Start-stop not working on C4 after battery changed

[DarthPyross]

Hello all,

I've seen a thread that a similar issue to mine was mentioned, but I didn't want to hijack it so I'm starting a new one.

I have a Citroen C4 2012 1.6 e-Hdi Exclusive. For about a month, the start-stop function did not work but I was able to drive the car with no issues. Two weeks ago, when I started the car, the service light was on, an error showed up on screen (engine fault) along with three warning beeps. I drove the car like that for the duration of the day, with no start-stop still, and then on the next day I took it to the repair shop. They hooked the car to the PC and told me that my battery was at 7% and needs to be changed. I confirmed it, they changed it, but they couldn't make the service warning disappear after (and start-stop was still not working). They said that I should drive for a while so that the new battery could charge up, and I should come back the next day so that they could try again. On the next day, they still couldn't fix the warning, they tried another brand new battery, but still nothing.

They sent me to someone else who was an expert on car batteries and "brains" (sorry, I don't know the actual technical term). He said the battery was at 79%, which was still low for a new battery. He told me to drive for a while and come back a couple of days later. He also mentioned that if the problem persists, they may need to change the "battery brain" or the "start-stop brain".

I would like to hear your opinions on this.

Thank you,

[PaulC5]

New batteries often need charging up before fitting since they have been sat on a shelf for some time. If you use a smart charger the battery can be charged on the car without needing to disconnect the battery but check the charger instructions first.

[DarthPyross]

My main concern is actually about the necessity of replacing the "start-stop brain". The repairman claims that it is faulty and apparently replacement parts are hard to come by (and expensive).

[PaulC5]

If after charging the battery does not help then I would go to a Citroen dealer if you have not already done this. The service light might also be on for a different reason to the stop/start. Your car might have an accumulator for the stop/start as well as the battery which might be faulty.

As for stop/start, it does not work on many cars with it if the battery is not fully charged - it does not work on our 308 and there are other things that prevent it working such as cold weather. Not working on our car saves me having to use the switch to turn it off which will save the expensive battery and starter from wearing out.

[GiveMeABreak]

It may be nothing at all to do with the main car battery - some of these vehicles have a separate Stop Start system battery or 'accumulator' that's essentially a large capacitor to store energy for the stop start system.

There can be many reasons why these fail and care needs to be taken when servicing this because of the high voltage risk, so I suggest you get it to your dealer who will be able to advise and diagnose it correctly. Most places won't even know about this system as it's hidden behind the left wheel arch.