Charging Amps engine alternator vs Generator

My inverter/charger routinely hits 150 amps when boondocking off the onan. The initial charge last several minutes, then when the bank hits 14.4 (temp compensated) the amps start to taper. Between 20 and 30 amps I usually shut down. That gives time for the hair drier (for those that still need one), and whatever else is needed to finish breakfast. The first few cups of coffee (keurig) are off the inverter as well as the TV's and the dozen or so chargers for things that kids and teenagers can't be without.
FWIW I have 2 10' lengths + & - of 4/0 between the inverter/charger and the battery bank. With 4/0 interconnects between the 3 batteries, and a 4/0 ground to the frame.