On my rig, the negative cable was about 4 feet long, went through the floor of the RV and bolted to the frame.
The positive cable was about 12 or 15 feet long, and ran to an outside electrical compartment where it hooked to a 45 amp circuit breaker (that I also upgraded to 55 amp). Then the other side of the circuit breaker had a 6g wire (that I also upgraded to a 4g wire) about 18 inches long that ran to the battery disconnect relay. The other side of the battery disconnect relay had a 1/0 g wire running to the battery.
Pulling the wire is not difficult if you don't mind rolling around under the RV in grease and dirt.
