Posted by
AJo
14 yrs ago
We live in Hong Kong but spend 4-5 weeks each summer in the UK (no maid here). My wife bought a 2005 Mini Cooper (not the 'S' model) Automatic 1,598cc earlier this year. I usually disconnect the batteries on our cars (I run a Toyota Camry) over the summer months to avoid arriving back to cars that won't start because of flat batteries. Both cars are kept in an open car port whilst we're away. When she bought the Mini, she mentioned this to the garage and they said it was not a good idea to disconnect the battery because "of the computer". Does anyone have any experience of leaving Mini's unattended over the summer? What do you do? What is different with the Mini that might cause concern if I leave the battery disconnected?
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AJo
14 yrs ago
Thanks - that was my reaction too... It's never harmed the Toyotas. I asked a car mechanic at the BMW/Mini repair centre what on earth could be harmed. His response? "Powered immobiliser system, timers, etc. The ECU is a computer that never completely switches off". All voodoo...? I can't believe a Mini is rocket science...
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sounds like he's(your mechanic) talking out of his ass...
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AJo
14 yrs ago
Thanks. Oddly, both the supply garage and the Mini Service Centre favoured leaving the battery connected (even though they conceded it will trickle down and go flat), rather than no battery connection for 5 weeks. Bizarre. A UK-based mechanic suggested leaving a battery conditioner attached but that's simply not practicable in my case. As I said before, what can be different from the Camry - which happily sits with its battery disconnected all summer. Is there a Mini owner out there with any experience of lay-ups?
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I guess it comes down to just how long you are away. There is a small on board battery that is trickled charged from your main battery. This small battery keeps all the settings the same if you disconnect the main battery.
If you are away for some time, then the little battery will discharge and all the settings and on board information will be lost.
Sure short time disconnects will cause no problems, but the longer times might/will cause problems.
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190k
14 yrs ago
Get a solar powered trickle charger from E-bay. Also brim the fuel tanks. that would minimise the build up of water in the tanks from condensation in the high summer humidity. It would aslobe worth pumping the tyres up to the max stated on the side wall info, that will help prevent the tyres from forming a flat spot. Best is to prop the cars up on axle stands if you can
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"When she bought the Mini, she mentioned this to the garage and they said it was not a good idea to disconnect the battery because "of the computer". Does anyone have any experience of leaving Mini's unattended over the summer? "
Quite a few modern car computers will have issues if you disconnect them too long. For example, they may set themselves to a failsafe condition and require an authorized mechanic to unlock.
The stuff you mentioned is what causes these "issues": "Powered immobiliser system, timers, etc. The ECU is a computer that never completely switches off".
"So it's a "computer or two" in a modern car - but even Desktops' / Laptops' / Netbooks' computer "brains" frequently get "re-booted".
Apples and oranges. We're not talking Windows. Solid state computers running in real time with custom operating systems.
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AJo
14 yrs ago
Thanks everyone. bob the builder - your points make good sense to me. This ties in (I think) with the suggestion to leave the battery connected even though it will go flat (I'm guessing) within 5 weeks. Perhaps the garage was suggesting that by doing so, the small battery you refer to which is fed from it stands a better chance of staying energized? What do you think?
I'm still puzzled why my Toyota Camry doesn't have a problem with it's battery being disconnected for five or six weeks. It must be more agricultural than I thought....
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If you disconnect the battery for that length of time then the immobiliser/alarm system will kick in to fully disable the car. Simply reconnecting the battery will not "un-immobilise" the car, it will need resetting by the garage (and how do you get it there?).
Don't you have a friend that could go and give it a turnover and a quick spin each week? That would solve the issue.
I suspect that your Camry is a lot more agricultural than your BMW Mini!
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AJo
14 yrs ago
I wish! On the basis that the car will be all on it's lonesome-ownsome for 5 weeks with just a disconnected Camry beside it for company, I'm leaning towards making sure the Mini battery is in good nick, leaving it connected and hoping that the small battery will retain sufficient charge to keep the immobiliser etc in check. For sure, it seems it won't stand a chance if I disconnect the main battery. Then after the five weeks I'll just have to jump-start it from the tractor...oops, sorry - Camry... Any last thoughts? Thanks for your help everyone - much appreciated!
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190k
14 yrs ago
Get one of these and problem solveded
http://cgi.ebay.com/12V-Solar-Trickle-Charger-Car-Truck-Lawn-Mower-Tractor-/220802571437?pt=LH_DefaultDomain_0&hash=item3368dbdcad
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AJo
14 yrs ago
interesting. It'd be just the job if it works. Any known stockist in Hong Kong?
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190k
14 yrs ago
got mine from E-bay works great connect to battery close hood, make sure no shorting, I cover with insulating tape and put the panel on the dash board. Also forgot to mention that you should leave the aircon air intake lever to outside air so there is pressure equalisation during the hot sunny day and cooler evenings. I have seen a few rear windscreens pop out because of that especially if a typhoon swings by and the atmospheric pressure drops a lot
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AJo
14 yrs ago
Good advice - thanks. Does it REALLY work by plugging into the fag lighter socket, too?
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190k
14 yrs ago
depends if your fag lighter works without the ignition key on. but for me that is going through the wiring harness so a lot of resistance and thus less charge to the battery
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AJo
14 yrs ago
Understood. Wonder if there'd be sufficient charge through the fag lighter connection to simply maintain "something" in the battery (sunshine permitting) then? I couldn't leave the car in the car port if I wanted sunshine, so it'd have to be parked outside - wire from the bonnet and through the door is just too irresistible to kids.... Thanks for your thoughts on this matter, incidentally - I really appreciate it.
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