Relocating the battery charger help

You just need to make your new deck mount converter, your portable charger using battery clamps on the output #4 wires (cut off jumper cable or whatever) No installation. Clamp on, turn on gen, plug in charger. If your trailer is plugged into the gen already so now its installed converter is on, you can leave it like that. It might even add some amps before its voltage (14.x) as seen at the battery becomes lower than the portable charger's voltage ( 14.8)

I use my PowerMax adjustable voltage one that way.