Motor Temperature Instability - Interference or Flaky Sensor?

Back story

I am running 6374 Haggy 170 KV motors on a Flipsky FSESC dual 6.6 (non-pro model). I have used the same VESC and 12S4P 20700B battery with a pair of 190 KV motors for about 120 miles with no issues. Those motors are waiting for new bearings and a bit of hardening…

The issue

With one of these motors, temperature readings spike randomly all over the place under load (think 60C to suddenly 120C). I remember that @longhairedboy talked about interference from the phase wires quite some time ago and I have not ruled this out completely. What is really strange, however, is that this does not happen at the beginning of a ride. I monitor with Bluetooth and everything is stable even when I pop the throttle. Once the motors reach about 145 F (62 C) I start to feel thermal cutoff. Monitoring reveals huge fluctuations even under no load when I give it high throttle input.


Random thermal cutoff on one wheel = bad. Who else has dealt with this, and is it possible that I have a flaky temp sensor? Or do I have terrible interference that I don’t seem to be able to mitigate? I’m curious how others have tackled this with cable routing and shielding.

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I just dealt with exactly this. I had simplify 6.6s, then bought a new mini dual 6.6. Same problem. Swapped out the motor and problem solved. You can disable motor temp throttling in the vesc tool, or unpin the white wire on your motor sensor wire. For me I would get thermal throttle at 85c but the motor was barely warm to the touch. So I know it was a sensor problem. I used traction control on my dual setup, so when 1 motor would thermal throttle, both would.

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Would fist check all connections and maybe open the motor to have a look at the temp sensor. if there is noting easy to find,
just disconnect the cable from the faulty temp sensor and you good to go,

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How actually hot are the motors? Touch will usually tell you. Sensors can be a curse.

I for one would never rely on a temp sensor for my ability to not streetface.
Hall sensors are fine but your motors can endure a hell of a lot more than the sensors tell you so cut that wire and carry on.

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Here you go. You were having the exact same issue.

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They couldn’t be more than 150… the reading seemed accurate while the board is it moving.

I absolutely agree and temporarily set cutoff to ridiculously high values. I would still like to have monitoring, but this doesn’t instill much confidence in cutoff.

I did this and it worked, my cut offs are at 190 and 210. But it still happens, so I’m going to disconnect temp sensor. In the mean time what I do when I notice it start to cut off, I rewrite my configuration using metr and it usualy resets and everything and works fine

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Here is an example of noise-free data on the Eskate Enterprise:

Motor temperature is very stable (more so than the FSESC temp) even under high current load. In this case, I have no problem using a gradual motor temperature cutoff.

Here are the minimum and maximum readings on a nearly identical build with different motors:

Testing complete - my issue was simply interference from the phase wires. Some motors are just wayyy more susceptible to interference than others.

Essentially I had to route the sensor wires along a different path just after they leave the motor. I’ve always been cognizant of interference… but this build was really a challenge.