Stuttering motor/loose wire? Conhismotor / golden motor

[TheBeastie]

Hey guys,
A friend of mine has a conhismotor or goldenmotor kit or clone that seems to stutter and run really slowly.
Sometimes it won't go and all but just rolling the back tyre/motor kicks it into action.

Anyone know what the problem is here?

Also the battery lacks labels or anything really its just tapped up but the back tapeing is falling apart, any one know what kind of battery chem this would be?
I thought LifePo4 comes in battery shaped cells?

 

[shorza]

Sounds like an incorrect hall/phase combo.

http://www.endless-sphere.com/w/index.php/Determining_the_Wiring_for_a_Brushless_Motor

 

[mmerlin]

Hi,

I'm the friend of TheBeastie whose bike motor is doing the stuttering

Thanks Shorza for suggestion of checking the hall/phase combo, I will confer with TheBeastie and see what he reckons.

The bike's been working awesomely for 6 months, thanks to Kepler's awesome skillz

However the stuttering has occurred a handful of times in the past, and when I first asked the original bike owner about it (the dude who build the bike), he said "check the green wire".

So in the past I just unplugged and replugged the green wire half a dozen times until the bike was all humming along nice and smooth once again.

"The green wire" is one of the main power wires that goes to the motor.

I think it's some kind of semi-broken wire connection somewhere... not sure if it's "the green wire" or not, but I suspect it is.

What's happened recently that disturbed the wiring, is my ebike was serviced by the local bike shop, and they took the back wheel off as part to the service (changed a flat the rear tube that could not be repaired any more). And the bike really needed a major service anyway and they did a great job, new brakes, tightened everything that was getting loose. But yeah I noticed the cabling had been moved (unavoidable when taking the back wheel off)

As I left the shop the motor stuttering was already back again. So I stopped and unplugged and replugged the power wires but the stuttering was still there.

Rode back to my office and halfway there the power just kicked back in full bore again, by itself, so I was happy.

Leaving work that evening, full smooth power was available for 5 minutes, until I jumped a gutter and the power cut out totally and the best I could get it back to was the stuttering effect.

So the wiring has been upset somehow, as evidenced by the intermittent changing from [no power / stuttering power / full power]

The current situation now is always stuttering, and interestingly... while testing, with the rear wheel up in the air, sometimes when putting the throttle on, the motor does not have any power at all until I move the back wheel slightly and then it starts again, but still just powered stuttering.

I'm a bit of an electronics neophyte, and TheBeastie is more tech savvy than me (built his own ebike) but we are not electrical engineers and not really sure exactly where to start looking, so posting here for some more suggestions and clues.

It seems to be the wiring, just how to figure out where the break/loose connection is, and how to go about diagnose it is where we are currently baffled.

The powered stuttering does still have some good torque behind it (e.g. going up a hill slowly) but just very slow maximum speed.

Our only other thought was the motor has somehow

 

[wesnewell]

There's 8 wires coming form the motor to controller. 3 individual larger wires of green, yellow, and blue with bullet connectors. and then there's 5 small wire that come from the hall sensors. One of these is not making good contact. Most likely one of the larger (phase) wires. Sometimes the bullets get squeezed tight and don't have much tension and tend to work loose. Use a small knife or something similar to spread them apart slightly so you get a tight fit when inserted into the bullet receptacle. It could be a broken wire some where, but more likely the connection.

 

[mmerlin]

Thank Wes,

Yes it's the bullet connectors that I was unplugging and replugging which got it going in the past but not any more.

Would it be a reasonable idea to just cut the bullets off and hard solder the green wires together for the ultimate connection?

 

[wesnewell]

Shouldn't need to do that, but it is an option as long as you know you'll have to desolder them or cut the wire if you need to remove the hub again. If they keep coming loose, either replace the connectors or re adjust them and then use shrink tubing over them so they won't come loose again.

 

[dogman dan]

Bad connections on any of the motor wires will cause the stutter. Another possibility to look for is nicks in the wires, typically at the hub axle, but they can happen anywhere.

Enough cut strands on the big wires, and the motor will run fine slow, but stutter at full throttle. Just as the same thing will happen if the connection is bad, and only a few amps can flow to one of the 3 windings. The motor then runs fast fast slow, fast fast slow. Causing the vibration. It's like running an engine without one spark plug.

 

[TheBeastie]

I suspect maybe even a bad hall sensor in the motor.
For this hall sensor tester circuit http://endless-sphere.com/forums/viewtopic.php?f=16&t=3484#p82465
is that a 470ohm or 470kohm resistor? (Very useful post btw)

Also it looks like I have dug up a premade hall sensor test unit on eBay: http://www.ebay.com.au/itm/G-T-GT-Power-LED-Lights-Motor-Sensor-Hall-Tester-for-sensored-motor-/190781001240?pt=AU_Toys_Hobbies_Radio_Controlled_Vehicles&hash=item2c6b6f0e18&_uhb=1#ht_3508wt_947
Can any one give a thumbs up that this will work or at least in theory is the correct thing to try?

I have bought some of these GT gadgets from ebay before, I wonder if these guys spy on the forum here looking for gadget ideas for stuff we might want to buy?

 

[wesnewell]

All you need to test the halls is a vom.
http://www.youtube.com/watch?v=efYFOHnXh0E

 

[mmerlin]

Bad connections on any of the motor wires will cause the stutter. ... look for is nicks in the wires, typically at the hub axle

Yes that's a possibility too, the axle hub wires got squashed flat when I first received the bike shipped from perth, and they are looking kinda loose and frayed a bit nowadays, I've been a bit scared to go there, but TheBeastie is braver than me with a multimeter and soldering iron

It's like running an engine without one spark plug.

Yep that's it alright! Stuttering the instant the throttle is applied.

 

[mmerlin]

All you need to test the halls is a vom.
http://www.youtube.com/watch?v=efYFOHnXh0E

That's awesome Wes, thanks for linking that vid, it really will help us out

 

[TheBeastie]

I did that hall sensor test and the green hall sensor wire failed to return any volts as we turned the wheel. The other two hall sensor wires cycle jumped up to 5v then off as we turned the wheel.

So we have for sure a bad hall sensor wire or sensor inside the motor.
Also I gave the entire motor lead a wiggle at the axle point and saw a spark. What's the best way to deal we this?
Cheers!

 

[wesnewell]

Disconnect your battery and inspect all the wires into the motor. Sounds like a broken or shorted hall wire. Maybe more than one. You will likely have to take the motor apart to fix it.

 

[TheBeastie]

I was thinking maybe I could buy a complete hall sensor/phase wire cable lead, any one know if that is possible?

 

[mmerlin]

Yesterday we peeled back the main control cable into the hub (which got badly mashed) and it looked like one tiny wire was almost sheared so we stripped it and re-soldered it (a bit dodgy but a better connection was made) but made no difference in the end... motor still a'stutterin.

Wondering if it's actually the hall sensor inside the hub now...

If so, is it easier to get a new motor (compared to taking one apart... need one of those gear puller tools, plus where to buy spare hall sensor...?)

 

[wesnewell]

You can test the halls easily with a vom. You can test the whole circuit leaving leaving the connector connected, or just the halls in the motor by using an external power source. Search testing hall sensors on youtube. If you need to take the motor apart, you can do it without a gear puller. I used 3 or 4 screwdrivers to pry the covers off.

 

[chvidgov.bc.ca]

You can also buy a cheap sensorless controller. If you are ok with "almost instant start, from less than .5mph of forward travel", as seen on the KU123 controller from bmsbattery.com. About fifty bucks. I like them with 9C or Conhis.

 

[mmerlin]

I am taking the bike over to Joe / Winkinatcha on Monday, will report back how we go!