[JimD]

A low current draw over an extended period of time can ruin a battery but it doesn't always. I've left something on for days and been able to recharge the battery. But I've lost them too. Most recently this happened when I left an interior light on in my non-bimmer SUV at the airport. The battery was old and did not recover.

If it was the comfort access, however, I don't see how this is operator error. I wouldn't store the spare key in the garage but if there is no warning I don't know why that would eliminate BMW's warranty. Batteries and other consumables often get different warranties than the rest of the car, however.

My fiancees 1 has comfort access so I will mention to her to keep the key away. But having the switched 12V on does not guarantee a load was applied. What load caused the battery drain? Just the car's computer? Or was a light or something lit? It would be even more curious if it is just the car's computer.

Jim