Accessory battery

Hi there. Can anyone help me? My main battery is fully charged but I understand that the car has a secondary battery which is flat and refuses to charge. The problem being that you can’t start the car and do anything. I really would rather avoid having recovery come and take the car. Surely there is a way of either replacing this battery or charging it directly? Anyone help me? I’m not technical whatsoever so please try and explain in layman’s terms!

many thanks


Welcome, Andrew.

Your traction battery might be fully charged but if something was left on it will drain your 12v battery. I would suggest you plug it in again for a couple of hours and see whether it will start again. I was recently stranded because I was driving lots of short distances with lights on. It drained the 12v and I couldn’t start. Pluging it in got it going again.

Good luck.

Welcome to the site.

There has to be a bit of 12V power to start charging of either battery. You can recharge the 12V battery separately by taking out form under the front cover. This requires you to un-blot the lower front panel. It is just a motor bike battery a bit like this Yuasa YPC14-12 Mobility / Golf Battery 12V 14Ah - Uprated version of 12V 12Ah. However I’m not suggesting you get one of these as it may void your Renault warranty. It is just an example of the terminal connections and happens to be a replacement.

You can effectively ‘jump start’ the charging by hooking up the 12 battery to give enough charge to start the on-board charger. You don’t want/need the donor battery to be on a running car, a small stand alone 12v battery will do.

That’s a good tip. Could it be done via the “cigarette lighter” socket? There are solar powered trickle chargers that do that, I believe.

Interesting! My accessory battery went flat over the easter break as I went away and didn’t use the Twizy for 4 days (I have things connected which use around 2.7Ah per day, so I knew it would happen). I parked it at work where I could plug it in to charge up again so I wasn’t stuck.
However, it got me thinking about the “jump starting” idea Osbrook mentions above; using another battery to provide the power to turn on the “ignition” and charging circuits.

A hobby LiPo battery such as this:
is small and light enough to keep in the boot (in a protective bag!). It’s the right voltage and has enough grunt and holds charge very well. With the right connectors and a bit of simple protection circuitry (diode and current limiter) it should do the job nicely as an emergency backup. I already have a charger which can top it up.
I wonder if anyone else would be interested? When I get all the bits together I can let you know how I get on.

I would be interested in your findings and the kit you come up with.
Please keep us informed.