Defective battery!
Hi, new member here (see my post in the New Member Introduction forum). FYI just wanted to chime in that I'm also dealing with a defective battery. I've only owned my 2010 CT for a short while, and it only has about 20,000 miles, but the car has died on me TWICE while I was playing with the Nav system when the car was not running (Accessory mode). The first time I shrugged it off, thinking maybe the car had sat on the dealer's lot for a while and I hadn't driven it enough for a good charge. The second time took less than 10 minutes. My brother-in-law witnessed it and said the battery was defective.
The battery test light is GREEN, but somehow it's not holding a charge when the car isn't running (bad cells?). Starting and driving it everyday is NOT a problem - I just can't turn off the motor and run anything in Accessory mode for any length of time.
I do keep my headlights on AUTO, but I don't think this is the problem after researching forum posts. (If it is, it shouldn't be!)
The battery is still under the original warranty, so hopefully no problem when I take it back to the dealer and ask for a new battery free of charge. Now I know why the Carfax report had "battery charging system inspected" on it TWO TIMES. I thought it was just part of the usual "inspections" with an oil change, etc.