Related to a post I did regarding my 2006 A6 battery wearing out after 18 months and the dealership diagnosis being that I simply need a replacement, I think I've identified a potential problem and wondering if anyone else is experiencing this. I felt something was putting a drain on the battery after shut down. I've heard some funny noises from the trunk area in the past in the location of the nav system. In looking at it further, I've noticed that the nav system lights stay on and I can hear some "humming" - as if the CD were rotating. I've since tried to eject the CD then re-insert it and sometimes the lights go off. What I think is happening is that the nav system is not shutting down and that may be causing my battery to drain. Usually the battery goes from full bars to only one if I don't drive the car for 24 hours. If it is less time than that, it stays at full bars. And not always, either....