By Rick Cotta
With “Electrified” meaning that it includes an electric motor, the four types of Electrified vehicles currently available are: Hybrid, Plug-in Hybrid, Battery-powered Electric Vehicle (what’s commonly meant by “Electric Vehicle” or “EV”), and Fuel-cell Vehicle. They are described in order below.
1. Hybrid (Sometimes referred to as an “HEV,” meaning “Hybrid Electric Vehicle”): The combination of a gas engine and electric motor(s) propel the vehicle, with the motor switching over to become a generator under deceleration and braking. (A motor — which is fed electricity and turns it into rotational force — and a generator — which is fed rotational force and turns it into electricity — are mechanically the same. Thus a motor can be turned into a generator and a generator into a motor.) This is enough to keep the relatively small battery charged, so a hybrid doesn’t need to be — and can’t be — “plugging in.”
Usually the gas engine does most of the “propelling,” with the electric motor primarily used to re-start the engine after it shuts off at stops (to save fuel) and help out under acceleration. The motor may also drive the wheels itself, though usually only under light-throttle conditions for short distances. Under deceleration and braking, the motor is switched over to become a generator that helps recharge the battery and also slow the vehicle down — a process called “Regenerative braking.” A Hybrid subset is the Mild Hybrid, which typically uses a lower-power motor and battery, but for similar purposes. The Toyota Prius is perhaps the best-known example of a Hybrid.
Side Note: Why Pairing a Gas Engine with an Electric Motor Makes for Such a Great Marriage (scroll to bottom)
2. Plug-in Hybrid (Sometimes called a “PHEV,” for “Plug-in Hybrid Electric Vehicle”): Also combines a gas engine with electric motor(s), but they usually have closer to equal power output than in a hybrid, and the much-larger battery can be plugged in to recharge it. In most cases, the vehicle can run on just electric power for roughly 20-40 miles until the battery runs down, after which the vehicle switches over primarily to gas power. As in a hybrid, the electric motor switches over to become a generator during deceleration and braking, which both recharges the battery and helps slow the vehicle down — a function known as “Regenerative braking.”
Plug-in Hybrids usually offer the ability to pre-heat or pre-cool the interior before you get in. Because this makes use of the vehicle’s electric climate-control system, you can do it in a closed garage, and in most cases, the vehicle has to be plugged in. Some plug-in hybrids offer the ability to “save” the battery power for later in a trip, running first on the gas engine, switching over to electric power at the driver’s direction.
3. Battery-powered Electric Vehicle (Sometime referred to as a “BEV,” for “Battery Electric Vehicle”): “Pure electric” that runs strictly on an electric motor powered by a large battery pack. This is what’s commonly meant when talking about an Electric Vehicle or EV (though “EV” can also mean “Electrified Vehicle,” which encompasses all four types), and is what’s making the biggest news nowadays. Under deceleration and braking, the electric motor switches over to become a generator that helps recharge the battery and slow the vehicle down. In some electric vehicles, this “Regenerative braking” can be set to be so strong that the driver may rarely need to hit the brake pedal; just lifting off the throttle will be sufficient to slow the vehicle under most conditions. The ability to slow quickly and come to a complete stop by just lifting off the throttle (which not all EVs can do) is sometimes referred to as “one-pedal driving,” and can be very helpful in stop-and-go traffic.
As with a Plug-in Hybrid, Battery-powered Electric Vehicles offer the ability to pre-heat or pre-cool the interior, even in a closed garage. But unlike most Plug-in Hybrids, some allow you to do so even if the vehicle isn’t plugged in, thanks in part to a typically much-larger battery.
A very few electric vehicles have offered a range extender, which is a small gas engine/generator combination that can recharge the battery, but perhaps not as fast as it’s depleted during constant-speed highway driving, and the gas engine doesn’t drive the wheels directly.
4. Fuel-Cell Vehicle (Sometimes called an “FCEV,” for “Fuel Cell Electric Vehicle”): Although it’s not included in the name, a Fuel-Cell Vehicle is an electric vehicle that gets its electric power primarily from a fuel-cell stack rather than a large battery pack. So “Fuel-Cell-powered Electric Vehicle” would be a more descriptive name, but also a longer one.
What helps the fuel-cell stack generate electricity is hydrogen — carried in a high-pressure, on-board tank — which combines with oxygen from the air to “feed” the fuel-cell stack. Hydrogen can be purchased and pumped in at a filling station much like those used for gasoline, though they are far fewer in number and currently found mostly in California around Los Angeles and San Francisco.
Although few in number now, Fuel-Cell Vehicles are considered the wave of the future, as it’s much faster to refill the hydrogen tank than to recharge an electric car’s depleted battery, and a fuel cell’s only “emission” is water vapor.
Why Pairing a Gas Engine with an Electric Motor Makes for Such a Great Marriage
Hybrids and Plug-in Hybrids both combine a gas engine with one or more electric motors to propel the car. But why is it worth the added weight and expense of not only having two power sources, but also the fuel tank and battery needed to feed them?
In short, because the strengths of each make up for the weaknesses of the other.
Gas engines produce relatively little power at low rotational speeds, gradually climbing to full power (what’s quoted in advertising) only as they reach the upper end of their speed ranges. By contrast, electric motors produce their full power as soon as they start to turn, with it remaining fairly steady through mid speed, typically dropping off rather notably at the upper end of their speed ranges.
Thus the electric motor sort of fills in at low speeds, with the gas engine taking over at the upper ranges where power of the electric motor trails off. So although “peak power” (again, what’s trumpeted in advertising) often isn’t much higher with the combination vs. the gas engine on its own, something close to that peak power is produced over a far wider range of the combined motor and gas engine speeds. This not only aids fuel economy, but also acceleration.
Rick Cotta
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