Battery Dead....Won't Hold Charge

[tomsawyer]

05 4.4i w/ 60K

Hi Everyone, I realize that battery drains, vehicles won't start, etc have been discussed ad nauseam on this site but I figured I would throw my current dilemma into the mix.

For the last couple of years, I have had a battery drain. What happens is if I don't drive the vehicle for 2 days, the 3rd day it won't start. So I always made sure the truck was driven and I never ran into a problem until I went away for vacation (I never attached a trickle charger).

Finally, in November 2012, fed up after calling triple A a bunch of times, I took it to the dealer. I had an Interstate batter in there and the first thing the advisor tells me is they want to install a BMW battery. I ok it and sure enough they wait 3 days and the car won't start. So the tech goes thru the various procedures and cannot find anything. I guess he started unplugging and replugging, testing, etc and then the drain goes away. They let the car sit for 5 days, 2 separate times and the truck started both times on the 5th day.

I took the truck back and everything seemed to be fine. I even went on vacation, came back, truck started right up.

All of a sudden, this past Saturday, the truck wouldn't start. Put the key in and click click click. I have a battery pack and jump the truck and drive it for 2 hours. Come home, turn off, lock it and the next day it's dead, won't start. I jump it again but this time I get a trans failsafe prog error, the outside temp is showing minus 40 degrees and the gas tank gauge shows empty but I know the tank is full.

I drive to get a cup of coffee, turn truck off, get coffee, try to restart but its dead again. I jump it and drive it to my friend who's a mechanic, but not a BMW specialist. He did his tests and told me yesterday the battery is completely dead and won't even hold a charge.

What could all of a sudden have happened that the truck is completely dead - having gone from a 3 day drain to "repaired" (in quotes b/c we really never found out what was corrected) to now completely dead?

Thanks to all who answer.