Noticed today after a 10km ride my 6485 138Kv motors are pretty hot to the touch, shouldn’t the milled radial vents and the mesh suck air through to keep them cool? I’m running 15A per motor on 18s with a 5:1 ratio in 8" tires.
Can I do something to keep them from overheating this summer? Besides only riding on cold days?
What were the temps?
Voyage tells me 47-48 degrees but they felt closer to 60 or 70
I know Reacher datasheet says they can handle up to 100C but this being my first motors with cooling, I kinda thought they’d run cooler.
I’m used to flipskys being this hot when I ride but I figured these wouldn’t be so hot.
Maybe I’m just freaking out over nothing.
Here’s the ride: May 30, 2025 - metr.at | 16akO
Did you adjust the beta value to 3950k?
Sorry ya lost me there… In vesctool? I usually don’t touch temp sensor stuff.
Yes, thermister will give the wrong temperature value if the beta value isn’t correct. The default thermister value in vesc tool doesnt match the correct beta value for reachers.
@janpom is there a way to apply this thermal modification to previously uploaded Voyage records? I never realized I had this value wrong the entire time.
Seems like it’s sorted. They definitely felt like 55 degrees after this ride.
Poke two holes in a bottle of water and hold it behind you.
Hilarious but I bet that would actually work lol
It can. I had a system with wet rags for cooling when i would go overtemp and have to stop.
55C is nothing haha. As they get hotter the cooling fan becomes more efficient. Usually pretty quick to get to 50-60 and a lot slower to get to 85+
Having acceleration temperature decrease settings at 100/115C helps you get to 100C without early throttling
So I shouldn’t have to worry too much about ambient heat then? It’ll get up to 45C some days in the summer here
Cooling efficiency increases with temperature difference. But electrical resistance and losses also increase with heat so they do get hot with hotter ambient temps.
Just keep an eye on temps and if you’re getting thermal throttle before the motors reach 95-100C you need to tweak settings to ensure you’re not leaving performance on the table.
Not sure if you can modify the records in the voyage cloud, but if you wanted to know the temperatures, the math is pretty easy.
multiply the temperature by the old beta value, then divide by the new beta value
Which setting would one tweak?
Motor temp cutoff start and end, and some people like acceleration temperature decrease below the default 15% although it works fine for me.
I have Reacher motors (Reacher 6385 V6.0 N45SH Brushless ESK8 Motor 48V 5000W KV245 Hall Sensor 12N14P Electric Skateboard BLDC High Power Belt) and FW 6.05 doesn’t let you use value 3950 K As Beta Value for Motor Themistor 
Choosing NTC Custom as Motor Temperature Sensor Type can’t fix this issue…
In VESC Parameter Editor, 3950 doesn’t appear out of limits.
I see the magnets are n45sh. They can go to 150c before irreversible damage
The wire is often rated 200c or 180c meaning it’s supposed to be able to do that temp for 30,000 hours and u can extrapolate from that
This is a blatant oversimplification.
The coils are “rated” to 220C, but in practice that isn’t the limiting factor. We previously used 170C enamel and were eventually cooking stators from repeated heat cycles despite the sensor probe that’s glued to the coils staying under 90C.
There are always local hot spots that can degrade the enamel despite the temp sensor reading in the safe zone.
Magnet ratings also don’t show the full picture.
Just because a magnet is “rated” to a certain temperature, that doesn’t mean it will happily run up to that temperature.
Field strength decreases with temperature (higher temp rating retains field strength at higher temps), and results in reduction of torque.
Running magnets closer to their temp rating also makes them more susceptible to permanent demagnetisation from vibration.
And often in reality the various adhesives used in the motor are the limiting factor for running motors hotter than 100C, but you get diminishing returns due to magnet field strength dropping and coil resistance increasing and causing even more heat.
