# Power generated in regenerative braking

• marellasunny
In summary, the diagram shows a general electric motor drive with two portions, the upper white portion symbolizing overdrive and the lower portion representing normal drive. The torque generated, denoted by M, is the direction of energy flow and is determined by the signs of M and n. Regenerative braking is only efficient when applied when hitting the brake pedal, as it allows for the generation of electric energy while braking. However, some e-mobiles apply regen braking when easing up on the throttle, which is less efficient than direct regen of kinetic energy, as seen in a bicycle.
marellasunny
The curve below is for a general electric motor drive(I'm guessing DC motor/possible 3phase induction). Would it be right to say that power generated in regenerative braking is the area under the curve in the 2nd quadrant ie the -ve M and +ve n(quadrant)?
There are 2 portions of the diagram. The upper white portion symbolises overdrive in a electric motor. I guess this is not at rated power but at maximum power,since P_max≠P_rated.

2.Regenerative braking would not gain energy in this area,am I correct?
http://imageshack.com/a/img46/5958/91vr.gif

Also,if looked at in a more accurate way,there is a additional 3rd portion which is the normal drive.

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What is M ?
What is n ?

M is the torque generated. n is the motor rpm

M is the torque generated. n is the motor rpm.

Power = torque * RPM
The sign of M*n is the direction of energy flow.

Quadrants are defined by the signs of M and n.

Energy will be consumed when the M*n product is positive.
Energy will be re-generated when the M*n product is negative.

A note: Regenerative breaking should only be applied if you actually hit the break pedal, if it occurs only when you ease up on the vehicles accelerator, it's far less efficient than a free-wheeling vehicle which regenerates the kinetic energy put into it by its motor in a direct and much more efficient way by freewheeling.

Think of a bicycle, you can pedal for a few seconds, then let it freewheel for a while, no regenerative system can compare to that in terms of energy effieciency.

I have an electric car with regenerative braking, and an elctric scooter without it, and the last one is far better at preserving the energy put into it from the battery.

commiesoft: But,regenerative braking could never applied for a freewheeling vehicle.The principle of regenerative braking (as I read) is that the electric motor/generator generates a rotating magnetic field in the opposite direction of the wheel + also generates electric energy at the same time.So,its doing 2 good things at the same time:1.generating electric energy 2.braking the wheel shaft. Hence,could never be used a freewheeling vehicle.'crusing' would never exist then.There's still a little doubt if the principle above I stated is correct.Please correct me if I was wrong.

Hi marellasunny :) Regen braking can be applied to a freewheeling vehicle if it is applied only when hitting the brake pedal.

In most e-mobiles regen 'braking' is applied when the driver eases up on the throttle, it has nothing to do with braking, it justs stops the vehicle from beeing able to act like a bicycle.

On a bicycle you pedal for some moments, then rolls along when you can. This is actually direct regen of kinetic energy, and is far superior to any electrical system.

Regen braking should not interfer with this much more efficient system, it should act as a compliment by beeing activated only when people hit the brake pedal. IMHO ;-)

## 1. How does regenerative braking work?

Regenerative braking is a mechanism used in electric and hybrid vehicles to convert kinetic energy into electrical energy. When the vehicle brakes, the electric motor acts as a generator, converting the vehicle's kinetic energy into electrical energy, which is then stored in the battery for later use.

## 2. What are the benefits of regenerative braking?

One of the main benefits of regenerative braking is that it helps to increase the efficiency of the vehicle. By converting the energy that would otherwise be lost during braking, regenerative braking can improve the overall fuel economy of the vehicle. It also reduces the wear and tear on the vehicle's brakes, leading to longer lasting brake pads.

## 3. How much power can be generated through regenerative braking?

The amount of power generated through regenerative braking varies depending on the vehicle's speed, weight, and braking force. On average, regenerative braking can generate up to 70% of the vehicle's kinetic energy during braking.

## 4. Can regenerative braking be used in all types of vehicles?

Regenerative braking is most commonly used in electric and hybrid vehicles, but it can also be implemented in some non-electric vehicles that have an electric motor or generator. However, traditional gasoline and diesel vehicles do not have the necessary components to utilize regenerative braking.

## 5. Are there any limitations to regenerative braking?

One limitation of regenerative braking is that it is most effective at lower speeds and during frequent braking. This means that it may not be as effective on highways or in vehicles that primarily use regenerative braking on longer, less frequent trips. Additionally, regenerative braking is less effective in colder temperatures, as the battery's efficiency decreases in cold weather.

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