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  #1  
Old 04-25-2016, 07:51 AM
jtppalmer050390 jtppalmer050390 is offline
 
Join Date: Apr 2009
Location: Calhoun, GA
Posts: 49
Default Master Left ON - Question about Charging

Ok, I flew out of town to visit family. When I returned to the plane 2 days later, battery completely dead. So, I decided to prop start the plane. Wasn't even sure if I could because my plane uses slick start system and I have never tried to prop start it. Anyway, it fired right up. However, never made any electricity. I then put a battery charger on it for a while and it started and alternator made electricity. My thought was that since the battery was completely dead, the p-lead never had any power to it to turn the alternator on. The pilot that was there with me said that shouldn't matter. That is the only thing that makes sense to me. Any thoughts??
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  #2  
Old 04-25-2016, 07:55 AM
AltonD's Avatar
AltonD AltonD is offline
 
Join Date: Sep 2005
Location: Dothan, Alabama
Posts: 1,492
Default

Unless it is a permanent magnet generator, it will need excitation (12v) to create a field. Sounds like it worked as it should.

I belong to the same club btw.
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  #3  
Old 04-25-2016, 07:58 AM
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Mel Mel is offline
 
Join Date: Mar 2005
Location: Dallas area
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"P" lead has nothing to do with the electrical system. It's strictly for the ignition system.
The reason it didn't charge was that with a completely dead battery the alternator had no voltage to "excite" the coils. It doesn't need much. But it does need some voltage.
Once you put a charger on it, you "excited" the field and everything back to normal.

Oops, Looks like Alton types faster than me.
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Last edited by Mel : 04-25-2016 at 08:01 AM.
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  #4  
Old 04-25-2016, 08:05 AM
BillL BillL is offline
 
Join Date: Sep 2007
Location: Central IL
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After the engine was running, a flashlight battery would have been enough to jump start the alternator. No field voltage, no magnetic field and, no output voltage. Like others said above.
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  #5  
Old 04-25-2016, 08:17 AM
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airguy airguy is offline
 
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Location: Garden City, Tx
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The second question is how badly you nerfed your battery by letting it drain completely flat - in my experience the PC680 only tolerates that abuse about twice, and then gives up the ghost.
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Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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  #6  
Old 04-25-2016, 08:26 AM
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Carl Froehlich Carl Froehlich is offline
 
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Location: Dogwood Airpark (VA42)
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Quote:
Originally Posted by airguy View Post
The second question is how badly you nerfed your battery by letting it drain completely flat - in my experience the PC680 only tolerates that abuse about twice, and then gives up the ghost.
You killed the battery - it is just not yet done dying. Replace it.

Also note that flying with a suspect battery translates to little electrical reserve.

Carl
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  #7  
Old 04-25-2016, 08:31 AM
jtppalmer050390 jtppalmer050390 is offline
 
Join Date: Apr 2009
Location: Calhoun, GA
Posts: 49
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Thanks for the input. So my concept was right, need a little current to make alternator work (even though it doesn't have to do with the p-lead). Anyway, I have a pretty cool very light battery that will charge a battery (or provide the small amount of electricity needed) via the aux cord. Note to anyone interested: Your backup spare battery charger does not help when it is sitting on your nightstand 150 miles away!!!
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  #8  
Old 04-25-2016, 08:33 AM
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Walt Walt is offline
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
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Not charging a dead battery before flying is what I call "serious alternator abuse", and foolish. The alternator is there to keep the battery topped off and to carry the aircraft electrical load, asking it to charge a fully depleted battery (which will take everything the poor little alternator can put out) and carry the aircraft loads at the same time, well, you're just asking for trouble.

Treat a dead battery like bad weather, sometimes you just gotta take a delay to do the right/safe thing.
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  #9  
Old 04-25-2016, 08:34 AM
Rupester Rupester is offline
 
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Location: Mahomet, Illinois
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I ran my PC680 stone cold dead nearly 3 yrs ago by leaving the master on. (imagine that! ) I charged it with a good charger that had an AGM setting for charging glass mat type batteries. It recovered fine, and I have flown it without trouble ever since.
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  #10  
Old 04-25-2016, 08:39 AM
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Sam Buchanan Sam Buchanan is offline
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Join Date: Dec 2004
Location: North Alabama
Posts: 4,466
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Quote:
Originally Posted by Walt View Post
Not charging a dead battery before flying is what I call "serious alternator abuse", and foolish. The alternator is there to keep the battery topped off and to carry the aircraft electrical load, asking it to charge a fully depleted battery (which will take everything the poor little alternator can put out) and carry the aircraft loads at the same time, well, you're just asking for trouble.

Treat a dead battery like bad weather, sometimes you just gotta take a delay to do the right/safe thing.
Yep, I ran the engine to charge a flat battery and saw the poor little 30 amp alternator putting out 49 amps in an attempt to refill the dead battery. The alternator was dead within the hour....

Charge the battery before starting the engine.
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