Hello, I have an issue with my Phantom 3 Advanced. From one flight to another, it started to ‘bounce’ during hover flight. There is a battery error coming up after a couple of seconds of flight. The cells voltages are completely unbalanced and are varying rapidly on all 4 cells. It was working perfectly the flight before.
Here is what I tried already:
Compass calibration
IMU calibration
Drain the battery drain under 5% and charge it again to 100%
Force-update the firmware (with the DEBUG file)
Nothing worked.
Here is a video showing the problem:
I’m not sure if the battery unstability is the cause or the consequence of the problem. I’m looking for someone who could lend me a battery for a quick test, but in the meantime I would appreciate your help.
Thanks
Fred
Hi there, so I bought and installed a new battery, I changed all the 4 propellers, but the problem is still there. I tried to adujst the gain settings as well with different values (I saw that 90 / 90 / 80 / 100 was supposed to work better), but it did not help either.
If you can provide the .DAT log file maybe we could determine the cause. Look here https://datfile.net/DatCon/retrieve.html
to see how to retrieve the .DAT. It will be large so you will need to use a public sharing site like Dropbox or GoogleDrive.
I looked at this some but don’t have a clear answer for you. FLY355.DAT shows the problem seen in your video. The motor pulsing can seen clearly in the motor speed data.
There is a very odd relationship between the commanded and observed vertical acceleration. Normally, the observed (green) follows the commanded (red) like here
A defective Z axis accelerometer could cause this but there isn’t data to support this. Has the P3 been dropped or otherwise been subjected to a high impact?
Thank you so much for taking the time to analyze this issue, I really appreciate. I think the second graph is not the right one (identical to the first one), but I got your point: the motors are behaving exactly the way the ‘brain’ orders them to, so it is not a motor / propeller / current or voltage loss / frame rigidity issue.
No, my P3 did not crash nor was dropped nor received a shock. This issue appeared out of nowhere, right after the first takeoff after powering it on. I had just charged the battery after the last flight which had no issue at all, everything was perfect and the landing was smooth.
I suspected a Z-axis accelerometer issue too, but you wrote that there is no data supporting this. What data are you thinking of? I guess there is no way to replace a single accelerometer ? Is the complete IMU replaceable ? Is it worth it ?
I don’t think that sending it to DJI for repair would be worth it, I can buy a used P3 Advanced with low hours, two batteries and two sets of spare propellers for around 160 US$, a repair would probably cost more than that.
Do you have some other ideas?
Thanks again for your help.
While sitting on the ground the Z axis accelerometer was constant at -0.99; theoretically it should be -1.0. That’s the correct value.
The IMU is replaceable. But, I agree, if you can get another for $160 it hardly seems worth replacing the IMU. Especially since it’s unclear, to me at least, if a new IMU would fix the problem.
