How Regenerative Braking Functions And Improves The Efficiency Of Electric And Hybrid Vehicles

It takes a lot of energy to get a car moving, but the same is true when stopping a car. In fact, stopping a motor vehicle consumes a considerable amount of energy, unfortunately much of which is wasted.

However, engineers are able to recover much of the wasted energy through the use of regenerative braking. Below is more information about this real-world technology and how it works when used in modern automobiles.

Yesterday's Technology: Friction Brakes

Conservation of momentum is a principle of basic physics, and it stipulates that the energy that causes an object to move is never "lost" or destroyed. This energy is always transferred somewhere else, even when the object itself stops moving.

This is important to understand when taking a closer look at the mechanics of car braking. Since the dawn of automobiles in the late 19th century, vehicles have used a straightforward system of braking. Some type of object applies force against spinning wheels, which, in turn, makes them stop rotating.

Remember that conservation of momentum demands the energy inside the rotating wheels can't simply disappear. Instead, the introduction of friction between a brake pad or shoe and the wheel results in an energy transformation. Rotary motion is merely converted to heat energy.

This heat energy, which is easily sufficient to boil brake fluid or melt metal, dissipates into the surrounding brake components and the atmosphere. Tremendous energy is released with no gain for the vehicle.

Fortunately, with the advent of electric and hybrid cars, automotive engineers have discovered a way to recover lost energy. Regenerative braking is the key to making this happen.

Today's Technology: Regenerative Braking

In its simplest terms, regenerative braking occurs whenever the momentum of a moving, but slowing, vehicle is transformed into electrical current. Before the dawn of pure electric vehicles and those containing hybrid technology, there was little use for regenerative braking.

The standard 12-volt battery used in modern automobiles is adequately charged through the use of an alternator, and there is no facility for storing recovered electricity. However, since electric and hybrid cars use massive battery storage to provide motive power, the electricity generated is now storable for future needs.

How Regenerative Brakes Work

As you may know, large electric motors, which receive current from the storage batteries, directly turn the powered wheels on electric and hybrid vehicles. However, electric motors have an "alter ego," which is their dual identity as a generator; if an electric motor is reversed, then it produces electric current.

Engineers have capitalized on this convenient trait in electric and hybrid cars by utilizing motors as generators during braking. Instead of applying friction to turning wheels, the energy produced by a rotating wheel is converted to electricity that is then stored.

As simple as regenerative braking sounds at a glance, there are complex issues involved in making it all come together. For example, there are times when regenerative braking alone is insufficient to stop a moving vehicle. In addition, electrical circuitry inside the motor/generator must be able to handle the rapid, frequent transitions between sending and receiving electric current.

Fortunately, a braking controller, which is a sophisticated computer inside the vehicle, is able to manage all of these functions for the purpose of maintaining smooth, safe operation. The braking controller ensures the mechanical and hydraulic brakes function, when needed, and it also changes the motor to a generator, and vice-versa, in split-seconds. In addition, braking controllers also re-route unneeded electrical current, thus preventing the storage batteries from overcharging; too much current flowing into the batteries can shorten their lifespan or cause them to fail.

For more information on this and other new technology in cars, contact an auto dealer or visit websites like