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charging at 14 amps

PMLviator

Active Member
cruising at 5300 rpm, showing 13.3 volts and 14 amps.Can someone help me understand the +14 charging amps?
 
Seems normal

Not a 12 but this should still be relevant. I have the ammeter in my 7 wired so that it reads amp output.

During normal flight, I see about 11 or 12 amps as the steady output. This is what it takes to power all my avionics. If I turn on lights, the number goes up. Turn on pitot heat and the output goes way up.

Right after engine start, the amp output will go way up - into the 30’s if I had to crank the engine more than normal. Once the battery is recharged, the amp reading drops down to the 11 amp range.

So a reading of 14 amps is probably just about right since your Rotax has an electronic ignition system.

EDIT:
Based on the posts that came after mine, I might be completely wrong with regards to the RV-12 systems.
 
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My Cherokee has a load meter that shows the alternator output. Unless things have changed from when I built my 12 our 12’s show battery flow (+ for charging and - for discharge). A brief indication of +14 amps might be OK after a long crank on the starter, but if it is persistent it seems either your indication is bad or your battery is toast. Try doing a load test on the battery to check it’s health. A sustained 14 amp charge rate could be a dangerous situation causing battery overheating.

Harbor Freight sells a 100 amp battery load tester pretty cheap. I check mine every annual.
 
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A sustained 14 amp rate with your voltage that low indicates a huge electrical drain.

I'd also be very concerned about destroying a very hot overheated Ducati Voltage Regulator at that rate, then having no current charging, at all.

I usually show 13.9 to 14.0V with a +1 amp charge rate at anywhere from 5000 to 5350 rpm.
 
The permanent magnet generator is rated at 240 watts which at 14 volts is about 17 amps sustained load. My 12 draws about 7 amps for avionics, so your situation would seem to be at least 21 amps out of the generator. The VR could probably take that overload, but it would be more than nominal design criteria.
 
Probably nothing wrong with your charging system

cruising at 5300 rpm, showing 13.3 volts and 14 amps.Can someone help me understand the +14 charging amps?

Unlike electromagnet alternators, [used in cars & trucks] you can not throttle the output of a permanent magnet alternator [more correctly called a magneto]. The faster a permanent magnet alternator spins, the more amps it puts out.

On an electromagnet alternator, you can throttle the output, by lowering the amount of current sent into the alternator's rotor [the electromagnet] Less current means a weaker magnet, which in turn means lower output.

Since you can not control the strength of the magnets in a permanent magnet alternator, the voltage regulator simply absorbs the excess current [amps] to keep the voltage within the correct range. In your case, somewhere between 13.3 and 15.0 volts. The Zener diodes used for voltage control on old [1960s - 1970s] British motorcycles work the same way. Now days, the Zener diode is replaced with a solid state voltage control unit. These devices act as an additional load [like a light bulb] to absorb the excess output. Without this, the voltage would sky rocket beyond 15 volts at high engine RPM. :eek: You could then kiss your expensive avionics and battery goodbye. Many modern avionics contain internal over voltage protection. But there are limits to that protection

Since you are showing 13.3 volts, it means that your battery is fully charged. If you battery needed to be charged, the voltage would be higher.
The other possibility is that your voltage regulator is absorbing to much current, assuming that your battery is not at or near a full charge. If your battery's "at rest" [engine off & no drain on the battery] voltage is between 12.8 & 13.2 volts, it is at or near full charge.
So a running voltage reading of 13.3 volts with a fully charged battery would be normal operation. Your voltage regulator has reduced the charging voltage so that the alternator does not over charge a fully charged battery. Batteries are ruined by over charging. Classic signs of a battery ruined by over charging, are bulging side walls on the battery.

https://alternatorparts.com/what-are-permanent-magnet-alternators-faq.html

https://circuitdigest.com/tutorial/zener-diode-types-applications-and-operational-principle/
 
My voltage usually drops when my amperage load increases. I will usually see 13.4V and 7 or more amps right after start up. This continues until my rpms exceed 2500 to 2600 rpm, at which point my voltage then increases to 13.7V with amperage remaining the same.

Once I start takeoff and my rpms see 5150 to 5200 rpm, I notice that my amps drawn eventually drop off to 1 to 2 amps charge rate and voltage at 13.9 to 14.0V depending on the OAT.

High voltage to 14.0 V and low current at 1 to 2 amps, indicates to me that my battery is fully charged. Voltage rises as a battery achieves full charge state.
 
Technically, the Rotax permanent magnet alternator is a dynamo.
The faster it turns, the more volts it puts out. The voltage regulator limits the output voltage to about 14 volts by shutting off part of the AC sinewave using SCRs. The output current is determined by the load. If the load is increased beyond the capability of the dynamo, then the voltage starts decreasing below the regulator set point. An electrical system voltage of 13.3 volts is too low at cruise RPM. That low voltage can be caused by too high of a load current (battery charging current plus aircraft loads). Test the battery.
 
Thanks everyone for the input. I will take the battery out and do a load test as per your suggestions. I usually show 13.7 volts and 1-2 amps but on the last flight it went to 14amps. Thanks.
 
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