Re: battery bank dual charger or triple charger?
I agree that the ACR is a simpler but not better solution than the Echo Charger. It also isn't that much cheaper ($146 vs $96 with no account at my local store).
The ACR works by combining all batteries together when there is a charge, but keeping them isolated when there is not.
The Echo Charger is a DC-DC charger that charges the starter battery from the house batteries. It only charges from the house batteries when they have >13v (so normally only when they are themselves charging).
boats that I sail on regularly: Pearson 28-2, Rondar 505, Yankee 30, Blanchard Junior