Alternator and Battery Compatibility

[Steve Mason]

Hey Boaters,
Working on a new battery bank install and all that goes along with that.

Installing a 500amp hour AGM house bank with a separate 100amp hour start battery. Just added a new Balmar 621 100amp with regulator to charge the house bank and the start bank through an ACR.

As I dig into the output profiles of the Balmar realistically I’m only going to get 50-70 amps out to my banks once you factor in the regulator adjusting for heat etc.

My question is will this alternator even be able to fully charge these two banks, from say 50-100%.. when you look at a recommended 20-25% alternator to battery ratio? Granted I could run the engine/alternator extended periods of time, but I’m cruising and that’s not always an option nor is weekly shore power to bring me back to 100%.

I’m considering dropping the house bank to 400 amp hours which I could do bringing me closer to the 20-25% rule.

Full time cruiser. Engine limitation is keeping me at 100amp alternator. Have 400 watts solar and no genset.

Thanks

[smac999]

Changing the bank size doesn’t change anything for your charging needs.

The ah you draw each day is the same. And the ah that needs to go back in is the same. No matter the bank size.

The rate % is for best long term care of the batteries. Which is a different issue.

With the 100a alt and 400w solar you should be able to get full. Run the engine first thing in morning to bulk. You might only need 30-60 mins a day. Depends on sun and how much power you use.

You will never get the batteries full with the alt. Unless you run 5-8 hours. The engine will get you to 80 in the morning and The solar will get you to 100