Good question - I'd like to know too, as I plan a couple imaging excursions soon.
The powerpack I bought will typically run the mount alone for 8 hours on a full charge. It has 2 USB power sockets on the back also. I am sure connecting the laptop would decimate the stored charge quickly though
I have a 10 metre long cigarette lighter cable that could power the mount at least from the car battery, but then to figure out a safe way to do the laptop.