0TreeLemur Posted January 19, 2021 Report Share Posted January 19, 2021 Today in cruising flight at 6500 the JPI EDM900 in our M20C gave a strange indication. The current fluctuated from moments of 4A to indicating spikes as large as 30-70A. Voltage varied from 14.1 to 14.2 V during the times I watched the current vary. I didn't think to download the data after shutdown. I'll get those in a day or two. Facts: We have a Delco-Remy 50A generator. Last O/H in 2007, about 950 h ago. Brushes inspected 2018. Concorde battery replaced in mid-2020. Zeftronic regulator. Day flight with only load GNS430W, KX155, intercom, nav lights. JPI EDM 900 installed 2018. Batt. voltage ok at shutdown after 1.5h flight. Seems like measurement error/noise to me. Unlikely that 50A generator would be putting out such large transients when the voltage is so stable. Could it be bad brushes? Regulator? Thanks - Fred Quote Link to comment Share on other sites More sharing options...
mike20papa Posted January 19, 2021 Report Share Posted January 19, 2021 I'd call Zeftronic. Sometimes the old guys will say ".. that's what you get for having all that fancy instrumentation .." 1 Quote Link to comment Share on other sites More sharing options...
Brian E. Posted January 19, 2021 Report Share Posted January 19, 2021 @0TreeLemurI'm similarly equipped as you: EDM900, generator and a zeftronics regulator. Most of my lighting is LED aside from the wing tip strobes. I commonly see fluctuations from a low of 4 - 7 amps to a max of 15 - ~20ish amps with everything on. Voltage always remains constant at 14.1 or 14.0 volts. If i saw a 30A or greater charge I would start looking for the smoke to be releasing from something. 1 Quote Link to comment Share on other sites More sharing options...
carusoam Posted January 19, 2021 Report Share Posted January 19, 2021 (edited) Preemptive inspection of the wires coming from the shunt to the JPI... The shunt is a low resistance resistor, and the JPI is reading the voltage difference across the calibrated resistor... It is reading a very small number... so any error can cause a really large number... Both wires are fused, in the event one shorts to ground... Sounds like one may be getting loose.... If 70amps is actually going directly to ground... sparks and the aroma of liquid metal would magically appear... Keep in mind the shunt may not be insulated in any way... so poking around trying to feel a loose connection may be a touch hazardous... PP thoughts only, not a mechanic... Best regards, -a- Edited January 19, 2021 by carusoam 2 Quote Link to comment Share on other sites More sharing options...
Ragsf15e Posted January 19, 2021 Report Share Posted January 19, 2021 2 hours ago, Brian E. said: @0TreeLemurI'm similarly equipped as you: EDM900, generator and a zeftronics regulator. Most of my lighting is LED aside from the wing tip strobes. I commonly see fluctuations from a low of 4 - 7 amps to a max of 15 - ~20ish amps with everything on. Voltage always remains constant at 14.1 or 14.0 volts. If i saw a 30A or greater charge I would start looking for the smoke to be releasing from something. Keep in mind that your EDM (or original gages) is reporting amperage to/from the battery. It’s only the charging amps. Or, in the case of alt/gen fail, it’s the discharge from the battery. You shouldn’t really have a change or increase with “everything on”. Now it might be higher just after engine start, and lower in cruise after the battery is recharged, but it shouldn’t change significantly with load as long as your charging system keeps up (voltage stays constant) because your battery will accept the same charging amps. After start your amps are higher because your battery is slightly discharged. My jpi930 does fluctuate a smidge between about 4-6amps during cruise which I just attribute to the jpi reading very accurately and the system trying to keep constant voltage with the strobes cycling. If you have a very high amp draw it could be a battery that is discharged or bad. Or it could just be instrumentation. Or other gremlins? 2 Quote Link to comment Share on other sites More sharing options...
Ragsf15e Posted January 19, 2021 Report Share Posted January 19, 2021 @PT20J has a good description in this recent thread about ammeters... 1 Quote Link to comment Share on other sites More sharing options...
1964-M20E Posted January 22, 2021 Report Share Posted January 22, 2021 Verify all wiring from alternator to firewall, to the battery and to the regulator. Once all connections are cleaned tight then start looking elsewhere. 1 Quote Link to comment Share on other sites More sharing options...
Ragsf15e Posted January 22, 2021 Report Share Posted January 22, 2021 (edited) 1 hour ago, 1964-M20E said: Verify all wiring from alternator to firewall, to the battery and to the regulator. Once all connections are cleaned tight then start looking elsewhere. I recently had some low voltage issues and eventually traced it to a slightly worn/corroded connection from the battery to the bus. Easiest way for me to trace it was to take a voltmeter and work my way back from the alternator running at 14V to the power conditioner, to the alternator circuit breaker, to the bus, to the battery connection at the bus. Solid 14v all the way until the battery wire connection at the bus. Sanded it, reattached, problem solved. Be careful checking alternator output because the engine is running! Use some wire clips to stand safely away. Zeftronics and PP voltage regulators have troubleshooting guides on their website that have you check voltage from the battery through the system to the alternator without the engine running. This got me close but I wasn’t sure until I measured with the alternator on. Edited January 22, 2021 by Ragsf15e 1 Quote Link to comment Share on other sites More sharing options...
0TreeLemur Posted January 22, 2021 Author Report Share Posted January 22, 2021 10 minutes ago, Ragsf15e said: I recently had some low voltage issues and eventually traced it to a slightly worn/corroded connection from the battery to the bus. Easiest way for me to trace it was to take a voltmeter and work my way back from the alternator running at 14V to the power conditioner, to the alternator circuit breaker, to the bus, to the battery connection at the bus. Solid 14v all the way until the battery wire connection at the bus. Sanded it, reattached, problem solved. Be careful checking alternator output because the engine is running! Use some wire clips to stand safely away. Zeftronics and PP voltage regulators have troubleshooting guides on their website that have you check voltage from the battery through the system to the alternator without the engine running. This got me close but I wasn’t sure until I measured with the alternator on. I sure hope that I can do it without running the engine. As in the original post, I have a generator, and it doesn't engage the VR until 1700-1800 rpm. Quote Link to comment Share on other sites More sharing options...
Ragsf15e Posted January 22, 2021 Report Share Posted January 22, 2021 Just now, 0TreeLemur said: I sure hope that I can do it without running the engine. As in the original post, I have a generator, and it doesn't engage the VR until 1700-1800 rpm. Ahh yes, that’s more difficult. I didn’t like doing it at 1000rpm with chocks and my wife on the brakes! I was able to check it at my power conditioner on the firewall through the oil dipstick door. 1 Quote Link to comment Share on other sites More sharing options...
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