What Are Hybrid Vehicles?

By Deanna Sclar from Auto Repair For Dummies, 2nd Edition

Hybrid vehicles are called hybrids because they use both a small internal combustion engine (ICE) and an electric motor to obtain maximum power and fuel economy with minimum emissions. How they do this varies from one model to another, with varying success.

What all hybrids have in common is the ability to generate electric current, store it in a large battery, and use that current to help drive the car. Hybrids capture electrical energy produced by a regenerative braking system, and their engines can power a generator, too. Hybrids can also conserve energy by shutting down the ICE when the vehicle is in Park, idling at a light, or stopped in traffic, or when the electric motor’s energy is sufficient to drive the vehicle without assistance from the ICE.

Hybrids have regenerative braking systems that generate electric power to help keep the batteries charged. When the driver applies the brakes, the electric motor turns into a generator, and the magnetic drag slows the vehicle down. For safety, however, there is also a normal hydraulic braking system that can stop the car when regenerative braking isn’t sufficient. There’s no difference in maintenance or repair except that the brake pads tend to last much longer because they don’t get used as much. In fact, if you drive a hybrid in a moderate manner, you almost never actually use the disc brakes on the wheels and may be able to go the life of the car without changing pads. The big difference is that regenerative brakes capture energy and turn it into electricity to charge the battery that provides power to an electric motor.

Parallel hybrids

A parallel hybrid uses both an electric motor and an ICE for propulsion. They can run in tandem, or one can be used as the primary power source with the other kicking in to assist when extra power is needed for starting off, climbing hills, and accelerating to pass other vehicles. Because both are connected to the drive train, they’re said to run “in parallel.”

How a parallel hybrid works.

Series hybrids

A series hybrid uses a gasoline or diesel ICE, coupled with a generator, to generate electricity but not to drive the car. The engine can send the electric current directly to the electric motor or charge a large battery that stores the electricity and delivers it to an electric motor on-demand. The electric motor propels the vehicle, using its power to rotate a driveshaft or a set of drive axles that turn the wheels.

A series hybrid.

Plug-in hybrids

Because plug-in hybrids feature larger batteries that can be charged at any ordinary 110-volt electrical socket, they have the capacity to extend the ability of the electric motor to drive the car farther without the need for starting the ICE and therefore substantially increase the vehicle’s fuel efficiency. Estimates have ranged as high as 100 mpg!

Some technologically savvy individuals have adapted their hybrid vehicles into plug-in hybrids, and automakers are in the process of developing and producing them (sometimes in cooperation with major utility companies). The development of new, smaller, high-capacity lithium-ion batteries that can be recharged many times is the key to making plug-in hybrids available to the general public. Estimates are that plug-in hybrids equipped with these more powerful batteries will have a range of as much as 125 miles before the charge is depleted and the vehicle reverts to standard hybrid mode.

A plug-in hybrid.

The main environmental problem with plug-in hybrids is that the electric current they draw is usually generated by utility companies powered by fossil fuels. The good news is that some major chains have committed to establishing charging stations powered by solar panels or wind energy, and many hybrid owners are willing to install solar panels to recharge these vehicles at home. Plug-in hybrids charged by commercial sources of electricity or solar panels will be less dependent on the ICE, but will still need it for long trips, climbing hills, and so on. Future hybrids may use a small fuel cell to make electricity from hydrogen, which would mean the ICE would have to run even less frequently.

Two-mode hybrids

Two-mode hybrids may be the key to a competitive place for the U.S. in the hybrid market. Instead of the large storage battery found on conventional hybrids, two-mode hybrids use smaller batteries and two electric motors located inside an automatic transmission with two sets of gears — one for the ICE and the other to amplify the power of the electric motors. The transmission can function as a continuously variable transmission, as well. In one mode, at lower speeds, the vehicle can run with one or both electric motors, with or without the ICE, or on the ICE alone. At higher speeds, the second mode kicks in, and the ICE runs continuously in its higher gear ratios.