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Discussion Starter · #1 ·
I swapped my Zoe for a 94ah i3 a few months ago and I'm much happier with the driving experience of the i3 - which is a relief.

Over the winter though I've noticed some variability in the regen braking and it seems more pronounced or common when around 0c. Sometimes there's just less regen braking/retardation despite the gauge sweeping into maximum regen (I'm assuming that's just a display graphics oversight).
It's not charge level related as I only charge at home to 80% which is plenty for local driving. Furthermore it can be normal going to my girlfriend's house a couple of miles away, but then less regen braking on the way back a few hours later with the same ambient temperature. It does seem to change mid journey too, but I can't find a pattern to it really.

On longer journeys I'm sure it's fine so it feels like it's possibly related to the internal battery temperature that perhaps stabilizes on anything but the really short journeys I usually make.

I've also noticed that the brake pedal itself seems to be firmer like there's less assistance when the regen is lower.

It's not so bad normally that I can't adapt and apply the brakes manually when necessary but occasionally I do worry it'll catch me out sometime as now and then it'll be like there's almost no regen at all.

Is all of the above "completely normal" or a known issue I need to get investigated while still under the remaining warranty?

Thanks. :)
 

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I swapped my Zoe for a 94ah i3 a few months ago and I'm much happier with the driving experience of the i3 - which is a relief.

Over the winter though I've noticed some variability in the regen braking and it seems more pronounced or common when around 0c. Sometimes there's just less regen braking/retardation despite the gauge sweeping into maximum regen (I'm assuming that's just a display graphics oversight).
It's not charge level related as I only charge at home to 80% which is plenty for local driving. Furthermore it can be normal going to my girlfriend's house a couple of miles away, but then less regen braking on the way back a few hours later with the same ambient temperature. It does seem to change mid journey too, but I can't find a pattern to it really.

On longer journeys I'm sure it's fine so it feels like it's possibly related to the internal battery temperature that perhaps stabilizes on anything but the really short journeys I usually make.

I've also noticed that the brake pedal itself seems to be firmer like there's less assistance when the regen is lower.

It's not so bad normally that I can't adapt and apply the brakes manually when necessary but occasionally I do worry it'll catch me out sometime as now and then it'll be like there's almost no regen at all.

Is all of the above "completely normal" or a known issue I need to get investigated while still under the remaining warranty?

Thanks. :)
Regeneration on an i3 varies with speed but I cannot say, after 6 years, that I have noticed much difference with outside air temperature. To work effectively, regeneration needs good tyre to road adhesion so is it possible that you are leaving it too late, and the tyres are struggling to stay in contact with a wet/damp/greasy road surface? Remember, regeneration is not as efficient as coasting. I rarely ever have to use standard braking on an i3.
 

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Discussion Starter · #3 ·
Regeneration on an i3 varies with speed but I cannot say, after 6 years, that I have noticed much difference with outside air temperature. To work effectively, regeneration needs good tyre to road adhesion so is it possible that you are leaving it too late, and the tyres are struggling to stay in contact with a wet/damp/greasy road surface? Remember, regeneration is not as efficient as coasting. I rarely ever have to use standard braking on an i3.
It's a very consistent route driven at 20-30 mph, which is why I'm able to notice the variance. It's not speed related I'm sure of that. Tyres are in good condition and if I do decide to give it a few more beans, there's plenty of traction available. I'm nowhere near the limit of adhesion and usually I'm lifting in plenty of time, except when there's suddenly much less regen available than expected and I have to apply the brake instead.
I'm not sure it's temperature related either, it's just that it started when it got cold but... it doesn't always happen when it's cold.

So as an example, there's a blind roundabout on my route, there's a 90d corner 30m before it so I'm always arriving sub 20mph in that section and lifting off in the same place as I need to check for nutters coming from the right... Most of the time it'll regen to a stop, sometimes it'll just carry on like there's no almost regen available. Or a little further on there's a raised speedbump crossing bit where I drop from 30 to 20 to go over the hump. Same story, much of the time it'll slow down as expected, sometimes it doesn't.

No errors are shown on the dash, it 'thinks' it's regen braking at full power either way. Is there anything I can use to check, a plug in tool if necessary or should I be reporting this to a dealer perhaps?
 

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2020 BMW i3S 120Ah BEV
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Can't say I've noticed this. Quite the opposite I've had full on opposite lock sideways drifts from the back end during lift-off in the snow and cold, but like so many cars there days it might totally depend on a) driving mode, b) precise firmware version or c) date of manufacture.
I have certainly noticed that regen feels pathetic at motorway legal limits, but I wondered if this wasn't just the fact that to maintain that speed you need to put in 60kw, by which comparison 50kw of regen braking is not that strong .. ?
 

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Discussion Starter · #6 ·
Ah thanks, that or similar what I was hoping to have confirmed. Thought it might have been battery temperature related but easing it off to prevent ice related incidents makes perfect sense.

Glad I can go back to not worrying about it being a fault then. :)
 

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I was out and about this morning on quiet but greasy roads - temperature -3C. As I said above, two i3’s on I have never experienced temperature related changes to the i3‘s regenerative braking. Everything seemed normal to me this morning, and my i3 experience goes back over 6 years. I well recall the days when an ACC disconnect at high speed on a motorway (due to low Winter sun) could result in the front gating of the car behind. BMW reduced regenerative braking in late 2015/early 2016. There was also a problem with the REx mounting bolts.
 

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I was out and about this morning on quiet but greasy roads - temperature -3C. As I said above, two i3’s on I have never experienced temperature related changes to the i3‘s regenerative braking. Everything seemed normal to me this morning, and my i3 experience goes back over 6 years. I well recall the days when an ACC disconnect at high speed on a motorway (due to low Winter sun) could result in the front gating of the car behind. BMW reduced regenerative braking in late 2015/early 2016. There was also a problem with the REx mounting bolts.
This was posted on another forum and I think that it offers an answer to reduced regen on some Winter roads:

Quote: I don't know your location or what tyres you use, but it is a known fact in Norway, that when using winter tyres with soft rubber, the i3 senses this movement in the tyres and reacts as if there is a little slippery road and hence reduce the regen. I had my i3 delivered with Nokian winter tyres, and noticed a big difference in regen from the i3 demo car tested with Bridgestone wintertyres. Now on summer tyres with harder rubber, the full regen is back.

Unquote

Traction control in play?
 

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The regen is reduced when the temperature falls to a specific figure for safety. Full regen on icy roads can cause skidding so the car softens the effect.
I checked this out this morning and you are on the button, when I set off no hard regen by the time I got back 50 miles later regen was better as it had warmed up outside. It wasnt fully charged when I set off so it wasnt a full battery stopping regen
 

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Also worth noting that the traction control activity is very much finer grained in Sport mode which I habitually use. I am aware that in comfort/eco it's very slow to react and tends to back off the power/regen aggressively for nearly half a second or so when any slippage is detected. In sport mode however the intervention is barely detectable in most circumstances (which I really like!).
 
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