To the OP - did you get this resolved? What did the dealer do on your second trip? I'm having the same issue with my 2011 335D. My dealer charge the battery about six weeks ago but now the problem has returned. I found that locking the door by pushing the button on the key fob I don't get the battery discharge error. Makes me think it has something to do with comfort access.
2014 335i Red - Saddle Interior / Premium / Nav / CA / HK, Satellite Radio