Is it normal that my cordless motor gets really hot within second with a 4000 mAh 3.7 V battery

Thread Starter

Omgil877

Joined Oct 7, 2018
7
I bought this small cordless motor for drones that is rated at 3.7 V and has an rpm of 48,000. I want to make a small centrifugal fan, so I made an impeller 55 mm wide with 16 blades. When I connected the motor to this lithium-Ion 18650 battery (4000 mah 3.7 v) it started to heat up pretty fast and I had to let go because it was too hot to hold. I bought a 40 ohm 1/2 in resistor and connect it and it moved very slowly. So I was wondering is it normal for the motor to heat up to a high temperature and if it's not what kind of resistor should I buy with wat resistance for the motor or what should I do in general.

https://www.ebay.com/itm/2-X-3-7V-4...e=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649
 

dendad

Joined Feb 20, 2016
3,885
That fan blade you printed looks way to big for the motor in my opinion. That is a pretty small motor. It may be just a case of overloading it.
Also, you probably need airflow past the motor to cool it.
 

oz93666

Joined Sep 7, 2010
737
This is a coreless motor ... not cordless ...perhaps someone here knows what that is , save me searching it ....

It is designed for the prop provided , connecting this motor to your centrifugal fan it will never reach the rated revs , perhaps only few thousand RMP .... ... as a result there will be very little back EMF ... so very high current .. it should soon burn out ...

If your fan was to reach 48K RPM I'd be willing to bet the fan would destroy itself , break apart from centrifugal forces..

What are you trying to achieve by this??

I'd be interested to know how much thrust this can generate when connected to the prop supplied, power consumption and mass of motor and prop...

Let me have a guess at what a coreless motor might be ...Could it be a motor without a (metal) core??? .... small motors like these usually have laminated metal cores , but at such high revs the magnetic field is switching very quickly , eddy current losses would be very high , so better without a core ... but then why not a ferrite core???
 
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Wolframore

Joined Jan 21, 2019
2,317
Coreless motors have the windings around the shell while removing the iron core and having magnet in the core. Coreless has a few advantages including lower inductance, easier to filter noise and lower inertial weight, less magnetic drag and more torque to weight and size. They make larger versions that have higher torque rating. Check the current your motor draws. That motor is designed for 70mA. Stall current is 950mA. If the motor is getting hot it’s because it’s generating more heat than motion. As stated above you need a bigger motor. Check the weight difference of the prop vs the impeller. It gets even worse if you try to vary the speed.

That looks like a turbine fan from thingiverse and if you want high RPM check MAXON who make large Coreless motors.

The motor part number is BY0612-Q these are designed for “toys”. Your motor is likely the same or similar.

2F17738D-3DE7-4D82-B396-941EE58C82D5.jpeg
 
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Thread Starter

Omgil877

Joined Oct 7, 2018
7
Coreless motors have the windings around the shell while removing the iron core and having magnet in the core. Coreless has a few advantages including lower inductance, easier to filter noise and lower inertial weight, less magnetic drag and more torque to weight and size. They make larger versions that have higher torque rating. Check the current your motor draws. That motor is designed for 70mA. Stall current is 950mA. If the motor is getting hot it’s because it’s generating more heat than motion. As stated above you need a bigger motor. Check the weight difference of the prop vs the impeller. It gets even worse if you try to vary the speed.

That looks like a turbine fan from thingiverse and if you want high RPM check MAXON who make large Coreless motors.

The motor part number is BY0612-Q these are designed for “toys”. Your motor is likely the same or similar.

View attachment 182154
Thank you so much this is soo useful!!
 
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