Motor temperature sensor?

[tostino]

Hello all, I was wondering what those of you who have installed a temp sensor in their motor were using. I would really like to get one with a digital read out that would stand up to the motor temperatures, I just haven't found one yet.

All I have seen on ebay have been either food ones that will stand up to the heat but don't have a remote temp probe
Or ones like this: http://cgi.ebay.com/Digital-LCD-Thermometer-Temperature-Sensor-Tester-NEW_W0QQitemZ260325891791QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item3c9ca1decf&_trksid=p3286.c0.m14&_trkparms=65%3A12|66%3A2|39%3A1|72%3A570|240%3A1318|301%3A1|293%3A2|294%3A50 that don't hold up to the temps (70c max).

I look forward to seeing what everyone else is using!

 

[dogman dan]

Mine is just a cheap Bell brand indoor outdoor thermometer for a car. About 10 bucks and it reads to 160F and then just says high temp. If my windings are at much more than that, I want to stop awhile so it's working ok so far. Once it is reading high temp, I can still guess pretty accurately what the temp is since I just watched it climb to there and have an Idea how many degrees per mile I am adding. If you stop and it returns to 158F pretty quick, chances are you were not above 170F. I try to ride below 150F as much as it's practical to. I can also monitor the hub cover temps with an infared thermometer, and comparing the two, I find that the inside runs about 30 F hotter than the cover at room temp weather, or 20 F hotter in cold weather. So if the hub covers are at say 150F, you are getting into the too hot zone inside. Or even simpler, if you can't hold your hand on the cover, Stop!

 

[tostino]

Mine is just a cheap Bell brand indoor outdoor thermometer for a car. About 10 bucks and it reads to 160F and then just says high temp. If my windings are at much more than that, I want to stop awhile so it's working ok so far. Once it is reading high temp, I can still guess pretty accurately what the temp is since I just watched it climb to there and have an Idea how many degrees per mile I am adding. If you stop and it returns to 158F pretty quick, chances are you were not above 170F. I try to ride below 150F as much as it's practical to. I can also monitor the hub cover temps with an infared thermometer, and comparing the two, I find that the inside runs about 30 F hotter than the cover at room temp weather, or 20 F hotter in cold weather. So if the hub covers are at say 150F, you are getting into the too hot zone inside. Or even simpler, if you can't hold your hand on the cover, Stop!

I have an infrared thermometer, but I have never measured my motor above 115f. I have a feeling that since it's a gear motor, it may make a difference for heat transfer.

 

[dogman dan]

I'm itching to put another thermometer in the fusin gearmotor I'm testing but I hesitate to start disasembling things right away. I need to put at least a few hundred more miles on it stock before I start making modifications to it. I don't think I have even seen 95F on my gearmotor covers but I have seen 115 on the axle itself. Isn't the axle pretty much connected to the windings on most brushless gearmotors? I have also seen slightly higher temps on the middle of the gearmotor rim than on the covers. Friction heat on the gears? Or just better heat transfer than the covers?

People talk about a cycleanalyst being mandatory, but where I live, and even in the winter , I find knowing if you are smoking the motor or not more crucial than battery level or amp draw.

Edit... I just came back from a ride up a big hill, and measured the axle where the wires come out at 141F, and the rest of the motor at about 109F.

 

[rkosiorek]

I use a cheap oven thermometer that i bought at Canadian Tire. on sale for $5.00. this is an oven thermometer not a meat thermometer.

it has a remote probe (thermo-couple i guess) that mounts inside the oven and connects via a couple of wires to an external LCD display. reads up to 550F.
i mounted the probe on the stator in contact with the windings.

rick

 

[GTA1]

Lead solder, which is not suppose to be used, but who knows, have a melting point of 183 C.

Say, safe operation would have temperatures kept at 50% of this on a continuous basis, to account for spikes in temperature.

That gets us 90 C.

 

[dogman dan]

Which is how much higher a temperature than the epoxy holding the magnets in place melts at? Both the motors I smoked failed on the magnets epoxy, not the windings. In one of em, the magnets were no longer magnets after they cooked. They would no longer even stick to the fridge. But hey, go smoke a few motors and then report back. I'm allways ready for more data that actually happened and was observed.

 

[JS Tyro]

Check robot hobby web shops. They sell lots of sensors, including temperature sensors. They are usually in a kit or an assembled circuit board. They can connect to other widgets with things like USB or more esoteric interfaces. If you have an old PDA, you could probably get it to interface with the thing to use as a display. How are your PDA coding skills?

 

[GTA1]

Infolytica was able to determine the exact temperature and time at which the magnets degraded — at 97 degrees C after a little more than two hours of runtime. This value will vary based on motor size, but these results can greatly help designers determine the best applications for each motor based on expected time in use. Coupled temperature and magnetic field simulation can also lead to optimized motor designs that will help shuttle away damaging heat.

http://www.deskeng.com/articles/aaajxp.htm


For those of you trying to fry motors --- apparently the temperature at which permanent magnets first begin to noticeably degrade is much lower than I first thought --- 97C.

Note that temperature inside the motor varies widely, and hot spots can happen even if the temperature probe (measuring air temp just outside) shows everything is fine.

For safety and serious durability, keeping the motor below 90C measured by a sensor that just pokes inside the case would be prudent.......


Not to say prudence governs here!

 

[tostino]

Wow, very good info on magnet degrading temperature! It really is a good idea to keep your motor as cool as possible.

 

[Fishmasterdan]

Someone here suggested an eagle tree and I liked that Idea. That is what I have http://www.eagletreesystems.com/MicroPower/micro.htm

Data logging is alot of fun also. You can monitor watts and directly relate it to temps and know how many watts you can pull before it over heats...

 

[JS Tyro]

That is what I have http://www.eagletreesystems.com/MicroPower/micro.htm

Toys!!! Oh boy!!! I want!!!

I was wondering how I could track wind speed in addition to bike speed - now I know where to get the sensor + recorder. I'll have to mount the wind speed widget on a wind vane to get it pointing the right way and put a position decoder on the vane so I know relative direction. I need that to determine absolute wind speed from relative + bike speed. Now should I just rely on GPS to determine absolute direction or should I add in an electronic compass sensor too?

Of course I need wind speed to track energy consumption and separate wind from grade resistance (apparent slope sensor + 3 axis accelerometer) and bike friction.

 

[Miles]

For those of you trying to fry motors --- apparently the temperature at which permanent magnets first begin to noticeably degrade is much lower than I first thought --- 97C.

Here are the maximum operating temperatures for the different grades of NdFeb magnets: http://www.engconcepts.net/Magnet_Ratings.htm . For motors using Samarium Cobalt magnets (Astro 3210 et al), magnet degradation isn't something we need to worry about...

 

[dogman dan]

I still say that above 160F... 70C or so, your magnet epoxy is going to be getting soft, and much above that, they are loose inside the motor.

In my riding with a temp sensor, one of the conclusions I have come to is that it's all about how many watts and for how long. Get the thing hot so the epoxy is nice and soft, and then keep riding and the high temp gets a lot of time to unstick the magnets. A riding style that allows the motor to cool when it gets too hot can make all the difference.

Even without a temp sensor, ya'll know that you're hammering the motor if you have 2500 watts going into it, and most likely ride shorter rides at full throttle. More subtle is a guy like me who rides home daily at 800 watts, and needs to know if todays headwind is heating the motor that much more than usual or not. Since the 24v heinzmann motor had a 70C cut off built into it, I think that is a good number to use for a guy who needs to get thousands of miles out of his motor commuting.

Fun bikes, of course, are made to be fried. It's entertainment budget then.

 

[Miles]

I still say that above 160F... 70C or so, your magnet epoxy is going to be getting soft, and much above that, they are loose inside the motor.

You can get high-temperature epoxy that has a maximum working temperature as high as any magnet (250 C.).

 

[rkosiorek]

Lead solder, which is not suppose to be used, but who knows, have a melting point of 183 C.

Say, safe operation would have temperatures kept at 50% of this on a continuous basis, to account for spikes in temperature.

That gets us 90 C.

normal solders are 360F (180C) melting point for electronics. for motor winding there are high temp varieties that go up to 540F (200C) or so. need a MAP torch to do those. i don't think that solder melting would be the issue.

the laquer used to insulate the wires has varios limits from 120C up to about 180C. motors generally use higher temp stuff.

likely dogman is closest (my bet anyway) that the glue holding the magnets in place will be one of the weakest links. be it epoxy or more likely a cyano-acrylate with some kind of filler or thickener that is most likely to fail first.

i also think that the widings themselves will get much hotter locally than the magnets/rotor. the windings can take significantly more heat than the magnet/rotor assembly. so how much of the heat will be transfered (radiant i guess) to the rotor? and how fast? that would depend a lot on each individual motor design.

rick

guinea pigs - need lots ad lots of guinea pigs - any volunteers? (besides doctorbass and steveo that is)

 

[GTA1]

For those of you trying to fry motors --- apparently the temperature at which permanent magnets first begin to noticeably degrade is much lower than I first thought --- 97C.

Here are the maximum operating temperatures for the different grades of NdFeb magnets: http://www.engconcepts.net/Magnet_Ratings.htm . For motors using Samarium Cobalt magnets (Astro 3210 et al), magnet degradation isn't something we need to worry about...

More like worry about the size and cost of the magnets:

Samarium Cobalt magnets have the highest working temperature of the rare earth magnets. SmCo magnets have a maximum operating temperature of 300C. SmCo will usually be 40-60% weaker than NdFeB but will cost up to 5 times as much due to the high cost of Cobalt.

Not many Chinese vendors selling motors on razor thin or negative gross margins are going to have Samarium Cobalt magnets... and if they do... not likely to be good quality unless you paid through the nose and other orifices.

 

[Miles]

True - but the discussion isn't limited to Chinese motors...

 

[dogman dan]

Well, my comments were. I bet you find some better everything in some of the RC motors, or other types of ev motors. I was refering to the garden variety bike kit hubmotors. In normal temperate climates keeping the motor at less than 170F is not all that hard. It's steep hills, long rides, heavy loads, and desert climates that can cause problems. I have three of the above, and found the extra heat of brushed motors made them unsuitable for me. Both the motors I smoked were brushed ones.

 

[icecube57]

I wish i could have checked the temperature on my WE brushed motor. 137A and 5880w at 60v. before death. I had smoke billowing out the axel you smelled the varnish coming off the winding. Water sizzled off the hub motor. I burned my fingerprints off checking it one day. The weird thing is the magnents didnt come off and were just as strong as the first day i bought it. I ran a brushed 409 at stock voltage 36v and magnents came off ... im like aint that a "glitch". I ended up putting the WE axel into the Clyte motor and it still runs fine til this day. Brushed motors should have had temp sensor a long time a go. We need to look into those thermal breakers like the ones on nimh pack and place them inside the hub and have it either interrupt the throttle circuit, alarm, or kick the controller into a legal limit reduce Amperage limp home mode until it cools down to resume normal operation.

 

[dogman dan]

Ebikes ca sells a temp switch for 70c. run the controller on off switch circuit through it and bingo, just like the 24v heinzmann motors. Install a jumper and you could override it if you need to bad enough, and limp home low throttle. Or just wait 15 minuites for the switch to turn back on.

 

[shinyballs]

How anyone tried this Temperature alarms? Since I haven't opened my motor yet, I'll mount the temp sensor outside the case set to 150°F. And also add another sensor connected to the Kelly controller.
There pocket-size model can monitor upto 302°F

http://www.extech.com/instruments/product.asp?catid=67&prodid=392
http://www.extech.com/instruments/product.asp?catid=67&prodid=402
http://www.newark.com/jsp/search/productdetail.jsp?SKU=27K9699&CMP=AFC-TL10000001

 

[dogman dan]

That's pretty cool. The car indoor outdoor thermometer is pretty inexpensive, and I love that. Tried to put one in my Fusin the other day, and found I couldn't fint another wire in the axle. So i have mounted the sensor to the axle, where the fusin shows the heat soonest. I am using 140 F as the best not to exceed point, since I have seen inside and outside temps as much as 30F hotter on the inside. I have yet to have any problems with a motor kept under 170F. With experience I may let that temp go a bit higher, but for now, I'm sick of smoking motors.

 

[docnjoj]

But you haven't lived till you melt the gears, dogman! I'm really interested in the Fusin cause it seems to have thicker nylon gear width than the Bafang. But don't melt one on my account!
otherDoc

 

[shinyballs]

I found that the sensor of the Temp alarm is in a flat hard plastic disc and cannot be fitted to my round axle. Will I just cut the wires and replace it with a different sensor and which one do you recommend?