How long has your OEM engine battery lasted? I'm still on my original battery from taking delivery off the truck in January 2013. It still works even in single digit (F) temperatures. The replacement is around $130 for BXT-96R-590 at Ford, and parts stores seem to be close to that other than a cheapo at Walmart going for just under $100 (but out of stock). I should probably just change it, but it is still functioning. The car is stored in a detached, unheated garage and is my daily driver. Maybe there are some long-standing members still on here who can share success or failure stories. I carry jumper cables with me and have AAA too lol. Cheers.