What is the symptom of a thermal cut off - Cyclone motor

[andrenoites]

Hello

Today my motor (Cyclone 1680W) cut off when I was at full load after 15 minutes riding at approximately 2800 rpm and 19amp

It was a different cut off because the motor only work after disconnecting power button and connect again.
The Kelly controller led's didn't gave any error, could this be a internal motor thermal cut off?

When touching the motor cover it seems to be at +/- 48ºC but surely in the inside the temperature was higher. The thermal cut off of this motor is at 80ºC
I also have aluminium fins in the casing.

Did anyone with this setup had this kind of error?

Tks,
André

 

[-Bugsy-]

I'm taking a guess here but if you don't believe the motor was hot enough to initiate thermal cut-out protection, could it have been an over-currrent cut-out in the controller? While I haven't yet seen it on my Kelly controller, a few other controllers have done this, where under high load the controller will shut down to protect itself. Requiring a power cycle (disconnect / re-connect batteries) to get it going again.
What was happening just before the cut-out?

 

[andrenoites]

Well, this is what i'm thinking:

The things that make me believe that it's not thermal related:

- After the cutoff I just reset the power button and continued my ride all full throttle with no more cutoff
Didn't need to let engine cool down to continue the journey.

- Although it's rare, I already had this kind of cutoff at low speed and with cool motor. It was before I correctly adjusted the throttle from pod to hall


The things that make me believe that maybe it's thermal related:

- Normally when a cutoff occurs the controller led blink with the error code. This time there was no blinking at all.

- It occurs after 10 minutes riding at full throttle and the motor is warm but not enough to burn my hand (+/- 48ºC).
This was the same ride that I have been making for the last 7 days at same speed (+/- 55km/h with 3% grade climbing)

Tomorrow I will test again with lower low voltage protection to see if voltage sag is causing this problem
See you soon

 

[tony67]

Thermal cut off from the motor will not be fixed by a power cycle. Only when the motor cools and the thermistor is sending the correct signal will the motor run again. If it took you a few mins to power cycle the system then the motor may have cooled sufficiently making you think it was the power cycle however if it was a simple flick of a switch then your controller is more than likely the culprit.
Tony

 

[andrenoites]

I took about one minute to power cycle the system so maybe it's not thermal related.

I lowed the low voltage protection from 40V to 39V and today the journey was flawless.
Maybe it was the voltage sag that activated the lvp. I remember one time I had the lvp higher and when the controller cutoff it was the same symptom.

I have 48V 12s 10000mAh 20C lipo and sometimes it sag at about 0,22V

In the next days I will know if lowing the lvp fixed the problem

Cheers

 

[tony67]

I definitely wouldn't lower the low voltage protection any more, 39v is 3.25v per cell. To maintain good pack life it is vital you don't over discharge the pack. Lipo is very stiff so your 20c packs should not be sagging much until they are low on energy especially since your probably only draining them at 2.5c at WOT. If you find yourself hitting lvp regularly, you may want to consider 2 more bricks

I noticed you refer to your pack as 48v 10000mah lipo. I just want to make sure your not charging it as you would a 48v lifepo4 (ie to ~58v). Your pack is actually a nominal 44.4v and should be charged to max 50.4v, although ideally no more than 49.2v.

Also, have you some way to balance your pack regularly? An out of balance pack will sag a lot more than a balanced pack and will fail far sooner possibly leading to one of the horror lipo stories we see on here from time to time. I am currently paying the price for not implementing battery management when I first built my headway pack. Cells 1, 13 and 16 in my pack have only 85% capacity now due to being overcharged regularly for the first few months of their life. I now balance during every charge with battery medics. I suggest you pick 4 up if you don't have a system in place. Just leave them connected to the balance leads in discharge mode to 4.1v and set your charger to 49.2v.

Tony

 

[andrenoites]

Tony I have found that one of the cells in the nº4 6s 5000mAh is discharging faster than the others 0,4V after balance charge to 4,1V and discharged until 3,8V.

I have replaced the faulty cell and will test to see if the all the cells now stay balanced.
I will now upper the LPV and post results as soon as I test the bike in the same trip.

Tks for the help

 

[andrenoites]

Today I got the same cutoff and this time it take a while to get the motor running again so definitively its thermal related

I do this same trip every day so I must do something to prevent the heating or it will happen again.
The motor cuts power at 85ºC but if I touch the motor cover its only at about 50ºC.
Adding cooling fins will not help because the heat is build up inside the motor

Any ideas?

 

[tony67]

I ran into this issue soon after I built my bike. I was conscious of the noise of the cyclone motor and in an effort to reduce this noise I began to run in higher gears meaning my motor was running slower and was not getting into its efficiency range supposed to be between 80-90% of max rpm.

I would suggest you put the bike in a gear where at wot on flat ground with no wind effect you are travelling approx 40kph. Your motor should be spinning fast, in the region of 80-90% of max rpm. This will mean you are drawing about 20-25 amps which the motor can handle all day long.

Using this method I avoid high temp cut out altogether. It should be noted your climate will be significantly warmer than mine, but even in summer I don't hit temp cut out so it is possible. Just get the motor spinning fast and keep the speed below 45kph

I don't have them but I have heard the cooling fins if fitted with appropriate heat conductive paste can help, to combat heat soak. The thermistor is mounted to the inside of the casing. I have a photo somewhere of the stator showing the thermistor wires. I'll try root it out. So anything you can do to pull heat from the case should help.

 

[cheekybloke]

hi andre
i would agree with tony67,keep the motor spinning pretty quick .another option would be the upgraded cooling fins from AFT, i use them and have never had a thermal cutout. but i am in the U.K and its mostly grim.
http://www.af-tech.com.au/Ebike%20Kit%20Upgrades.html
i have most of the upgrades and they really help
darren

 

[andrenoites]

Did anyone try using thermal paste between the stator and the motor housing?



The motor cover was warm to the touch (about 49ºC) when the the thermal cut off was activated (stator at 85ªC)
Improving the heat transfer from the stator to the housing surely could fix the problem.

I will follow your advices regarding the high rev use of the motor but I enjoyed cruising at +55km/h and will try to use a lower gear to see if I can obtain the same speed

Is it bad for the motor running for long periods at max revs?

 

[tony67]

The stator is bonded to the motor case to stop it from spinning due to reactive torque, so using thermal paste is not possible unless some kind of thermally conductive adhesive exists.

"but I enjoyed cruising at +55km/h" There is your problem. In my experience the cyclone motor just can't do this for extended periods, in standard trim anyway. At this speed my bike needs to be in too short a gear maybe 5th/6th and this just won't let the motor spin out to get into the high efficiency band so it pulls high amps and just converts them into heat. For your next journey shift 2 gears longer i.e. instead of 5th use 3rd this will decrease your road speed increase your motor speed and lower your current, you want your motor screaming, then you know your not pumping heat into the it.

Unlike ICE motors, electric motors need to spin fast thats what they are designed for so in answer to your question, running at max revs and therefore lower current is better than running at mid revs and high current. This is what your motor is telling you by cutting out.

Also when accelerating go, WOT but when your at full speed back off on the throttle until you hear the motor slow just a touch and hold the throttle there, this ensures you are not pumping amps into a motor that cannot increase its speed due to load, just incase you are still in too short a gear.

Good Luck
Tony

 

[andrenoites]

Thanks for the advice Tony!

I am now officially clarified about the correct use of the motor

Today I went for the same trip and didn't have any thermal cutoff.

For short times it gave 35Amps to motor but after that i'm running at about 19Amps
Also I upper the LVP from 39V to 41V

My motor controller configuration are now as follows:

Max motor current: 40Amp
Max battery current: 40Amp

Cheers,
André

 

[tony67]

Perfect. For short bursts < 30 seconds the motor can take quite a bit of power, well over 2kw but it is too small to take that level of power continuously, it just can't shed the heat quickly enough. You should be good to go now.
Best of luck.
Tony