This paper explores the Brayton Moser passivity-based controller design for an on-board integrated battery charger system. The proposed controller is based on energy concept theory which ensures asymptotic stability against load variability. To design proposed controller, first, average dynamic equations of the proposed system have been developed through energy-based formulation namely Brayton Moser. In order to obtain robust controller and correspondingly robust charger against dynamics and external disturbances, a PI controller is integrated with the proposed controller. The proposed system is employed for electric vehicles battery charger which is charged by using CC/CV technique and their effectiveness has been evaluated through Simulink toolbox of MATLAB 2014. Furthermore, the benchmark PI controller is preferred for comparison and discussion. Additionally, the effectiveness of the system is verified via OP-5142 real time simulator.