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Old 05-07-2017, 02:27 AM
bardample bardample is offline
Join Date: Jun 2011
Location: Mansfield Australia
Posts: 20
Default Erratic Ammeter Readings

I need some help. I have a single Dynon Skyview in my RV7 with a recently installed EarthX ETX680 Lithium FePo4battery, a Plane Power 60 A Alternator (internal Regulator) . My ammeter measures Alternator output( Position B as per Dynon).

For 2 recent successive flights, my' amps low' warning flashed and the ammeter was reading erratically minus 8-25A and occasionally reading normal( i.e. pos 6-7A). Throughout these flights of several hours bus voltage remained at 14.1- 14.2v. If I flicked the Alternator off and then on again the ammeter reading would briefly read 'normal' + 6-7 Amp for a few moments before returning to erratic negative values. I assumed that the fault lay with the ammeter connections or in the EMS monitor of the Skyview.

Normally after each flight my EarthX battery reads 13.4v and drops to 13.2 over the next 24-48 hrs. Just after my erratic ammeter reading episodes, I found a screw on the ammeter attachment to the Dynon supplied shunt, was a little loose. I tightened this screw and checked the other.

The next 2 flights have indicated 'normal' +6-7Amps with so far no erratic readings.

Before one recent flight, I noticed the EarthX battery Voltage was only 13.0 V ( even tho before previous flight shutdown bus voltage was 14.2V). This suggested the battery had discharged. After startup on this time the ammeter ( i.e. Alternator output) was outputting at first 55Amp and stayed high for at least 10 mins , suggesting the battery was accepting lots of charge.

My most recent flight was normal. i.e. prestart Batt voltage 13.1V, 'normal' ammeter output 25 Amp for 5 mins , settling to 6-7 Amps when airborne, and a flight bus Voltage of 14.3v .

The problems have settled but will this all occur again. Can anyone offer insights as to the real problem? Dynon say send the EMS back to the US if needed . Kathy at EarthX says if the battery is not holding charge it will be faulty . Sorry for long story . Jeff R Australia
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Old 05-07-2017, 05:41 AM
vic syracuse vic syracuse is offline
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Join Date: May 2005
Location: Locust Grove, GA
Posts: 2,714

A couple of thoughts for you----my guess is that your loose connection on the ammeter shunt, IF it was the larger primary lead and not the smaller 22 GA instrument leads, was the cause of your problem. 13 volts with the master switch on is not out of line for the Earthx Battery, and they do seem to be pretty good at indicating a fault light if there is a problem. You do have the fault light wired to the instrument panel or to an EFIS input, right?

The high charge as you indicated was most likely due to the loose charging wire not giving the battery a complete charge on prior flights.

I would watch the Dynon for proper indication of amps. Kudos to you for paying attention to the volts reading! I have seen the Dynon EMS units have a problem with the amps indication even though nothing was really wrong with the actual aircraft.

Vic Syracuse

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Old 05-07-2017, 12:43 PM
DennisRhodes DennisRhodes is offline
Join Date: Jul 2007
Location: Taylorsville, Ga
Posts: 886

What Vic says. Mine did that and found that the signal wires on the shunt ( small 22 gauge ones) had a bad crimp connection due to wrong size crimps used on the small wire. It however operated 400 hours flawlessly in spite of that ! Amps will not be that erratic with voltage remaining that constant. Can't happen. My first effort at repairing got me a new alternator.
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Old 05-07-2017, 02:54 PM
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jsharkey jsharkey is offline
Join Date: Nov 2006
Location: Bennington, Vermont USA
Posts: 1,302

I have a much simpler set up that measures current flow to and from the battery and had a similar problem with an erratic Van's ammeter. After I started seeing some needle jumping on the oil pressure gauge too I traced the problem to a loose screw on the breaker terminal that feeds the electrically powered instruments. After tightening the screw all of the instruments were rock solid.

I had a similar problem with a GTX327 transponder cutting out but which always restarted. I traced that back to a cracked in-line fuse holder that flexed under vibration and allowed for occasional and momentary current interruption. The GTX327 has a "soft switch" that switches to off if there is loss of power and has to be actively switched back on even after the power is restored. I ended up replacing the in-line fuse with a panel mounted one.

At the annual I always crawl under the panel and check for loose terminal screws or other loose connections.
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Old 05-07-2017, 04:16 PM
bardample bardample is offline
Join Date: Jun 2011
Location: Mansfield Australia
Posts: 20
Default Erratic Ammeter Readings

Thank you for your thoughts. I do have the Earth X battery wired to the Skyview on the panel . No warning light seen.
I shall be more obsesssive in checking connections in future. I remain suspicious of the EMS however.
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Old 05-08-2017, 05:01 PM
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nigelspeedy nigelspeedy is offline
Join Date: Dec 2008
Location: Tehachapi, CA
Posts: 154
Default I've had that too

I have a have seen the Amps reading on my Skyview go screwy as well. Turned out to be a bad connection at the ammeter shunt. Like you cross checking the bus voltage helps you see what is really happening.


Nigel Speedy
Tehachapi CA
I paid my -VAF- dues July 2018
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Old 05-13-2017, 10:00 AM
Robert Anglin Robert Anglin is offline
Join Date: Mar 2008
Location: houston, texas
Posts: 900
Default Agree with Vic.

I agree with Vic and have found with a couple of the other battery types that an even lower standing voltage is good for a full charge check. I use 12.8 as a good rule of thumb when we turn a system on first thing in the morning. I too think you found your problem, but the battery company is correct, if the battery keeps showing low voltage and takes a bit longer to charge back up after start-up and run, it would mean there is an internal fault in the battery.
just 2 cents from the peanut section. Yours, R.E.A. III #80888
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Old 05-13-2017, 10:16 AM
Aggie78 Aggie78 is offline
Join Date: May 2014
Location: New Braunfels, Texas
Posts: 450
Default Don't forget to look at the alternator

I had this issue as well, and the easy part to inspect (the shunt) was fine.

So...I de-cowled and started a deeper look there, didn't have to go far. The hold down nut on the main power terminal on my Plane Power alternator had backed off to the last thread, allowing the main wire lead to bounce around on the terminal in turbulence, giving me the erratic voltage/amps readings.

The rubber weather cover over the bolt had hidden this issue from view.

Torqued the nut, went and flew...alles ist gut!

Something I look at EVERYTIME the cowl is off now for ANY reason.
Rob Schroer
New Braunfels, Texas (KBAZ)
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Old 04-09-2020, 10:47 PM
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sglynn sglynn is offline
Join Date: Mar 2008
Location: Anacortes, WA
Posts: 833
Default Erratic amp reading

Thanks for this thread. I?m flying with Dynon HDX, their EMS amd power supply Vp-X type. I just finished first annual inspection. About 60 hours. Today my amp reading started jumping around. Sometimes negative. At idle it seemed fine. But when reving it up it jumped around. It was like the vibrations caused it to jump around. Volts are a solid 14.4. Thanks to this thread I?m hoping to find a loose wire tomorrow. Dang I have to remove the cowl again so soon.
Steve Lynn
Built RV-7A
Flying It
Anacortes, WA
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Old 04-12-2020, 12:09 PM
sglynn's Avatar
sglynn sglynn is offline
Join Date: Mar 2008
Location: Anacortes, WA
Posts: 833
Default Erratic Amp meter

As a follow-up for those in the future who may read this. My amp meter starting jumping around going negative and positive. After reading this thread I hoped to find a loose wire.

I did. But the wire was only slightly loose. The nut on the battery solenoid where the lead that turns on (or closes) the solenoid switch had come slightly loose. I could wiggle the ring terminal a little. I took it off, added a little blue sealant and tightened it back on. Everything works.

But it sure wasn't loose much. But I can see that under vibration it could be letting 12V go on and off the battery solenoid and I guess that would cause a problem. The indication was the erratic amp meter.

My personal lesson learned is, don't let weird stuff go unchecked.
Steve Lynn
Built RV-7A
Flying It
Anacortes, WA
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