# Incorrect battery0 voltage on QGC

Source: https://forum.modalai.com/topic/4568/incorrect-battery0-voltage-on-qgc
Category: General Questions (https://forum.modalai.com/category/2/general-questions)
Posted: 2025-07-04 22:01:26 UTC by george kollamkulam
Replies: 9 · Views: 1724

## george kollamkulam · 2025-07-04 22:01:26 UTC

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. ![Batt_params3.png](https://forum.modalai.com/assets/uploads/files/1751666422050-batt_params3.png) ![Batt_params2.png](https://forum.modalai.com/assets/uploads/files/1751666422087-batt_params2.png) ![Batt_params.png](https://forum.modalai.com/assets/uploads/files/1751666422125-batt_params.png) 

Thanks!

## Reply by Alex Kushleyev (ModalAI staff) · 2025-07-09 18:22:16 UTC

@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

## Reply by george kollamkulam · 2025-07-23 19:02:13 UTC (in reply to Alex Kushleyev)

@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

## Reply by Eric Katzfey (ModalAI staff) · 2025-07-25 16:33:43 UTC (in reply to george kollamkulam)

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

## Reply by Alex Kushleyev (ModalAI staff) · 2025-07-25 19:07:14 UTC (in reply to Eric Katzfey)

@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

## Reply by constantines · 2025-07-27 12:54:58 UTC (in reply to george kollamkulam)

@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](https://github.com/mavlink/qgroundcontrol/issues/13174). This is definetely not a VOXL or Modalai problem

This is how it looks with QGC v5.0.6
![9be8595c-5410-403a-8cec-2689f5abaf37-image.png](https://forum.modalai.com/assets/uploads/files/1753620874562-9be8595c-5410-403a-8cec-2689f5abaf37-image.png)

And this is the same system but with QGC v4.4.4
![5da677a0-dd8b-42eb-a9a2-7fb3d755d312-image.png](https://forum.modalai.com/assets/uploads/files/1753621087578-5da677a0-dd8b-42eb-a9a2-7fb3d755d312-image.png)

## Reply by george kollamkulam · 2025-07-28 14:25:17 UTC (in reply to constantines)

@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

## Reply by constantines · 2025-07-29 06:58:34 UTC (in reply to george kollamkulam)

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

According to [this](https://github.com/mavlink/qgroundcontrol/issues/13174#issuecomment-3127877634) the Modalai PX4 uses the voltages_ext field of the [BATTERY_STATUS](https://mavlink.io/en/messages/common.html#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 :confused:

## Reply by Eric Katzfey (ModalAI staff) · 2025-07-29 15:52:43 UTC (in reply to constantines)

@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.

## Reply by Eric Katzfey (ModalAI staff) · 2025-07-31 21:50:37 UTC (in reply to 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