NOVELTY - Fuel flexible fuel cell system comprises hydrogen-containing fuel source connected to fuel processor (14) that produces hydrogen from fuel; heater for fuel processor; and high temperature proton exchange membrane (PEM) fuel cell (16), capable of being operated at least 100 degrees C; where fuel processor is in contact with fuel cell such that hydrogen produced by fuel processor is supplied to fuel cell during both transient conditions and steady state conditions of fuel cell; and where fuel processor is autothermal reformer, microlith/monolith autothermal reformer or steam reformer.    USE - As vehicle power plant device for generation and storage of electrical energy to support vehicle propulsion.    ADVANTAGE - The system can provide for vehicle with much higher driving range at potentially lower cost than equivalent range battery-only electric vehicle. The integration of the components into a single system allows the vehicle to be fuel flexible, that is, capable of being fueled with wide range of fuels without hardware changes in system. The battery pack can supply most of the vehicle electric power demands; while fuel cell can support either average drive cycle power requirement or average daily vehicle power requirements. This reduces the required power output of fuel cell in comparison to pure fuel cell vehicle. A reduction in fuel cell power requirements results in lower fuel cell generator costs and reduces size and cost of the reformer. The use of a high temperature PEM fuel cell system allows for fuel flexibility and the reformer can provide heat to cabin while recharging batteries in winter months. If recharging is done while the vehicle is parked, the user can return to a vehicle already warmed and acclimated.    DESCRIPTION OF DRAWING(S) - The figure shows diagrammatic view of energy flow in electric vehicle having power plant system.    Power plant system (10)    Vehicle (12)    Fuel processor (14)    High temperature proton exchange membrane (PEM) fuel cell (16)    Battery pack (18)    Fuel source (28)