This paper proposes a hybrid energy storage system (HESS) and smart charging mechanism for plug-in hybrid electric vehicles (PHEVs) with the aim of reducing greenhouse gas emissions and fossil fuel consumption. The HESS includes a battery as the main energy source and an ultra-capacitor (UC) as an auxiliary source. Both the power sources are connected to the DC bus through power conditioning circuitry. To regulate the system’s output variable, a barrier function-based adaptive sliding mode controller is proposed, which will achieve finite-time convergence and robustness against disturbances and uncertainties without requiring prior knowledge of the upper bounds of the system. The controller aims to reduce chattering and ensure various control objectives, such as tight regulation of output voltage, perfect tracking of reference currents for the UC and battery, and power factor correction in the grid-to-vehicle (G2V) mode. Simulation results using MATLAB/Simulink show that the proposed controller outperformed sliding mode control (SMC) and finite-time synergetic control (FTSC). The proposed strategy has been validated through real-time hardware-in-the-loop (HIL) experiments using C2000 Delfino Microcontroller F28379D Launchpad.