Online State of Charge estimation in electrochemical batteries: Application of pattern recognition techniques

High precision State-of-Charge (SOC) estimation in electrochemical batteries is an integral part of an effective energy management system. This paper proposes two pattern recognition methods for online estimation of SOC using the impulse response of the battery. By capturing the impulse responses at various levels of SOC, one can use the proposed pattern recognition methods in time domain or in frequency domain to determine the SOC of the battery. These two techniques have been studied in details and their precisions have been compared by simulation and experiment. The results show that the frequency domain method offers higher resolution in SOC estimation and lower computational complexity.