Fractional calculus based modeling of open circuit voltage of lithium-ion batteries for electric vehicles

Abstract

Abstract Open circuit voltage (OCV) and state of charge (SOC) are key characteristic parameters of power batteries for electric vehicles. The OCV-SOC model is an integral of the design of the effective model and SOC estimation of the battery. However, there is a strong nonlinear relationship between OCV and SOC of lithium-ion batteries (LIBs). A novel OCV-SOC model of LIBs based on fractional calculus was proposed for the first time in this paper. The root mean squared error and the coefficient of determination were compared with the benchmarking models under a relatively fair condition. The sensitivity of the accuracy of the OCV-SOC models to temperature, numbers of data points, and SOC regions, were verified by the experimental results respectively, which showed that the proposed OCV-SOC model has good performance under different conditions, satisfying the accuracy requirements for modeling and state estimation of the battery in battery management systems.