Dynon ACM electrics issue

[kestrel]

Which amps is this? System load? Battery? Alternator? I'm guessing this is the system load?

Things like lights can cause quite a load. How much power do your lights take? ...do you have any? What other large loads might you have?

If it weren't for the low voltage warning that may have correlated with a current spike, I would wonder if it was a sensor problem.

What does the start of the 2nd flight look like? Does it have a high load plus spike like the first does?

What does the current look like with the engine off? How many current measurements do you have? (I have 2, one for battery charge/discharge and one on the alternator. I recall that you have a field current sensor?)

Data can be tricky and sometimes you have to look at it very carefully/closely to read it correctly. You want to look for multiple signals that confirm any theory, such as a voltage drop correlated with an increase in current. There may be a combination of a problem and mis-calibrated senors.

[Nev]

Which amps is this? System load? Battery? Alternator?

My understanding at this stage is that it is the left value on the diagram below (sent to me from Dynon) showing Alternator Amps. However it's also the only Amps readout I've got available in the downloaded data. There's also no voltage data there (in the download), so I think I need to check how I've configured it in the Dynon ACM.

1360A72C-51BB-4D4E-B001-5CD896A5AC03.png

The second flight shows 3 large spikes after engine start. However this might be explained by me taking photos of the screen in between turning on the Avionics etc. Inflight, the landing light stays on, and the fuel pump is used for takeoff and landing, so neither of them explain the spikes in-flight - I was able to check this by zooming in on the graph.

I plan to work out how to capture the volts and other amperage readings in the data, probably a matter of configuration on the EMS inputs. Makes my head hurt .

[kestrel]

At least as much as the initial spike, I am interested in the ~5-8A period right around start-up that has the spike with-in it. The goal is to try to explain as much of that graph as we can and separate out what still needs explaining. This is also to try to establish if the zero offset is correct.

[Nev]

Here's what the start up looked like with 3 spikes.

5545CA6B-C6B2-4943-B710-19BEE47EFAA5.jpg

[kestrel]

Getting the bus voltage and other currents logged will help a lot. This does look like alternator current. I see it sitting at zero for the first 15 seconds. The zero offset for this current sensor looks good. Then at about 00:00:45, the engine is started and the alternator comes up to about 18 amps and recharges the battery. From there we see a slow decay in charge current until about 00:02:30 where I would guess that the RPM was brought up which raised the alternator/bus voltage which resulted in more current going into the battery. This peaks at about 00:02:45 when I would guess the RPM was lowered again.

The 4 spikes are quite concerning. There is also a 5th small one just before liftoff. They indicate probably 50+ amps being drawn through your shunt from the alternator. A few possibilities:

* A spike in field current raised the alternator output and cause a current spike
* A short somewhere after the current shunt cause a current spike
* A bad connection on the current shunt resulted in abnormally high voltage across the shunt and no actual current spike

Maybe others I didn't think of.

If your shunt has a bad connection, the actual current will have dropped while the voltage across the shunt increased and looked like an increase in current.

If the real current did increase and it isn't a shunt problem, then you need to look for a problem with the voltage regulator running too much field current (or perhaps a different reason for too much field current) or a short to ground on main bus somewhere after the current shunt.

Need more data! :-)