This paper deals with the development of a hardware-in-the-loop (HIL) real-time simulation setup for vehicular systems. In modeling a vehicular drivetrain, the battery model poses the greatest challenge. Mathematical battery models suitable for real-time and transient simulation are often inaccurate due to internal electrochemical reactions in the battery and external factors such as loading conditions. To model these phenomena precisely while maintaining low computational intensity as required for real-time simulation is a prohibitively difficult task. In lieu of a mathematical model, this paper presents a simulation setup where actual batteries are interfaced with a real-time simulator. It provides a platform to test the emerging battery technologies for which dependable models may not be readily accessible. Results are presented for an HIL model of a planetary-gear-system hybrid electric vehicle with actual batteries in the loop of the simulation.