Abstract
Accurate estimation of battery state of charge (SOC) is of great significance for extending battery life, improving battery utilization, and ensuring battery safety. Aiming to improve the accuracy of SOC estimation, in this paper, a temperature-dependent second-order RC equivalent circuit model is established for lithium-ion batteries, based on the battery electrical characteristics at different ambient temperatures. Then, a dual Kalman filter algorithm is proposed to estimate the battery SOC, using the proposed equivalent circuit model. The SOC estimation results are compared with the SOC value obtained from experiments, and the estimation errors under different temperature conditions are found to be within ±0.4%. These results prove that the proposed SOC estimation algorithm, based on a temperature-dependent second-order RC equivalent circuit model, provides accurate SOC estimation performance with high temperature adaptability and robustness.
Highlights
One fundamental challenge in the commercialization of electric vehicles is the battery system, and a safe and efficient battery system hinges on a reliable battery management system (BMS) [1]
In order to further improve the accuracy of state of charge (SOC) estimation, in this paper, the electrical characteristics of lithium-ion batteries under different ambient temperatures are analyzed, and a temperature-dependent second-order RC model is established
The output from the extended Kalman filter (EKF) is deal with the uncertainties caused by modeling imperfections, thereby improving the SOC estimation fed to the proposed battery model to produce a corrected SOC estimate, SOCEKF
Summary
One fundamental challenge in the commercialization of electric vehicles is the battery system, and a safe and efficient battery system hinges on a reliable battery management system (BMS) [1]. In order to further improve the accuracy of SOC estimation, in this paper, the electrical characteristics of lithium-ion batteries under different ambient temperatures are analyzed, and a temperature-dependent second-order RC model is established. The structure of the proposed model is shown, where V t represents the battery terminal voltage, Vocv indicates the OCV, V 1 and V 2 denote the voltages generated by the polarization phenomenon, I stands for the current (positive for charging and negative for discharging), T represents the ambient temperature, R0 is the ohmic internal resistance, R1 and R2 are the polarization internal resistances, and. We shall explain in detail how these unknown parameters can be identified
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