Hybrids combine an electric motor and a small gas engine to provide the propulsive force required to move a car or truck or minivan or SUV along the highway or through busy city streets.
How the Toyota Prius Works
Toyota's Prius initially operates on electric power; when the car is turned on and begins to move, its electric motor provides the main propulsion. The gas engine kicks in at around 10 or 12miles per hour which is why this car gets better gas mileage in the city than on the highway, as indicated in the Table below.
When on the highway, however, the gas engine provides much of the thrust. The electric motor supplies boost power. When you need extra power, for example, to climb a hill or pass a slow-moving vehicle, the electric motor kicks in. Electricity flows from the light-weight battery (nickel metal hydride) behind the back seat to the electric motor to provide additional power.
When slowing down or going down a hill, however, the vehicle uses very little power at all. In fact, the gas engine may shut off entirely. The instantaneous gas mileage readout in the Prius, which is located on a computer screen in the center of the dashboard, records gas mileages of 100 miles per gallon, indicating that the car is coasting. When the vehicle comes to a stop at a stop light, the engine shuts off. When the gas pedal is pressed, however, the electric motor kicks in, followed by the gas motor. You're off and running without hesitation.
How Honda's Hybrid's Work
Editor's Note: This article was written prior to release of the 2009 Honda Insight
Honda's hybrids are similar in many respects. They contain a gas engine and an electric motor, but the electric motor is much smaller than the Prius'. As a result, it can't be used to start the car from a standstill.
When a Honda Civic Hybrid is turned on, then, the gas engine kicks in immediately. It provides the power to move the car and most of the propulsion from that point on. The electric motor kicks in when additional power is needed, for example, when climbing a hill or passing another vehicle. Because the gas engine starts up immediately, city mileage in all Hondas is lower than highway mileage.
In the modern language of computers, this car "defaults" to the gas engine, says Shari Prange of Electro Automotive in Felton, California, who's written many fantastic articles in Home Power magazine on hybrids and electric cars. Moreover, the electric motors and the batteries in the car are not sufficient to drive the car on their own. This car will never move solely under electrical power.
In the Prius, the electric drive system is "more nearly an equal partner," notes Prange in an article in Home Power magazine, issue 83. As Prange notes, this car "defaults to the electric motor, and brings the gas engine online as needed." The electric motor of the Prius can drive the car, and often does at low speeds, without the assistance of the gas engine (which isn't even running at these times). The electric motor provides all of the power when the car is backing up.
But what about the batteries of a hybrid car? Do they need to be charged each night?
They're charged continuously by the car during normal operation.
In Honda's hybrids, for instance, the electric motor doubles as an alternator, providing propulsion and also producing electricity to charge the batteries. ....read more