For the better part of two years I have had this problem. If I don't drive my 2005 at least once every two days, on the third day the battery is dead. I have put a meter on and get a .4 milliamp reading, pretty normal. Had the car into the dealer several times, they could not find the fault (one symptom is that the spoiler deploys when you boost the battery). On my most recent attempt I have been told that the "Body Control Module" is responding. It seems that it wakes up periodically and drains the battery. The replacement cost is just under $3,000. Not planning to do this put will install a trickle charger instead. Any thoughts , comments ?