I'd been having starting issues with my 3.0D auto a few weeks back so took it to a few garages (non-BMW) who all diagnosed a knackered battery not holding a charge. I asked them to double check that it was the battery and not the alternator, and they all agreed it was the battery.

So I replaced it with the correct-sized Bosch battery, and all was well. However I noticed this morning that it seemed a touch sluggish to start, but put that down to the -7 temperature in the UK. However this evening it wouldn't start at all! Turned over once then the relays started clicking like mad. I got the jump leads out and it started first time.

I use the car every day, but my commute is only 2 miles each way, then I do about 50 miles over the weekend.

Any suggestions? Is there any way I can test the alternator myself, or for a power drain?