Incorrect battery0 voltage on QGC

[george kollamkulam]

Hi,

I'm seeing incorrect battery0 voltage on QGC. Would appreciate your help in resolving this issue.

I'm using the 2S Amprius battery packs on my Starling 2 and the battery parameters are attached below.

Thanks!

[Alex Kushleyev]

@george-kollamkulam , something seems fishy here.

The Starling 2 drone has the VOXL Mini ESC, which acts as the APM (measures voltage and total current). The ESC sends this data to PX4 via UART together with regular ESC telelmetry.

The Battery status packet is an uint16 with 0.001V resolution, so the maximum voltage it could report would be about 65V (2^16 millivolts).

packet definition:
https://github.com/modalai/px4-firmware/blob/voxl-dev/src/drivers/actuators/voxl_esc/qc_esc_packet.h#L157

packet parsing:
https://github.com/modalai/px4-firmware/blob/voxl-dev/src/drivers/actuators/voxl_esc/voxl_esc.cpp#L577

I suspect something else is going on. Maybe you need to choose a different Source for the battery monitoring (not Power Module)?

Is this voltage 267.55V updating or just stuck at that value?

Alex

[george kollamkulam]

@Alex-Kushleyev Sorry for the delay.

The voltage value seems to have decreased a little with time, but I don't think this is following the battery discharge trend. I started at 270.31 V just before take-off, and I was at 269.24 V after roughly 15 mins of flying. What could be the next steps to troubleshooting this issue?

Thanks,
George

[Eric Katzfey]

@george-kollamkulam In console can you do a listener battery_status to see what the PX4 topic has in it?

[Alex Kushleyev]

@george-kollamkulam , also are you able to use voxl-esc tools to verify the voltage?

You can run the following command, which will not actually spin the motors, but will communicate with the ESC and receive feedback:

#stop px4
systemctl stop voxl-px4

cd /usr/share/modalai/voxl-esc-tools
./voxl-esc-spin.py --id 255 --power 0

The script should run and print out the voltage reported by the ESC.

Alex

[constantines]

@george-kollamkulam @Alex-Kushleyev @Eric-Katzfey
Can confirm the same.
But it happens only with QGC version 5 and later. With previous versions of QGC everything works as it should. I opened an issue at QGC github. This is definetely not a VOXL or Modalai problem

This is how it looks with QGC v5.0.6

And this is the same system but with QGC v4.4.4

[george kollamkulam]

@constantines @Eric-Katzfey @Alex-Kushleyev voxl-esc is reporting the correct voltage. It looks like changing the QGC version has fixed the issue.

Thanks for your inputs.
George

[constantines]

@george-kollamkulam @Eric-Katzfey @Alex-Kushleyev

According to this the Modalai PX4 uses the voltages_ext field of the BATTERY_STATUS message incorrectly. That fields does not use UINT16_MAX (65535) to indicate no value. It should use 0, otherwise they are added to the battery voltage

[Eric Katzfey]

@constantines Up until version 1.13.3 PX4 set all these fields to UINT16_MAX. We forked right before they updated to make those voltage_ext fields 0. So, we'll need to pull that update into our fork.

[Eric Katzfey]

@Eric-Katzfey The update has been pulled into our fork now. You can access the updated package here: http://voxl-packages.modalai.com/dists/qrb5165/dev/binary-arm64/voxl-px4_1.14.0-2.0.106-202507311432_arm64.deb