Intermittent SERV light - get fault codes from OVMS?

Since my service (2016 Twizy, first MOT and service in August), I’ve had an intermittent SERV light and associated minor (but noticeable) loss of power. It tends to come on after about 3-5 minutes of driving, and sometimes disappears during a trip but often stays on until I stop. There’s also a battery indicator above the speed (battery with “!” shown), I think relating to the big battery.

I’ve bought a 12V battery to replace the original one as it’s a cheap option and rules that out as a fault. As yet I haven’t fitted it, and looking through the forums I’m not sure the 12V battery is the issue.

I’ve got OVMS (v3), and when the car is off (now) the 12V battery is showing as 12.3V and the main battery is 53.5V.

It’s charging OK (at least if goes up to 100% when I charge it, and nothing seems untoward on the charge indicator).

Does anyone know how to use OVMS to read fault codes? I’ve tried various things but can’t get a sensible view so far.

Any other suggestions (obviously taking it to Renault is one, but it’s a bit of a pain to get there, and will end up costing just for diagnosis I’m sure!)

Thanks for any help!

Just by the sounds of it - looks like the 12V battery is not charging while driving.

12.3v is too low. After a charge and a rest of say 30 Mins it should be at 12.7 volts at rest ie. no load from the Twizy and lights.

It would be worth swapping the battery since you have and trying that.

Great, that’s really useful. I’ll get that changed at the weekend and see if it helps. Thanks :+1:

You should consider connecting a maintenance charger.
eg CTEK or similar to maintain it when you are not driving.

the traction battery will keep the 12V battery topped up when it drops below a certain value , if the 12V battery is in good heath.

Only if the charger is second generation.


I found that when I swapped to the new charger my 12v is topped up all the time (even with car fully off) by the traction battery as Peter says above.

Right, 12V battery swapped (took about 10 minutes in total, really easy to do!)

Went for a 10 minute drive and almost made it home with no SERV light, but it came on just as I approached home. However, I did wonder if the 12V battery is low (as it’s new) and needs a bit of charging so I’ve stuck it on charge and will try again tonight when everything’s had a few hours to charge up.

Incidentally, OVMS now reports the 12V battery at 14.1V (up from 12.3V) which suggests it’s fairly well charged, although it is also on charge now which may mean that I’m reading the charger supply voltage and not the actual battery voltage.

Will update later…

OK… definitely not fixed (although I do now have a shiny new 12V battery).

I’m starting to think the SERV light appears a bit after some continuous regen, so if I decelerate from 40mph to 20mph for example, with the battery charging during that time, then the SERV light seems to come on within about 10 seconds of this happening, although I’m not absolutely sure yet.

Will continue to investigate - next step is probably to disconnect the OVMS as I notice there was new firmware on 25th September and there’s a slight chance it’s upsetting the car.