Excerpt: The OEM battery may cost more. Some things you can use aftermarket batteries for since they do not draw nearly as much power. The GoPro goes through a lot when you use the camera. It gets banged around and it has a lot of function.
Excerpt: This little things is awesome! On a Hero4 you have great access to your settings and can frame your shot. I use it on my Hero4 & 3+ mounted to a Feiyu G4, make flying shots easy to frame. Does eat battery, so have some spare bats handy!
Excerpt: Works good. The camera is capable of charging both the internal battery and the BacPac! The only downside is that the camera uses the BacPac first by default - I would prefer it the other way, or even better would be a software update which would allow the order of use to be selected.