Toyota Prius Hybrid and the Ford Escape Hybrid are examples of cars and SUVs incorporating full hybrid-electric systems, allowing the motor and engine to function independently. Power can come exclusively from the motor, the engine or the two simultaneously. Initial acceleration is often a silent operation of the electric motor itself, prior to the engine's automatic startup as speed increases. Under heavy acceleration, both power sources may run at full output.
The mild hybrid system (Honda Insight Hybrid, Civic and Accord hybrids) uses the electric motor to boost engine power. Both continually operate at varying degrees, contingent upon driving conditions. The motor and engine cannot supply power independently; consequently, the engine must be running during acceleration.
Early Chevy Silverado and GMC Sierra full-size pickup HEVs were considered micro hybrids. Regenerative braking helps charge the battery, like other hybrid systems, but the electric motor does not assist engine power. The automatic engine shutoff/restart feature, which decreases fuel burned at idle, is its single means of increasing fuel economy and decreasing emissions. Auxiliary electric power allows you to plug in anything from a laptop computer to a power drill.
2008 GM full-size pickups and SUVs became available with a revolutionary two-mode hybrid system. This is basically a full-hybrid powertrain incorporating two electric motors in a rear-wheel-drive transmission. The transmission applies different gear ratios to the motors during city and highway driving conditions. The second of the two modes makes power assist from the electric motor practical at highway speeds, therefore aiding in highway miles-per-gallon, as opposed to only city, like a standard hybrid.
We will see Plug-in Hybrid Electric Vehicles (PHEV) reaching retail production status through a number of manufacturers beginning with the 2010 model year. This is a typical full-hybrid system with a twist. You can plug a PHEV's higher capacity lithium-ion batteries into a home electrical outlet to enable a much longer range of electric assist. Plug-in Hybrids will also be calibrated to achieve higher speeds in an all-electric mode. The fact that approximately only 3% of U.S. home electricity is produced by petroleum may prove Plug-in Hybrids efficient in decreasing dependency on foreign oil.
A series hybrid is powered by the electric motor alone. There is an internal combustion engine onboard, but it drives the generator to charge the battery or supply current directly to the motor. The gas engine is never physically connected to the wheels as a means of propulsion. The Chevy Volt, due out for the 2010 model year, is a Plug-in Hybrid utilizing a series hybrid powertrain.