Alternator output

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N804RV

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Jun 9, 2013
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Mount Vernon, WA
I have a Kohler style 20amp alternator with an external rectifier/regulator in the Sonerai. I installed an alt. warning light/circuit and removed the analog volt meter to make room for a G-meter.

The old analog volt meter showed about 14.5vdc inflight. But, the alt. warning light indicates an occasional over voltage condition.

I put a digital volt meter across the battery terminals and went flying. It shows 15.3 - 15.4vdc when the over volts condition is indicated. Apparently, the alt warning circuit's over-volt threshold is set to 15.2 volts.

My question: How high is too high? I've heard that automotive type charging circuits can see as high as 16vdc.
 

Daleandee

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Sep 11, 2015
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SC
How high is too high? I've heard that automotive type charging circuits can see as high as 16vdc.
My Cleanex uses a Yanmar 20 amp dynamo (PM alternator) with an external regulator. My charging voltage usually reads 14.7-14.8 after take-off. This works well with my Odyssey PC 680 battery as they recommend charging at 14.4-14.7 or float charging 8-10 hours at at 13.6. Most automotive alternators that I've checked lately will charge between 13.8-14.2.

Not sure what battery you are using as that will have a great deal to do with the charging rate. I can't answer your question for you but for me, yes, 16.0 is much too high. 14.8 is the limit I like but that is what works best in the system I have. If you have one of the newer technology batteries ... everything above is incorrect.
 

Dan Thomas

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Sep 17, 2008
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5,298
Check the grounding of the regulator/rectifier unit. A poor ground gives the regulator a lower voltage reference and it will increase the output to compensate.

Otherwise, the unit might be shot.
 

N804RV

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Joined
Jun 9, 2013
Messages
211
Location
Mount Vernon, WA
Check the grounding of the regulator/rectifier unit. A poor ground gives the regulator a lower voltage reference and it will increase the output to compensate.

Otherwise, the unit might be shot.
Good call Dan! Put a new rectifier/regulator on it today. Took all of 10 minutes. Verified the case-ground was adequate. 1.8 hours flight time today with no over-volts warning. Little digital meter showed pretty steady 14.4vdc.
 
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