Regen Braking, Electric Braking and Physical Brakes

[EvFan]

I was reading an article recently where Porsche said they weren't going to introduce one pedal driving because it was more efficient to use electric brakes i.e the foot pedal.
This got me thinking that my knowledge was rusty. I thought that when you pressed the foot pedal you were using the physical brakes, and not electric braking. Porsche seem to say that physical brakes only kick in a low speeds when electric braking runs out or during an emergency stop.
I know that when you step on the brake pedal that the needle goes into Regen but to be honest I thought that was an EV quirk but wasn't really regenerative braking.
Have I misunderstood?

 

[aread2]

When you step on the brake pedal, the car starts regeneratively braking. If you demand more braking effort beyond what can be done with regen, the physical brakes are used to supply the extra effort. As you slow down, the regen is less effective (the electric motor is turning more slowly so the amount of energy the regeneration can extract is reduced), so more of the braking effort is supplied by the physical brakes. As you get near to halting, all the braking effort is supplied by the physical brakes because the electric motor is spinning too slowly to supply any significant braking effort. When the battery is full, there's nowhere to put the energy the motor would provide, so the car will make up the braking effort with the physical brakes.

 

[EvFan]

When you step on the brake pedal, the car starts regeneratively braking. If you demand more braking effort beyond what can be done with regen, the physical brakes are used to supply the extra effort. As you slow down, the regen is less effective (the electric motor is turning more slowly so the amount of energy the regeneration can extract is reduced), so more of the braking effort is supplied by the physical brakes. As you get near to halting, all the braking effort is supplied by the physical brakes because the electric motor is spinning too slowly to supply any significant braking effort. When the battery is full, there's nowhere to put the energy the motor would provide, so the car will make up the braking effort with the physical brakes.

I knew about the lower end being completed by the physical brakes as with full one pedal driving the Regen is blended with the physical to make it a smooth stop. But wasn't sure about from high speed.
I guess all that means that the larger the electric motor the more Regen it should be able to harness. As the available power for Regen should be more. So a Tuycan say should have more Regen power than a MG5. Just not sure how using the brake pedal is more efficient as porsche say it is?

 

[aread2]

I'm pretty sure the regen is dependent on what the charging equipment can handle. So about 75 kW for the MG. My Leaf can handle 50kW DC charging and that's where its regen tops out.

 

[Steveg]

I knew about the lower end being completed by the physical brakes as with full one pedal driving the Regen is blended with the physical to make it a smooth stop. But wasn't sure about from high speed.
I guess all that means that the larger the electric motor the more Regen it should be able to harness. As the available power for Regen should be more. So a Tuycan say should have more Regen power than a MG5. Just not sure how using the brake pedal is more efficient as porsche say it is?

I don’t know the details - but in layman terms this is how I understand it - it’s not like a physical friction dynamo on a bicycle, with modern EV motors when you want to recoup energy through regenerative braking you place a motor into negative drive. Hence you can on some EVs set the level or regen braking. At each level you’re applying more negative drive (torque).

In one pedal driving with high levels of regen, it’s effectively like an on/off switch. You apply positive drive to go forward, as soon as you lift off it applies a set level of negative drive to effectively reverse the motor and this allows the motor recovery energy and brake the vehicle. A simple on/off function is often not the most efficient.

So, instead if you modulate the level of negative drive and in turn hav e variable regenerative braking based on the inputs of the brake pedal it can potentially be more efficient. So in this scenario when you lift off, there's little or no regen braking, but if you start to apply the brake pedal negative drive is applied based on the level of your braking. So you have variable regen braking as well as the physical brakes being modulated by the inputs of the braking pedal.

Naturally, you can replicate all of this with sensors, so that the vehicle can vary the regen braking based on what’s required like you do in autonomous vehicles, but that becomes driver assistance.

 

[Jomarkh]

I'm pretty sure the regen is dependent on what the charging equipment can handle. So about 75 kW for the MG. My Leaf can handle 50kW DC charging and that's where its regen tops out.

It is also about space in the battery, you can't turn kers3 on until the battery has dropped to 96-97% and even then regen is weak, I find in need to get to nearer 80% before regen has a real effect.
If you look at the regen bar you can see what's going back into the battery or toggle through to the V and A screen.