Cruise control does use regen!

[JodyS21]

The thing is Jody is that the ACC has been taken directly from the ICE version of the ZS and has no software or programming to engage the regen on the EV therefore it works exactly the same as the ICE version of the car. We know that sounds crazy but that is what SAIC have done ?

I've not tried it out so am going by what folk are saying that the kers mode alters the deceleration rate/feeling.

What your saying though adds weight to my theory;
The ACC is just from the ICE, so when it wants to slow down it disengages the accelerator and engages the (friction) brakes.
A by product of this could well be that on the EV car; disengaging the accelerator, as we know, automatically engages Regen based on the KERS mode.
This would explain why it always uses the friction brakes, but also that the Regen/KERS seems to be still doing something.

comments????

 

[GordieG]

Does it really matter?? As long as you get to the speed you want to be travelling at - job done. Life’s too short!

 

[SCB86]

The ICE ZS was never available with ACC, not in the UK anyway.

 

[Dave S]

KERS etc covered well on the MGEVs Community Podcast - all your questions answered!!

 

[Tim Green]

That info from Electrified does not tell us much. On an ICE car when you decelerate there is inherent slowing effect from the over-run of the engine. On an EV when you decelerate you should get a slowing effect from Kers. I would suggest it is more difficult to design it out than leave it in. However, I could imagine that the Kers would be set to a low level, possibly less that the K1 level, to avoid "kangarooing".

 

[nik233]

Friction braking makes sense to me, as a full battery would allow no or very little regen braking. It seems for the sake of safety and consistency it has to use the brakes under these circumstances.

 

[Tim Green]

Well I tried it today on a steep hill nearby and I can confirm that certainly at the speed I was going (25mph) on ACC the Kers system is NOT activated and maintaining the 25 was done purely using brakes. As JodyS21 points out, this could be because the Kers value is dependent on battery charge. (However, from an engineering point of view, any feedback system could cope with that, but it would take more development).

 

[Mgkev]

Could it be that the car simulates the Kers levels when using ACC to keep the driving experience the same for the driver. No regen when in ACC maybe a cost saving.

 

[Cocijo]

I think that they have probably taken the easier option rather than looking in more detail at regen braking when using ACC. Programming this in would need to use both friction and regen to be completely effective at holding a speed and more rules for their use would need to be built in, rather than just using the easier friction option. As far as the regen button impacting friction brake usage I’m still not sure why this would be.

 

[Tim Green]

You may be correct Cocijo. However, the emergency braking system seems to be active all the time, ie when in ACC and when not. This implies that linking should not be too hard!

 

[Cocijo]

Yes - good point. I think it may be down to a combination of not identifying requirements correctly with good experienced user input, what was considered an acceptable level and the time to market. I don‘t think that it’s a difficult peice of work.

 

[JodyS21]

I got to do some testing this morning.
No regen no matter what was going on (other than the occasional flicker to -1Amp).
(Couldn't see if/when brake lights were coming on)
(N3 - everything was warm and regen was available)
(Car registered 12/2020 with BMS 15/1 A01)

Tried the following a few times:

• ACC set to 20 odd mph less than current speed, lifted off accelerator. Amps went down to 1 and car just seemed to slow down with drag until it reached the preset speed - didn't feel like the friction brakes were applied.
• ACC set to X speed and was doing the X speed, caught up with a slower car. Car slowed down to match car in front, no regen (negative) amps, must have just used friction brakes.
• ACC set and following car, let the ACC automatically follow the car infant to a stop at junction. No regen (negative) amps, friction brakes applied.
  * At one point I added a bit of brake pedal myself and instantly regen (negative amps) registered, I didn't brake any harder than it was automatically already doing so but it did cause it to do some regen.

I didn't get to test anything out on a big down hill section for regen purposes.

 

[Cocijo]

I think when you touched the brake the ACC probably disengaged and then you got some regen.

 

[vimalkumar]

I know there have been discussions on the cruise control not using regen on the ZS, but today I found out regen is used!

I was going down a hill with the ACC set to 20MPH and the car started to gain momentum over the set speed. Changing the KERS mode increased or decreased the braking action of the car depending on if it's set to 1, 2 or 3.

Then I tried the ACC on a flat road; coming up behind slowing traffic for a traffic light I adjusted the KERS mode up and down, each mode increased or decreased the braking force.

It actually made the braking action of the ACC less aggressive when slowing down in KERS mode 1 compared to 3.

Hi
Which variant of MG ZS EV do you have?

My car does not use regen in ACC, power metre reads zero going down a hill with ACC set.
Brakes are hot at the bottom of the hill, disc rust cleaned, do it once week.
It should use regen in ACC. ACC is too aggressive on undulating roads

Hi Phil
Which variant of MG ZS EV do you have?

I’ve just had a play on my way home and these are my results.
I drove down a steep hill at 50mph and then set the ACC to 40mph. This was while in regen 1 in normal mode.
I then flicked through from regen 1 to 2 to 3 to see what effect it had while under ACC and still slowing to reach the set speed.
Each time I increased the regen setting I heard the friction brake pump briefly activate. Increasing the regen level appeared to increase braking effect until the set speed was reached.
I didn’t see any regen evidence on either the main power gauge or the electrical information screen.
It looks like the regen button is connected to the friction brakes when using ACC, although I don’t know exactly why.
Under a lighter regen (say regen1) the ACC also seems much smoother generally during braking. Whilst I could be wrong I can see no evidence that regen is used under ACC.

Hi Cocijo
Is there any possibility that the 2 variants are behaving differently because of lets say absence of a feature like "Hill Descent control"?

While i did raise this query on another thread, i am quite confused with the mixed response, there are customers who have observed regen and some who are sure no regen was observed.
Regen on cruisecontrol?

Just trying to find a common platform or common contacts who could test across both the variants

 

[Cocijo]

I replied on your other thread. I’m not sure if there's link with hill descent, but my experince is there’s no regen on cruise control. I know other owners may differ.

 

[vimalkumar]

I replied on your other thread. I’m not sure if there's link with hill descent, but my experince is there’s no regen on cruise control. I know other owners may differ.

Thanks. Did go through it. Will be trying it if possible and this time carrying a camera for recording it

 

[bzr160]

Could it have anything to do with hill descent control? Never used myself but it might explain the differing results.

 

[Coulomb]

Surely it's obvious: ACC on the older ZS EV uses no regen as it connects directly to the mechanical brake system.

But it can be more or less aggressive at maintaining speed,both accelerating and decelerating. What better signal for this than the KERS switch? So SAIC connected the two. It makes good sense to me.