"The “stop start” has never worked on my wife’s 2013 Mini diesel "
It's funny you say that. Good ladies is an R56 Cooper S Auto. According to Mini and all the aftermarket parts sites it is stop-start and is listed as such at our local Mini dealership. I can say with confidence it has never done the dance in the 10 years we have had it. When the battery failed during the pandemic I spoke to the local Mini dealer (Harwoods) and they listed an AGM battery as it was stop start. I challenged them to take it for a drive and show me it stopping at junctions.
Anyway they wanted £400 for a battery swap and re-code. So lets just agree that an AGM battery is better (more power, less loss) if a little more expensive. I looked at the battery and went on the web sites. It was pretty obvious what model it needed. So I went to a local independent specialist and they said they would use Varta AGM and fitted the same one from the web site.
I think there is a lot of fudge in the parts and service industry.
