Battery modeling is of major concern for Hybrid Electric Vehicle (HEV) and Electric vehicle (EV) modeling. The major issue lies in characterizing the battery power output in relation to battery's State of Charge (SOC) in various application conditions. In particular, the challenge is associated with the difficulty that the characteristic parameters of the battery, i.e. the accurate data on the open circuit voltage and the internal resistance are hardly obtainable in practical conditions.In this paper, a battery capacity representation and a practical way of battery modeling is introduced for simulation model development based on the experimental data. A realistic way of battery SOC representation is generated from the battery output data. Empirical formulation is derived from the data to correlate the battery current, voltage output with the battery SOC.The methodology provides an alternative for battery modeling when battery open circuit voltage, Voc, and resistant, R, as a function of battery SOC are not available. It generates up-to-date representation of the battery power capacity. The battery modeling is interchangeable with the model developed with Voc, and R specification. It is also adaptable for different power control strategy with interchangeable input and output parameters for battery modeling. The accuracy of the model is validated by comparison of the output between the new approach with that based on Voc and R as in ADVISOR, a HEV simulation model developed by National Renewable Energy Laboratory.