"Avionics power low: 4.78 V" battery.

gauravshukla914 · 2 Apr 2021, 16:52

Hi, We are observing a strange behavior wrt to our Lipo battery, while flying our voxl flight deck enabled drone. We are using a Lipo 3s 2200 MaH battery. Our battery is fully charged. However, while testing, we hear this from Qgroundcontrol station "

Avionics power low: 4.78 V".
And as a result the drone goes into uncontrollable state and hits the ceiling.
While our debugging, we observed that the voltage on pin1 of J1 connector, we are getting voltage of 4.8V DV instead of 5V which is required.
Please let us know what could be a problem here and how can we proceed from here. Looking forward to your reply.

modaltb · 2 Apr 2021, 17:50

Hi @gauravshukla914 ,

Are you using the VOXL Power Module? What is your measurement Vbat?

The output of the power module output to J1 like you said should be 5VDC.

The voltage reported to QGC isn't the "companion computer power supply voltage" but rather the battery voltage, so it won't report the voltage coming out of the power module, but rather the voltage the ESCs are seeing.

Thanks!

In QGC, what have you setup for battery cells? Our default params are 4S.

gauravshukla914 · 2 Apr 2021, 18:16

Hi @modaltb Thanks for your reply.
Yes, we are using the VOXL power module.

Yes, after measuring the pin1 of J1, we are getting output as 4.78V DC instead of 5V.

The voltage that we reported as 4.78V, was the voltage coming out of the power module.

We even tested with different batteries like 3S mentioned above and 4S, but its still the same.
In QGC, we did change our parameters from 4S to 3S to suit our requirements.
Just to let you know, we have been working with this exact same setup for over a month now, and successfully did our flying tests, but this is the first time that this issue has come up.

modaltb · 2 Apr 2021, 18:33

Hi @gauravshukla914 OK we will want to replace your power module with a new one and get yours back to investigate.

Unfortunately we are out of power modules until next week.... Is this OK for you timing wise?

gauravshukla914 · 2 Apr 2021, 23:50

hi @modaltb Sure. Thank you. That works with us. Could you let me know the return process, or what do we need to do it from our end?

modaltb · 3 Apr 2021, 00:34

@gauravshukla914 yes we'll get an email going, I'll use the email that's tied to your account here.

gauravshukla914 · 5 Apr 2021, 15:51

@modaltb Hi. I have submitted my response to the firm that was sent to me. Looking forward for the replacement. Do let me know if there's anything else I need to do from my end. Thank you again.

modaltb · 16 Apr 2021, 22:54

@gauravshukla914 ,

I for the first time got the "avionics power low" message! I turned off the ADCs on FlightCore for a test and got this error.

PX4 monitors the 5VDC rail (and 3.3VDC), and this makes sense now, as the output of that power module was lower than expected.

Anyhow, I remembered this post so figured I'd put some details here while I saw it