Solar wiring question

[Blazing zipp]

I've seen several videos where the wiring from the solar charge controller is ran to the trailer wiring between the trailer charge controller to the batteries. Hope I'm making sense. In fact, we bought a used trailer that the solar used to be connected in this manner.
The wiring from the charge controller seems to be pretty hefty, but I can't recall the gauge.
On our rig, the solar cables could run down the bath sink vent, to the solar controller, and through the cabinet to the trailer charge controller.
Comments????

[Vintage465]

Comes down to this in my opinion. Mount the controller as close to the batteries as possible/logical. Use BIG wires between the batteries and the controller. I use #2. From the controller to the combiner box/panel array take the shortest route and again BIG wire. I used #4. I’m not a fan of finding an existing penetrations like vents unless it’s the shortest route. A nice mppt controller is great but because of my arrangement with big wire and location of the controller I’m never below 85% state of charge with a real nice 30 amp PWM controller

[BeatCJ]

I agree, everything comes down to that.