Buzzing and vibration since battery change

[Kintaro84]

Hi guys.
I've replaced my old battery a few weeks ago, from a 36v 12amps battery to a 36v 15amps, so no voltage change, only in the capacity.
Since the change there's a buzzing sound and a weak vibration coming out of the engine when I try to accelerate from a slow speed or accelerating uphill.
As you can see in the video, the bike starts good from a standing position but will buzz immediately after.
When the buzzing sound is heard I can feel that I lose acceleration momentum.
Please helppp!
https://youtu.be/OqaotXPoI2g

 

[fechter]

It sounds like one of the hall sensor signals is gone. Unplug the wires from the motor to controller and check the contacts. Reconnect and see if it's any different. If still bad, you can test the hall signals with a voltmeter.

 

[Kintaro84]

I've found one white wire that was unplugged, plugging it caused the throttle to drop the speed to almost nothing (pedal assistant still worked at the normal speed). I've cleaned all the connectors with a contact cleaner and plugged them back in firmly. I'm now back where I've started with the buzzing.
I can't seem to find any diagram for my controller wiring so I can't check the hall sensor since I don't know what wire to check.

 

[fechter]

Wow, that's a tiny little thing. Between the motor and controller, there will be 3 fatter wires (phase wires) and usually 5 skinny wires for the hall signals. If one of the fat wires had a bad connection, it could do what you describe, but more likely a hall signal problem.

The 5 skinny wires would be ground, +5v, and 3 separate hall signal lines. The hall signals switch between near zero and near 5v every time a motor magnet passes the sensor. To test, you turn on the controller and measure all the voltages on the skinny wires as you slowly turn the motor by hand. Since you don't know which wires they are, you probe all of them and see if 3 of them toggle with motor movement. Typical colors for the hall signals are yellow, green, blue, but this varies widely between manufacturers.

You could also lose this signal inside the controller where the wires attach to the circuit board. I've seen this several times.

 

[amberwolf]

I've replaced my old battery a few weeks ago, from a 36v 12amps battery to a 36v 15amps, so no voltage change, only in the capacity.
Since the change there's a buzzing sound and a weak vibration coming out of the engine when I try to accelerate from a slow speed or accelerating uphill.

Did this start on the very first test after replacing the battery, or did it start later, or after something else happened?

What happens if you put the old battery back in?

What else was done while changing the battery?

If any other wiring was touched or moved, it is possible one of the wires to the motor hall sensors or phases has become internally partially disconected or broken, where the contacts in a connector don't fully mate, or the conductors inside the wire insulation arent' making full contact anymore. These are typically problems you can't see, and may require measuring things with a multimeter to verify.

It is also possible that the new battery itself has a problem causing excessive voltage sag (or some other issue) and the controller is responding to this causing what you see/hear/feel.