I have had other cars which rapidly drain the battery when not driven. In one case it was a program error which was fixed with a computer reflash. This was a C6 Corvette.

Is it common for the M45 to drain the battery this fast? Thanks

The usually battery life is ~ <3 years.

Assuming that there is nothing wrong with some car component that is draining the battery (have the dealer check it out for current draw when turned off!), then it is most likely that some light was left on during that time, or the door was ajar, or something like that anyway.

Something similar happened to me a while back ... I was on a business trip and left my car at the airport parking lot for about 4 days. When I came back, the battery was stone cold dead and needed a jump start from the parking lot folks (free jumps at San Jose Airport Parking ... one saving grace for the high cost of parking there).

After I got the jump, I discovered that my son had left both the rear reading lamps on when I dropped him to school that morning, before I went to the airport. Since I parked outside (in broad daylight), I did not catch the lights being left on - I probably should have, in retrospect, but I was rushing to catch my flight!

Sure enough, this was enough to drain the battery ...

Z

Fuel pump [7], ignition [8], injectors [6], fan [10], radio [10].............
A nearly dead battery may require 5-6 hours at 60 mph to recharge to 80% if ac fan is on low and headlights are off.

What happens is a typical half charged battery unless you are careful to modify driving style to keep it properly fully charged.

That 30 minute cummute may leave it worse off than when you started.

Z

The first thing that I did with my new M35 when I got it home was hook it up to my Battery Tender. It took almost a full day to get the battery up to full charge.

New cars are started, moved around the lot, into service, etc. and the battery never does anything but discharge.

Anyway, try to trickle charge it and see how long it lasts. If it still runs down in a week or so, I would have the electrical system checked.

Good advice.

Z

One thing I love about my 06' M35 is that if I leave the map lights on by accident, the car will automatically turn them off for me (when engine is off) because the system knows I did it accidentally. So then it would be impossible for battery to drain with map lights on.