Analysing the Temperature Influence on State of Charge Estimation for an Electric Vehicle

In an electric vehicle technology, the battery is an integral component of the system. The available charge of the battery is represented in terms of the state of charge (SOC). A battery management system (BMS) is implemented in EV to calculate the accurate SOC and to control the battery behaviour. In literature, there are different methods mentioned to estimate SOC of battery. However, these proposed methods have many limitations like complex algorithm, high computation cost. Out of all these methods the major drawbacks is that it has not considered the effect of factors like aging, temperature, internal chemical composition, it's charging/discharging rate on SOC estimation of the battery. Against this background, the paper proposes a method to analyze the effect of these factors on SOC for its accurate estimation. For highlighting the effect of the temperature on the SOC, an existing state-space model of battery is reconstructed using the temperature coefficient. For estimation purpose, an extended Kalman filter (EKF) method is employed in the modified battery model. Further, it is implemented in the MATLAB environment and obtained results help to analyze the impact of temperature on open-circuit voltage (OCV) and SOC of the battery.