Five pages of posts and no one has mentioned this yet. You also could/should consider a larger alternator. Mechman makes SIX phase alternators (normal is three phase) and the six phase has twelve diodes. They have units up to about 370 amps (which would require an increase in the size of the alternator output to vehicle battery cable)
My RAM 2500 has a lowly 160 amp alternator and I am considering installing larger cables, Anderson connector, and DC-DC charger and more/larger batteries, next year. Part of the upgrade will be a Mechman Alternator.
https://www.mechman.com/The DC=DC chargers, powered by 4 or 6 gauge cables from the vehicles batteries and connected to the trailer by Anderson connectors is becoming common and was pioneered by the Australians for their touring and offroad vehicles. It is a system that works well and eliminates the problems of the usually small power wire to the 7 pin (many vehicles cannot squeeze 10 good amps thru). I think the truck manufacturers installed the power to the 7 pin to charge the small SLA batteries used as emergency braking power on flat bed and cargo trailers and didn't expect to be charging huge banks of batteries in RV's
Charles
