My green light goes off or possibly very dim ( can't see green in day light ) usually when the computer is off. The icon on top of screen shows it plugged in a fully charged when I turn it on. The unit seems to be charging fine. If I unplug the power adaptor from the computer then plug it in immediately the green light will come on and usually stays on the entire time I am using it. I have searched the discussions and have not found a black and white solution. It is a Mac Book pro purchased in Nov 2007.