Voxl flight deck - issues with flying and power



  • Hi, This will be bit of a long post as I'm currently facing bunch of issues.
    I'm currently using a voxl-flight-deck enabled drone. My system image is system-image: ModalAI 3.3.0
    We have a basic python script that we run to test basic flight using vio, to see our drone flies in various positions. We have been using this for almost a year now, every-time we want to test everything is fine with the drone. From past few days, I'm facing not so consistent issues.

    1 - The drone is flying properly only if placed in a certain direction. Example, if I place the drone facing south, then the drone flies properly. But as soon as I turn it off and change its direction like facing North, East or West than drone does not fly. To the best of my knowledge all these direction have equally abundant features for VIO to recognize and register the orientation. But drone cease to do so. as soon as I place the drone facing south it operates fine.

    2 - Immediately getting low battery alerts - I'm currently using 3S lipo batteries with 2200 mah capacity. Even though I full charge my battery before testing, as soon as the drone starts flying, QGC starts to report bunch of issues like "Low battery level! Return advised", "Critical battery level, landing advised", "Dangerous battery level, please land". I have attached a screenshot of the same. In the power setup inside QGC, I have set it up the following -
    Number of cells(in Series) - 3S
    Full Voltage(Per cell) - 4.05
    Empty Voltage (Per cell) - 3.50

    3 - Avionics Power low - 4.66 v/4.72V,4.75V - I first got this power avionics problem about 3-4 weeks ago, luckily at that time I replaced the power module with another module (I had extra voxl power module), and that seemed to solve the problem then.
    However, since last two days I have again started to face Avionics power low issues.This happened twice yesterday, and then did not. And today after the first unsuccessful flight test, during which time it did not say avionics power low, it again started throwing power avionics problems from the next tests and because of which the motors would spin with very power as if it would go and hit the ceiling. I immediately press kill switch to avoid any accident.

    Currently these are the issues that I'm facing. Looking forward for getting help on this. Thank you
    battery_issue.png avionics_powerlow.png


  • Dev Team

    How old is your battery?



  • @Chad-Sweet can't seem to remember, but definitely older then 6-7 months or may be even more, but not sure about that.


  • Dev Team

    Your symptoms sound like a dead battery. Batteries have a limited number of charge cycles



  • @Chad-Sweet thanks for the reply. But the voxl-inspect-battery command inside voxl shows the correct value on the terminal. Also I have a separate external device that gives the voltage of each cell, and it looks correct to me. Could it still be a bad battery?



  • @Chad-Sweet I just replaced my 3S lipo battery with a new 4S lipo battery. I performed sensor calibration as well, just to not leave anything behind. I tried to fly the drone 3 times, although I did not get Avionics power low error, however my drone is going haywire every time I'm trying to fly. In all my 3 tests, I had to quickly use kill switch or else it would have hit something real bad. Also, the one area where my drone was flying perfectly before, it failed even there with bad flight behavior. I made sure I was getting correctly odometry at origin.


  • Dev Team

    you need to retune the flight PID loops if you change battery voltages (going from 3S to 4S)


  • Dev Team

    The issues you are having are not related to the VOXL. The PX4 documentation covers PID tuning. If you want your aircraft to behave as it was before, you'll need to use a battery with the same specs as before.



  • Thanks @Chad-Sweet for your reply. So I did not try the PID method, but instead used a new 3S lipo battery to replicate the previous flight behaviour. The first test was a huge success and the drone flew well even while facing the other sides. But further tests, the power avionics issue has come back again and the tests are now inconsistent. Sometimes it flies well and sometimes its going haywire, but almost getting the avionics power low issue every time.

    Could this be the power module issue? Anyway I've ordered power module and my next step is to replace with a new power module and test. But is there anything that you could suggest?


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