Online SoC Estimation for Lithium-Ion Batteries Based on the OCV Online Calculation and Coulomb Counting Method

State of charge (SoC) evaluation is one of the main responsibilities of battery management system. This article introduced a method for online calculation of battery open circuit voltage (OCV) through battery port voltage and current. The mathematical expression between OCV and port voltage and current was derived, and an online OCV solution method based on RLS was presented. Then, an online SoC estimation method combined the advantages of the coulomb counting (CC) method and the online OCV solution method is proposed. The implementation process of the proposed online SoC algorithm was introduced in detail, and its estimation accuracy and computational complexity were experimentally analyzed. The research results show that the accuracy of the proposed online SoC estimation algorithm is almost identical to that of the EKF method, and the computational complexity of the proposed algorithm is less than half that of the EKF method, indicating that the proposed method can be applied to online SoC estimation.