May I follow up your response in Issue 345 to Terry Raynor, regarding the start-stop system fitted to his Kia ceeíd? My seven year-old BMW 320d is start-stop equipped, but for some time it hadnít worked. My excellent independent specialist explained that, in the case of this BMW at least, the alternator is set to cut out at a slightly lower voltage than is usual to extend the energy saving regime. My battery was just down on capacity in mid-winter, probably as these days the car covers only 5,000 miles a year. Replacing the AGM battery was likely to cost over £300 and I was advised to try trickle charging my battery with a low-output device. So, out came my trusty old Gamages charger ñ this one is vintage 1960s, and it cost 15/- or 75p. Does anyone remember Gamages in Holborn? It started charging at just 3amps, which then quickly fell back to 1amp as the voltage rose, which looked ideal, and 12 hours of charging cost next to nothing, of course. Repeated weekly or so in winter, the start-stop system now works exactly as it should, and the battery has always given perfect starting performance. But do I want the engine to stop every time the car comes to a halt? A small amount of diesel is saved, and some emissions are prevented, but at what cost in wear and tear to the starter motor and ring gear? Not long ago, we were told not to stop a hot, turbocharged engine instantly, but allow it to idle for at least a minute. So, in my car, the start-stop system is disabled more often than not. Iíve always used a simple mechanical start-stop system when I wanted to. Itís called The Driver. 

M.B. Hants.

I cannot disagree with you. Of course you can significantly improve the (incredible) EC fuel figures when testing on the Urban Cycle and using stop/start, which was probably the great attraction for the manufacturers. There is always a significantly more robust starter supplied for stop/start equipped cars, so it means that your own item will last for a good few years yet. Funnily enough my wife runs a 12-year old BMW 318i petrol that does no more than 2,000 to 3,000 miles a year.

Gamages? Well, I thought that nobody remembered the name anymore! What a quality piece of equipment that charger has turned out to be. I remember when they used to advertise mail order bicycles, washing machines and just about whatever else you can think of. Companies like that still exist in the USA, and any small farmer out there still buys lots of things mail order from a Sears or JC Penney catalogue, although I guess they have gone online by now, and I suppose that Amazon is probably the Gamages of today.

Did they have AGM batteries eight years ago when your BMW was made, I am wondering? My research reveals that AGM means ‘Absorbed Glass Mat’ not ‘Advanced Glass Mat’, as I had been led to believe, and apparently they were first used in military aircraft and business jets back in the mid-eighties. I was getting a bit concerned about the battery on our BMW, as we know that it is at least eight years old, and quite possibly even 12 years old. But it suffers occasional two to three week breaks between runs without showing any problems (although this is a mild winter, of course), and I guess that it must just be a quality battery – it is totally sealed and maintenance-free, by the way, as is yours probably.

I do take your point about not stopping hot turbochargers, but I think that the advice has been somewhat overtaken by the use of water-cooled turbocharger bearings, and possibly better oils. Reference the £300 for a replacement AGM battery – that must surely be a BMW garage price? (M.B. advised me that the independent garage that he uses always recommended the use of genuine BMW parts on account of the high quality and an excellent two-year guarantee. That’s worth bearing in mind by BMW owners using independent garages – and probably why my wife’s original BMW battery is lasting so very well, although the AGM battery was only introduced by them in 2007, so hers is apparently merely a very good quality conventional one.

Doc