Kers

[whittlesb91]

We're on a drive and notice that the Kers 3 isn’t working correctly. Usually it regenerates -20 but it’s only giving -7. Why could this be? Car is currently 95% charged.

 

[Coulomb]

Car is currently 95% charged.

I think you're right on the borderline where KERS is reduced, perhaps especially if the battery is cold. Look again in a few miles.

 

[SteveBirchall]

Yes, if the battery is basically full it isn’t able to store the Kers charge fully. So it reduces the regen.

 

[Jomarkh]

Kers works better as the battery SOC reduces. I find under 80% kers3 is most effective.

 

[WRS]

Hello, KERS was dropping to -25 level in its 3rd stage. After my last AC charge, my vehicle was charged to 100% and then KERS started working strangely. Now I can only see the -20 level and the brake grip has decreased, it feels like I am in level 2 KERS mode. I thought it was because the charge was full, but even though it dropped to 65% charge, KERS is still holding low. What is the reason? MG ZS EV

 

[fred12345]

mine is 2022 model, only ever going to about -20, just sometimes -21 ...

 

[Coulomb]

What is the reason?

There are many factors affecting maximum regeneration power, including HV battery temperature, and how balanced the cells are.

 

[fred12345]

funny thing happened today, I charged to about 78% overnight and KERS 3 I always use was not really slowing the car down, it would go to -4 or so as if the car was charged to about 95% .. No explanation but over the next 15-20 min drive, it picked up towards the end of the drive and started slowing down and going down to -15 or so ...
No idea why, first time this happened ... Cycled KERS switch from 3 to 1 and on and off but that didn't do anything ...

I'll see how it goes on my next drive in an hour or so and update here. Quite random, can't think of anything ...

EDIT: an hour later, on another short drive, all working fine as it should...

 

[Tim Green]

I think the external air temperature affects the level of Kers, at least until the car is "warmed up".

 

[fred12345]

I think the external air temperature affects the level of Kers, at least until the car is "warmed up".

It was quite warm today and it never happened before even on a cold morning... Anyway, just one of those things...

Edit
I went for another 2 short drives tonight, first one KERS worked as normal, and just now, again weak KERS for first 10 min, then started working again...

Weird thing is that the main battery still showing 78% charge from this morning... Should have gone down by few % ...

 

[hmadsen]

I bet this will be down to temperature.

In my Tesla there is a icon on screen if the regeneration is limited, i have seen this icon even when the car was at ~50% SoT on cold days.

The icon means "The maximum current dumped into the battery when doing regenrative braking exceeds the maximum current the battery will be able to accept with the parameters being as they are right now".