Battery Discharge Bmw Cooper S Mkii

[dibble1]

I have a BMW mini & thought I had a battery problem as the car could go from 100% charge to virtually 0 in 6 hours with nothing on, keys out. After getting the battery & alternator checked (both fine) I was mystified! However it did it again yesterday & then it clicked, the hot weather. On the occasions the battery discharged I'd left the windows open. Before taking it to an expensive sparky for diagnosis has anyone any ideas why leaving the windows open would drain the battery?
A thousand thanks!

[ukbod2015]

Thats a new one on me - how about a battery test?

[bhg481]

A possible reason is that the alarm kept going off - the movement sensor inside the car will react to the air moving with an open window.

[paddywak]

Personally I'd be getting the electrics checked.It takes quite a lot to drain a fully charged battery in 6 hours and I can't see any reasons why leaving the windows open will be drawing any currant at all,let alone enough to drain a fully charged battery in six hours.

[bhg481]

Maybe there's a problem with one of your window motors or switches. Try taking the fuse out and see if the problem goes away.

[Togo]

Dibbie Does your mini have a minidisc player. I remember a work mate of mine had this prob. but only in the winter. But you did leave your windows open, so it may have gone pretty cold that night. If it happens again try removing the disc player fuse at night to see if that stops it. Funny enough when I was in Cornwall at the end of may I had to jump start a mini with my leads after their battery had gone flat overnight. Were they in a panic. Hope they got back to Southampton safely.

[Hymie]

To discharge a 40Ah battery within 6 hours requires a discharge rate in excess of 6A.

I know 3 series BMWs suffer from a fault in the ‘Hedgehog’ within the aircon system, resulting in the element being permanently energized, even with the ignition switched off.

It may be that BMW have carried forward this design to the Mini.

[BRIGHT SPARK]

Do you know anyone with a d.c clampmeter.Clamp this over the battery lead and have a look if any current is leaking.

[Khandro]

Does the window winder motor work for a few minutes after you've switched off the ignition, my last Audi did. If the timer isn't switching the window motor off it could be draining the juice.

[johnny37]

had a mg once. battery used to drain overnight. a new security system fitted by an over zealous previous owner turned out to be the prob. took it out. prob solved.

[TWR]

When you lock the car, stop with it & make sure the interior lights go out, also check your boot light & if there's one fitted under the bonnet, check that.

[Baldric]

///If the timer isn't switching the window motor off it could be draining the juice.///

Just out of curiosity how would it do that unless the windows are going up and down?

[bhg481]

Motor winds the window down, stopped by end of travel, still taking current and trying to wind window past end-stop.

[Baldric]

And this happens when dibble has parked up, locked up and walked away, might just be a bit obvious imo!

[Baldric]

bhg, would that also not cause the window motor to ignite or at least blow a fuse?

[bhg481]

I wouldn't know, Baldric; I was only offering a way that the motor could still take current when apparently not operating. Further more I don't know for how long the window electrics are "live" after the ignition is switched off and the car locked on a BMW Mini. On my Volvo the windows are "live" for a while after the ignition is switched off but they are "killed" as soon as the car is locked, so not a possible scenario for my car.

[Khandro]

baldric; It's a very useful device, on an Audi at least.it was just a thought and I don't know which other cars have it; say you drive into a multi storey where the light's a bit dim having opened you window to collect the ticket, you park, switch off, remove the keys, get out and ***! the window's still open. Instead of having to climb back in and switch on, you simply activate the window motor. It isn't still trying to activate the window it's just on standby and live - mine for about 3 minutes then the timer switches it off.
- Phew!

[Khandro]

having read bhg, I think he's right and its probably the locking of the door that switches it off, however whatever it is, if it doesn't function, the motor would still be live.

[Baldric]

///the motor would still be live./// yes, but not taking any power unless operating.

We have the same system on our BMW 320.

[bhg481]

Yes Khandro - you've reminded me that, even though locking the car kills the window in mid-wind, I can use the remote to open or close the windows at ANY time, thus proving that the motor has permanent live feed to it.

[Khandro]

baldric; When a motor just like your television set is on 'standby' it is using electricity, - as the little red light indicates. only when it is 'Off' does it not use any.