3 + wires one broken

Hi I was working on my 96 6×6 Big Boss 500 today and noticed that there is 2 wires going to the + terminal of the battery. There is also a 3rd one that is broken off, seems to been like that for quite a while by the looks. It goes into the wiring harness just behind the battery. I think it might be to the auxiliary power, wherever that is ?
If not can someone lead me in the right direction?
thanks KK4