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Author Topic: Wrong motor temperature  (Read 470 times)

gt13013

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Wrong motor temperature
« on: August 01, 2017, 07:52:58 AM »

Hello
After resting (unplugged, without any activity) for several hours in my basement where the temperature is around 25°C, my Zero 2016 FXS indicates that its motor temperature is around 37°C. Obviously, it should be at the same temperature as the environment, i.e. around 25°C.
I join a picture, and also a log file (see for instance at 07/30/2017 11:32:51).
Do you get the same strange temperature indications on your bike?
Does it mean that something is wrong in my bike?
Regards,
Gerard
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Doug S

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Re: Wrong motor temperature
« Reply #1 on: August 01, 2017, 08:40:31 AM »

I noticed that in the first week I had my 2014 SR. Others confirmed theirs did the same thing. Still happens on my bike, still doesn't seem to be a problem. I'm assuming it's a cheap temp sensor, perhaps a thermistor or even just a diode, and it's intended to be accurate at temperatures near the high end, not ambient.
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gt13013

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Re: Wrong motor temperature
« Reply #2 on: August 01, 2017, 05:21:40 PM »

Thanks Doug for this information.

By the way, I noticed that the temperature warning light starts blinking orange at exactly 75°C on my bike. By these hot days here, just riding on the motorway at 100 km/h makes it blink.
« Last Edit: August 01, 2017, 07:28:27 PM by gt13013 »
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hubert

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Re: Wrong motor temperature
« Reply #3 on: August 02, 2017, 12:45:58 AM »

Same with my 2014 S, about 10 to 15°C above ambient when "cold". No idea about the error at hi temp. The warning lamp blinks at 100°C, but which is the real one? Anyway, it is not really an issue, since the high motor temp does not cause early aging of the motor, unlike the battery.
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Fred

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Re: Wrong motor temperature
« Reply #4 on: August 02, 2017, 12:57:01 AM »

Mine too. Glad it's not just my bike.
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remmie

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Re: Wrong motor temperature
« Reply #5 on: August 02, 2017, 01:02:55 AM »

Same here as well, about 10 degrees above ambient (actually the dash displays 33 C while the temperature in the garage is a steady 22 C.

the temperature warning starts to blink at 100 degrees C, The light becomes steady at 110 C and power cutback starts at 120 C.

But there's no real way to determine if the high end of the scale is more accurate than the lower scale. It would be a real shame if power cutback is active while the temperature is nowhere near the critical point.
I experience a blinking temperature warning quite easily with some spirited launches, especially with riding two-up. A few weeks ago on vacation in the mountains it was even worse, just a few hairpins uphill and not just a steady temperature warning but even power cut-back. Makes me long for the IPM motor introduced in 2016 :)

If it's a simple 2-wire resistor temperature sensor it could be that the resistance of the wiring is not taken into account and that that makes the reading high (the resistance of the wiring makes the MBB think the temperature of the motor is higher than it is)

As it seems to be a consistent error, it should be able to be corrected with firmware. But it can only be corrected if Zero knows about it (and wants to do something about it). Even if the reading at high temperatures is more accurate and power cutback takes place at the correct temperature it is possible to correct the high readings at low temperature using firmware and it would suit Zero if they correct it in a future firmware update.

I have an appointment for a firmware update in 3 weeks, let's see if it's resolved then ;)
If not I will make a comment to Zero Europe who will hopefully relay it to Zero HQ
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gt13013

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Re: Wrong motor temperature
« Reply #6 on: August 02, 2017, 02:29:27 AM »

@ Remmie and Hubert : you say that your warning lamp starts blinking at 100°C, but mine starts at 75°C.
Your motors are from 2014 and mine is from 2016. Probably the difference comes from there.
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remmie

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Re: Wrong motor temperature
« Reply #7 on: August 02, 2017, 12:15:08 PM »

It could also be a S/DS/DSR/SR  versus FX/FXS difference
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grandpa

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Re: Wrong motor temperature
« Reply #8 on: August 02, 2017, 03:31:55 PM »

My 2016 S start blinking at 75°C too. and power outback start near 110°C.
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BrianTRice

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Re: Wrong motor temperature
« Reply #9 on: August 03, 2017, 09:05:15 AM »

The economics of sensors mean that these will only be calibrated and chosen for the right precision for the range where they need to be, at the high end.

It would be nice to be able to perform a graduated calibration to minimize error across the full range of temperatures down to ambient, but I don't think we'll get that. We can doublecheck MBB settings at least.

Also, the motor probably just doesn't shed heat from where the sensor is that quickly while it's not spinning or moving through the air.

The sensor is likely to be in the hottest part of the stator. I think the drawings online might make it a little clearer so I'll take a look later.
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gt13013

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Re: Wrong motor temperature
« Reply #10 on: August 03, 2017, 01:35:52 PM »

OK. For me it is sufficient to know that the reported motor temperature in cold condition is erroneous, but it is normal. Perhaps Zero could state it somewhere in their manual...
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remmie

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Re: Wrong motor temperature
« Reply #11 on: August 03, 2017, 11:06:24 PM »

Why should the sensor only be incorrect at cold temperatures ??
The other 2 sensors (battery and controller) are reporting a temperature within 1 or 2 degrees from ambient.

See the attached picture where the bike has been sitting in the garage for 2 weeks now due to a rear shock failure and the motor temperature is still 10 degrees too high (ambient temp in the garage is 22.6 degrees) so it's highly unlikely that even if the sensor is burried in the hottest part of the motor, the motor would retain heat during that entire period.

Temperature sensors are very cheap, even a sensor for over 120 C. And their behaviour is very predictable (both for resistance or semiconductor types) unless you don't factor in wiring resistance (or just get the formula or hardware wrong). There is absolutely no reason to report a temperature which is 11 degrees Celsius too high. Especially since the sensor can be corrected using firmware. And since they report the temperature on the App and on the dash they want the user to know at what temperature the motor is. HOWEVER it is wrong.

We can determine that the sensor is wrong at the cold/ambient end. My major concern is that the same of maybe even a worse error is present at the high end of the scale (reading 11 degrees or more too high). This would mean that we would get power cut-back prematurely  :o !!!
And since the 2014's and 2015's heat up a lot quicker and higher than the IPM motors we need every degree we can  8)
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gt13013

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Re: Wrong motor temperature
« Reply #12 on: August 04, 2017, 01:10:56 AM »

My point of view : since the reported temperature seems to be equally wrong for all of us, and since Zero is aware of that, I assume that they have put their warnings and motor cutoff accordingly. I do not care about knowing the exact motor temperature. The only thing I want is that the motor is correctly protected and that my bike works fine  ;)
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BrianTRice

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Re: Wrong motor temperature
« Reply #13 on: August 05, 2017, 01:14:52 AM »

Not all temperature sensors are made for the same conditions, but remmie you seem aware of that. The sensor inside the motor is less accessible or fixable than a controller sensor, and it's probably an RTD made just for that kind of use.

For what it's worth, I found one Motenergy drawing (for an older motor model) to reference its temperature sensor part, leading to this sort of FYI datasheet that may be roughly relevant:
http://www.nxp.com/docs/en/data-sheet/KTY84_SER.pdf

I don't want anyone over-interpreting what I'm saying, though! I'm not a professional, just a former technician who's worked sensor calibration in a power plant. It just occurs to me that Zero or Motenergy or whoever gets little value from sensor accuracy or precision at the low end of the range.

If a sensor is mis-calibrated near where the cutback range is, that'd be a problem for sure, but I haven't heard that yet. It is unfortunate that we as customers don't have much to judge other than noting when cutbacks happen, and checking the MBB event logs later against the local weather report. Aiming a FLIR camera or just an IR laser sensor gets a surface temperature but doesn't tell us how hot the windings get.
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Keith

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Re: Wrong motor temperature
« Reply #14 on: August 05, 2017, 06:16:02 AM »

I've wondered if the "noise" that the motor uses to sense rotation could actually raise the winding temperature as indicated by the reading. Seems like a lot of power to waste if so but it could be part of the reason.
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