Nomis Posted September 9, 2023 Share Posted September 9, 2023 My MCM5, ridden by my girlfriend, shut off immediately causing her to faceplant. She was riding approximately 5 kph and not accelerating. The wheel is dead and I can't seem to find anything visually wrong with it ord the control board. Any suggestions on what I can do or test on the wheel? Quote Link to comment Share on other sites More sharing options...
alcatraz Posted September 9, 2023 Share Posted September 9, 2023 I had a low speed shutoff on my similar wheel (msx84). I couldn't find the damage until taking the heatsink off the board. A mosfet had blown. I'm not exactly sure what caused it but I am riding that same board today without issues. I believe it was that the screws holding the mosfets down onto to heatsink had loosened and slowly cooked one of the mosfets. The board can report a low temperature but your mosfets can still overheat if they aren't bolted down (with loctite, to prevent them from losening). One clue that this could be happening was that my board never really got warm. I never saw temps over 43C. Now after fixing the board I have seen temps of 50C, which is good. It means the heat is being dumped into the heatsink. I also added two extra fans. Quote Link to comment Share on other sites More sharing options...
Nomis Posted September 9, 2023 Author Share Posted September 9, 2023 (edited) Thanks. Allready checked the Mosfets and also measured the individual Mosfets according to this video and all seem fine: Furthermore the wheel spins freely and blocks when connecting the motor wires, so nothing wrong there either. Edited September 9, 2023 by Nomis Quote Link to comment Share on other sites More sharing options...
alcatraz Posted September 10, 2023 Share Posted September 10, 2023 There shouldn't be added motor resistance when connecting the motor wires to the board. Only when shorting them (if memory serves). If you've got resistance then I believe some of the mosfets have failed, without visible damage. I might have misunderstood you though. Quote Link to comment Share on other sites More sharing options...
Nomis Posted September 10, 2023 Author Share Posted September 10, 2023 (edited) Yeah it was badly worded. There wasn't any resistance when the motor wires were plugged in the board. When disconnecting them from the board and shorting them together, the resistance is there, as expected. Edited September 10, 2023 by Nomis Typos Quote Link to comment Share on other sites More sharing options...
alcatraz Posted September 10, 2023 Share Posted September 10, 2023 (edited) You could check the 5v power supply. I'm not sure but maybe the controller chip runs off of 5v. Might want to check for low resistance to ground at the output of the psu, indicating a short/failed component somewhere. Edited September 10, 2023 by alcatraz Quote Link to comment Share on other sites More sharing options...
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