In this paper, a new wide conversion ratio step-up/down bi-directional converter is presented. The proposed converter is derived from the conventional Single Ended Primary Inductor Converter (SEPIC) topology and it can operate into a capacitor-diode voltage multiplier, which offers simple structure, reduced electromagnetic interference (EMI), and reduced semiconductors' voltage stresses. Other advantages include: continuous input/output current, extended step-up and step-down voltage conversion ratio without extreme low or high duty-cycle, simple control circuitry, and near zero input and output current ripples compared to other converter topologies. The low current ripple and high gain features result in a longer life-span and lower cost of the energy storage battery system. The theoretical analysis results obtained with the proposed structure are compared with other bi-direction converter topologies. Simulation and experimental results are presented to verify the performance of the proposed bi-directional converter.