10-15 amp draw?

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U2Hoog
Posts: 42
Joined: Tue Apr 23, 2002 4:27 am

10-15 amp draw?

Post by U2Hoog »

This year at annual time we replaced our old generator with a Jasco Alternator system. Seems to work well, except on the test flight, we saw a 20 amp charge to the battery initially after start, NOTHING running which then dropped to about 12 amps or so. I've got a brand new battery, fully charged. We changed out ammeters to make sure it wasn't a guage. System voltage with the engine running is about 14.5 volts, with battery only, about 12.5. My concern is that after flying for an hour, the lowest I saw the amps going to the battery at about 11 or 12. Oh, I also have an EDMO warning system for system voltage too high or low, and that indicated normal during flight.

All systems seem to operate normally (radios, transponder, lights) -- except the elusive 12 amp charge (draw?) to (through?) the battery.

Ideas?

Stephen Hoogasian
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GAHorn
Posts: 20968
Joined: Fri Apr 12, 2002 8:45 pm

new alternator

Post by GAHorn »

Steve, it looks to me like it's doing what it's supposed to!
After you use the battery to make an engine start, even with nothing else online, the battery wants to be replenished, so that's what your alternator is doing! Later inflight, you've got other appliances on and your alternator is supplying that as well! No problem.
U2Hoog
Posts: 42
Joined: Tue Apr 23, 2002 4:27 am

More on the Amperage

Post by U2Hoog »

Well, that's comforting, but I just never saw that with the old generator. The ammeter just sat there around 0-3 or so. And as I understand the ammeter, it is merely showing charge to / from the battery, correct? IE, if the ammeter is showing +15 amps, that's going to the battery, and if it's showing -5 amps, that's drain FROM the battery. Or at least that's the way I've always understood it. I just don't want to burn up a new battery by "hoping everythings ok" or worse, have an electrical fire in flight.
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GAHorn
Posts: 20968
Joined: Fri Apr 12, 2002 8:45 pm

alternator

Post by GAHorn »

Most alternators have solid state regulators which are pretty accurate. Your 14.5 volts is correct. It's possible that your old gen system regulator was set low, so the comparison may not be valid. True, if the output equals the draw, then with a fully charged battery then eventually your ammeter should level out near zero, but only after your battery is fully charged. It may take a few flights if that battery had already spent a former lifetime serviced by a low-output charging system.
Keep an eye on your battery water. If you have a fairly new battery and yet have to keep replenishing it with water constantly, then you may need to have your alt regulator adjusted downward. 13.5-14.5 volts is the correct range, however.
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