How to hand-test a BLDC motor [SERIOUS]

Sometimes if you’re buying used, or troubleshooting, and need a quick way to see if anything might be wrong, you can test a BLDC motor with only your hands. It’s not the most accurate test in the world, but catches most problems.

  1. Ensure motor phase wires are not connected to an ESC or anything else.
  2. Verify the motor spins without grinding or rubbing. Put a tad of sideways stress on the shaft and push it and pull it (while turning) to verify it feels smooth.
  3. connect phase A to phase B and verify by hand-spinning that there are moderate choppy brakes
  4. connect phase A to phase C and verify by hand-spinning that there are moderate choppy brakes
  5. connect phase B to phase C and verify by hand-spinning that there are moderate choppy brakes
  6. connect phase A to phase B to phase C and verify by hand-spinning that there are strong smooth brakes
  7. the first 3 should all feel exactly the same strength (important)
  8. verify with A, B, and C disconnected that there are no brakes

This quick hand test can weed out most major motor problems quickly.

If you’re having a problem you’re trying to diagnose, this test can also quickly tell you if the problem you’re having might be in the ESC or wheel drive assembly instead of inside the motor.


For further testing, check this article


how to check a motor
how to test a motor
hand test
motor troubleshooting

81 Likes
Archived: the OG noob question thread! :grinning:
Blown Focbox .. ( was Help diagnose cutouts. Dual focbox | can bus | 6384 maytech/lacroix motors | flipshit vx1 | metr logs )
One Motor Not Spinning After Successful Motor Setup
FSESC Failure, Motors smoke
Motor Locked up
Noob question thread! 2020_Summer
ESC getting really hot
Help identifying problem
[SOLVED...?] Weird issue, please aide
Noob question thread! 2020_Summer
Flux linkage fail.
Stormcore 100D Repair Help
Flipsky Mini FSESC4.20 DRV FAULT
Hulk Shorty | TB 6380 | DIY FB Enclosure | Maker X mini FOC plus ESC | 12s3p 40T |
Noob question thread! 2020_Summer
Help! Trampa HD-60T Vesc broke upon set up ( Motor Detection )
Flipsky 6384 (battle hardened) high resistance?
Noob question thread! 2020_Summer
How to test my new motor
Torqueboards customer service?
Assembling a BLDC motor [serious]
Noob question thread! 2020_Summer
TorqueBoards Direct Drive Motor Kit
Noob question thread! 2020_Summer
Motor not spinning freely, feels like its constantly slightly braking
Torqueboards customer service?
Noob question thread! 2020_Summer
Need Help. Motor not spinning and high pitched noise. Vesc possibly fried
HELP DIAGNOSE BATTERY DRAIN | 10S6P | FLIPSHIT VESC 6.6 DUAL | FLIPSKY 6374 190KV MOTORS | GENERIC REMOTE
Noob question thread! 2020_Summer
Help this user sort his TB DD issue
Torqueboards customer service?
Noob question thread! 2020_Summer
Noob question thread! 2020_Summer
ESCapes shitting the bed? Could be a motor problem. In progress
Noob question thread! 2020_Summer
Baby Monster Range Haya 83 build
Archived: the OG noob question thread! :grinning:
Archived: the OG noob question thread! :grinning:
Archived: the OG noob question thread! :grinning:
Maker-X Go-FOC DV4 (upgraded version) ----- Most Affordable Dual Drive ESC
WTF did I break now (help)
First build! | New to esk8 | Parts check
DarkMatter Motor Follow-up
What's wrong with this motor?
Archived: the OG noob question thread! :grinning:
Flux linkage detection failed (Motor detection)
Archived: the OG noob question thread! :grinning:
Archived: the OG noob question thread! :grinning:
Archived: the OG noob question thread! :grinning:
Archived: the OG noob question thread! :grinning:
FSESC Failure, Motors smoke
Archived: the OG noob question thread! :grinning:
Archived: the OG noob question thread! :grinning:
Motor coming loose
setting up p42a 12s4p on stormcore 60d+
Archived: the OG noob question thread! :grinning:
Archived: the OG noob question thread! :grinning:
Archived: the OG noob question thread! :grinning:
Archived: the OG noob question thread! :grinning:
Archived: the OG noob question thread! :grinning:
Archived: the OG noob question thread! :grinning:
Archived: the OG noob question thread! :grinning:
Archived: the OG noob question thread! :grinning:
Flipsky 6384 seized motors
Motor issues- help!!
Motor not spinning anymore
Noob question thread! 2020_Summer
Can somone fix broken Focbox Tanka
VESC/Motor Screech
Focbox Unity burned out twice

Awesome, @b264 thank you for putting this up. The magic of this test must somehow be related to the magic of “It dosen’t matter how you plug in the phase wires, except if it goes backward, switch any two connections”

I can’t wrap my peanut brain around why it works ,but it does.

4 Likes

Great write up… #article-requests @BillGordon?

2 Likes

I’ve tried to entice Brian before with promises of money and fame. I’ll be happy to work with him on any write-ups he’s interested in putting together.

7 Likes

Wow, six and a half months with 40 likes and no replies, I thought this was the biggest mic drop of all time but wasn’t going to say anything lest I prod comments. But now that it’s been broken I can speak :rofl:

9 Likes

Be proud and be loud.

5 Likes

very good post

4 Likes

@Full-send do this

1 Like

Roger that. Will give it a go when I get home. Thank you sir!

Searched for “how to check a motor” didn’t find this thread. adding kw. “how to test a motor” did find this thread.

4 Likes

Search keywords added :+1:

1 Like

Mirroring this content here in case that site goes down later

2 Likes

It’s because you reverse the direction of the rotating magnetic field. With three phases 120 degrees mechanically and electrically separated if you write out the phasors by hand and solve for the B field you’ll see that one is a sin + cos and one is a sin - cos meaning it gets reversed.

3 Likes

aint nobody understood a word

2 Likes