One of the trends for low-voltage dc grids is the use of a two-line dc distribution in order to facilitate the interface to present-time ac grids, and also to allow the flexible use of diverse loads. Another feature of such dc grids is the distributed storage elements in houses and buildings. This storage system needs an isolated power converter to interface battery and grid. This paper presents the analysis, design and experimental validation of a 30 kW two-stage dual converter, interfacing a ±350 Vdc or battery ±380 Vdc grid and a bank. The first stage consists of a non-isolated synchronous Boost converter with current control. Whereas the second stage is an isolated bidirectional C3LC converter providing same static characteristics in both ways of energy transfer.