Pixhawk 2.1 spraying drone not rising above 1 meter altitude and giving some warning beeps

I have built an agricultural spraying drone to lift 5L, approx. 8Kg all up weight. The power system produces 18Kg of thrust theoretically.
While testing though I only added 2L of water, waited for the GPS on Position mode so that it’s more stable, changed the mode to Stabilize and then armed the drone. It took off perfectly but at 75% Throttle which in earlier test took off at 50% throttle. Also it did not rise above a meter in altitude and started giving what I think were some kind of warning beeps.
I am attaching here the log files of the test. Please somebody tell me what went wrong here.
Log files-
https://drive.google.com/drive/folders/1uxzCgMvakYEAYZR1WfCjbVMLTv5texGP?usp=sharing

hi,

Giving a quick look, with a single 25V will be very difucult to lift 18kg.
This image show how the voltage went from 25V to 21V on 10 seconds. your warning beeps I suppose were the battery failsafe went on. I cant see how much amps you are using as you havent have the current sensor configured.

This could mean 2 things, your baterry is preatty dead already and you have not it use it to flight, or the battery was overloeaded and couldnt handle the power the drone require.

1 Like

I am using 2 22.2V 10,000Mah batteries in parallel making it 20,000 and This wasn’t the case in previous tests. Also, the battery is still at 24.3V. could there be a connection issue?

Also, in the chart I can see that the voltage drops from 24 to 21 and then rises again to 24. Shouldn’t it be a constant decrease?
could you also tell me which application do u use to open these bin files?

Hi,

It really seems like a power issue. What kind of motors and ESCs are you using? What is the “C” rate of your batteries? We produce crop sprayer UAVs using Cube Orange for 10L (25kg MTOW) and we use 2x 6S 20C batteries.

1 Like

I have built an agricultural spraying drone to lift 5L, approx. 8Kg all up weight. The power system produces 18Kg of thrust theoretically.

You are almost certainly underpowered. You may have other issues but this configuration as it is will not ever perform very well.

5L of liquid is going to weigh about 5Kg, Let us assume you estimation of 18 Kg of thrust is correct.

If you were to stay under 50% hover throttle (which is the absolute most I would recommend, better would be <35%) you are only leaving 3Kg for batteries, propulsion, frame. I doubt all of that only weighs 3Kg on your drone.

When you took off and “Only” needed 50% throttle, did you have any liquid onboard? If not that is probably the difference right there.

If you really need a 5L payload this drone is less than half the size / power it should be.

As for the voltage moving up and down radically, it sure seems like an electrical issue, but it is hard to tell without a current measurement.

1 Like