Method for assessing SOH (state of health) of lithium ion battery

Abstract

The invention discloses a method for assessing an SOH (state of health) of a lithium ion battery. The method comprises the following steps: a, establishing an internal resistance model of the lithium ion battery; b, acquiring current and terminal voltage data of the lithium ion battery under different SOCs (states of charge), and storing the data if the change rate of two adjacent current values is not greater than a set value; c, performing fitting on the stored data by utilizing the internal resistance model of the lithium ion battery to obtain an R2-SOC curve and a tau-SOC curve of the lithium ion battery during a discharge process, and further, working out the ohmic resistance and the diffusion resistance of the lithium ion battery at the T moment; d, calculating the SOH value of the lithium ion battery; e, performing assessment on the SOH of the battery according to the SOH value of the lithium ion battery. According to the method for assessing the SOH of the lithium ion battery disclosed by the invention, different SOH assessment methods are adopted by the lithium ion battery under different SOCs, and therefore, the accuracy of an assessment result is greatly improved. By adopting the method, maintenance personnel can discover and eliminate hidden troubles of the battery in time to ensure the normal operation of an electric vehicle.

Description

technical field [0001] The invention relates to a method capable of accurately evaluating the state of health (SOH) of a lithium-ion battery used in an electric vehicle, belonging to the technical field of automobiles. Background technique [0002] The battery system of an electric vehicle is composed of multiple lithium-ion batteries connected in series and parallel. After the battery system has been running for a period of time, the SOH (abbreviation for State of Health, that is, the state of charge) of different lithium-ion batteries may vary greatly. , the deterioration of the health status of individual batteries will have a greater impact on the performance of the entire battery system. Therefore, accurate assessment of the health status of each lithium-ion battery is of great significance for timely troubleshooting of battery failures. [0003] At present, there are many methods for evaluating the state of health of a battery, but none of these methods consider the SO...

AI Technical Summary

Problems solved by technology

[0003] At present, there are many methods for evaluating the state of health of a battery, but none of these methods consider the SOC of the battery (abbreviation for state of charge, a term used in the battery industry, referring to the state of charge, also known as the remaining capacity, when the battery is used for a period of time or left for a long time The ratio of the remaining capacity after no use to the capacity of the fully charged state is usually expressed as a percentage. SOC=1 means that the battery is fully charged, and the state of charge of the battery must be considered when controlling the operation of the battery), so the evaluation accuracy is not ideal.

For example, the commonly used safety method cannot be accurate under the full SOC of HEV (abbreviation for Hybrid Electric Vehicle, that is, hybrid electric vehicle) and PHEV (plug in hybrid electric vehicle, specifically refers to a hybrid electric vehicle that is charged by plugging in). Assessing the State of Health of Lithium-Ion Batteries

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