Regen. when braking - how?

[Paulj]

I've noticed that I get quite of lot of regen. when actually braking, as opposed to allowing the kers to slow the car down, great, but can anyone tell me how that actually works?

 

[zatras9911]

Regenerative braking means the electric motor is operated in reverse, thereby applying a braking force through electromagnetism. This recaptures some of the vehicle's kinetic energy by charging the battery. Some electric vehicle models have specific driving modes that incorporate varying levels of regenerative braking.

 

[Paulj]

I understand that, but how do the brakes make electricity when applied?

 

[Jomarkh]

When you press the brake pedal it doesn't actually put the pads on the discs if the regen slows it enough push the pedal hard and it will.

 

[HarryTheGreyhound]

I understand that, but how do the brakes make electricity when applied?

It's not the brakes, but the regen is likely to contain a generator that will convert the kinetic energy into electricity.

 

[Alb]

The motor can act as either a motor or generator through simple electrical reconfiguration. When you slow down using KERS to any extent, it is electronically switched to configure as a generator and thus applies a braking torque.

 

[busa]

there's a few videos on YouTube that explain it

 

[Paulj]

Yes, I get that the motor acts as a generator when in 'overun' mode, however that doesn't explain why, when already slowing, with regen showing a positive current, applying the brakes quite hard will increase the positive current, according to the needle anyway.

 

[biffo]

Yes, I get that the motor acts as a generator when in 'overun' mode, however that doesn't explain why, when already slowing, with regen showing a positive current, applying the brakes quite hard will increase the positive current, according to the needle anyway.

It sounds like the motor has different levels - we know about KERs 1, 2 and 3 - suppose as you're seeing a higher current when braking, the this is essentially a level 4? Which would mean that the one foot driving concept could be possible in the MG (via software?)

 

[Deleted member 3150]

In a vehicle with regen, the act of using the break pedal will cause increased de-acceleration which in turns provides more back emf and greater regen

 

[Paulj]

Surely applying the brakes will take some load off the regen rather than applying more?

It can't be just my car, next time you all have a drive, do an actual test and see if this happens. Obviously you won't be braking for very far, so it is pretty momentary, unless descending a steep hill of course.

 

[Deleted member 3150]

Regen works by resistance it’s not the act of breaking itself it’s the kinetic energy transference based on speed and resistance/ friction. Deaccelerating faster by breaking generates more force https://mdpi-res.com/d_attachment/energies/energies-10-01875/article_deploy/energies-10-01875-v2.pdf See pages 9 and 10

 

[Harbour]

Surely applying the brakes will take some load off the regen rather than applying more?

I think pressing the brake pedal actually does not - at first - apply brakes, but allows the wheels to spin the motor creating regen instead. I believe it does this because the car is more "drive by wire" and complicated alogrithms are in play, so the ECU decides what method to use to slow the car. A sharper pedal press will activate the brakes. I see similar behaviour in our current Mitsubishi PHEV

 

[EVsince2016]

KERS 1,2,3 are set levels of regen braking.

The brakes use the max regen available before any brake pads make contact.

 

[aread2]

KERS 1,2,3 are set levels of regen braking.

The brakes use the max regen available before any brake pads make contact.

Exactly this. My Leaf can get up to 30kW in regen. If you demand more braking force, it starts to apply the physical brakes. The blend between regen and physical braking is almost unnoticeable. Physical braking is blended in as speed drops, taking over fully somewhere below 15mph because the wheels can't spin the motor fast enough to take enough energy to slow the car down.

 

[Petriix]

Surely applying the brakes will take some load off the regen rather than applying more?

It can't be just my car, next time you all have a drive, do an actual test and see if this happens. Obviously you won't be braking for very far, so it is pretty momentary, unless descending a steep hill of course.

'Applying the brakes' doesn't mean that the brake pads are used. The car will progressively increase the regen level as you press the brake pedal and will not use the friction brakes until maximum regen is achieved.

 

[Stuart Wright]

The friction brakes can actually suffer from rust because they are used so little. A mechanic at my Hyundai dealership told me that he saw an Ionic (first generation) with 100,000 miles and the disks and pads were like new.

 

[AnonymouseDriva]

I've noticed that I get quite of lot of region when actually braking, as opposed to allowing the kers to slow the car down, great, but can anyone tell me how that actually works?

Page 168 of the (LR) manual
Cooperative Regenerative Braking System
(CRBS)
The vehicle is equipped with a cooperative regenerative
braking system, this converts the kinetic energy of the
vehicle into electric energy while braking and stores the
energy in the HV battery, so as to prolong the driving range.
Note: When the cooperative regenerative braking
energy function is triggered, the driver may hear
a small motor operational noise and feel a slight
vibration on the brake pedal at low road speeds. This
is a normal sensation when the system is triggered.

basically, the brake pedal doesn't just apply the brake pads, it also applies a higher level of KERS 'co-operatively'. This is higher than you get even in KERS3.

 

[AnonymouseDriva]

It sounds like the motor has different levels - we know about KERs 1, 2 and 3 - suppose as you're seeing a higher current when braking, the this is essentially a level 4? Which would mean that the one foot driving concept could be possible in the MG (via software?)

Yeah, I was hoping that when they do the brake light fix for KERS, they would up KERS3 to the max at the same time. Seems not though.

 

[smokie]

The friction brakes can actually suffer from rust because they are used so little. A mechanic at my Hyundai dealership told me that he saw an Ionic (first generation) with 100,000 miles and the disks and pads were like new.

Think I already posted elsewhere that my Ampera rear discs and pads had to be replaced at about 50k due to being worn down because they'd more or less seized through lack of use.

There was an unofficial technique on that car to make it use friction braking once in a while to prevent that. You put it into neutral while on the move (the faster the netter) and you needed to slow, then applied the brakes. This meant the KERS didn't get involved in the braking so the pads and discs didn't end up with a build up of crud, or seizing. Ideal place was coming off a motorway down a long slip road but any longish downward would do. Not yet having my MG, I don't know if you can put it into neutral on the move.