This present paper introduces a battery management system using nonlinear model predictive control for a hybrid electric vehicle. This paper adds two new contributions to this field. First, the apparent relationship between the battery power and the future road load is addressed in the cost function of the fuel economy optimal control problem with a simplified hybrid electric vehicle energy management system model. Second, it examines quantitatively the effects of operating the engine along the best efficiency line of the engine with a continuously variable transmission using a commercially available hybrid electric vehicle energy management electronic control unit simulator. Effectiveness of the proposed algorithm is validated by the JSAE-SICE benchmark problem II simulator.