I was going to power a relay from battery, but need a control signal source from ignition.
Idea being pull from the fuse box, run the power to signal the 10amp mini relay and also power some led illuminated switches, which will themselves just be controlling relays, so pretty low load hopefully, but it may end up being a lot of switches (i added a lot of empty switch locations, but don't really have a plan for them yet, I removed the sandwich tray and the ash tray, replacing both with switch panels. It looks a lot like the trailtrailor/cruiserhead cnc aluminum replacement with all the switches, but low-buck. Used Carling switches an over counter bezels.
I actually have a 10 mini relay installed behind the switch panel for powering the usb, & switches, but I had it connected to the cig lighter for signal, which was always on.
I moved it to radio fuse, but apparently, that's always on too.
I just wondered which switched circuit in the fuse box had the most "head room" instead of just picking one arbitrarily.
My goal is to have everything I add to the dash either powered from that 10a relay, or just controlling a relay in the engine compartment.
Right now it's a light bar, a usb port with voltage, etc
Eventually i want to ad a winch control switch, with a switch to power that switch, but again, relays to the winch.