Simple "temperature cutoff" for hub motor with thermostat

[nikolay]

I installed very basic and simple "somewhat" temperature control. I initially wanted to have a thermistor but on this motor is difficult to install extra wire and I didn't wanted to reuse the speedo hall cable since I want to have the speed all the time. Then I come to the idea to use the thermostat to cut the speedometer hall. I bought the smallest thermal switch for 90 degC which can fit: https://uk.farnell.com/microtherm/t11a09005u112l310100/thermal-switch-nc-250vac/dp/2428740?CMP=i-ddd7-00001003 and sticked it with epoxy to the windinds. Now when the windings reach about 90degC I will lost the speed on the display. It's not ideal but it is some protection...

 

[qwerkus]

I installed very basic and simple "somewhat" temperature control. I initially wanted to have a thermistor but on this motor is difficult to install extra wire and I didn't wanted to reuse the speedo hall cable since I want to have the speed all the time. Then I come to the idea to use the thermostat to cut the speedometer hall. I bought the smallest thermal switch for 90 degC which can fit: https://uk.farnell.com/microtherm/t11a09005u112l310100/thermal-switch-nc-250vac/dp/2428740?CMP=i-ddd7-00001003 and sticked it with epoxy to the windinds. Now when the windings reach about 90degC I will lost the speed on the display. It's not ideal but it is some protection...

Nicely done! Though I don't see how shutting down the speed signal effectively shuts down the motor. That probably depends on the controller you have and what securities it has built in. My cheap Kt controller works even without speed signal...
Also, why 90°C ? Most hubs can do 120 without any problems in my experience. Hall sensors usually die at 140-150°C and nylong gears melt a bit later, like 180-200°C depends on what compound was used.

 

[nikolay]

It does not cut anything, I just know that the windings are at 90 degrees and it's getting hot. It's real data, not like touching the outer casing with fingers. For the temperature selection I read a lot and I think you should not go much more than 90 degC for a geared motor if you want reliability. I guess the windings can take more heat but then if that heat transfer to the nylon gears they start to soften even at 70-80 degrees C. Of course this is only when you pull it on longer hills, my regular commute is mostly flat with some longer ascends of 2% average so not a big deal. I need mostly speed on flats and easy hills...

 

[qwerkus]

It does not cut anything, I just know that the windings are at 90 degrees and it's getting hot. It's real data, not like touching the outer casing with fingers.

LOL - like a disappearing warning signal - then 90°C make sense, since the motor doesn t start throttling. Smart indeed. Did you have any problem closing the hub shell again ?

 

[nikolay]

No problem closing it, just found a place on the windings where it it stays as much lower as possible, also a bit angled. Put the shell without gluing it to verify and opened again to glue it. This switch is relatively thick - like 6mm, but I couldn't find anything smaller.