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Old 20-08-2014, 07:46   #1
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18 amp gen/alternator produces only 3amps

I have completely rewired and installed all new devices on my 1961 Graymarine 4 cylinder engine. The generator is original and I had it rebuilt last winter too. The shop that rebuilt (and they are a fourth generation shop) said it looked like it was brand new inside and they haven't seen that quality of build in a while. He said the voltage regulator controls the output in a way and he said the 10amp generator he bench tested and had it producing closer to 18 amps. The generator direct drives my water pump so getting a new alternator is not so simple.

I an only getting 3 Amps max produced by the generator. If I turn on my 6 amp blower fan, I have a net loss of amps as read on my new blue seas vsm422 monitor. New blue seas automatic charge relay. New battery switch. New panels. New wires.

While charging my start battery is at 14.4 volts (charging) but the house remains at 11.9 or where it was before charging. The BAT wire from generator goes to my starting circuit at solenoid.

Thanks for any help. Would love to see about 10 amps coming out of that old generator.


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Old 20-08-2014, 07:58   #2
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Re: 18 amp gen/alternator produces only 3amps

I was going to say the problem was likely engine rpm. The reason car manufacturers went from generators to alternators was generators have to be spinning fast before they put out much current.

But, you say the start battery is at 14.4 volts and the house isn't. This can't happen unless something is wired wrong or your wires are very undersized. If the combiner is on the two batteries are wired in parallel, and every point on those wires are at the same voltage. Reasons that they wouldn't be are either small enough wires that the resistance in the wires is high enough to cause a voltage drop, or the two batteries aren't really connected like you think they are.

Post a diagram.
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Old 20-08-2014, 08:11   #3
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Re: 18 amp gen/alternator produces only 3amps

Thanks for the help. I will post a diagram but it will be in ten days after I can get back to boat.

Wires are 8awg and are less than 18 inches long except for 3 foot wire from solenoid.


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Old 20-08-2014, 08:16   #4
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Re: 18 amp gen/alternator produces only 3amps

Hi Christian,

Could be a number of things going on here. If your battery monitor is new is it possible that it isn't wired in correctly? It is very possible to wire it so amps going out are shown correctly but amps going back in are not. Check where all the grounds are connected to the shunt.

Is that the only way you are confirming the output of the generator? If you have access to a clamp on ammeter that will confirm what the generator is truly putting out.

Agree with Cal40John that there must be some kind of problem if you are not seeing charging voltage to your house batteries. Either wiring or the ACR is not working correctly.
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Old 22-08-2014, 18:37   #5
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Re: 18 amp gen/alternator produces only 3amps

if this is an ac generator (you keep using term for different things) . it should have it's own battery and only charge it's own battery. trying to charge a house battery sharing a 10a alt is just silly. the generator should be powering an ac charger which charges the house bank.

if this is your main engine. then you should look into adding another alt for the house bank. and leave the 10a one on the start bank since you say it's not changeable. you are wasting so much time and fuel if you are trying to charge a house bank from a 10a alt. the engine alone probably needs most of that already.


also generally you don't have a shunt on an engine battery. so you wouldn't be seeing amps on the start battery anyway. I certainly wouldn't be using battery gauges to determin alt output. because they show a net on one battery. you need a clamp meter on the alt wire.
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Old 22-08-2014, 19:20   #6
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Re: 18 amp gen/alternator produces only 3amps

Quote:
Originally Posted by Ketchgould View Post
I have completely rewired and installed all new devices on my 1961 Graymarine 4 cylinder engine. The generator is original and I had it rebuilt last winter too. The shop that rebuilt (and they are a fourth generation shop) said it looked like it was brand new inside and they haven't seen that quality of build in a while. He said the voltage regulator controls the output in a way and he said the 10amp generator he bench tested and had it producing closer to 18 amps. The generator direct drives my water pump so getting a new alternator is not so simple.

I an only getting 3 Amps max produced by the generator. If I turn on my 6 amp blower fan, I have a net loss of amps as read on my new blue seas vsm422 monitor. New blue seas automatic charge relay. New battery switch. New panels. New wires.

While charging my start battery is at 14.4 volts (charging) but the house remains at 11.9 or where it was before charging. The BAT wire from generator goes to my starting circuit at solenoid.

Thanks for any help. Would love to see about 10 amps coming out of that old generator.


Christian Gould
St. Paul, MN
S/V Sea Dog
Apostle Islands Lake Superior
If you are getting 14.4 volts on the start side then the generator is producing. Considering that the Bat wire goes to the starter. If connected to the solenoid as you state I think this is in error. The generator supply would be better served being on the battery primary wire. The solenoid wires may not be large enough to carry the load.

If the house side remains at 11.9 then the Blue Seas ACR is not paralleling.

If you have a 1-2-both switch what happens when you switch to "both" - If you have separate on-off switches for the 2 banks what happens when both are "on" - this essentially makes the ACR moot as you are manually paralleling the banks..

The amps are more confusing. You don't say how the monitor is hooked up.

If the shunt is installed properly you should be reading the amps on one bank only. You also don't say which bank is supplying the load to the blower. And you don't state if you have any other charge source (i.e. solar)

To simplify you should consider applying all charge sources including the generator to the house side. This means the BAT wire and the regulator sense wire should be upstream of the switch on the house side.

The only downside of this is that there is potential on the sense wire and the Batt wire at all times and these should be fused at the battery end to protect the wires in case of a short.

Then leave the ACR to take care of the start battery.
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Old 22-08-2014, 22:20   #7
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Re: 18 amp gen/alternator produces only 3amps

Perhaps I missed it, but where does he say there is a combiner (ACR)? He mentions a monitor... does that imply a combiner? If indeed there is no combiner, it sounds like a simple case of the output of the generator going only to the start battery via the connection at the solenoid.

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Old 22-08-2014, 22:37   #8
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Re: 18 amp gen/alternator produces only 3amps

Quote:
Originally Posted by Ketchgould View Post
I an only getting 3 Amps max produced by the generator. If I turn on my 6 amp blower fan, I have a net loss of amps as read on my new blue seas vsm422 monitor. New blue seas automatic charge relay. New battery switch. New panels. New wires.

While charging my start battery is at 14.4 volts (charging) but the house remains at 11.9 or where it was before charging. The BAT wire from generator goes to my starting circuit at solenoid.

Quote:
Originally Posted by Jim Cate View Post
Perhaps I missed it, but where does he say there is a combiner (ACR)? He mentions a monitor... does that imply a combiner? If indeed there is no combiner, it sounds like a simple case of the output of the generator going only to the start battery via the connection at the solenoid.

Jim
Hard to troubleshoot without a wiring diagram...

The 3 amps is a red herring at this point because it appears the generator is only charging the start batt which is probably near full so the regulator is dialed down.

Need to get the house or both banks on line to see what the generator is capable of.
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Old 23-08-2014, 00:44   #9
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Re: 18 amp gen/alternator produces only 3amps

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Originally Posted by Ex-Calif View Post
Hard to troubleshoot without a wiring diagram...

The 3 amps is a red herring at this point because it appears the generator is only charging the start batt which is probably near full so the regulator is dialed down.

Need to get the house or both banks on line to see what the generator is capable of.
Well, dang! I did miss it!

Sorry 'bout that.

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Old 23-08-2014, 07:53   #10
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Re: 18 amp gen/alternator produces only 3amps

I do have an ACR. If I switch the battery selector to combine then both batteries read charging voltages.

I thought about wiring the dc generator to the house and having the ACR do it's job from there. However, the start battery will be isolated until the house gets to a healthy 12.7 level I believe.

I guess I would have to monitor my start battery and if it gets down to 12.4 or somewhere critical (not sure where that would be) I could manually charge both on combine.

Sound like the best solution?


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Old 23-08-2014, 08:08   #11
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Re: 18 amp gen/alternator produces only 3amps

The combiner will kick in as soon as the charge voltage reaches 13.6 volts. I may be wrong on the exact voltage set point. The reasoning behind going from DC Generator to the house bank, then to the start battery is that the start battery will need very little input to top it up. Usually the start battery will use a small amount of capacity to start the engine. You are running a very, very small generator so it will do well if it supplies enough current to charge the house. Good luck. It sounds like maybe your ACR is wired backwards for the way you are running the output to the start battery. That should work if you run the output of the gen. to the house battery.
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Old 23-08-2014, 08:47   #12
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Re: 18 amp gen/alternator produces only 3amps

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The combiner will kick in as soon as the charge voltage reaches 13.6 volts. I may be wrong on the exact voltage set point. The reasoning behind going from DC Generator to the house bank, then to the start battery is that the start battery will need very little input to top it up. Usually the start battery will use a small amount of capacity to start the engine. You are running a very, very small generator so it will do well if it supplies enough current to charge the house. Good luck. It sounds like maybe your ACR is wired backwards for the way you are running the output to the start battery. That should work if you run the output of the gen. to the house battery.
The Blue Seas combiner I looked at stated it checked voltage on both sides, so it shouldn't matter how you hook it up. OP should measure voltage on both sides, and read the manual to see if his requires it to be hooked up one way or the other.
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Old 23-08-2014, 09:01   #13
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Re: 18 amp gen/alternator produces only 3amps

Ah, something new to me. Thanks.
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Old 23-08-2014, 10:13   #14
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Re: 18 amp gen/alternator produces only 3amps

Quote:
Originally Posted by Ketchgould View Post
I do have an ACR. If I switch the battery selector to combine then both batteries read charging voltages.

I thought about wiring the dc generator to the house and having the ACR do it's job from there. However, the start battery will be isolated until the house gets to a healthy 12.7 level I believe.

I guess I would have to monitor my start battery and if it gets down to 12.4 or somewhere critical (not sure where that would be) I could manually charge both on combine.

Sound like the best solution?


Christian Gould
St. Paul, MN
S/V Sea Dog
Apostle Islands Lake Superior
If both batteries are seeing charge voltage when the batteries are on both (combine) then the ACR is failed or the ACR is wired wrong.

It is a pretty simple piece of kit and if new as you state than if not wired wrong Blue Seas should replace it.

BTW - The batteries combine when the "bus" voltage is above 13.6 on either side. Technically it's not waiting for the battery voltage to come up. If the generator is putting out 14.4 that's good enough for the ACR.

Quote:
Originally Posted by cal40john View Post
The Blue Seas combiner I looked at stated it checked voltage on both sides, so it shouldn't matter how you hook it up. OP should measure voltage on both sides, and read the manual to see if his requires it to be hooked up one way or the other.
Correct, The Blue Seas ACR senses both sides -
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Old 23-08-2014, 13:15   #15
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Re: 18 amp gen/alternator produces only 3amps

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.
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