I went through the same thing. Battery warnings and losing 5 minutes every time it gave me that warning.
I purchased a battery charger per my service advisor to see if I could bring it back to life. I drive an '08 with the original battery. Since I've charged, no further warnings/clock adjustments.
My advisor also told me that no matter how long or at what RPM you drive, the "charging system" in the car isn't designed to bring the battery back to life, but is only designed to maintain it. Giving it a good overnight charge seemed to work for me. YMMV, but having a good charger around is always a good idea. I picked one up that's a smart charger, which senses how much charge is needed and adjust its output based on that, all the way down to a "trickle" mode. Cool, and less than $100.00.
Last edited by Rudeman; 11-19-2012 at 06:49 PM.