BAFANG M560 MOTOR JITTERING

[George Kinsey]

Hello everyone i am new to the bike community and i have recently brought a second hand bike with a m560 bafang mid drive motor in it.
It was riding perfectly first couple months and i ride pretty vigorously, but my motor has started getting stuck on something inside while its trying to accelerate and makes a horrible noise of throwing a wrench into a gear and i thought it might be a derailer problem as maybe its the swing arm is bent so the chain cathes and so on but i got my bike back today and again a few minutes later it started happening again.
i am not at all there when it comes to electronics but it feels like a belt inside the motor has to much slack causing it to catch in itself and jam but i do not want to take it apart as i have no clue what im doing and cant find any information about this problem online.
thank you for reading that long story and any help would be much appreciated thank you very much!!.

 

[cyclebuddy]

...and i ride pretty vigorously...

This may or may not be your problem, but it does result in Bafang torque sensor mid-motors like your M560 stuttering...

I have a Bafang M400 on a bike that uses smaller 10.4Ah batteries... when ridden "vigorously" and the battery is below full capacity, you can reach a state where the battery starts sagging to meet demand from the motor. What results is a state of rapid stuttering from the motor, and the instant remedy is to back-off pedaling quite so hard which is demanding more power from the motor than the battery can cope with. Note the battery stays on - it's the controller that's very rapidly cutting and restoring power, not the battery.

What's happening in my case is with my battery the LVC is pre-set in the BMS to 28v on the 36v battery. The LVC of the controller is by default higher at 32v. Aggressive pedaling makes the motor demand more than the battery can still give in its partially depleted state which makes the battery sag below the controller LVC, and that makes the controller cut-out. That cut-out gives the battery the opportunity to recover and the controller restores power to the motor... and for as long as you keep demanding so much power (pressing on the pedals so hard) you get this really rapid stuttering - yes, it does feel like a mechanical issue, but (at least in my case) isn't.

What I'm getting to is that - if this is your issue - your battery is probably at least partially knackered - or at least no longer capable of delivering the high levels of current your quite powerful M560 is demanding when being ridden hard. When it next happens, try pedaling less forcefully and demanding so much and see if the problem disappears.

 

[saneagle]

The above is a plausible explanation, but if the battery is good and it happens when the battery is full, it would do that if the phase wire connectors are loose, which has a high probability if the previous owner did something with the controller, like replaced it.

 

[George Kinsey]

This may or may not be your problem, but it does result in Bafang torque sensor mid-motors like your M560 stuttering...

I have a Bafang M400 on a bike that uses smaller 10.4Ah batteries... when ridden "vigorously" and the battery is below full capacity, you can reach a state where the battery starts sagging to meet demand from the motor. What results is a state of rapid stuttering from the motor, and the instant remedy is to back-off pedaling quite so hard which is demanding more power from the motor than the battery can cope with. Note the battery stays on - it's the controller that's very rapidly cutting and restoring power, not the battery.

What's happening in my case is with my battery the LVC is pre-set in the BMS to 28v on the 36v battery. The LVC of the controller is by default higher at 32v. Aggressive pedaling makes the motor demand more than the battery can still give in its partially depleted state which makes the battery sag below the controller LVC, and that makes the controller cut-out. That cut-out gives the battery the opportunity to recover and the controller restores power to the motor... and for as long as you keep demanding so much power (pressing on the pedals so hard) you get this really rapid stuttering - yes, it does feel like a mechanical issue, but (at least in my case) isn't.

What I'm getting to is that - if this is your issue - your battery is probably at least partially knackered - or at least no longer capable of delivering the high levels of current your quite powerful M560 is demanding when being ridden hard. When it next happens, try pedaling less forcefully and demanding so much and see if the problem disappears.

Yes it does sound like a similar problem but it happens even when i am going slow and pedaling up a hill i think it’s something to do with the actual motor underneath the frame.

Whatever makes the motor spin/crank i think is broken or has to much slack and needs tightening.

but no bike shops near me work on bafang batteries as i called up five shops none do anything to do with bafang so am new to this with little knowledge of how to dismantle and restore the motor.

 

[cyclebuddy]

...it happens even when i am going slow and pedaling up a hill...

Speed has nothing to do with it. It's about how much energy you're trying to pull from the battery. Going up hills requires quite a bit of energy because by definition you're still pushing on the pedals even if in a lower gear and spinning a bit faster. It's pushing on the pedals that triggers the torque sensor that determines how much power the motor gives and therefore how much it's trying to draw from the battery.

Try cycling up a hill with the motor turned off and see if it still does it.

PS: The controller is in the motor.

 

[guerney]

Is there a voltage readout on your display, or can you switch to it if not? If it's the same phenomenon, I've experienced it with my Bafang BBS01B mid-drive, on the very rare occasion when I'm down to lithium fumes at very low battery a sort of whirry scritching with no assistance uphill, because the battery is incapable of supplying enough power, evident by very low voltage showing on the display. Triggers the Low Voltage Cutoff programmed in the controller eventually.

 

[saneagle]

Yes it does sound like a similar problem but it happens even when i am going slow and pedaling up a hill i think it’s something to do with the actual motor underneath the frame.

Whatever makes the motor spin/crank i think is broken or has to much slack and needs tightening.

but no bike shops near me work on bafang batteries as i called up five shops none do anything to do with bafang so am new to this with little knowledge of how to dismantle and restore the motor.

The slower the motor turns, the more current it draws, so any connection or battery issues happen at low speed, not high speed.