For a Hero3 Silver, the practical options are external power via USB: plug the camera into wall power, a powered USB source, or a USB battery pack. That’s the simplest way to get past the internal battery’s short runtime.

Be cautious with portable power banks, though. Some packs may stop supplying power once the camera’s internal battery is topped up, which can cause the camera to shut off during a long unattended timelapse. So test any battery pack before relying on it.

A timelapse controller that powers the camera down between shots can greatly extend battery life, but according to the community answers, the Cam-Do controller is not compatible with the Hero3 Silver (it works with other Hero models, but not this one).

So for your specific camera, the best answer is external USB power from a reliable continuous source, with a full test run beforehand to confirm it won’t switch off mid-shoot.