Alternator or the battery

To determine which it is, you will need to test both the battery and the alternator. It really could be either. I do not recommend buying either one before the complete charging system is tested, and the problem is verified. To have this done, I advise taking it to one of the certified shops in our network. You can find a list of them in your are here: http://repairpal.com/mercedes-benz-within-10-miles-of-hollywood-florida-33024

and hope it's not the alternator,cause if a shop does the work >>$673.00-$1382.00,which it sounds like it is the alternator and not he battery!