A question about Regen

Skippa

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May 28, 2025
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Location
NE38 0QD
Driving
HS PHEV
Sometimes (usually first drive of the day) when I select high regen nothing seems to happen - we carry on down the road as if in low regen. It's quite disconcerting. Eventually the high regen will work as expected - sometimes the high regen seems to work at a stronger level than others. Happy to hear your comments on this.
 
Yes, I have experienced the exact same thing several times myself. Again, always the first drive of the day. I put it down to the brakes/system not being 'warmed up' yet.
  • As you say, it seems to sort itself out after a few minutes of driving, so therefore I simply ignore it
 
I have been experiencing the same, but I am assuming that as the battery is full, (ie it has just been charged and this is the first time I am using the car since charging) there is no spare room for any electricity to go, so the regen won’t work until there is space to take the charge.
I don’t know if this is right, but it seems logical to me.
 
You’re correct in your assumption. I have some experience in integrating electric drivelines in special vehicles. There won’t be any regen if the battery capacity is at 100% with no space to store charge.
 
Car behaved fine on first drive this morning - battery at about 66% (50 miles remaining) - so maybe @BoJoUK is right. Thanks all for your comments.
 
This is from the MG4 manual but the same is true of most BEV/PHEV cars, as you have already surmised a full battery is not able to accept more charge from regen (or any other source)

Screenshot 2025-06-23 at 11.08.29.webp
 
Having driven a rental hybrid Toyota CRV in Corsica I'm well aware that regeneration brakes don't work when the battery is full.
We have very few places in the UK where you will refill an HS battery running downhill, but beware! Once the battery becomes full the regen braking will disconnect and if you are running downhill into a hairpin bend you will suddenly speed up.
I don't know if the HS is programmed to bing or bong if this situation is approaching but the CRV certainly wasn't.
 
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