OP sorry to hear about this incident, I am of the camp that a battery goes, you drive to Sears or Wal Mart, get one, put it in, and throw the old one in the woods off the interstate highway (j/k). This forum was the first place I ever heard of having to "register" the battery to the car.
I was thinking of getting my battery replaced yesterday on my appt., but prior, I've never seen anyone getting one under warranty. My SA told me 5-6 years is expected, and BMW will rarely replace a battery under warranty (my car is 49 mos.). I saw another thread where the OP said his battery was tested, charged, and the dealership told him he doesn't drive the car enough to charge it properly--I think I am still in this situation as well.
Anyway, after looking through the DIY for the E9x battery, for now, I'm pretty much decided I wouldn't DIY due to the potential for consequential damage.
So if it's any consoloation to the OP, he's doing a good thing when he says "so this doesn't happen to your E9x." That's making a positive out of a bad situation. Merry Christmas OP, thanks for sharing.
