Originally Posted by Raspy
This is a very good plan. A common way to do it is with a Ford type, continuous duty relay, but I'm sure there are other good ones too.
We installed an isolator in our van a full size Chevy. The isolator was just a little silver canister about 3 inches tall and 1 1/2 to 2 inches across. It isolated the vehicle battery
from the trailer battery
so that they both charged but the vehicle battery
couldn't be drained. We used a 30 amp fuse on it per the instructions that came with it. Very simple installation with the charge wire running to a 7 pin connector. The hot wire ran from a hot spot under the hood that was only hot when the engine ran. Full price was probably under $40 for isolator, fuse and wiring. We wired the entire 7 pin connector for charging, brakes
and all lights
. We used the color wires per the instructions. We put the brake controller in also. Really good instructions come with these things.