I think the control box need the radio signal to "control" the gear, but the draw of the motors is off the other battery.
If I remember correct there is a jumper or different plug when you use the separate battery.
Mine all on the radio batteries, but I have 7000mah there.
Also, you might want to extend your fueling line so you have a foot or so rolled up in there. I often spill a little when refueling and you sure don't want it in that bare wood interior.
Les