cell SOC The consistency parameter is multiplied by the battery cell voltage consistency parameter to obtain the battery consistency parameter; Based on battery cells SOH Calculate the power battery health status based on the battery consistency parameters.

2. The power battery health status assessment method according to claim 1, characterized in that: The calculation formula for the change in battery cell capacity during the charging process is: ， in, I is the charging current, t For charging time, It is the change of battery cell capacity during charging process.

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

4. The method for evaluating the health status of a power battery according to claim 1, characterized in that: The calculation formula of the available capacity of the battery cell is: ， in, C R is the available capacity of the battery cell, is the change in battery cell capacity during charging. For battery cells SOC Amount of change.

5. The method for evaluating 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 is the rated capacity of the battery cell, C R is the available capacity of the battery cell, σ is the capacity factor, and SOH is the health status of the battery cell.

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

7. The method for evaluating the health status of a power battery according to claim 1, characterized in that: The calculation formula of the battery cell voltage consistency parameter is: ， in, V i is the voltage extreme difference threshold of the battery cell in the interval, V emi is the minimum voltage of the battery cell, V ema It is the maximum voltage of the battery cell.

8. The method for evaluating the health status of a power battery according to claim 1, characterized in that: The calculation formula of the power battery health status is: ， in, HI Is the health status of the power battery, It is a battery consistency parameter, and SOH is the health status of the battery cell.

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