Hybrids like Toyota’s Prius and plug-in vehicles such as the Chevrolet Volt run on systems other than purely gas-fired engines. The systems, or powertrains, that drive the so-called greener cars use electricity generated by batteries and electric motors to either supplement or largely take the place of internal-combustion engines. The Chevrolet Volt, billed as a rechargeable electric car, gets most of its power from an electric motor and a battery pack with a 40-mile range.
