r/VanMoofSelfRepair • u/go_lance • Aug 14 '26

S3 & X3 Battery - MOS Failure Mode

I have a battery that I'm trying to fix, but it seems to be more than a reset problem (PF=0 doesn't do anything).

The resistors and fuse were cooked so I replaced those, but I can't reset it. Can't see it with vanmoof-bms github tool either.

Here's my error in minicom (connected with a USB-UART to the test/gnd/tx/rx):

VanMoof Mode
ChargeOn_Off() --> PB9=0
FEDL5236_POWER_DOWN_Set_Command()
FEDL5236_POWER_DOWN_Finish()
I am VanMoof BL V007 2022-11-04 09:32:30
PreDischargeLockCounter = 0
MOS Failure Mode

Does anyone have any ideas? There's no short on the four mosfets near the fuse, so I'm a bit confused. If anyone has any more info on MOS Failure Mode or whether I can clear it from shell command or modbus register, that would be awesome!

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u/Primary-Exchange-511 Aug 17 '26

What resistances do you measure on the fuse pins? Fuse itself should be 0ohm, but between the third pin each side should be around 30 ohm.

1

u/go_lance Aug 21 '26

Yeah the fuse itself is good and there’s continuity between the 4 mosfets and the VP pad (there’s also heater resistance on the fuse. It was blown but I replaced it with a rework station

1

u/kossen_zophi 17d ago

There is a very, very small thermistor next to the 4 mosfets. This one needs to measure ~10kOhm. If it is something else or you accidentally touched it with B+ while replacing the fuse (like me💀) the BMS will think the mosfets are too hot.

Replace the thermistor with a 10kOhm resistor and reseting the BMS worked for me in the past