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Alternator putting out too much amperage

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rv7a(at)cox.net
Guest

Posted: Thu Aug 19, 2010 8:45 am Post subject: Alternator putting out too much amperage

This is a problem I am having that is starting to concern  me.  I have an RV7A with the standard Van's internally regulated  alternator.  My Dynon D-180 shows that when I am running it is producing  13.6 volts but the amps can be as high as 42 Amps.  I have turned off the  strobes and wig-wags and it will drop a few amps but continues at and  excessively high rate.  The battery is a new PC-680 with a full  charge.  My questions are this: Will the high amperage fry my radios and  EFIS even though it shows it is only putting out 13.6 volts. Two where do I  start looking for the problem?  This is very concerning to me.

  

 Jim Thorne

 RV7A CHD

    [quote][b]

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Neal.George(at)hurlburt.a
Guest

Posted: Thu Aug 19, 2010 9:11 am Post subject: Alternator putting out too much amperage

Jim - 



Have you confirmed with separate instruments of known quality/calibration

that your alternator is in fact making 42-amps at 13.6-vdc?



How do you measure the current?  Hall-effect transducer or current shunt?  



Are you confident that the measuring device (shunt or HET) is matched to the

display instrument?  A 60-amp, 50mv shunt will not interact correctly with a

meter that expects to be paired with a 40-amp, 50mv shunt.



neal

CherokeeJet N9586J 

RV-7 N8ZG



--

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nuckolls.bob(at)aeroelect
Guest

Posted: Thu Aug 19, 2010 12:41 pm Post subject: Alternator putting out too much amperage

At 12:11 PM 8/19/2010, you wrote:

 	  Quote: 	
		  Jim -



Have you confirmed with separate instruments of known quality/calibration

that your alternator is in fact making 42-amps at 13.6-vdc?



How do you measure the current?  Hall-effect transducer or current shunt?



Are you confident that the measuring device (shunt or HET) is matched to the

display instrument?  A 60-amp, 50mv shunt will not interact correctly with a

meter that expects to be paired with a 40-amp, 50mv shunt.



neal

CherokeeJet N9586J


	


    Good ideas Neal. This does sound like an

    instrument calibration/scale-factor problem.



   Bob . . .

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user9253

Joined: 28 Mar 2008
Posts: 1938
Location: Riley TWP Michigan

Posted: Fri Aug 20, 2010 3:48 pm Post subject: Re: Alternator putting out too much amperage

 	  Quote: 	
		  My questions are this: Will the high amperage fry my radios and EFIS even though it shows it is only putting out 13.6 volts. 	


No it will not.  Chances are that the ammeter is lying to you. Even if it is telling the truth and the alternator is putting out high amperage, that high current is only being delivered to equipment that asks for it.  Your electronics will only use the current that they were designed to use, regardless of the alternator current output (as long as there is not an over-voltage condition).  The exception is defective equipment that asks for more current than normal.  In that case, it is not the alternator's fault for delivering too much current.  It is the defective equipment's fault for asking for too much.  Even if some device fails and draws too much current, that will not cause other devices to use higher current.

  It is highly unlikely that there is actually 40amps of current being used by anything on your aircraft.  First of all, it would probably blow a fuse.  If there is no fuse, 40amps times 13.6volts = over 500 watts.  That is a lot of heat and it would be very noticeable.

  Like Bob and Neal suggested, most likely the current sensor is the wrong size or the ammeter is not calibrated correctly.  Good luck, Jim.

Joe

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