TLDR: What happened (most likely) is that hall sensor ground shorted to phase wires with the controller turned off but still plugged into the battery when brake disc rotor bolts chewed through insulation as the wires exist the axle. The short caused sparks and plume of smoke so there was a decent amount of energy. Since the controller was off, how was this possible? Is there always voltage in the phase wires even when the controller is turned off?
Full story:
Today I went out on a ride on my QS 273 and Sabvoton 72200-M bike. About a mile in I got an error on my display "Controller protect" which happens once every few months when I go over a hard bump, turning off and on the controller makes it go away and I can continue, not today. Everytime I turned it back on and tried to set off with the throttle, the bike would nudge forwards before cutting off power and throwing "Controller protect" error. Only having allen keys with me, I took off controller cover and did a quick inspection of wiring and connections but everything looked fine so I decided to put the cover back on and just push it back home since I was a mile away.
As I started pushing it, I noticed that there was resistance in the motor which told me that there's something wrong with my phase wires but the resistance wasn't constant, it was on and off and the frequency would change depending how fast or slow I was pushing the bike, at a quick look, I noticed that the 6 bolts holding on the disc rotor to the motor, were rubbing against the phase/hall wires as they come out of the axle and as the wheel was turning, the bolts would touch the phase wires, short them out causing resistance then there would be a gap which would get rid of the short and repeat, this would also explain why the controller kept going into protection mode after nudging forwards because it would nudge forward, a disc rotor bolt would pass the phase wires shorting them causing the controller to go into protection mode.
Since I knew the issue, I ripped of the zip ties holding the phase wires to the frame so I could move them or reposition them so they would not be touching the bolts so I could at the very least get home, as I moved the phase wires, suddenly sparks started shooting out from underneath my controller cover followed by a constant plume of smoke for solid 2 seconds, I quickly started moving the phase wires forward and backwards and the sparks and smoke stopped. I quickly disconnected the battery after that. On the bright side after that smoke show, there was no longer resistance in the motor allowing me to push it home
When I got home, first thing I did was grab a fire extinguisher and then try reconnecting the battery which was uneventful but the controller was not turning on nor the display. I also noticed that the whole controller was covered in soot, at closer inspection I noticed that there was a large amount of soot at the wires as they come out the controller with a melted black wire which is the hall sensor ground, here's a picture, all the black stuff that you can see is not dirt and it's straight soot, the controller was very clean.
I haven't taken off the motor yet to inspect where the motor wires were rubbing but what most likely happened was that the bolts also rubbed off insulation from the hall sensor ground wire, when I was moving the wires to get them away from the disc rotor, the hall sensor ground must've shorted to the phase wires. I'm unsure what was causing the sparks but the smoke was most likely the ground wire just melting because it's thin and had a lot of resistance.
I tested my display and it still works so since it doesn't turn on with it plugged into the controller, this means that the controller doesn't even pass the battery voltage to the display so it's probably decently cooked. Since there was no longer resistance in the motor after the smoke show, most likely the FETs also blew which on the bright side it allowed me to push the bike home without much effort which I don't care since the controller was very likely cooked anyway even if the FETs weren't blown since it doesn't pass voltage to the display. My guess is that the hall sensor are probably dead too but fortunately QS 273 has two sets so I can use the other one.
When I was moving the phase wires right before sparks and smoke, the controller was turned off but still plugged into the battery so I'm unsure how shorting ground to the phase wires caused this? I'm unsure how controllers work but if the controller is turned off, shouldn't there be no power in the phase wires? I'm trying to figure this out as I always want to learn from my mistakes to not repeat them. I already ordered a new controller which should be with me in about a week which is more than enough time for me to take off the motor and repair the insulation.
Full story:
Today I went out on a ride on my QS 273 and Sabvoton 72200-M bike. About a mile in I got an error on my display "Controller protect" which happens once every few months when I go over a hard bump, turning off and on the controller makes it go away and I can continue, not today. Everytime I turned it back on and tried to set off with the throttle, the bike would nudge forwards before cutting off power and throwing "Controller protect" error. Only having allen keys with me, I took off controller cover and did a quick inspection of wiring and connections but everything looked fine so I decided to put the cover back on and just push it back home since I was a mile away.
As I started pushing it, I noticed that there was resistance in the motor which told me that there's something wrong with my phase wires but the resistance wasn't constant, it was on and off and the frequency would change depending how fast or slow I was pushing the bike, at a quick look, I noticed that the 6 bolts holding on the disc rotor to the motor, were rubbing against the phase/hall wires as they come out of the axle and as the wheel was turning, the bolts would touch the phase wires, short them out causing resistance then there would be a gap which would get rid of the short and repeat, this would also explain why the controller kept going into protection mode after nudging forwards because it would nudge forward, a disc rotor bolt would pass the phase wires shorting them causing the controller to go into protection mode.
Since I knew the issue, I ripped of the zip ties holding the phase wires to the frame so I could move them or reposition them so they would not be touching the bolts so I could at the very least get home, as I moved the phase wires, suddenly sparks started shooting out from underneath my controller cover followed by a constant plume of smoke for solid 2 seconds, I quickly started moving the phase wires forward and backwards and the sparks and smoke stopped. I quickly disconnected the battery after that. On the bright side after that smoke show, there was no longer resistance in the motor allowing me to push it home
When I got home, first thing I did was grab a fire extinguisher and then try reconnecting the battery which was uneventful but the controller was not turning on nor the display. I also noticed that the whole controller was covered in soot, at closer inspection I noticed that there was a large amount of soot at the wires as they come out the controller with a melted black wire which is the hall sensor ground, here's a picture, all the black stuff that you can see is not dirt and it's straight soot, the controller was very clean.
I haven't taken off the motor yet to inspect where the motor wires were rubbing but what most likely happened was that the bolts also rubbed off insulation from the hall sensor ground wire, when I was moving the wires to get them away from the disc rotor, the hall sensor ground must've shorted to the phase wires. I'm unsure what was causing the sparks but the smoke was most likely the ground wire just melting because it's thin and had a lot of resistance.
I tested my display and it still works so since it doesn't turn on with it plugged into the controller, this means that the controller doesn't even pass the battery voltage to the display so it's probably decently cooked. Since there was no longer resistance in the motor after the smoke show, most likely the FETs also blew which on the bright side it allowed me to push the bike home without much effort which I don't care since the controller was very likely cooked anyway even if the FETs weren't blown since it doesn't pass voltage to the display. My guess is that the hall sensor are probably dead too but fortunately QS 273 has two sets so I can use the other one.
When I was moving the phase wires right before sparks and smoke, the controller was turned off but still plugged into the battery so I'm unsure how shorting ground to the phase wires caused this? I'm unsure how controllers work but if the controller is turned off, shouldn't there be no power in the phase wires? I'm trying to figure this out as I always want to learn from my mistakes to not repeat them. I already ordered a new controller which should be with me in about a week which is more than enough time for me to take off the motor and repair the insulation.