It seems it's just the two of us left standing [emoji846]
So here's my thinking...
You want a single house bank and two start banks, with all being charged when underway or when on shore power. When at anchor, all loads are on the house bank.
You haven't talked about your house needs. You probably don't know, but just a rough estimate. That dictates the size of your house bank, and possibly the charging architecture and battery type. If you're planning for overnight followed by a day's run you're not overly concerned with recharge time.
You've got good alternators but relatively crude regulation. You'd rather not spend $1,500+ on external regulators. The downside of relying on existing regulators is that a) the alternator is not heat protected, and if run at full capacity for long periods it will likely die a premature death, and b) the charging profile is sub optimal and somewhat arbitrary, so your battery choices are limited.
That argues for old school SLA start batteries, with each engine charging its own start battery. The alternators and AC charger will keep them happy. Simple and reliable.
How to charge house? Use a pair of 30a chargers, each drawing on a start battery. Configure them to only turn on when the source battery is being charged, either from alternator or shore power. They'll be independent but should play nice with each othe
This gives you completely independent regulation of your house bank, so you're free to choose your chemistry of choice.
The downside is that your recharge rate is capped at 60a, but that's probably NBD. That's offset by the maximum 30a additional load on the alternator, which prevents alternator overloading.
Upside is that you can use existing cabling to start batteries, and everything new is only carrying 30a, so easy and relatively cheap to do correctly.
A single 200ah AGM may be sufficient for a 'starter' house bank. Or two. Whatever. With a good quality charger your options are open and the batteries should be well cared for.
I'd also add a shunt to your house bank. I use the Victron Bluetooth unit, and at something like $125 it's a no brainer. The chargers will give you good voltage monitoring on the start batteries and house bank, so between them you'll have good insight into the system performance.
Maybe others can poke holes in this. I'm happy to have this critiqued.
Sent from my moto g play (2021) using
Trawler Forum mobile app