The coulomb counting method gives vital information for determination of state-of-charge (SOC) of battery, which in turn is a useful method for range determination of an electric vehicle. By investigating the charging and discharging characteristics for a number of cycles of operation, coulombic efficiency of the battery is determined. The variation observed in coulombic efficiency with respect to the number of cycle was empirically modeled with the help of polynomial as well as exponential curve fitting method in Matlab. Models thus developed was again validated for the later cycles of operation. The empirical model derived with the polynomial curve fitting was found to be the best suited for the requirement of the range detection system of an electric vehicle. A hardware related to this work is also developed.