The button they are talking about is not for the battery. You are correct that it is the button on the side of the DVR. What it is used for is that once you set everything to how you want it - Video, Audio, Date Stamp, loop recording, etc. You then push that button and it will ensure that if the screen is touched say while it is in you pants pocket, that the screen will not accidentally change the settings. It also should show a little picture of a lock on the screen.