In this paper, a high efficiency bidirectional dc-dc converter with wide dc gain range face to photovoltaic energy storage system (PESS) based on the 48 V battery module is proposed. The dc-dc converter uses two-stage topology, which meets the demand of wide gain range in PESS. The characteristics and design rules of the converter was discussed in detail. A 5 kW prototype was built and the experimental results were given in the paper.