This paper presents an in-depth analysis of a Gallium Nitride (GaN) Dual Active Bridge (DAB)-based on-board battery charger for electric and hybrid vehicles. It focuses on the superior efficiency and reliability of GaN-based power electronics over traditional Silicon-based systems. The study explores the implementation of the DAB topology, recognized for its bidirectional power flow and high efficiency, in enhancing vehicle charging infrastructure. Efficiency analysis, switching behavior and losses are thoroughly examined. Simulation results in PSIM software validate the theoretical predictions, showing significant improvements in operational flexibility and energy efficiency.