Model-based methods for state of charge estimation in Lithium-Ion batteries have been widely employed. In this paper a novel filtering model-based algorithm is developed to estimate the state of charge. An 1RC equivalent circuit model and a piecewise linear approximation of the relationship between Open Circuit Voltage and State Of Charge are utilized for modelling the system of interest. A simulation study that consideres pulsed current discharge is developed. To validate these results, real battery data are utilized under various dynamic test profiles. The performance of the proposed filtering algorithm is compared with Extended Kalman Filter and Particle Filter.