On-line estimation of dynamic state-of-charge for lead acid battery based on fuzzy logic

The performance and life expectancy of battery depend heavily on the battery management based on SOC estimation in photovoltaic systems and electric vehicles. The objective of work presented in this paper is to develop a novel on-line estimation of SOC for the lead acid battery. The proposed method consists of two major subroutines: Open-Circuit-Voltage (OCV) extrapolation and fuzzy logic compensation. The determination of initial SOC based on OCV extrapolation functions as the basis of Coulomb counting process. Thereafter the estimation of dynamic SOC is compensated by the fuzzy logic model, which adopted discharging current and temperature as input variables to calculate the compensation coefficient. Results of the simulations as well as experiment on a VRLA lead-acid battery is also included that indicate the validity of the proposed methodology.