18 amp gen/alternator produces only 3amps

[Ex-Calif]

Originally Posted by smac999

the acr probably comes on and off every 30 secs. there is no way a 10a alt is going to maintain charging voltage on a discharged house bank. even 60-80a ones have issues with a large discharged bank. though I'm guessing your's isn't too big. seriously you need to get rid of the 10a gen. this is not a solution. it's only job is to keep your engine running. charging the start battery.

Why would the ACR do that?

[cal40john]

Originally Posted by Ex-Calif

Why would the ACR do that?

Deeply discharged house bank pulls more current than the generator can produce, voltage falls, ACR opens connection, start battery voltage increases, ACR closes, repeat cycle.

SI-ACR Automatic Charging Relay - 12/24V DC 120A - Blue Sea Systems

Has a 10 sec delay at 12.36 and 30 sec delay to open at 12.75 volts

[Ex-Calif]

However he didn't describe those symptoms - that would result in cycling voltage on the house side.

He's also stated that when the batteries are paralleled using the switches both sides are seeing the voltage.

I agree the 10amp generator is undersized. He has stated he can't change it out because apparently it is geared to another pump.

[cal40john]

Put on another pulley and add an alternator.

[Ex-Calif]

Originally Posted by cal40john

Put on another pulley and add an alternator.

Sure - That is an obvious solution that will clearly run a few boat bucks.

I think OP is trying to get maximum use of the 10 amps he has, as meager as it may be.

And to the OP - The one thing that has been nagging me is the bench test claiming 18 amps output. I presume this was with a bench regulator. Your external (mechanical I presume) regulator will not likely ever let the generator produce 18 amps.

As calJohn says this is a really pitiful charging source for any modern battery. It was surely designed to only top up a start battery and maybe run the blinkers, headlights and an AM radio (poorly I might add) circa 1965.

To use this as a charging system for a multi-battery house bank is really futile and you could really end up crapping your batteries out.

[Ketchgould]

The generator rebuilders mentioned old generators like the one I have are capable of outputting more than they are rated at. The regulator was the real device that controls output. He said he "turned it up" and we should see amps closer to 18.

Also, after I completely rebuilt the boat for four years; our power demands are very light. All cabin lights draw 1.7 amps per hour. Anchor light is .2. Gps is .6. No frige, 8" handbuilt icebox. Manual head, whale foot valves, whale manual bilge before the electric bilge pump too. The most we draw is with blower on at about 6 amps. 180 amp reserve battery; 20 amp ac 3 bank Charles charger at dock where we only leave to anchor out for five nights at a time between ac charges.


Christian Gould
St. Paul, MN
S/V Sea Dog
Apostle Islands Lake Superior