R50 Cooper draining its battery

[D-Angle]

I have an R50 Cooper that won't keep a charge in its battery. It will fire up fine from a jump start and drive well once running, but I left it for 2 days and the battery was dead again when I went to start it this morning. I tested the battery with a multimeter and got 12.66 volts which suggests it's healthy, that just leaves something draining the battery when it's parked. I'm gong to get an automotive electrician out to it next week to have a look, is there anything in particular we should be checking thats a known problem?

[CarsOrBikes]

last one I had doing it that quick was the radio causing it

[E-bmw]

D-Angle said:

I tested the battery with a multimeter and got 12.66 volts which suggests it's healthy,

When did you get this result in your testing?

12.66 suggests a fully charged battery, so if that was tested when the car wouldn't start, I would be looking at engine/battery/alternator/starter connections properly, as in remove, clean and refit.

If it was after the car has been run, you need to test again when it won't start.

[Master Of Puppets]

Also check that all lights are extinguishing when doors and boot lid is shut and the one in the glovebox and bottom of the doorcards, above the
foot pedals etc, the R50 has loads of these lights that come on when anything is opened, I've known people getting so P'd off with
them draining the battery that they disconnected every single one of them.

If you have an after market stereo it could also be a potential culprit.

[bangerhoarder]

You can also do a drain test at the fuse box - multimeter on current setting, remove fuse, put the multimeter into series instead of the fuse. Can be awkward doing so with the doors closed.

Did this on my TT, found the cigar lighter circuit was doing it. Pulled the fuse, not sure what the actual fault there is.