Q: I am the owner of a 1992 Cadillac Allante, so I could ask you hundreds of questions about the unusual things that car does. But since it would only appeal to a small number of your readers, I am asking the question below about electric cars.

Ever since they invented a battery ignition, we have been able to recharge that battery with an alternator or voltage regulator. Why can’t they develop a similar device that would allow for the recharging of the electric car batteries as you drive the vehicle? Wouldn’t that be great? I might even buy one.

— John Kanon

A: Talk about dodging a bullet. To Cadillac’s credit, their current vehicles are light-years ahead of the Allante.

Generating electricity on the fly is done in several ways with conventional, hybrid and full electric vehicles. To do so requires a conversion from mechanical or kinetic energy to electrical energy. Mechanical energy, whether it’s the vehicle’s alternator — a component that recharges the battery and powers the electrical system —or a mechanically driven generator, requires input energy, which begins at the fuel tank. Fuel must be burned to create the force to spin the generator, so there’s no free lunch. Kinetic energy from the vehicle’s motion, however, can be harvested as the vehicle coasts or brakes. Conventional vehicles may crank up the alternator during coasting and braking, a trick borrowed from hybrid and electric vehicles, making up for allowing the alternator to goof off at other times. Selective usage of the alternator saves a small but measurable quantity of fuel.

Regenerative braking is used by hybrid and full electric vehicles to harvest kinetic energy that is lost during braking. Rather than converting energy to brake heat, it can be channeled back to the drive battery by using the generator to slow the vehicle. The Chevrolet Volt goes a step further when the plug-in battery pack becomes depleted. A modest gasoline-powered engine spins a generator, providing energy for the electric drive motor. This extends the car’s range far beyond the battery pack’s moderate capacity.

Here’s what all this boils down to: Aside from regenerative energy, which is free for the taking, you need to bring most of the energy along from home or the filling station. Other means of energy storage are not far off, such as super-capacitors for electricity, flywheels to store kinetic energy, hydraulic accumulators and compressed air.

There’s plenty of energy management taking place in conventional vehicles as well. Many employ electric air conditioning and power steering, reducing the mechanical burden on the engine.

— Bergholdt teaches automotive technology. Email questions to under-the-hood@earthlink.net.