There's nothing new under the sun. Back in the 1970s (IIRC) the Mother Earth News sold me plans for just this: a car propelled by an electric motor, connected

There's nothing new under the sun. Back in the 1970s (IIRC) the Mother Earth News sold me plans for just this: a car propelled by an electric motor, connected to a generator connected to a small gasoline engine that ran (when needed) at optimum speed and torque. Rather than normal automobile batteries, they recommended using deep-cycle marine batteries.