Even 100A @28V is a LOT of power. 2.8KW. The issue with the 100A dual volts is that the load on the 12v side reduces its output by 1/3, to ~1950W when both sides are fully loaded. If S&S would have put in a straight 24v alt and a converter/equalizer, these trucks would have been bulletproof electrically until they fielded AGM batteries. At straight 28V a 4 battery 240AH wet cell bank is only looking for 60A out of the alt. I would be surprised if the truck 28V load is over 10A and the 12v loads converted to 24V are under 15A@28v max, so 85% alt load worst case hell a 140A alt would support four 6T AGMs reasonably well at ~95% load worst case/dead battery…
Worst case my group 31’s want 25A(AGMs 45A), but if they are charged, being smaller, they should peak fairly quickly after a start, so should stay at a higher state of charge even if only driven low hours. With my 100A alt, and charged batts, I am left with the 25A@28V of peak truck load when everything is turned on. That means I have 50+A@28V(1400W) available to throw at house battery charging and still only be at 75% alt load… If I covered my habitat roof with solar, i might could get 1500W peak…
Going over 150A@28V is crazy talk IMHO. Unless you are doing something really off the wall, The truck simply does not need it...