[henk888]

Good morning everybody,

I noticed a while ago that the breaks where no longer regenerating: take the car to 30 mph, let go of the accelerator, instantaneous power goes to -10 kW or so, then gently press the brake and it should go to -15 or -20 kW. This is also visible in the battery range which has dropped 10-20% or so (big hills mean a lot of regenerative breaking normally)

* has anybody else seen this?
* the garage is baffled - they have had it for a week now and don't know how to fix it!

Any advice appreciated.

 

[srichards]

Does it charge normally on 22kw posts?

Sounds like the regen braking system is broken if it charges at the same rates ok. Or it's something really dumb like a brake switch is faulty so it doesn't realise the brake pedal is pressed so doesn't do any regen beyond the lifting off kind.

 

[cah197]

Have you selected B or D mode?

 

[henk888]

Have you selected B or D mode?

There is only D on our car - and it used to regenerate...

 

[henk888]

Does it charge normally on 22kw posts?

Sounds like the regen braking system is broken if it charges at the same rates ok. Or it's something really dumb like a brake switch is faulty so it doesn't realise the brake pedal is pressed so doesn't do any regen beyond the lifting off kind.

It charges fine, it regenerates during one-pedal driving, so I would think that it is a broken switch, but the garage would spot that in an instant I would hope. Also, it stopped working when it came back from its MOT, this may be coincidence, but I was wondering whether they needed to switch it off for the MOT.

 

[cah197]

There is only D on our car - and it used to regenerate...

You haven't told us what car you have.

 

[henk888]

You haven't told us what car you have.

Whoops

Zoe 40 kW, 3 years old

 

[cah197]

Whoops

Zoe 40 kW, 3 years old

What was the battery SOC at the time?

 

[henk888]

What was the battery SOC at the time?

It happens with any battery charge, between 20 and 100%, we rarely gee it below 20 so I cannot confirm that it still fails there.
Thanks!

 

[henk888]

Thanks for everybody's replies.

An update: the day I posted this the garage got to the bottom of it. Apparently this happens when the tyres are not the same size within some pretty fine tolerance.

When we hit a pot-hole and we needed a new tyre fast we had the tyres shuffled so that we had two identical tyres up from and two identical tyres on the back, but apparently as they are from different manufacturers they aren't exactly the same size, and the computer says NO.

 

[cah197]

Hmmm. Not sure about that one.

I ran different make tyres on my Zoe 40 without issue.

Make sure that actually solves the problem before you pay for new tyres.

 

[henk888]

Make sure that actually solves the problem before you pay for new tyres.

I am skeptical, and herein lies the challenge!

This is the official response from Renault head quarters, so I cannot ignore it. I am planning to buy two new tyres to make one complete set of four, and keep the old ones. There are plenty of potholes here so if it doesn't work I will have some spare tyres for when we destroy one.

 

[cah197]

I am skeptical, and herein lies the challenge!

This is the official response from Renault head quarters, so I cannot ignore it. I am planning to buy two new tyres to make one complete set of four, and keep the old ones. There are plenty of potholes here so if it doesn't work I will have some spare tyres for when we destroy one.

They’re clutching at straws.

I would tell them to buy the tyre and then you’ll pay them if it solves the problem.

This would only be an issue is if you got the profile size wrong.

 

[Andy-Zoé-User]

would you be able to walk around the car and tell us the dimensions of the tyres on your car (like 195/55/16 for example) or even better take photos of the tyres (at the position where the tyre size is) and post it on here if thats possible? - I am sceptical too it would be this though.

DDT4ALL has a section for UBP (uncoupled braking) but nothing can be set on it. I dont know if other garages can change it with DDT2000 or CLIP either .

They should have facility though to read codes and see if they clear - even I can read UBP with PyREN with a diagnostics adaptor and clear the error DTC codes with it and then see if it comes back so I am sure they would be able to do this and not just be clutching at straws.

 

[Zarni]

On my ZE40 18, I am running a nice new pair of Crossclimates+ on the front and the original tyres on the rear without issues. Exactly the same as I had on my old ZE20, no issue there either.

Can I go back to your first comment for clarification. When you are at 30mph and let off of the accelerator you are saying it does NOT now go to a negative power consumption but it used to?
I assume the brake lights come on when you press the brake pedal? I do not know how the system steps up the regen whilst braking though. I'd expect the brake switch to be part of that decision though.
I also assume there are no warnings on the dash if it has been back to a garage?

Assuming it is a Renault garage then a very quick test would be to swap two wheels from another car on the forecourt. A bit to obvious for some dealers though.

Blimey loads of assumptions there. Do I get a badge or something for that lot?

 

[Smart51]

A new tyre is about 12mm bigger in diameter than one that is worn smooth. That's about 2%. They're also a bit bigger when fully inflated than when let down a bit. And also hot vs cold. The car can tolerate a reasonable difference in diameters. For comparison, the difference in static laden radius between a 185 65 15 and a 185 60 15 is about 3%.

As said above, what are the sizes of each of the tyres? And how worn is each tyre?

 

[cah197]

Garages like to fall back on this if they don’t know the real cause of the problem. Tesla said this to me once and I told them to stop talking rubbish.

Lots of cars have odd tyres.

I’ve only seen this be a problem when someone has specked the wrong size by accident.

 

[henk888]

would you be able to walk around the car and tell us the dimensions of the tyres on your car (like 195/55/16 for example) or even better take photos of the tyres (at the position where the tyre size is) and post it on here if thats possible? - I am sceptical too it would be this though.

Once we have the car back I will have a look. From memory they are all 195/55R16, but there are probably a few more letters after that relating to the speed that could be different.

Can I go back to your first comment for clarification. When you are at 30mph and let off of the accelerator you are saying it does NOT now go to a negative power consumption but it used to?
I assume the brake lights come on when you press the brake pedal?
I also assume there are no warnings on the dash if it has been back to a garage?
Assuming it is a Renault garage then a very quick test would be to swap two wheels from another car on the forecourt. A bit to obvious for some dealers though.

When you let go of the accelerator at 30 mph it does go to a nice negative number (-10 kW), which it always used to do. When you tap the brake it used to go more negative (say, -15, -20 kW), but no more - it just applies the mechanical brakes.

Brake lights come on fine, and there are no warning lights.

A good thought about swapping wheels - they don't have any Zoes on the forecourt though, and I think they rather charge us for four new tyres.

As said above, what are the sizes of each of the tyres? And how worn is each tyre?

Two of them are brand new, two of them are worn; the two worn one on the back I believe. The worn ones are in good shape and perfectly road legal, but also a different make. The front ones are Michelin energy savers (probably quite stiff rubber?) the back ones are some cheap make as I got fed up discarding expensive tyres with a big hole in the side.

 

[Hilltop Dave]

Brake lights come on fine, and there are no warning lights.

So the brake light switch is working OK. What about any connections from the brake light circuit to the power control circuit? Do you have any over-ride switch for any wheel slip sensors (but if the tyre difference is causing theese to function, then this should power up a warning light), and if so, does the problem remain if the wheel slip over-ride switch is pressed?

My guess is that there is a broken wire (or unplugged connector - unplugged by the MOT tester?) in the circuit that tells the power/regen control circuit that the brake pedal has been pressed.

 

[BogieMan]

Is the car still under warranty ?