Since gopro battery offers you at most 3 hours of shooting in time lapse mode, you need to use external power supply to power up your cam. To do that you will need case with hole to connect mini usb cable, and external power suply.
I still wanted waterproof camera, because I want to shoot pictures outside and even if it is raining.
First I drilled hole in case with step drill so I can plug in micro usb cable.
For external power supply I used 12v 9ah motorcycle pb battery. That would provide power to gopro for at least one week.
Because micro usb voltage is 5v I used car usb charger. So I soldered car plug, usefull so you can disconnect it.
I sealed hole with patafix.
Here is how it looked at the and.
With 32 gb sd card, I can shoot pictures for more than 4 days, if I take picture every 60 seconds.