Integration of Coulomb Counting Method in Battery Management System for Electric Vehicle

Abstract

The coulomb counting (CC) approach is widely used in SOC estimation due to its simplicity and low calculation cost. However, in practical applications, the lack of error correction ability limits its accuracy due to the measured noise in the practical occasion. To address the issue, an improved CC (ICC) approach based on numerical iteration is proposed in this paper. In the proposed approach, a battery model based on a 2nd-order, RC circuit is first formulated to determine the SOC-OCV curve, R-OCV curve, and inner parameters. In the model, the slow dynamic and fast dynamic voltages are described separately, and are utilized for battery state assessment. Then, the SOC will be estimated by the CC approach at the unsteady state but through a numerical iteration approach at steady state. Consequently, the accumulative SOC error from the CC approach will be corrected when the numerical iteration approach is applied. INDEX TERMS: Improved coulomb counting (ICC), state of charge (SOC), accumulative error correction, numerical iteration, error accumulation rate.