I use my gopro to take a lot of outdoor stop motion, and long term projects.
The only problem is that the batteries are not meant to last longer than an hour or two.
You can use their "frame" mount so that you can keep the camera plugged in, but that takes away any water resistance that the camera has, leaving it open to moisture.
at one point i was using the skeleton back and covering it with a plastic bag.
I was looking for a way to power the camera while keeping it in the water tight enclosure.
I started with the battery backpack, and a 6 ft USB cable.
I took the USB cable and removed the female end, I stripped 4 inches of the jacket, and removed the green and white data wires leaving only the red and back.
I took apart the battery backpack, hooked it to a usb charger, and measured the voltage from the charger. i found the 5V on the anode of the larger diode next the USB, and ground on the structural mounts.
I removed the USB Connector from the battery with a soldering iron to make an opening for the wire.
then i removed the waterproof button that is normally used to check the battery level
after feeding the wire through the hole left by the button, i ran the wire through the case and then the old USB cutout.
I soldered the red wire to the non banded end of the large diode, and the black to the mounting points for the USB jack.
after the wiring was done, i re assembled the battery backpack. then i used RTV silicone to seal the wire into the hole from the button. I wouldn't quite trust my silicone work to go 6ft under water with such an expensive camera, but its definitely good enough to keep rain out while you are filming outdoors for hours days or weeks.
the only thing left to do is run the wire so it will fit around the camera while closed