This paper proposes and analyzes a two-stage isolated dc-dc converter for electric vehicle charging applications, where high efficiency over a wide range of battery voltages is required. The proposed converter employs a first dual-output isolation stage, and a second dual-input buck post-regulator. In such a post-regulator, the reduced voltage stress on the switching devices allows low conversion losses even with output voltages that may vary over a wide range. The isolation stage is always operated at resonance, it behaves as a dual-output dc-transformer (DCX), ensuring very high efficiency. The conversion structure, analysis, and design considerations are shown considering an experimental prototype rated 10 kW and interfacing a 800 V dc-link with an output bus in the voltage range 250 V - 500 V, which is common in electric vehicle battery-charging applications.