The effect of operating parameters such as the duty ratio, the pulse frequency and design parameters (the capacitor configuration index) on the performance of a battery/hybrid system were studied in detail. The highest value of the fractional capacity increase was observed at duty ratios of 0.2-0.3 depending on the frequency of operation. The increase of the discharge capacity of the hybrid system was limited above the maximum Eigen frequency. The hybrid system has smaller internal ohmic losses when compared to the battery. Higher power can be withdrawn from the hybrid system which has the same energy as that of the battery. However when compared on a mass basis, the Ragone plots indicated that the hybrid has lower power and energy densities. (C) 2004 Elsevier B.V. All rights reserved.