Flat battery

[V8Rumble]

My LS400 went in for some touch ups on the bumpers over the last three days but when they went to start it the Battery was flat.

This happened when I had the cam belt done.

The car stood for twelve days when I went on holiday and started on the button when I came back.

It would seem that when it is left unlocked or with the boot open etc the Battery flattens.

The Battery shows up as fine once charged and a discharge test is done.

Any ideas?

[steve2006]

I've noticed the Battery goes flat pretty quickly if the doors are open or the stereo is left on for an hour or 2 but when you think how many interior lights are on with doors open, dome light,puddle lights, seatbelt buckle lights, ignition lock light these do draw some current.

[Verbout]

Is this why some cars, my uncles ML Mercedes, have two batteries?