In principle, the Chevrolet Volt is simple: It’s an electric car with a gas-powered generator for backup. Yet the machinery under the hood is complex. The overarching goal is to wring maximum miles out of the Volt’s lithium-ion battery and, when gasoline is necessary, to use it frugally. This requires the Volt’s drivetrain—composed of two electric motors, a gasoline engine, three clutches and a planetary gearset—to blend power from different sources to find the perfect balance in every driving situation. Here’s how it happens.