BBS02 mid drive pulsing, or twitching

[Idgtech]

Hi All I have a Bafang BBS02 which I have been running for over 12 months without any problems. On the last couple of trips out, I have noticed the pedals twitching or pulsing with loss and regaining of power. It is like 3 or 5 times a second so quite fast, but constant. It is more noticable when I am using more leg power.
The bike still pulls, but the twitching means it is not smooth.
I do not have brake sensors fitted, but I do have a gear change sensor.
Any ideas

 

[il Munduato]

I'd start by unplugging the gear sensor.
Any errors on the display?
Any brake indicator blinking on the display?
Do you have a throttle? If so does that work correctly?

 

[Idgtech]

Hi, no error indication on the display.
The bike has a throttle and works fine.
I unplugged the gear sensor and gave it a short ride. It seemed to stop the fast twitching. I rode to work next day and thought all was solved. However on the way home, the bike was again losing power but differently. It was more of a loose connection.
At one point it completely died. I reached down to see if the battery was hot. As soon as I touched the battery it sparked into life.
I quickly established a connection problem at the battery. When I got home I took it of to find a black burned pin on the plug between battery and base. It has clearly been getting hot. I have ordered a new one but wonder if this is a cause of the original pulsing or a consequence of it.

 

[il Munduato]

The battery connection goes bad from vibration and/or water ingress.
I'd guess that the battery was starting to have a problem and that the gear sensor accelerated it with pulsing power on/off.
If you briefly pause pedaling before shifting there's no need for the gear sensor.
12k mi/3 yrs without one and never broke a chain or had drivetrain issues.

 

[PedalUma]

I would check the PAS calibration.

 

[Idgtech]

Hi, what do you mean by calibration? Settings using the programming cable? Or some other method?
Thanks

 

[il Munduato]

I don't believe there is such a thing. Perhaps calibration isn't the correct term?

A fouled battery connection you know and can definitely show itself in that pulsing manner.
Now your other troubleshooting that showed that the throttle was working fine and that the shift sensor may be faulty I'd start there.
It is possible you have a loose connection in the motor, faulty Cadence sensor or controller... But I would start with the battery repair and confirm that the shift sensor is ok or disconnected before contemplating further.