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  #1  
Old 01-31-2022, 06:46 PM
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Champ Champ is offline
 
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Location: Kingsville, Ontario, Canada
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Default High Voltage

I have a Plane Power AL 12-EI60/V alternator and a 4 year old rear mounted PC680 battery with 200 hrs on it.
Static charge on the battery is 12.8v on its terminals and 12.4v on the buss - both on my Dynon EMS D10 and a multimeter.

In flight buss voltage has gone from 14.3v to 14.8v avg with a saw tooth pattern varying between 14.4v & 15v and a couple spikes to 15.1v. All with constant load. Buss amperage varies as well between -6.6a & +10.5a.

Note: volt/rpm/amp data graph. Dip at 18 min was when I briefly took the alternator off line - here voltage dropped to 11.5v & amperage to -25a.

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Amperage variation is very strange with load being constant. Terminals on the shunt are tight.
Should I be saving up for a new alternator or battery or both or is there something else going on?
I've got a ticket in a Savvy looking for their input as well.
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  #2  
Old 01-31-2022, 09:15 PM
Mich48041 Mich48041 is offline
 
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Location: Riley TWP MI
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Default

As long as system voltage is above 13 volts, then the battery is out of the picture and is not a problem.
I question the accuracy of the ammeter, specifically the zero reference line. Aircraft electrical loads will ALWAYS draw current from the source with the highest voltage. Since the voltage is above 14 volts for the most part, then it is impossible for the current to be negative. Loads will NOT draw current from the battery when 14+ volts are available from the alternator.
Can you post a drawing of the electrical system showing the battery and contactor and shunt and alternator B lead connection and diode and bus?
See my post #9 below.
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Last edited by Mich48041 : 02-03-2022 at 10:54 AM. Reason: Admitted being wrong
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  #3  
Old 01-31-2022, 09:16 PM
PilotjohnS PilotjohnS is offline
 
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Default My experience

In my experience this has been caused by corroded connections. I have t figured out why it happens this way but it did.
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  #4  
Old 02-01-2022, 06:58 AM
pat76cj pat76cj is offline
 
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Location: Western edge, Iowa
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Default

agree on connections. Check connections between battery, alternator, and buss for tightness and corrosion. Corrosion might cause reg/rec to think the battery needs more juice, hence the spike.
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  #5  
Old 02-01-2022, 07:37 AM
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Quote:
Originally Posted by PilotjohnS View Post
In my experience this has been caused by corroded connections.
...or the terminals in the field plug, a known issue.

https://vansairforce.net/community/s...d.php?t=125262
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  #6  
Old 02-01-2022, 09:25 AM
3bythelake 3bythelake is offline
 
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Location: Lakeport, CA
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Default Master

I had a Cessna style master switch intermittently cause voltage in the mid to high 15v range. Replaced with new and voltage returned to normal mid 14 volts.
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  #7  
Old 02-01-2022, 09:44 PM
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vlittle vlittle is offline
 
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Quote:
Originally Posted by 3bythelake View Post
I had a Cessna style master switch intermittently cause voltage in the mid to high 15v range. Replaced with new and voltage returned to normal mid 14 volts.
A bad alternator field switch or terminals is #1 on the list. On my 9A, I ended up using a relay controlled by my Alt switch to directly connect the Field to the B lead with short wires. External OVP turn the relay off by tripping the field breaker.

Question… are you hearing whining in the headset? This is also a symptom of a poorly regulated alternator or a failing alternator.

VV
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  #8  
Old 02-02-2022, 07:23 AM
lr172 lr172 is offline
 
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Quote:
Originally Posted by Champ View Post
Static charge on the battery is 12.8v on its terminals and 12.4v on the buss .
That points to your problem. Somewhere between the battery and the buss, you have excess resistance that is producing the voltage drop. Likely a bad connection or corrosion and likely varies with vibration. This can cause numerous issues, including problems with conssistent voltage from the VR. Get your VOM out and start looking for the problem.

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  #9  
Old 02-03-2022, 10:53 AM
Mich48041 Mich48041 is offline
 
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I hate to admit it, but I was wrong in my post #2 above. I failed to realize that the battery voltage is at 14 volts for a short period of time after the alternator quits working. Before the battery voltage drops very much, the alternator starts working again when the loose connection remakes contact. The majority of electrical problems are caused by bad connections.
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  #10  
Old 02-03-2022, 12:50 PM
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Quote:
Originally Posted by Champ
Static charge on the battery is 12.8v on its terminals and 12.4v on the buss.
Quote:
Originally Posted by lr172 View Post
That points to your problem. Somewhere between the battery and the buss, you have excess resistance that is producing the voltage drop...
Fair point, but these days, when someone mentions bus voltage, they are typically reading it from an EFIS/EIS, which often has internal diodes in dual 12V+ inputs.
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