Automotive battery manufacturers make two basic kinds of battery, one that provides you with a high current punch (SLI battery) - perfect for starting a car, the other is a deep-cycle battery, used for golf carts. You should not run an SLI battery more than 80% flat (60% for a gel battery), and you should not put high loads (car starting) on deep-cycle batteries. So really your car should carry two batteries - one for starting, one for operating the roof. This would increase weight by a few kilo's so consequently car manufacturers prefer you to either keep your engine running, or top-up (charge) your battery regularly.
Apparently manufacturers are working on Zinc-Air batteries and Nickel-Metal-Hydride batteries capable of starting a car, but these are are still in development.
The best you can do at the moment is make sure your old batteries are recycled properly and keep your current battery well charged. I've just bought a charger from these chaps - most impressive bit of kit...
I was talking to someone today who has bought a marine battery for his classic Mini that is only used occasionally. Do you reckon that's a good way to go?
Depends on what you're using it for. If it's for starting the car, then no. Marine batteries are deep-cycle batteries, designed for running low current appliances. They should not be used for the high current demand of car starting. I'd just stick with the normal battery.
Thanks for that - I think he only used the car about once a month and was planning to use the marine battery to keep the alarm and tracker going in between times.
As you say, the ideal would be to have one battery to power the alarm and another to start the engine but think I'll make do wth the standard battery and make sure it's kept charged if the car isn't used for a while.
May 2003 MCS, original battery! I've done 65,800 miles but haven't driven it much at all this year, in fact it hasn't been started for 2 or 3 months and I know the battery will be flat. I've resurrected it from dead twice already so I guess I'll have to get a new one now. I've been very impressed with the battery, which I've never laid eyes on and am interested to find out what make and capacity it is, that's if I can find it )
Nov 2003 cooper S 60,000 miles from new on original battery, when it comes for replacement i'll prob go for another Bosh battery. car hasn't been used for a couple of weeks, checked the battery indicator yesterday was showing black not green,still started ok( but not a fast turnover 0c outside air temp).
Tried to start the car today, hasn't had a good run for two weeks now, would not start,checked out replacement battery prices from Halfords,Euro car parts ect, but these were for a 45Ah battery were mine is a 55AH,
phoned the local BMW/Mini dealer,£102 for an original replacement 55AH battery(which i thought was going to be mega bucks)
When changing over the battery used a spare 12v 17AH motorcycle battery jumped onto the engine bay connections, so as not to cause any problems like spikes or having to reinitialise the key fob.
Minis with stop start and brake energy recycling have AGM
batterys fitted as standard. These can stand heavy discharge
and high recharge rates. I think it stands for Absorbed Glass
Mat (AGM) if you were wondering.
Thanks for the info Cooper S Jon, the Varta battery is half the price and a higher AH rating,but thats an online price( next day/two day del time) but i needed something off the shelf quickly, and considering the original battery lasted 9 odd years,which is good going, i thought i'd go for exactly the same unit, plus stops the ol lady giving me jib cause her motors off the road
Just had to replace my MCS battery which was the original 2003 factory fitted unit with 65,000 miles under its belt.
If you are a member of the RAC worth checking their deals as they supplied and fitted mine (at home) for £95.
Also, be careful when ordering or buying a replacement MCS battery as it needs to be taller than many of the batteries listed as replacements at most motor factors otherwise it won't be secured by the top clamping bar in the boot.
Finally, watch out for removing the clamping bar retaining bolt. Mine sheared off in the captive nut in the boot floor due to corrosion. It took the RAC guy ages to drill out the end of the old bolt and re-tap the thread for a replacement. Glad he had to do this rather than me as I nearly went to Halfords to buy and fit the replacement myself!
Replaced mine couple months ago, it went dead first day I had it, all that showing off with the doors open!
It was a 2002 cooper with 93000, so was about time to get a new battery!
Got it from euro car parts...
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Battery 
, the Varta battery is half the price and a higher AH rating,but thats an online price( next day/two day del time) but i needed something off the shelf quickly, and considering the original battery lasted 9 odd years,which is good going, i thought i'd go for exactly the same unit, plus stops the ol lady giving me jib cause her motors off the road
