Hi there - help! I too have the dreaded battery drain. I have isolated it to the fuse which operates the comand (fuse 54 - I think). I have the same symptoms as mentioned here, other than I had the comand fitted recently and so thought this could be the issue, now I am starting to think it is a coincidence with the seat module (though I don't have memory seats, they are electric).
I have a W220 on a 1999 plate. It had had a standard audio 10 for a number of years and no issues with the battery. I recently upgraded to a 2nd hand comand 2.5 and this works great, though since I have had it I have noticed significant battery drain (overnight a new battery drops from 13.3 to 10.2v) - I had the battery replaced by mercedes last month. It is a really frustrating issue. I have even swapped out the comand for another replacement thinking the comand may have been faulty - still have the battery drain. The current comand is setup with the telephone feature (even though I do not use this) - could these additional features cause a drain if they are not present?
Failing this, it could be the seat module. I am about to give up and let merecedes diagnose, but, I would rather save the money and find a fix myself. Is there anyway to further test and identify if the problem is with the comand / module? I guess I could remove the comand but leave the 54 fuse in?
Help please as it has cost me a new battery already and I am really frustrated as to having to drive with the 54 fuse out and not being able to use the comand. Any help would be greatly appreciated and if you could post the instructions of your fix 'Trainer' it would be fantastic and so appreciated.
Thanks in advance.