An extended-range electric vehicle (EREV), also called a range-extended electric vehicle (REEV), is an electric vehicle fitted with a fuel-powered internal combustion engine, acting as a range extender that drives a generator to recharge the traction battery when it is depleted. Unlike a conventional plug-in hybrid electric vehicle (PHEV), in which the combustion engine may drive the wheels directly, the engine in an extended-range electric vehicle has no mechanical connection to the drivetrain; the wheels are driven exclusively by the electric motor. Extended-range electric vehicles can usually be charged from the electrical grid as well as from the onboard generator, and are therefore classified as a subcategory of plug-in hybrid electric vehicles by most regulators, though some markets, notably China, treat them as a distinct segment.