I have a Hero Black 3 and use it quite a bit for cycling. I use the battery backpack for power, it will use the backpack first then the camera battery. So when I see the power is drained from the backpack I put a new one on.

I have also used a USB cable from a cigarette lighter and plugged it into the backpack to use the camera all day streaming video to an iPad and then using an HDMI adapter to watch it on a TV for a work demonstration. Worked great. You need the housing with the gap and not the full housing obviously.