This article presents a wide conversion ratio bidirectional dc-dc converter based on a bidirectional modified Single-ended primary-inductor converter (SEPIC converter). A key feature of this modified SEPIC converter is the non-dissipative current snubber circuit, which is used to achieve zero current switching and to suppress voltage spikes that occur during MOSFET switching. The snubber is made up of a capacitor, an inductor, and a diode that work together to form a resonant circuit that absorbs the voltage spike and returns it to the circuit without dissipating it. Even with conventional MOSFETs, high efficiency is achieved. The SEPIC converter differs from other bi-directional DC-DC converters in that it provides continuous output current, has fewer components, and can provide high conversion ratios of step-up and step-down voltage without exceedingly low or high duty-cycle. This paper presents a theoretical analysis with stages of operation in both step-up and step-down modes, theoretical waveforms, and the design procedure, as well as a comparison with other bidirectional dc-dc converter topologies. The experimental results are presented to validate the performance of the proposed converter using a 500-W prototype with Voltage Source V1 = 48 V and Voltage SourceV2 = 300 V.