The State of Charge estimation employing empirical parameters measurements for various temperatures

The state of charge (SOC) estimation algorithm uses the model parameter, which includes capacity, open circuit voltage (OCV), resistance and capacitance. These model parameter values are subject to be changed at varying temperatures. In order to estimate SOC for temperature variation, it is indispensable to include the temperature effect on battery´s performance. In this paper, the state of charge estimation employing empirical parameters measurements is introduced for SOC estimation for various temperatures. The internal parameters are measured on Li-ion batteries from 10degC through 50degC at an interval of 10degC. Especially, the modified parameters are applied to estimate SOC at below room temperature and low SOC. The measured results are incorporated in the extend Kalman filter (EKF) algorithm and verified by comparison of Ah-counting and EKF result. The estimation and the results are shown to be under 3%.