Alternator Output

[Thomv]

I decided to check my output voltages on both alternators by placing my ground wire on the negative post on my battery and the positive lead off of the orange wire post on my alternators. Both alternators output voltage was lower than each batteries reference voltage. Could I have two bad alternators or am I hooked up to the wrong post on my alternators?

 

[Bt Doctur]

Re: Alternator Output

Sounds correct but you should see around 14v at 1000 rpm.Reading the orange output should give you the battery voltage anyway
with the engine off. running is around 14v at the battery or the alt output.

 

[smassey22180]

Re: Alternator Output

I had mine tested by a local alternator shop. Cost $8 and the test lasted 30 minutes. Good piece of mind that it was good to go.

 

[Thomv]

Re: Alternator Output

I had mine tested by a local alternator shop. Cost $8 and the test lasted 30 minutes. Good piece of mind that it was good to go.

I believe Advance Auto will also test the unit so it like like I will be going that route. The only problem is that if they are indeed bad Advance will try and sell me a replacement which would not be marine grade if there even is such a thing. Because I have three batteries and a three bank automatic charger I have not had any issues with dead batteries when I do go out.

 

[Outsider]

Re: Alternator Output

The only problem is that if they are indeed bad Advance will try and sell me a replacement which would not be marine grade if there even is such a thing.

Just say 'no' ... :faint2:

 

[alldodge]

Re: Alternator Output

I decided to check my output voltages on both alternators by placing my ground wire on the negative post on my battery and the positive lead off of the orange wire post on my alternators. Both alternators output voltage was lower than each batteries reference voltage. Could I have two bad alternators or am I hooked up to the wrong post on my alternators?

What was the voltage reading you obtaned?

I believe Advance Auto will also test the unit so it like like I will be going that route. The only problem is that if they are indeed bad Advance will try and sell me a replacement which would not be marine grade if there even is such a thing. Because I have three batteries and a three bank automatic charger I have not had any issues with dead batteries when I do go out.

With a three bank charger I'm pretty sure you have an isolator in the circuit, right?

 

[smassey22180]

Re: Alternator Output

The auto parts test is short at a single RPM. Alternator shop test is at all RPMs. They also get it hot for a load test. Advance is not going to try to sell you one. Marine grade alternators are for preventing sparks/fires.

 

[Thomv]

Re: Alternator Output

What was the voltage reading you obtaned?

n was 9.4 volts while the other was 12.3 volts. Both were below the battery voltage on 13.5.

With a three bank charger I'm pretty sure you have an isolator in the circuit, right?

Not that I am aware of unless it was internal to the 3 bank battery charger.

 

[achris]

Re: Alternator Output

The only problem is that if they are indeed bad Advance will try and sell me a replacement which would not be marine grade if there even is such a thing.

There most certainly is!!! And it's all about spark and explosion suppression. It's all internal so an automotive and marine alternator can look the same.... DON'T BE FOOLED!!!

Not that I am aware of unless it was internal to the 3 bank battery charger.

Thomv. Did you give the engines a rev before checking the voltage output? Some of the older alternators needed a bit of a rev spike to get the excitation circuit working....

Chris.....

 

[alldodge]

Re: Alternator Output

Not that I am aware of unless it was internal to the 3 bank battery charger.

The 9.4 volts is off and as Chris mentioned a rev may be needed, The 12.3 to 13.5 is not off if an isolator is in use. An isolator is placing a diode in line to allow more then one battery to be changed by one source (Alternator). The diode allows current to flow in one direction but not the reverse. The voltage drop of a diode is 1.5 volts and meter tollerances can be the rest of the differences being seen. So the one showing 12.3 could be just fine, but the 9.4 needs more research.

 

[achris]

Re: Alternator Output

... The voltage drop of a diode is 1.5 volts ....

Voltage drop across a silicon rectifier diode (the ones commonly found in battery isolators) is 0.7 volts. Across a germanium signal diode is 0.3 volts.... (Introduction : Diodes And Rectifiers)

 

[alldodge]

Re: Alternator Output

Voltage drop across a silicon rectifier diode (the ones commonly found in battery isolators) is 0.7 volts. Across a germanium signal diode is 0.3 volts.... (Introduction : Diodes And Rectifiers)

Your right chris, have been an electronic tech half my carrier before switching to another field, and mixed up the battery cell with the rectifier. Old guy stuff strikes again :facepalm:

 

[achris]

Re: Alternator Output

Your right chris, have been an electronic tech half my carrier before switching to another field, and mixed up the battery cell with the rectifier. Old guy stuff strikes again :facepalm:

Easy done... As long as we all keep each other honest here, thngs will be great... I remember having to really be sure of my facts. Don was verbal dynamite on me when I slipped up (and rightly so...)

Cheers....