This paper explores a bidirectional DC-DC converter for Supercapacitor-based energy storage systems in automotive applications. The presented converter consists of a Half-Bridge converter and a Current-Fed Push-Pull inverter with a transformer-isolation. Owing to the isolation topology, the supercapacitor can be operated in the wide voltage range, which results in an increase in the utilization of supercapacitor-stored energy. In order to reduce the switching losses in the half-bridge converter, Zero Voltage Switching technology is employed in the half-bridge converter. In addition, Synchronous Rectification is employed in the push-pull inverter so that the device conduction losses in the low voltage side is reduced. The proposed converter operation is verified by the simulation and the system feasibility is discussed from the view point of the practical automotive electrical systems.