Observer for Lithium-Ion Battery State of Charge Estimation in Electric Vehicles

Abstract

This paper recommends a new method for SOC estimation. In this technique, a new equivalent circuit battery model with one RC block is designed considering self-discharge. Associated with theconventional methods, some improvements have been chieved. Firstly, a Sliding Mode Observer (SMO) is adopted to estimatethe SOC. Secondly, the new method divides the SOC estimation into two stages which include charging stage and dischargingstage according to the battery status. The series resistance and parallel resistance of RC block in the battery model are taken intoaccount to estimate the SOC in discharging of battery. It enhances the SOC estimation accuracy especially for large dischargecurrent. Finally, a simulation is conducted to verify the performance of the method.