What Is a Series Hybrid? 

A series hybrid is a vehicle design in which the internal combustion engine does not directly drive the wheels but instead acts as a generator to charge the vehicle’s batteries — often known as a range extender engine design. Vehicles with this design included the BMW i3 with Range Extender. Under most conditions, the Chevrolet Volt was also a series hybrid, but there were conditions under which the Volt’s engine could drive the wheels.