12V battery died

Hello I have been in quarintine for 3 months and havent used my twizy in that time. A week ago I checked it and it wouldnt start. The 12V battery was dead so I charged the car which was still on 80% and everything seemed to be working fine. Yesterday I checked the car again and it was dead so I plugged it in and went for a drive and then today I wanted to take it out again and at the start the screens turned on and everything seemed fine until everything turned off without even having time to start the car. Is there anything I can do to recover the battery or should I just get a replacement?

Two things

  1. the 12v Lead acid battery (all lead acid batteries) do not like to be heavily discharged and will neve fully recover. It sounds like your 12v battery is now dead.

  2. Your traction battery should be stored at less then 80% certainly not at 100% to prevent damage.

However as the Traction battery is still well charge and the 12V battery dead it could be that your charger is on the way out as it should have kept the 12V battery charged and taken power from the traction battery.

Next time keep the 12V charged, trickle charger adn don;t leave the Twizy withe either a full or empty (sub 20%) when leaving for a few days.

As Osbrook said you 12v battery is most likely dead.

However the 12v battery is only charged from the traction battery, when parked, if your Twizy has a later revision of charger.

You can buy a standard battery for about 15 pounds, you don’t need the Renault one. Look online for a Frenchman who shows how to fit it easily. I followed his instructions and it has worked fine, except the SERV light stays on.

my twiz has had 3 non renault 12V batterys in its lifetime and the SERV light never stays on.

Did it come on at all? In that case I don’t know why mine is on… Any ideas?

I’ve had 2 totally dead 12v batteries and I’ve tried using a normal ‘jumper’ pack to put some charge into it. I’ve not had the service light come on for the 12v.
Have you taken it to Renault for them to actually run a diagnostic? That tends to be the best way and far easier to find out what the problem is and to have fault codes removed than guessing.
If you go to the dealership and ask them to do a battery State of Health check because you might be buying the traction battery, they’ll normally do a CLIP for free as they have to plug it anyway.

@EVnBeyond Will they really tell you the SOH of your traction battery? I need this before I buy out my battery. I have no other means of checking it.

The Bristol Renault dealership did for me. I just called them, booked in a SoH check and that was that. Free of charge. They even charged it and were going to valet it too.

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If it’s simply a case of reading the value from the ECU then I could help with that (once social distancing is no longer an issue).

Both my PowerBox and diagnostic software can read it.


Thanks Peter - I’d just meet you at Tescos when you come over.

there should be no SERV light on after you replaced the 12V battery , maybe you have another fault with the twizy.

worth borrowing or investing in a delphi clip or icarsoft module to reset any fault codes.

Just been out in the garage with the Twizy, it’s around 0c at the moment.
I’ve not driven the Twizy for 3 weeks or so and left it with a 3/4 full traction battery.

Turned the ignition on and for the first time with this car – nothing, no dash light, no clicks from relays etc, nothing. Sound very much light the report from @Rubeb above.
I plugged the charger in and waited a couple of mins and the airbag light came on, then a couple more and the dash lit initially with two horizontal lines, then the charger started (currently at 72% SOC).

I turned off the charger and all looked OK, I checked the 12v battery with a little volt meter I have plugged into the 12v socket, 15v? This was straight after the charging was stopped.
Turned it all off and went inside for half an hour.
Came out and did the same, turned on, nothing and then the same as above …
While it was playing up second time around I turned on the Powerbox to get some readings – it was reporting Not what we’ve looking for, Found No Name, connecting to ,Found No Name, Not what we’ve looking for.
Once things had returned to normal again the powerbox was connecting fine, showing 100% SOH and the same SOC as the Twizy dash is showing and all the traction battery voltages look good too.

I’m guessing it might well be a knackered 12v battery? I have a 2015 Twizy and I think it has the old charger so doesn’t charge the 12v with ignition off.

I’ve currently left the ignition on while I write this in hope of charging the 12v a little.
I have a 12v trickle charge motorcycle charger, I wonder if I should leave that plugged into the 12v for these winter cold snaps?

Yep the 12V is knackered.

Replace it or charge it overnight separate from the Twizy , its a good idea to keep the trickle charger attached during the winter months.

Many thanks, I thought it would be the 12v but still was quite a shock to see nothing when I turned the key :frowning:
I’ll give it a go on that trickle charger, its supposed to condition batteries too from memory, we’ll see.
The 12v has always looked healthy in terms of voltage so I was surprised if its gone, but I guess sometime they just let go in winter.

I’ve been through 3 12v batteries in my 8 years ownership of the Twizy , lack of winter use leads to quick failure of the battery because the alarm system is drawing current from the battery all the time , later Twizy’s top up the 12v battery from the traction battery.

The last year and a bit I kept a 12V trickle charger attached during the winter months.

I have the standard alarm but not turned on, as you say I’m sure that’s drawing a little. I’m going to see if its dead again a little later and if so put my trickle charger on it and keep my fingers crossed - I expect another battery will be needed though.
Have others bought a replacement recently, this one seems about the best value I could find: https://www.tayna.co.uk/car-batteries/exide/ek143/?gclid=EAIaIQobChMI6J_t973n7gIVWuJ3Ch1vcwrwEAQYAyABEgIvs_D_BwE

Yep that looks good.

I changed my connections years ago because this battery was hard to find and very expensive so I modded the connections for the cheaper £20 battery , they last about two to three years on light usage of the Twizy.

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I did the same. I now have some connectors but all I did was make an adaptor from ring to spade and then covered it with heat shrink. I can always remove them to go back to original fittings.


I charged the 12v on my Optimate (https://www.optimate.co.uk/) for a couple of days and left it sitting in the garage unconnected / no load.
It was about 13v after I disconnected it from the charger and dropped to 12.6v 12 hours later. 48 hours on its down to 12.57v.
For those who know more about 12v batteries, does that sound healthy?
Looks like this battery is just under 3 years old.

Also, when I still had motorbikes (BC) I had the optimate connected to the bike battery all the time in situ i.e. with some additional wires provided when it was still connected to the bike, when the bike was not in use.
Is there any reason why I shouldn’t do this with the Twizy?
I could connect this specially designed wire along with the normal 12v cables and poke the other end into the charging cable area (it has a waterproof plug on the end of it). Then a simple matter of connecting the optimate up.