Congrats, it's a cool tool / toy... if you can get it setup to work with your setup well. Mine was a pain initially. Once I got my ballistics I didn't really need it any more.
I used a 22,000 maH battery, and after a couple of hours it was only down about 25%. So at that rate, it would deplete your 12K maH battery in 2-3 hours.
So I would carry a second 12K maH battery until you get yourself dialed in.