[Mike244]

Steve,

I'm using the API 120 alternator on my my A-4 charging (4) 130 Ah Trojan lead acid batteries as a single bank. I have changed the pullies to 1/2" to keep the belt from slinging dressing all over the place. I'm also running an Indigo Electronics 3 blade prop. I can cruise at at 1900 -2000 rpm with 2450 rpm at WOT. At 2000 rpm the API 120 amp alternator is ONLY putting out around 60 amps. It's also costing me almost 2 hp of the 20 hp an A4 makes at that rpm.

When at the dock I have a true charge 40 on 24/7. I keep the frige on all the time so the charger keeps the batteries topped of and the beer cold as well.


I plan to ditch the API unit in favor of a Balmar 70 or 90 amp unit with an external regulator.With luck I'll find an alternator that will produce the juice at a lower rpm than the API. I am also going to downsize my house bank to (3) 110 ah AGMs.

If you still have the typical too large prop on your A4 your max rpm is around what, 1400-1500 rpm? At that rpm your 120 amp alternator will only produce around 30 -40 amps.

you can't go wrong with Don Moyer at moyermarine for all your A4 needs.

Mike