High capacity alternators
I have a very similar battery bank to you. Also 880ah. Realize you don''t use your engine a lot however the 80 amp alternator is very small for that bank. For comparison I have a 270 amp alternator [dual belt] that is externally regulated Link 2000R and electronically limited to 220 amps when living aboard or 150 amps when in weekend cruising mode. You need to be able to throw enough amps into that large of a bankto properly charge. Don''t remember the exact recommended ratio but something on the order of 25% of capacity.