A hybrid-electric vehicle combines an internal-combustion engine and an electric motor powered by batteries. The electric motor and batteries help the conventional engine operate more efficiently, cutting down on fuel use and emissions. The gasoline engine increases the limited driving range of an electric vehicle.

There are three types of hybrid drivetrains:

Series drivetrain: The simplest hybrid configuration, it will be used in the Chevy Volt. The electric motor is the only means of propulsion. The motor receives electric power from the battery pack or from a generator run by a gasoline engine. The engine is smaller and the battery pack more powerful than in the other hybrid technologies.

Parallel drivetrain: The engine and the electric motor generate power to drive the wheels. Parallel hybrids can use a smaller battery pack, enhanced mainly by regenerative braking to help keep it charged. When power demands are low, parallel hybrids also use the drive motor as a generator for recharging, much like an alternator in conventional cars. This is the configuration used by Honda.

Series/parallel drivetrain: By combining the two designs, the engine can drive the wheels directly (as in the parallel drivetrain) at high speeds and be disconnected from the wheels so that only the electric motor powers the wheels at low speeds, such as in heavy traffic (as in the series drivetrain). Toyota uses this system, and Ford has adapted it for use in its Escape hybrid.

 For more information, visit www.hybridcenter.org.

SOURCE: hybridcenter.org