During the previous section, we learned that gasoline-electric hybrid vehicles marry a gasoline-powered internal combustion engine and an electric motor together to capture energy that's usually lost when a driver brakes. This energy is stored into a battery pack that provides the power for the vehicle to run. The batteries are constantly being charged while the car is in motion. The two types of hybrids that fit in the gasoline-electric categories are the series hybrid and the parallel hybrid.
In a series hybrid, the electric motor handles all the driving and the gasoline engine only recharges the battery pack. When the driver starts the engine, power is received from the battery pack to the electric motor which turns the wheels. On longer trips (beyond 50 miles or so), the gas engine provides power. Series hybrids are more expensive than parallel hybrids because they carry larger batteries to provide power for higher speeds [source: HybridCenter]. The Fisker Karma is an example of a series plug-in hybrid.
Just like the series hybrid, the parallel hybrid uses both an internal combustion and electric engine. But this is where the similarities end. In the parallel hybrid, the conventional and electric engines are attached to one transmission which allows both of them to power the car at the same time. The fuel tank supplies gasoline to the engine while the generator charges the batteries. This type of hybrid is more suitable for traveling long distances. More drivers prefer parallel hybrids to series hybrids because they are more fuel-efficient. Examples of parallel hybrid vehicles are the Honda Insight, the Chevy Malibu and the Toyota Prius [source: Hybridcars.com].
There's also a variation called a mild hybrid, the least expensive of the hybrid bunch. The mild hybrid doesn't function on just the electric engine. Its electric motor assists the gas engine when more power is needed. When the car begins to slow down or sits still, the control unit shuts down the engine so the vehicle is not burning fuel or polluting the air like a conventional car. When the driver puts the car in gear or accelerates, the battery starts the motor again [source: Hybridcars.com]. In full hybrids, the electrical and gas engines can propel the motor by working together or operating on their own.
What's next for hybrids? Find out on the next page.