I would assume that there is some kind of way to be able to provide power to camera via 1 battery at a time (since I currently have 3 I figured this would be plenty of power). I'm not to sure where or what exactly I need though to be able to do this, anyone out there can help me with this?
You would need an adaptor to work with the BMCC. Hawks Wood make adaptors for many batteries.
The external battery charges the internal battery. When the external battery dies you'll know that it has as the camera no longer shows a charging icon. You then swap the external battery while the camera is still powered by the internal battery.