State of health estimation of VRLA batteries using fuzzy logic

State of Health (SOH) is an important characteristic in determining the overall profile of a battery. SOH is a measure of the remaining full charge capacity of a battery with respect to its nominal capacity. As continuously charged and discharged and battery ages, the chemical composition starts to degrade. This paper describes a novel online method to determine the SOH of a battery. In the proposed method, the SOH of Valve-Regulated Lead-Acid (VRLA) batteries is estimated using the relation between the State of Charge (SOC) and the battery open-circuit terminal voltage (Voc). This estimation is performed using the least-square method and the fuzzy logic. Experimental results show good estimation of the SOH in relatively short time.