by noseoil » Mon Jun 20, 2016 7:37 am
Max, I have the "heavy" setup, but don't have brakes or a 12 volt charge-while-towing setup. My decision was made prior to the complete electrical system, but there's nothing wrong with extra capacity when you need it. Our electric needs come from a 100 watt solar panel & group 27 size battery. I was going to do the charge while towing system, but I found that an AGM battery doesn't like the high voltage from a car alternator, combined with high heat (Tucson), so the solar system works very well for our needs. A regular flooded lead-acid car battery will take the heat & high voltage without a problem.
If you don't have brakes on the trailer & don't plan on charging, the light duty (4 pin) harness works fine. If you think there might be an upgrade in the future, by all means, use the 7 pin harness.