Hi folks! I've mentioned here before that I've had an intermittent problem with the start stop function on my 2009 Mini Cooper Convertible - a few times a month, the engine shuts down as normal when I go into neutral and put the handbrake on, but then when I press the clutch to restart it, the engine completely switches off instead of restarting - although the dashboard display appears as if the engine has restarted. The car is under warranty till the end of July so I booked it into Sytner Cardiff yesterday for them to have a look.

Sytner reported that they think the problem is my battery being very low - they reckon it was only 29% charged yesterday. They suggested I use the air con less and use the car more often - but I hardly use the air con and use the car at least six days a week for journeys of at least 10 miles each way, so I'm not convinced that's why the battery is low. They say they charged it yesterday and will check it again when it goes for its MOT at the end of July. Any ideas why my battery would be so low, and would it really be the case that an intermittent problem with start stop restarting would be the only sign of such a low battery? Sytner said I should have noticed that the car was much "sparkier" after the battery was recharged yesterday but to be honest I can't feel any difference!

I have exactly the same issue on the same age of car that has been gradually growing since it was a year old. My stop-start completely disappeared last winter and has only just started working again this month. I've had a couple of restart failures since then.

In my case, I'm convinced the battery has deteriorated significantly and that is why the stop-start went away. As I charged my battery myself at home, I had a voltmeter on it and from the way the voltage rose too quickly when being charged, I'm sure my battery has one duff cell in it.

I suspect you have exactly the same poor battery condition and so you have a choice between trying to get the battery replaced under warranty, when neither you nor Sytners have any definitive evidence that the battery is at fault (it starts the car every morning, doesn't it?), or you could just accept that the battery is a consumable item and pay for it to be replaced. If you're not intending to sell the car in the next year or two, you'll probably end up paying for a battery when the car's out of warranty, so instead paying for it now isn't that bad a deal.

I also have a sneaking suspicion that there is a technique to restarting the car by stop-start. I think if the clutch pedal is pressed 'lazily', the clutch isn't fully disengaged by the time the computer disconnects the starter motor and then the engine stalls. I've found that the restart failure never happens when I press the clutch firmly/quickly down.

The stop/start seems to be a fairly sophisticated battery condition monitor!

A friend of mine took her MINI into the garage because she had been having starting problems and the garage told her it was because her battery was flat, and she said "Well! what shape should it be"? :D

Angib - that's really helpful and really interesting - and very nice to know I'm not alone! And I will definitely be concentrating a lot harder on how I depress the clutch from now on. Interestingly enough, when I discussed with Sytner yesterday that they would check the battery again when they MOT the car, there did seem to be an implication that they would replace it under warranty if it was still on the low side. I may have got that wrong, but if worst comes to worst I don't imagine a new battery will bankrupt me. In fairness they've been pretty good so far - yesterday the car was collected from my office, returned washed and hoovered and with a fully charged battery, and it cost not a penny.

The only other thing I've wondered about - my car was 12 months old when I bought it and only had 2,000 miles on the clock, having been used as a demo model by the dealership and presumably having spent a lot of time on the forecourt not doing much. Might that impact on the battery life, or is my understanding of how batteries work not right?

And as for you, The Nun, I fear I will be telling that joke myself - it did make me chuckle :D

I brought my mini back due to low battery problem and it turned out the alternator belt needed to be replaced. Bit shocking as the car was only 3 years old at the time!

Might be something similar in your case?

Sounds like you may have a dead cell and definitely check the alternator. The new cars are so sensitive to changes in the strength of the battery. Bite the bullet and install a new battery and take it off your list of possible issues.