Research on the Capacity Fading Characteristics of a Li-ion Battery based on an Equivalent Thermal Model

Temperature has a direct impact on the capacity fading of a power Li-ion battery during the battery's lifecycle; however, the inner temperature of the battery cannot be measured directly because of the sealed structure. To address this problem, we estimate the inner temperature of a Li-ion battery by measuring the surface and ambient temperature using an equivalent thermal model to build the ETM-Arrhenius (equivalent thermal model-Arrhenius) model that models the dependence of the battery capacity fading on the inner temperature to enable the accurate prediction of the capacity fading characteristics of a Li-ion battery during its lifecycle. We conducted a lifecycle test on a Li-ion battery at different temperatures, and the results indicate that the ETM-Arrhenius model can predict the capacity fading characteristics of a Li-ion battery accurately during its lifecycle; in addition, when the model is used in EFK, UKF and other common state-of-charge (SOC) estimation algorithms, the accuracy of the SOC estimation can be improved significantly.