T-Motor F40 2500kv review – Part II

In Part II of my F40 motor review I am going to share the results from the thrust tests, as well as some pictures of the inner side of the T-Motor. Sadly my sample motor burned during the tests and I haven’t managed to finish all I have planned.

The first test was with the pretty new KISS24A ESC and HQ5045 propeller on 4S. As always I am using a MultiStar 16.000mAh 10C battery, which is capable of safely providing a constant of 160A.

KISS24A – HQ5×4.5 propeller – 4S 16.000mAh 10C Multistar

  50% Throttle 364g thrust   5.04A current
100% Throttle 994g thrust 26.09A current

Response to throttle is great. I got not a single sync issue, even the F40 is 2500kv motor, while rapidly changing throttle. The motor stays warm at about 50°C after 30sec on 70% throttle, which is absolutely fine for static thrust test.

Then I decided to test the motor with another popular ESC – the LittleBee 20A with BLHeli firmware. Here are the results with same HQ5045 prop and 4S LiPo battery.

LittleBee 20A – HQ5×4.5 propeller – 4S 16.000mAh 10C Multistar

  50% Throttle 406g thrust   6.34A current
100% Throttle 971g thrust 25.78A current


I wanted to test for sync issues with this ESC and sadly got these, while changing the throttle fast in the low 20% range. The result: smoke and burned ESC + motor. I am not sure if the problem is because of the LittleBee ESC, but probably because of the BLHeli firmware. I think it is because of the “Active Braking” feature. I can confirm similar behavior with another BLHeli ESC with “Damped Light” enabled. This test is not representative for sync problems, because it is really hard for the ESC to response to actively braking to 0% Throttle, ms later to 20% and then again to 0%. Even the fast KISS24A had some problems responding so fast to my throttle change in that range.

I decided to open the dameged motor and make some pictures of its inner side. It’s hard to see the damaged windings, but I couldn’t make a closer picture with my current equipment.


I took another one of the F40 2500kv motors, soldered the gold connectors and prepared the thrust stand again for my tests. I used the XRotor 15A ESC for the test, which I think is identical to the T-Motor Air 15A ESC. Here are the new results:

XRotor 15A – HQ5×4.5 propeller – 4S 16.000mAh 10C Multistar

  50% Throttle 340g thrust   5.20A current
100% Throttle 954g thrust 24.83A current


XRotor 15A – KingKong 5×4 propeller – 4S 16.000mAh 10C Multistar

  50% Throttle 315g thrust   5.38A current
100% Throttle 1006g thrust 26.14A current


It was a surprise for me, that I got more thrust with my new KingKong 5×4 propeller, but this is the case :-). Then I made a test with 6×4 propeller for those of you flying on 3S LiPo.

XRotor 15A – KingKong 6×4 propeller – 3S 2.200mAh 45-90C Nano-Tech

  50% Throttle 303g thrust   5.40A current
100% Throttle 852g thrust 24.41A current


And lastly I wanted to try the F40 2500kv on a 6S LiPo. I only tested it on 50% throttle, because I didn’t want to damage another one motor.

XRotor 15A – HQ5×4.5 propeller – 6S 1.300mAh 45-90C Nano-Tech

  50% Throttle 635g thrust   9.13A current
100% Throttle –   g thrust     –   A current



The F40 2500kv have provided 1kg of static thrust with a 5” propeller, which is awesome. It is definitely due to the high 2500kv, but this could be a problem for some ESCs too. Overall I am very happy with the F40 2500kv T-Motor and will make another build log as soon as I get one spare motor.

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