Mine just arrived and I have plugged it up but have not turned it on. The light on the power connector is blue. Does it change color when it is fully charged / charging? The instructions ( such as they are ) just say to plug it in and turn it on. No mention of charging the battery first. Should I charge it first? How long does it take? I downloaded the user guide, but it really doesn't tell you much about getting started as far as battery operation goes.