Yesterday, I got in my car and it was DEAD. Needed a jump to get it started so that I could drive it to the dealer. I had read posts about Battery Saver messages and mentioned that to the service guy. They put my battery on a charger for a couple hours and then it tested out perfectly fine. When I asked why this happened, all they could tell me is that "maybe something was left on". Isn't this car smart enough to shut things down after you exit? When I later started my car, I noticed that the clock and seat settings were messed up and had to reset them. I also noticed that the chime I was hearing every time I turned on the car (sort of a "La Ti Da" x 3 chime) was gone. I wonder if that chime started about the same time as the Battery Saver messages. ??? Anyway, I'm going to watch for that. My theory on this whole thing is that the car (computer) is not properly shutting things down upon exit. I am very good about turning things off before I get out of the car and I do not charge my phone, use USB drives and I don't have a Nav system. When I turn off the car, I get out.
The computers and such run 24/7. They don't stop when the car is turned off. It is also very easy to leave the inside reading lights on and not notice it when you get out of the car. They do turn off after about 15 or 30 minutes, I forget which.
I have a battery charger that can display the percent charge level of the battery while charging the battery. I hadn't used the car over the weekend and put the charger on it yesterday. It indicated that the battery was at 55% charge level.
I wish I could find the specs on the battery but it is a Ford proprietary battery. Since it is not used to start the car it should be a deep discharge battery in this application. A standard car battery can be destroyed by allowing it to discharge completely. They are designed to supply short bursts of high current and then immediately be recharged.