Hope this helps, per the instructions that come with the HD Sport II, 3 hours is the minimum charge time. Peter Stoddard, as far as the buttons being usable with the housing open, they are still operable, though you do need to memorize what each button is for. The far left 2 buttons are the up and down buttons to navigate through settings and play back videos. These will further be used to scroll down to the charge option, then push the center button (the OK button) to select. As mentioned above, while the camera is in MSDC mode or other option the camera will charge, however will take longer because you are using battery power at the same rate you are charging, essentially just like leaving a laptop plugged up while using the computer, or even leaving a cell phone plugged up while talking on it. Hope this helps answer some of the questions.