Motor cutting out when under strain

aardvark5

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Jan 25, 2014
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I have two virtually identical bikes, all the same parts except one has a 26" motor and the other 700c
.For a while I thought that a paranormal event was happening with my MTB every time I got to a certain place my motor would cut out so I'd turn the LED off and turn back on again.
Yesterday I was riding up a steep hill and it cut out 3 times which said to me that it doesn't like the extra strain of a hill.
I have two identical batteries and it happens with both, it doesn't happen with my Hybrid bike so which is more likely to be causing the problem : the motor, controller or even computer?
 

saneagle

Esteemed Pedelecer
Oct 10, 2010
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I have two virtually identical bikes, all the same parts except one has a 26" motor and the other 700c
.For a while I thought that a paranormal event was happening with my MTB every time I got to a certain place my motor would cut out so I'd turn the LED off and turn back on again.
Yesterday I was riding up a steep hill and it cut out 3 times which said to me that it doesn't like the extra strain of a hill.
I have two identical batteries and it happens with both, it doesn't happen with my Hybrid bike so which is more likely to be causing the problem : the motor, controller or even computer?
Do the motor's have the rpm written on them?

700c motors often have slower windings than a 26" one, so they run with higher efficiency (less heat) and less current when hill-climbing compared with the 26" one if they're both in the same sized wheel. If your batteries are a bit marginal on power, it's quite feasible that the 26" one would cut out but not the 700c one.

If you had identical motors and put one in a 26" wheel and one in a 700c wheel, the reverse would happen, in that the 700c would operate less efficiently.
 

Nealh

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Aug 7, 2014
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How fast was you riding up the hill and which power assist level ?
 

aardvark5

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Jan 25, 2014
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Sorry I took so long to reply, problems.

I've had these bikes for a long time and back in January 2020 I changed both batteries over to Green Cell's.
Both bikes acted normal with no problems but it was only last year I noticed the MTB started to cut out on a hill.
So as an example last year riding up here to the top was no problem, there is a flat bit then goes up again - https://www.google.com/maps/@52.9823958,-2.1569676,3a,75y,77.31h,75.14t/data=!3m6!1e1!3m4!1sKnYl496mUj-iH5_MlsBcaA!2e0!7i16384!8i8192?authuser=0&entry=ttu
Last week I stopped 3 times on my MTB.
 

Peter.Bridge

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Apr 19, 2023
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I guess it is either the controller overheating or the motor overheating - but I don't know how to tell the difference - somebody here will though :) According to the Woosh predictor, the max incline is 13%. What speed are you cycling up the hill ? What assist level are you using ? And , if you don't mind me asking, how heavy are you ?
 

aardvark5

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Jan 25, 2014
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I guess it is either the controller overheating or the motor overheating - but I don't know how to tell the difference - somebody here will though :) According to the Woosh predictor, the max incline is 13%. What speed are you cycling up the hill ? What assist level are you using ? And , if you don't mind me asking, how heavy are you ?
Like I said I've never had a problem since 2010 but now my MTB is playing up.
No idea what speed but slow, assist level 5 and weight I'm the lowest I've been since I had them.
I do know I'm 5ft 6ins and two stone overweight.
Cycling up with my virtually identical Hybrid is no problem.

HOWEVER it's worse than I thought, cycling into work this morning I stopped 3 times on the flat and 3 times on slight banks.
Even here it cut out -
 

Nealh

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Riding very slowly up hill can cause controller Mosfet overheat/thermal cut , if one can access the controller the temperature will instantly be known as the heat is a kin to a very hot potato that one can't handle and one will for sure would cause second degree burns . Thermal cut outs cause mosfets to temporary short out once cooled they will operate again until the next occurrence which is likely very soon .

If it is not the controller then the battery is more then likely the culprit.
 

aardvark5

Esteemed Pedelecer
Jan 25, 2014
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Riding very slowly up hill can cause controller Mosfet overheat/thermal cut , if one can access the controller the temperature will instantly be known as the heat is a kin to a very hot potato that one can't handle and one will for sure would cause second degree burns . Thermal cut outs cause mosfets to temporary short out once cooled they will operate again until the next occurrence which is likely very soon .

If it is not the controller then the battery is more then likely the culprit.
It happens with my identical battery also.
I do have a spare controller so will fit that one day this week.

Thanks
 

aardvark5

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Jan 25, 2014
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If it is not the controller then the battery is more then likely the culprit.
I'm talking rubbish :)
Just identified my batteries, been out for a big bank ride and one of them does cut out while the other stays on.
Funnily enough the one that stays on is the battery I posted about where a wire came off the other week.
Is there a fix for the duff battery or is it a new one?
 
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Nealh

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Once one see's cut outs due to battery issues then replacing is the only real option.

Repairing just afew cells isnt't cost effective or very practical.
 
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aardvark5

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Jan 25, 2014
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Thought I'd keep you updated.
I didn't buy a battery straight away, I wanted to see how my good battery coped on my normal commute to work because I only go in once a week.
Even though my good battery got me up a big bank four times the other day, today it cut out 6 times - WTF?
So I'm going to fit my spare controller to see if that solves it.
If that doesn't work then it's got to be the motor.
 

aardvark5

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Jan 25, 2014
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I'll keep this updated just in case people have similar problems.

A couple of years ago I bought a Yose Power kit and only used the front motor with my older Cycloticity electrics and all seemed fine until a few months ago when my motor kept cutting out more and more.
Since it was doing the same with both of my batteries last week I decided to change the controller with the one that came with the Yose Power kit however my thumb throttle wouldn't work.
Messed about with no luck and then decided to use the digital display from the Yose kit and went for a ride with everything working.
I'm a bit amazed that the old Cyclotricity digital display wouldn't work with the new controller since they are a K2 system.
I still need to take it for more of a test with a few banks but looking good so far.

There is another bit to this.
I said that I had no problems with the Yose motor on the old Cyclotricity K2 system but I did have something that happened every day on my commute, the motor cut off in exactly the same place very day which was very weird.
So what I'm experiencing really bad now did used to happen only once and in virtually the same place.
I've got a friend into the supernatural (I AM NOT) and for a wee take I made a video of my motor cutting off, digital display still on full and nothing happening, of course he put it down to the supernatural but I was none the wiser but thinking if there was some kind of power surge in the area.
So the reason for this is that I now think I've always had the problem but only once a day and from the very start when I put the motor on I should have replaced the controller and digital display at the same time.
 

aardvark5

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Jan 25, 2014
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If anybody is interested another FINAL update to my problem.

Gave the bike a proper ride to work and back today and it was wonderful. My pedal assist never worked correctly so I always used the thumb control but the PAS that came with the kit is working perfectly.

So my advice is, if you are ever doing your own conversion fit all the parts that came with that conversion kit. I thought being K2 parts they would work with each other but in this instance it seems they are tuned to each other.

Thanks for listening to an old man rant.
 
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saneagle

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Nealh

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I have never had an issue with any KT bit of kit , it has always worked .
Generally any issue is down to the user and the fitting, the pedal sensor fititng seems to be the cause of alot of issues with self builders and we do see a lot of issues on here with them. The 12 pole 2 part PAS should be avoided as should the all in one unit that goes on the LHS, stick to a 5 , 8 or 10 pole disc set up.
After fitting issues which a few can't get right the next issue is often an incorrect parameter setting.
 

aardvark5

Esteemed Pedelecer
Jan 25, 2014
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I have never had an issue with any KT bit of kit , it has always worked .
Generally any issue is down to the user and the fitting, the pedal sensor fititng seems to be the cause of alot of issues with self builders and we do see a lot of issues on here with them. The 12 pole 2 part PAS should be avoided as should the all in one unit that goes on the LHS, stick to a 5 , 8 or 10 pole disc set up.
After fitting issues which a few can't get right the next issue is often an incorrect parameter setting.
Perhaps but the K2 kit on the bike was Cyclotricity, I changed only the motor from the Yose Power K2 kit and then realised after a couple of years I was having problems which were getting worse.
Take into account I only commute once a week and I have two eBikes depending on the weather.
I originally thought one of my batteries was buggered but it ended up being that I didn't put the rest of the Yose Power kit on when I had it.
It's now working great with the controller, digital display and PAS that came with the motor.
Also bare in mind that the Cyclotricity digital display won't work with the Yose controller which I thought was strange.

I've converted at least 25 bikes for other people but of course I always put all the kit on and not mix and match like I did with my bike - typical.