The ContourHD Spare Lithium-ion Battery gives you the freedom to extend
your recording time by having double the battery life. Take one or more
spares with you and enjoy loads the battery life.
To charge the batteries insert them (one at a time) into the camera and
connect the camera to your computer using the USB cable (which comes
with your camera). It will take an average of 3hrs to fully charge one
battery and, once fully charged, the battery should last up to 2hrs (in
SD setting).