Ok, you say the battery is fully charged (12.5volts) I take it you check this with a multimeter. Now just because you are showing 12.5 volts with a multimeter doesn't mean your battery isn't bad. And what is most likely the problem with the battery is the CCA (Cold Cranking Amps) for which you cannot check with a multimeter.
While cleaning cables did you clean the ground or negative connection on the engine block.
I suggest you remove the battery and take to your local auto parts store and have them check it.
Also I would recommend removing the batter or disconnecting it when you are storing it. Or start the vehicle once or twice a month and let it run for 15 - 30 min.
Monday, September 22nd, 2008 AT 3:36 PM