QS138 70H stuttering

[Helienduro]

I finally finished my build including an EBMX X9000 V3 controller and harness paired to a QS138 V3 motor and a 72v 60ah battery mounted on a 2014 TM Racing 450mx chassis.

I did the full setup as required and everything worked fine, then I took the bike for test ride but unfortunately when putting it under heavy loads, it stuttered and made horrible noises that had me thinking I had broken the gearbox.

I inspected the gearbox and it was perfect (it’s the newer, reinforced with bigger bearings and a CNC cover from Electro&Co) so I did a search and found that sometimes the phase wires, specially under heavy loads, might produce EMI (electro magnetic interference) to the sensor wires and cause stuttering.

So I separated the sensor wires from the phase wires as much as possible (I had them bundled up together before) and I also eliminated the sensor-wires plug-in connector and instead welded all the wires directly to the controller, as several people recommended. I also recalibrated the controller in case it was a controller setup issue.

I then took the bike for a ride and it was much better, almost perfect. Only occasionally and for short bursts did I get stuttering, but again, only under very heavy loads like starting up a steep hill from zero or near zero speed. The rest of the time it ran beautifully.

So, it seems that the problem might be EMI related and I read that adding ferrite rings to the phase wires might help. I ordered some and hope the problem gets resolved, but I would very much appreciate any advice and/or suggestions.

Otherwise the bike is a dream, beautiful aluminum chassis with great suspension (KYB forks with JBI kit and a TM brand CNC shock), it weighs less than my YZ250 plus, and as you all know, nothing beats electric power delivery! Thanks

 

[El Duderino]

Sweet build! Love that TM chassis, such cool bikes.

I don't have direct experience with the qs138 and emi, but at my day job we use braided sheathing to eliminate emi from position sensors on our electric motors.

We have measured the emi with a picoscope and saw a significant reduction using braided sheathing that is grounded. This could be a next step if your ferrite chokes don't work.

Here is an example. Amazon sells it.

Tinned Copper Braided Sleeving | Tinned Copper Braid Shield

Ground and shield harnesses and cables with tinned copper braided sleeving from Cable Ties And More. Our braid shields provide EMI, RFI & ESD protection.

www.cabletiesandmore.com

 

[Helienduro]

I also read about the grounded sheathing but didn’t think much of it, but I’m definitely not knowledgeable enough so I’ll follow your advice. Hope that works. Thanks a lot .

 

[Helienduro]

And yes, I was very lucky to find a TM rolling chassis. They are amazing, hand built (crafted I would say) Italian bikes. Thanks again.

 

[VINSANITY]

I have the same controller and the same studdering problem - it happens in a hole shot situation every time - full acceleration with good traction - if I lower the power level it stops - I will try the sheathing, do it put it on the sensor wires or the phase wires.

 

[El Duderino]

I have the same controller and the same studdering problem - it happens in a hole shot situation every time - full acceleration with good traction - if I lower the power level it stops - I will try the sheathing, do it put it on the sensor wires or the phase wires.

Sensor wires, You want to shield them from the interference.