In this study, Thévenin-equivalent circuit-based lithium-ion battery is modeled for State of Charge (SoC) estimation via sliding mode technique. Internal resistance and open-circuit potentials for different charge and discharge rates are included as look-up tables for precise energy based modeling of the lithium-ion battery. A solution for SoC estimation is proposed under two assumptions which simplifies battery model and estimates the states with sliding mode observation techniques. The method gives a chance for general usage of various battery chemistries. Successful simulations have been performed to illustrate the effectiveness of the proposed solution technique.