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??

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.

"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.

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.

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

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!!!

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.

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.

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.