Why Mini Quad Motors Getting too Hot?

by Oscar

Are the motors on your mini quad getting very hot after flight and you are wondering what’s causing it? Here are some tips to troubleshoot motor overheating issues.

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Why is Hot Motor a Bad Thing?

  • Motor can burn! When the motor gets too hot, the coating on the winding can melt and cause electrical shorts, smoke + permanent damage to the motor
  • Motor performance will decrease faster over time as the magnets lose magnetic strength because of overheat; Some types of magnet might have higher heat resistance than others
  • Energy is wasted as heat, leads to shorter flight time

How Hot is Too Hot?

It’s normal that motors on a mini quad get warm after a flight, because they can spin up to a few hundreds times per second. But you might have a problem if they get too hot.

So how hot is too hot?

An easy way to tell is to pinch the motor by the bell with your fingertips, ideally right after landing. If you can hold your fingers there for more than 10 seconds comfortably, then it’s fine. If it’s too hot to hold, then it’s definitely a sign of overheating motor.

The Causes of Hot Motors

Your motors will get hot after some aggressive flying. To properly diagnose the issue you should fly slowly – 40% to 70% throttle is a good range, and one or two flips and rolls here and there are fine.

Motor Bolts Too Long

With hot motors, the very first thing I’d check would be if your motor screws are touching the windings.

PID Tuning and Filter Settings

PID and Filter tuning in Betaflight can be a rabbit hole. If you are getting hot motors after changing PID and filter settings in Betaflight, you should reset these settings back to default.

Default settings in Betaflight is known to be conservative and generally pretty good to avoid oscillations and hot motors. Once you’ve made sure you don’t get hot motors anymore, you can start tuning it more aggressively, one setting at a time. Common things to pay attention to are:

If you are still getting hot motors with default PID and filter settings, then that’s an indication that the problem might be mechanical.

Something might be wrong with hardware, keep reading for more tips on troubleshooting.

Mechanical Problem?

Maybe something isn’t done properly with the build.

  • Make sure all the screws are tight (frame and motors)
  • Are all the arms stiff and rigid?
  • FC is installed snugly and doesn’t move (nylon screws and standoffs in the stack)

FC Soft-Mounting

If you are not soft-mounting the FC, then you should! As long as you are soft mounting the FC properly, you don’t need to worry about soft mounting the motors.

Adding More Capacitors!

Adding extra capacitors to the ESC power or XT60 pads, will help reduce the amount of noise in your power. Thus reducing the noise in the gyro data too!

Center of Gravity

If two of the motors are hotter than the others, it could be caused by unbalanced weight distribution. If your quad is front heavy, or tail heavy, two of the motors will have to work harder and therefore get hotter. Make sure the COG is right in the center for the best possible performance.

Motor or Propeller Jammed

Make sure the propellers are not hitting anything on your frame (battery strap, zip tie, standoffs etc), and that the motors are not getting jammed by dirt or grass… If this is the case you should usually hear it when the motors are spinning.

Also make sure the props are not bent. It’s quite hard to tell visually sometimes, change them out if in doubt.

Faulty Motor?

It’s possible that you have one or multiple faulty motors. Maybe the bearing is bad, or the motor bell is scraping the stator due to bent shaft, or a unbalanced motor bell…

If you have one motor that is hotter than the rest, and nothing mentioned above helped, try swapping around the problematic motor with a fine motor on the same quad, see if that’s still the issue with that motor.

It’s Too Hot Outside?

Take into account the ambient temperature outside, your motors will have a harder to time to cool down on a hot day. Black motors will be affected even more when you are flying under the sun.

If this is the case, try again under the shade or in the evening.

Conclusion

These are probably the most common reasons for hot motors in a mini quad. If nothing above helped, you can try to get some help from our forum: IntoFPV.com

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14 comments

A khan 25th November 2022 - 7:40 pm

What is the basis of pwm output generation which gets fed into the esc to control motors on a quadcopter ? i am trying to build a custom 4 in 1 ESC which can be used for flying quadcopters with various open source autopilot projects like Ardupilot, PX4 and INAV.

But running into some issues where to hover the quadcopter stably at one point, 1 or 2 ESCs needs more pwm value as compared to the rest of 2-3 ESCs due to which 1-2 motors are getting hot to very high temperatures. We have identified this behaviour from the autopilot logs. It’s not a build and tuning issue because we have tested the same setup with mamba 4 in 1 esc, on which everything is working very well. The issue is related to the custom 4 in 1 ESC which we are trying to build.

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Kristian Snjegota 8th October 2021 - 12:16 am

Hi, I have brand new build and I’m having a problem with my motors all four are getting hot from just hovering, I have a diatone taycan mxc 6s tmotor 1507 2700kv with tmotor t76 props tri-blade. Tried dshot 300 and 600 also on default tune. Any ideas what it could be? Cheers

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Ayaskanta Jena 16th June 2021 - 8:57 am

i m getting all hot motors in my 85x build having 1103 motors 8000kv runing on 3s . Tried out all shots of troubleshooting but didnt worked out . still getting hot motors after every flight . the filtering values are default and the screws are not touching any of the windings . Any idea how to resolve the issue ??

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Oscar 17th June 2021 - 2:39 pm

KV sounds a bit high for 3S already. I am using 5500KV on quad-blade.
Maybe you can try using lighter props.

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Kade 21st December 2020 - 9:55 pm

Hi Oscar,
I have a custom Tbs source one build with emax eco motors and there is nothing mechanically wrong (using your troubleshooting methods) but the motors ALWAYS come back burning (not burnt out but really hot). I reckon it is either the filter settings (not pids because d term was low) or its just me ripping too hard. Please help

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Oscar 11th January 2021 - 3:30 pm

Without blackbox log it’s hard to know.
You can however try easing the filter values, lowering PID values and see if any of these make a difference.

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Robert Griffith 16th November 2020 - 2:17 am

Nov.15. 2020
I’m new to FPV just getting smooth in flying
On my Eachine Cvatar 4s Cinewhoop the number 4 motor left front smoked and I think the esc has likely gone away as well.
Is there a motor(s) temperature probe sensor which can show the hot motor or provide an alert on the OSD or some other manner?
Kindest Regards,
Bob Griffith
Winter Haven, Fl

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Ryan 24th May 2020 - 12:48 am

Hey Oscar, thanks for all the great info! I burnt out a motor on my naked gopro rig the other day because of airmode. After replacing the motor (1204-5000kv) with a new one. The drone flies, but the new motor comes back warmer than the rest and seems to lag slightly on startup. I’m using a 20A AIO whoop board, do you think one of the esc’s is starting to fail? Or maybe i just got a bad motor?

Thanks again!

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Oscar 3rd June 2020 - 12:55 am

Sounds like the ESC might be giving out due to the motor failure last time? You can try swapping the two motors and see if the same happens.

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Rajeev Gopal 3rd April 2020 - 6:19 pm

Hi Oscar my new cinewhoop build with bumblebee frame with Hglrc F428 geprc 1408 3500kv mot. It weigh about 600g.

From first flight irself my motors are getting very hot cant even hold for 10sec. Now i used jesc firmware to flash blheli_S esc and running rpm filter. The quad flyes so smooth now but still i have hot motors. I checked the motor screws its not short. Dont know whats wrong. Is it because quad is heavy that the motors cant take the load. Can i fly like this. I have flown about 15 times now. Iam worried abt the motors burning. Need your help sir.

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Oscar 14th May 2019 - 4:00 pm

Hi Oscar,

Few days ago I fried a motor after having insisted too much for take-off. One of the prop was stuck in the grass and I applied full power. The coating of the winding burnt, and after un-plugging the battery and pluging it again, the esc fried because of a supposedly short circuit in the motor winding.
Is it normal that the esc didn’t protect from overcurrent or jammed motor? I thought esc has this kind of protection.
Thanks for your input,

Oscar

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Francois 10th May 2019 - 2:10 am

I am not a pro. But i think one of the strand (assuming it’ a multistrand winding on each phase not one solid core) had a short and fuse out. So the remaining (let say two strands) are keeping the motor up and running. Maybe you will not see the end of it. Or maybe you will need to learn the beauty of making your own coils.

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Jae 6th May 2019 - 6:47 pm

Hi Oscar,
While testing motors without props, one motor got very hot and I saw smoke. I think coating or something burnt. But after then, motor works OK with props (just warm, no smoke any more). I hovered more than 5 minutes, and it looks good.
Would it be OK to continue using that motor? Is there any possibility that motor fails during flight?
Thanks.

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Oscar 13th May 2019 - 2:34 pm

For practice, yea, but I would not trust it’s reliability though. Just don’t do any risky thing with it :) Like flying over water or tall trees :)
Keep an eye on temperature of that motor too.

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