Hi, another noob question, sorry guys.

Today I have been flying my mini whoop (iFlight Alpha A75 HD) indoors and I noticed that after a mild bump on the ceiling the motors sounded different, like with a higher and louder pitch. When I landed the drone, the motors were very hot, I'm not sure if due to the bump or the recovery throttle boost I had to apply.
Very hot meaning I could not hold my finger on them (even on the 4 mounting screws) and there was a bit of smell but no smoke.
This happened twice already, always in the same situation, hopefully I have not damaged my motors.
The normal sound and temperature would resume on the next flight after cooling the motors down.

A few things are different compared to the past:
1) I activated Vbat Sag Compensation at 100%
2) I activated Dynamic Idle using a value (65) suggested in a Chris Rosser video for my props size (1.6 inches)
3) I am using a different battery: usually I fly the suggested 3s 450mAh, today I tried a 3s 550mAh from Tattu R-Line, but this should not have any impact as it's a 3s and the weight is less than 1 gr more than the standard batteries.

I am starting now another troubleshooting adventure, any ideas to guide me would be highly appreciated!

The minor “bump into the ceiling” may have caused a “physical” condition and why your issue..
Plug it into betaflight, add a lipo and hold the quad down and slightly ramp up each motor individually.. you will hear and FEEL a difference .. this will help isolate where it is..
No amount of tuning will “fix” physical problems.. if it does .. the results are short lived

a quad with motor heat issue holded to the bench might just fry a motor or esc. that test doesnt help, so much other things to check.... never any bench tests with props on, its destroying not troubleshooting. motors needs to be tested in a flight situation or without rotors.

did you switch rotors?
if you use it like iflight does, the push on props goes bad in crashes and can slip than.
start there if you didnt already.

check for bended motorshafts, hairs in the motor...
loosen things, motorscrews, boaedmount...
if you cant find anything, my test would be an additional external condensator; a rubycon 25v 220uf
that would help against noise in the system, i would personaly add one anyway to protect and increase performance and handling. 3s on such small rotors and weight might gain benefits by a condensator.
check the frame stiffness, any cracked part? other vibration sources

550mah tattu fresh could be a difference about power, not because of the weight difference.


if you did smell cooking motor, there is still some damage for sure, but it can maybe fly well as befor.
to much cooking will result in a burned motor overtime.

(29-Feb-2024, 11:02 PM)Rob Axel Wrote: The minor “bump into the ceiling” may have caused a “physical” condition and why your issue..
 Plug it into betaflight, add a lipo and hold the quad down and slightly ramp up each motor individually.. you will hear and FEEL a difference .. this will help isolate where it is..
 No amount of tuning will “fix” physical problems.. if it does .. the results are short lived

Thanks, the issue was for sure on all motors, not only one. All of them were super hot.

(01-Mar-2024, 12:31 AM)hugnosed_bat Wrote: a quad with motor heat issue holded to the bench might just fry a motor or esc. that test doesnt help, so much other things to check.... never any bench tests with props on, its destroying not troubleshooting. motors needs to be tested in a flight situation or without rotors.

did you switch rotors?
if you use it like iflight does, the push on props goes bad in crashes and can slip than.
start there if you didnt already.

check for bended motorshafts, hairs in the motor...
loosen things, motorscrews, boaedmount...
if you cant find anything, my test would be an additional external condensator; a rubycon 25v 220uf
that would help against noise in the system, i would personaly add one anyway to protect and increase performance and handling. 3s on such small rotors and weight might gain benefits by a condensator.
check the frame stiffness, any cracked part? other vibration sources

550mah tattu fresh could be a difference about power, not because of the weight difference.


if you did smell cooking motor, there is still some damage for sure, but it can maybe fly well as befor.
to much cooking will result in a burned motor overtime.

Thanks.
I did not switch rotors and props are mounted with 2 screws, not push-on.
Motor axes are fine and no dirt/debris on them. Actually, the motors are brand new with only a few hours of flight on them.
The frame is intact, as I said the bump was really minor, I really don't think it's a mechanical issue, but than again, I learned in FPV to NEVER assume anything!

Why do you say that "550mah tattu fresh could be a difference about power"? voltage is still the same and so must be power, right?

"if you did smell cooking motor, there is still some damage for sure" that's what hurts the most, and the fear of flying a crippled quad without even knowing it's not performing well, because I don't have the experience. This is really frustrating especially because motors are new!

Anyhow, yesterday I did another 3 flights with my standard batteries and no issue appeared, no overheating and apparently the quad was in very good shape. very responsive, fast and I did over 4.5 mins with a 450mAh battery.

voltage is one part, the otherside is ampdraw together it gives the true energy: watts
if a battery does perform better, it does deliver as much as requested, it can result very different in response and topend and can result different.

its also that one bad motor can give a crazy job for tve whole system which can result in motorheat on all motors.

i would suggest to add a cap and see if it doesnt come back than.
personal i would try if powerdifference can be the issue, if so; adjust pids and firlters.

aa you told you did follow suggestions, did you adjust the filters?
you can increase filtering, to hide motorheat

(01-Mar-2024, 09:29 AM)hugnosed_bat Wrote: voltage is one part, the otherside is ampdraw together it gives the true energy: watts
if a battery does perform better, it does deliver as much as requested, it can result very different in response and topend and can result different.

its also that one bad motor can give a crazy job for tve whole system which can result in motorheat on all motors.

i would suggest to add a cap and see if it doesnt come back than.
personal i would try if powerdifference can be the issue, if so; adjust pids and firlters.

aa you told you did follow suggestions, did you adjust the filters?
you can increase filtering, to hide motorheat

I see your point on the batteries, indeed they are 95C vs 75C of the standard ones, which means a higher peak of current in manouvers like recovering from a ceiling bump to avoid crashing is very possible.
I think I will give a go to the idea of adding a cap, but I have never done that so I will have to do some research before firing up the soldering iron.

Regarding the filters, I am really a total noob here, I have no idea where to start from....
I just understood that if there is a filtering problem I could analyze it from the blackbox results, but again, I don't know how to do that. I downloaded the software to analyze the files but once opened I don't know what to do...

i would start by the condensator, it might solve all.

just about undersranding, our liops does sag in voltage because they doesnt like to provide as much as requested. lower voltage does result in less energy, watt, even on the same current. a less saging lipo can provide much more energy just by keeping a higher voltage.
the lipo doesnt decide, its the motor request only does determinate, but a lipo can follow the request or just suffer by sagging.
for the more energy, pid adjustements and filters could be an issue.

generaly that alpha seems pretty full loaded for the rotorsize, alot of rpms on that small props needed to even liftoff. the ability for more performance on that weight and power could be the issue either.

(01-Mar-2024, 11:21 PM)hugnosed_bat Wrote: i would start by the condensator, it might solve all.

just about undersranding, our liops does sag in voltage because they doesnt like to provide as much as requested. lower voltage does result in less energy, watt, even on the same current. a less saging lipo can provide much more energy just by keeping a higher voltage.
the lipo doesnt decide, its the motor request only does determinate, but a lipo can follow the request or just suffer by sagging.  
for the more energy, pid adjustements and filters could be an issue.

generaly that alpha seems pretty full loaded for the rotorsize, alot of rpms on that small props needed to even liftoff. the ability for more performance on that weight and power could be the issue either.

I finally got it on video, HERE!

I hope someone can tell me what the hell this is.
After this noise starts, the motors (all 4 of them) get cooking hot.

Now that I think about it, I have updated the ESC software from Bluejay 0.16 to 0.19, not sure if something happened there...

check if 1s is enabled or 2s+
that would give a wrong startup power

maybe do a backup and just try bf defaults, chris suggestions need caution. rotorsize is just one part, his suggestion might be for common 1.6inch on 2s batteries. anyway i believe his suggestions goes often incomplete or wrong by try to make it as simple as possible.
tuning is huge, there isnt such simple solution for a beginner.

some might know where that comes from, past analog aera xD "dont follow us, go out and fly"

(03-Mar-2024, 12:55 AM)hugnosed_bat Wrote: check if 1s is enabled or 2s+
that would give a wrong startup power

maybe do a backup and just try bf defaults, chris suggestions need caution. rotorsize is just one part, his suggestion might be for common 1.6inch on 2s batteries. anyway i believe his suggestions goes often incomplete or wrong by try to make it as simple as possible.
tuning is huge, there isnt such simple solution for a beginner.

some might know where that comes from, past analog aera xD "dont follow us, go out and fly"

Thanks for your reply and I agree, tuning is a necessary suffering, which pushes all of us to learn and there is no shortcut.


I reverted back to the original configuration out of the box (BetaFlight 4.3) with the exact configuration which I had saved before doing any changes.

Unfortunately even with dynamic idle deactivated and everything as standard, the motors randomly start sounding weird and get super hot. I am quite disappointed.
I wrote to iFlight support today, let's see what they say.

sad, it seems a hardware issue, hopefully you get luck with iflight support.

you could check the gyro signal in betaflight configurator (and additionly the rc signal)

A very easy experiment is to increase the rpm filtering a little.  In BF in the PID Tuning menu, select the rpm filtering tab on the right.  Move both sliders a little to the left to increase rpm filtering.  Try going from 1.0 to 0.8.  That has fixed a similar problem I had with a 2S build.  Don't touch any other PID settings.

If it does not solve the problem, it is easy to simply return the sliders back to 1.0.  Not complicated.

Yes, if the motor is untouchably hot, it could be trying to jump back and forth from the ESC control pulses.  Adding some rpm filtering, as mentioned here, would be a really easy test, reversible if it doesn't solve the problem.

Thanks for your replies guys, the problem is not yet solved.
I shipped the drone back to iFlight in Europe, let’s see how it goes.

I’m not sure really what to expect, if it was a hardware issue it would probably always there. Conversely, it is not. The engines (all together) suddenly snap into this weird, noisy and vibrating spinning mode and it would stop only power cycling the drone.
Some times, if the motors are too hot, even power cycling would not bring the motors back to their normal rotation.

Let’s see what they say.