fitting NTC thermistor to hub motor

Just had a pile of new thermistors arrive to fit in my motor..but how to do it?

I see the ones from e-bike.ca seem to have been dipped after wiring, where as these bare ones look very delicate.


The plan was solder up to the 30 gauge wires, heat shrink each wire, then one piece of heat shrink over the top.

and cable tie to the stator, near the coils at the top of the motor.

But what about heat transfer.
Should I really be using heat shrink over the thermistor head?
How about epoxy the bare head to the metal.?

how as every one else gone about this ?

If you want more instantaneous readings, you could leave out any thermal insulation between thermistor and what it's attached to. If you put heatshrink around it, or something else, then whatever it's thermal resistance is will determine how long it takes for it to respond to changes in temperature around it. That might be good or bad depending on what you're doing with it and how important it is ot know exactly what it's temperature is at every instant.

Most likely any typical heatshrink/etc you put on it it won't delay a reading long enough to matter; a few seconds maybe? (you could test the delay first, before mounting).


Not sure if leaving the heatshrink off will affect it's mechanical integrity with vibration/etc. Some o fthose things are a little on the delicate side. I suspect that if you're epoxying it anyway, it'll be fine, but I haven't tried it.

"Temp sensor that's too cool not to share" 3-pages
http://endless-sphere.com/forums/viewtopic.php?f=1&t=25502

LM35 at 3:00 O'Clock position, dab of JB-Weld epoxy...

Ok, thanks..don't know how I missed that thread. I'll stick my 10k where I was first thinking then, just below the windings on the stator, glued in with DP420

Tucked into or snugged up against the windings.

I used cheapie JB Weld. It's steel-filled so should conduct heat pretty well, but non-conductive and good for 500degC.
Save the DP420 ($$$) for hi-strength stuff...

Yes, there has been some discussion about the "best" place to catch temporary peak heat spikes...any spot right where the stator touches a part of the copper windings seems to be the absolute "best" spot to catch peak heat readings.

My view is to place the temp sensor where it is easy to attach and easy to reach (for repair?), and then set the temp "roll back" feature about ten degrees F lower (5 degrees C?) than what I assume the copper will feel.

LM35 reads out actual temp on a cheap digital voltage meter, 0.80V = 80-degrees in Celsius, with 200F / 93C being a reasonably safe cap (lower being better), the 10K thermistor (thermally variable resistor) is best for availing the rider of the many useful features in the V3 Cycle Analyst. At "X" temp the amps will be automatically limited, and at "Y" temp, the amps will be cut completely. When the temps cool down to below "X", the power will automatically be restored.

Making sure that the motor and controller does NOT get fried is worth the $200 price of the V3. Three temp tracking inputs, one each for the motor, battery, and controller.

spinningmagnets said:

Making sure that the motor and controller does NOT get fried is worth the $200 price of the V3. Three temp tracking inputs, one each for the motor, battery, and controller.

Click to expand...

CA3-DP = $150
1 temp input

3 temp inputs?

Click to expand...

I read that...hmmm...I will have to investigate, to insure I am not spreading mis-information.

edit: found it!...you mount two component inputs in-line (the likely hottest and coolest) an also mount the middle hottest component with a second thermistor in parallel with the other thermistor. The CA-V3 will see the highest voltage, regardless of which input provided it.

http://endless-sphere.com/forums/viewtopic.php?f=4&t=37964#p553383

In the real world, you put a 10K thermistor on the hottest component, and that's the only one that needs to provide heat data...

Sure - there are many hacks for the V3, but at the end of the day it absolutely has exactly ONE temp input.
You cannot get more than a single temp to display.

You are claiming hardware features that simply do not exist.

I apologize...yes you are correct. There is only one temp input on the Cycle Analyst.

I had considered using three too, but switchable, then decided it was too much hassle.

Setting up as mentioned, two series with one in parallel is interesting, do you then do a custom setup rather than the standard 10k CAv3 menu item?

Or use four of them ?

Hi Neil,
This is how I did, so far 3000km off road without problems.
http://endless-sphere.com/forums/viewtopic.php?f=6&t=23996&p=865316&hilit=gasket#p865316

One thing with eopxy, it will not be easy to remove the sensor if you need to replace it. You will destroy the protection on the windings, that is why I chose high temp gasket - good up to 310C

Yes, I did think about that too, so may go with high temp RTV sealant.

I think I am going to fit mine snug up near the windings, but on the stator steel, on the inside, rather than on the windings themselves.
As others have pointed out this will give a more average reading and not transienent spikes every time you blip the throttle.

This little bike build is only running a 6 FET controller, so there is a fair chance that the controller will be getting hotter than the motor, so will need a few test rides over a known route with temp feed coming from different places each time.

But what about back in yup to page one of the CAv3 thread, where Justin says:

justin_le said:

But your other suggestion actually works OK with NTC thermistors. If you get two 20K thermistors and wire them up in parallel, then it behaves like a single 10K thermistor that (due to the high nonlinearity) is mostly weighted to show the higher of the two temps.

You could also have two semiconductor resistors that have a voltage output and link them up to the temp input via a diode, and then just the highest one would show.


-Justin

Click to expand...

The second part about the two semiconductor resistors and diodes. I have no ability to know how to go about finding the correct components to do that, but if any one else wants to make me up a list of components, I will happily try it out. I have a few weeks to kill now on my GT LTS build while I wait for a second new freewheel to arrive. A story of impatience and stupidity

I am looking for a real small NTC 10K probe. Anyone any suggestion ?
I am preferring a both legs parallel and and not radial one.

Send me a PM to remind me,

I just bought parallel wire ones where the heads are less than 1mm diameter.

Or search my other posts, where I asked the question of which was the best from a selection of 3