Regen and friction brakes - do/how do they work together?

[Tim Green]

The brake lights do come on when using Kers only (no footbrake), but only on level 3 kers which I use all the time. You can check this by driving at night and looking in the rear view mirror.

 

[Deleted member 2439]

“My bad”. Misread - sorry ?

 

[Cocijo]

The brake lights do come on when using Kers only (no footbrake), but only on level 3 kers which I use all the time. You can check this by driving at night and looking in the rear view mirror.

Do the brake lights come on when the friction brakes are used to auto control the set speed under ACC do you know?

 

[Tim Green]

If you use the brake pedal at any time then the brake lights will work. Also if you slow under kers braking, or radar braking they will come on if in kers 3. Not sure about other settings of kers.

 

[Cocijo]

My question was about automatic braking under ACC when regen is not used and the brake pedal is not depressed manually.

 

[Cocijo]

I think our cars also have emergency braking warning rapid flash brake lights - I assume they work by sensing the rapid deceleration?

 

[macd2401]

My question was about automatic braking under ACC when regen is not used and the brake pedal is not depressed manually.

I've not used it for a while, but I think it does.

 

[Deleted member 2439]

I think our cars also have emergency braking warning rapid flash brake lights - I assume they work by sensing the rapid deceleration?

Yes ?

 

[Kithmo]

I think our cars also have emergency braking warning rapid flash brake lights - I assume they work by sensing the rapid deceleration?

They come on when EBA (Emergency Brake Assist) comes into action i.e. when you press the brake pedal quickly, no need for sensing the deceleration. The EBA ECU monitors the speed of the pedal press via the potentiometer on the brake pedal (not how hard it's pressed).

 

[Cocijo]

I didn’t realise that - so it can be created whilst stationary by pressing the brake quickly? And what about the situation where you start off with gentle braking and then increase by slowing pressing but you end up with a lot of braking force and slowing down quite quickly?

 

[Deleted member 2439]

I didn’t realise that - so it can be created whilst stationary by pressing the brake quickly? And what about the situation where you start off with gentle braking and then increase by slowing pressing but you end up with a lot of braking force and slowing down quite quickly?

Give it a try

 

[Cocijo]

Give what a try?

 

[Jaygee]

In my experience I have not noticed the brake pedal providing any additional regen. I always have it in kers 3.
This I think is unique to the mg.
In my Mitsubishi outlander phev and Lexus rx450h the brake pedal increase the amount of regen first before the friction brakes kick in. I can’t recall what it did in the first gen Nissan Leaf.

 

[JodyS21]

In my experience I have not noticed the brake pedal providing any additional regen. I always have it in kers 3.
This I think is unique to the mg.
In my Mitsubishi outlander phev and Lexus rx450h the brake pedal increase the amount of regen first before the friction brakes kick in. I can’t recall what it did in the first gen Nissan Leaf.

The brake pedal def causes regen in my car.
I drive with the Amps on display all of the time, it definitely increases (or decreases!) to a higher regen figure/lower negative value, when I press the brake pedal slightly.

 

[Elec Car Aust]

This has been discussed in other threads But as far as I can tell no dedicated post.
My main queries are around the relationship between application of the footbrake and regen.
Does the first part of depressing the pedal always engage regen first and then if further depressed the friction brakes also?
We know that we get regen when we release the accelerator and that this is incremental.
If in regen3 we lift fully off, does then applying the footbrake give even more regen braking? A sort of extra boost that is more than fully lifted off regen3? I don’t really notice this when driving if it does.
I’ve read in a few posts that using the footbrake engages more regen - I think someone has measured this? Is there a direct link between the footbrake and regen or do the two systems work completely independently of each other? I also believe Miles mentioned this on one of the podcasts but can’t find his commnents.
It makes sense to use regen instead of friction brakes where possible but how does this work on the MG when the footbrake is applied?
Regen is definitely speed and momentum related and I wonder if applying the footbrake and reducing the speed gives the impression of additional regen? I’m just surmising here and giving my experiences - I don’t know the answer - i’m interesting to hear what members think.

Hi Cocijo, yes I have found with ours if you watch the amps, when you apply the brake pedal lightly the regen cuts in more, i.e. you can feel the car slowing down faster and the amps going back into the battery increases over and above what your Kers setting (we use 3) is.

 

[Tim Green]

Ref cocijo’s question, if the car is slowing under ACC then the car will not be powering the wheels and the brakes will be on and thus the car will also be under Kers so (if on Kers3) the brake lights will certainly be on. I’m not sure about the brake pedal having a potentiometer but I think it unlikely. All information about rate of slowing is easily available in software by using rate-of-change of motor speed. As a system I think it works well.

 

[Cocijo]

Interesting observations - thank you. I don’t think that regen operates at all, regardless of mode, when using ACC - slowing the car if needed is purely friction brakes.

 

[Cocijo]

Hi Cocijo, yes I have found with ours if you watch the amps, when you apply the brake pedal lightly the regen cuts in more, i.e. you can feel the car slowing down faster and the amps going back into the battery increases over and above what your Kers setting (we use 3) is.

Yes - this seems to be the general consensus. Are you sure it’s not just increasing as the car slows down because the regen is not linear and not due to the footbake being pressed?

 

[Tim Green]

Regen won’t be linear but it will definitely decrease as you get slower. Looking at the current as you slow down, you can see the system ramps up to a maximum in negative
And flattens off. I still think regency will work in ACC mode, whatever would they go to the hassle of stopping it?