This paper describes a 750-V, 100-kW, 20-kHz bidirectional isolated dc/dc converter with the “dual-active-bridge” configuration using four SiC-MOSFET/SBD two-in-one modules. It pays particular attention to conversion efficiency and power-loss breakdown. The overall maximum efficiency from the dc-input to the dc-output terminals is measured accurately to be 98.7%, excluding the gate-drive and control circuit losses from the overall power loss. A power-loss breakdown at the rated (100kW) operation is carried out to separate conduction, switching, iron, copper, and unknown losses from the overall loss. The power loss breakdown indicates that the sum of the conduction and switching losses produced in the four SiC modules is about 60% of the overall loss, and that the conduction loss is almost equal to the switching loss. Moreover, this paper provides theoretical and experimental discussions on a range of dead times for achieving zero-voltage switching (ZVS).