What is regenerative braking?

Question

What is regenerative braking?

Answer 1

Regenerative brake is a mechanism that reduces vehicle speed by converting some of its kinetic energy into another useful form of energy. Like slowing down a car by having the brakes turn a generator to generate electricity in order to charge a battery.

A good example you can experience is get your car up to speed - then release the gas pedal and coast. Now turn on the air conditioner and you will feel the car slow down.

Answer 2

Regenerative braking is not just a term in hybrid autos. Its a common term for using a generator as a brake. This may mean using the motor as a generator as in autos or small motors. In large motor shops, it may be a generator connected to the motor on test..

In autos this power is put into the batteries. In mains systems, it may be either dissipated into resistors or put back to the mains in larger systems.

Answer 3

Regenerative braking is a system in which the electric motor that normally drives a hybrid or pure electric vehicle is essentially operated in reverse (electrically) during braking or coasting. Instead of consuming energy to propel a vehicle, the motor acts as a generator that charges the onboard batteries with electrical energy that would normally be lost as heat through traditional mechanical friction brakes. As the motor “acts in reverse,” it generates electricity. The accompanying friction (electrical resistance) assists the normal brake pads in overcoming inertia and helps slow the vehicle.

Also Known As: May be confused with dynamic braking, which dissipates the energy as heat, but does not recapture it.

Examples: All hybrid and electric vehicles use regenerative braking to generate electricity to help recharge their batteries.

The process of regeneration is entirely automatic and occurs when the motor over-runs (or the demand speed is reduced) so that the motor's back EMF is greater than the output voltage from the controller.

It is best treated as braking (which just happens to feed the braking energy back to the battery) rather than a means of saving lots of energy. This is because most motors and drive systems are inefficient and you won't save a lot of battery! However there are applications - such as Go-Karts with the Lynch motor - where the energy re-generated can make a significant difference to the battery life.

It is actually the battery which is doing the braking, not the controller, since the braking energy gets dumped into the battery. For this reason regen braking should not be considered as a safety or emergency braking system. A properly designed vehicle will also have an adequate mechanical brake, for emergencies.

Regen braking is indeed variable. In the same way as you adjust the acceleration (power to the motor) by advancing the speed control, you adjust the braking (power from the motor) by reducing the speed.

There are adjustable acceleration and deceleration ramps which vary the maximum acceleration and deceleration rates.

Answer 4

Regenerative braking is used on hybrid autos. The electric motor functions in reverse to convert mechanical power into electrical power, which is used to charge the battery.

Regular brakes convert forward motion or kinetic energy into heat via the brake pads and disks. Regenerative braking instead converts the kinetic energy into electric power.

In actual use, you can tell the difference in the brake petal "feel".  Push it partly down and the car slows down via regenerative braking. But in a hard stop, regenerative braking alone is not enough, so the mechanical disk brakes also turn on.

Which is another good reason to start braking well in advance of a stop.

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