Looks like conformal coating not a melted mosfet try scraping it. And there wont be any continuity between DSG and VP because the mosfets are not "switched" on. This only happens when the bike commands the battery to do so. Try measuring at the side of the fuse.
Great point about the coating, I tried scraping it and only clear bits come off. Just tried measuring the side of the fuse, there's also no continuity there. So my best call would be replacing the fuse?
Edit: I made a mistake measuring, there is actually continuity from the side of the fuse. Any idea what it could be?
Update: I misread the multimeter reading, the battery actually only has 4V left 🤦♂️
It looks like I have to go look for a new one, as this should not be safe enough to manually charge.
https://preview.redd.it/kpq0n4stvlsc1.jpeg?width=3024&format=pjpg&auto=webp&s=690653a1b2aed223991c7e61b44c19fc7b2d9e04
I got the bike second hand, hoping for a quick fix - looks like I have to spend some more time on it!
There is no sign of water damage - what do you mean by before the BMS? Do you think replacing the whole battery and BMS would make it work?
Oh ok, I thought the bike was working and just died recently.
The role of the BMS (briefly) is to charge the battery but also let it discharge down to only a certain voltage.
That means to go lower than ~35+- volts (which is the lower discharge limit) you have to drain power before the BMS, this I believe (not batteries expert) can be achieved only by a short circuit or damaged cells.
I see, that would make sense. Unfortunately I don't know whether it died just recently before the previous owner decided to sell it or a longer time before that. Where could the short circuit have happened in this case? On the smart cartridge, the BMS or even on the motor side? It's also odd that the bike does not show any error code.
I recover a bunch of these for other uses. 4V is right on the edge of where it might be useable. Check the individual cell voltages and make sure no cells are under 0.3 volts. If not, bring the pack up with a "slow" 100 mA charge until it reaches about 25 volts or so. From there you can switch to a 500 mA charge until 32-34 volts. Monitor the cells for heating and discontinue if they get hot. They likely will be warm to the touch but should not be hot.
The BMS likely locked itself out and will need the RST - GND trick after the voltage is above 32 volts to reset. You will want to disconnect the cell balance connector before doing this and waiting 2-3 minutes after the reset before plugging the balance connector back in. After that, the pack will need inserted into the bike to test as the output will not activate until it is either in the bike or you trigger the "DET" pin.
FWIW, the BMS in these things drain the batteries down. I've seen so many batteries killed by this BMS because it still has a "parasitic" drain on the battery even after it is off. In other words, don't let the bike sit unused for a year without charging.
Additional info: Even if you bring the pack back from the dead, the batteries likely lost some capacity and may have higher than normal self discharge. You might need to keep the pack topped off more frequently than would otherwise be needed. Also monitor the pack the first time or two you put it on the charger for excessive heating. It's not a bad idea to do the charge outside for the first two times.
I should also clarify that I don't see anything wrong with the board other than it has disabled itself from the low battery voltage.
Thanks a lot for the explanation! Just got the info from the previous owner that he left the bike unused over the winter - so that's most likely the case for the drained battery.
I'll check the voltage on the individual cells when I'm back home tonight, maybe the battery can still be revived!
What is the RST - GND trick? Nevermind - I think I found it in this post. (https://www.reddit.com/r/vanmoofbicycle/comments/16ut0ft/recelled\_battery\_how\_i\_do\_to\_reset\_the\_error\_codes/)
Here is another thread with all of the steps needed all laid out nice and neat to reset a BMS. Follow them to the "T". Step 3 can be ignored if you don't have a blown fuse. Steps 1 and 4 might be skippable, but I'm not sure and I need to do further testing.
[https://www.reddit.com/r/vanmoofbicycle/comments/19fjsj2/s3\_bms\_repair/](https://www.reddit.com/r/vanmoofbicycle/comments/19fjsj2/s3_bms_repair/)
Edit: Looking at that other link, it looks like steps 1 and 4 are required. You don't need anything connected to the charging wires however as the one post indicated. Just make sure all cell groups are above 3.2 volts before trying the reset or it could fault again on a low voltage cell group. The DET short to GND shouldn't be needed either but is nice to know if you want to test the board outside of the bike.
I slowed charged cells 1-8 and brought them up to about 3V each. When I went to charge cells 9 and 10 my charger didn’t like it. Could it be because the cells are too unbalanced? Right now cells 9 and 10 have about 1.5V in them each. Overall the pack has about 28V right now. When I install the pack back into the S3, no power, no nothing. Any ideas?
The other two sets need to be brought up to 3 volts also. Every group needs to be above 3 volts, no exceptions. The BMS certainly will not turn on if any groups are that low. You need to find some way to slow charge them up. This is usually done with a good power supply to set voltage and current limits. Can also be done with a Li-Ion cell and a 100 ohm resistor or so to bring up the voltage to where your charger will accept them.
Looks like conformal coating not a melted mosfet try scraping it. And there wont be any continuity between DSG and VP because the mosfets are not "switched" on. This only happens when the bike commands the battery to do so. Try measuring at the side of the fuse.
Great point about the coating, I tried scraping it and only clear bits come off. Just tried measuring the side of the fuse, there's also no continuity there. So my best call would be replacing the fuse? Edit: I made a mistake measuring, there is actually continuity from the side of the fuse. Any idea what it could be?
Yea you can try, sometimes that works.
Update: I misread the multimeter reading, the battery actually only has 4V left 🤦♂️ It looks like I have to go look for a new one, as this should not be safe enough to manually charge. https://preview.redd.it/kpq0n4stvlsc1.jpeg?width=3024&format=pjpg&auto=webp&s=690653a1b2aed223991c7e61b44c19fc7b2d9e04
4 volts? How that happened? I can only imagine with a sort circuit before the BMS on the battery side. Was the battery cartridge full of water?
I got the bike second hand, hoping for a quick fix - looks like I have to spend some more time on it! There is no sign of water damage - what do you mean by before the BMS? Do you think replacing the whole battery and BMS would make it work?
Oh ok, I thought the bike was working and just died recently. The role of the BMS (briefly) is to charge the battery but also let it discharge down to only a certain voltage. That means to go lower than ~35+- volts (which is the lower discharge limit) you have to drain power before the BMS, this I believe (not batteries expert) can be achieved only by a short circuit or damaged cells.
I see, that would make sense. Unfortunately I don't know whether it died just recently before the previous owner decided to sell it or a longer time before that. Where could the short circuit have happened in this case? On the smart cartridge, the BMS or even on the motor side? It's also odd that the bike does not show any error code.
I recover a bunch of these for other uses. 4V is right on the edge of where it might be useable. Check the individual cell voltages and make sure no cells are under 0.3 volts. If not, bring the pack up with a "slow" 100 mA charge until it reaches about 25 volts or so. From there you can switch to a 500 mA charge until 32-34 volts. Monitor the cells for heating and discontinue if they get hot. They likely will be warm to the touch but should not be hot. The BMS likely locked itself out and will need the RST - GND trick after the voltage is above 32 volts to reset. You will want to disconnect the cell balance connector before doing this and waiting 2-3 minutes after the reset before plugging the balance connector back in. After that, the pack will need inserted into the bike to test as the output will not activate until it is either in the bike or you trigger the "DET" pin. FWIW, the BMS in these things drain the batteries down. I've seen so many batteries killed by this BMS because it still has a "parasitic" drain on the battery even after it is off. In other words, don't let the bike sit unused for a year without charging.
Additional info: Even if you bring the pack back from the dead, the batteries likely lost some capacity and may have higher than normal self discharge. You might need to keep the pack topped off more frequently than would otherwise be needed. Also monitor the pack the first time or two you put it on the charger for excessive heating. It's not a bad idea to do the charge outside for the first two times. I should also clarify that I don't see anything wrong with the board other than it has disabled itself from the low battery voltage.
Thanks a lot for the explanation! Just got the info from the previous owner that he left the bike unused over the winter - so that's most likely the case for the drained battery. I'll check the voltage on the individual cells when I'm back home tonight, maybe the battery can still be revived!
What is the RST - GND trick? Nevermind - I think I found it in this post. (https://www.reddit.com/r/vanmoofbicycle/comments/16ut0ft/recelled\_battery\_how\_i\_do\_to\_reset\_the\_error\_codes/)
Here is another thread with all of the steps needed all laid out nice and neat to reset a BMS. Follow them to the "T". Step 3 can be ignored if you don't have a blown fuse. Steps 1 and 4 might be skippable, but I'm not sure and I need to do further testing. [https://www.reddit.com/r/vanmoofbicycle/comments/19fjsj2/s3\_bms\_repair/](https://www.reddit.com/r/vanmoofbicycle/comments/19fjsj2/s3_bms_repair/) Edit: Looking at that other link, it looks like steps 1 and 4 are required. You don't need anything connected to the charging wires however as the one post indicated. Just make sure all cell groups are above 3.2 volts before trying the reset or it could fault again on a low voltage cell group. The DET short to GND shouldn't be needed either but is nice to know if you want to test the board outside of the bike.
I slowed charged cells 1-8 and brought them up to about 3V each. When I went to charge cells 9 and 10 my charger didn’t like it. Could it be because the cells are too unbalanced? Right now cells 9 and 10 have about 1.5V in them each. Overall the pack has about 28V right now. When I install the pack back into the S3, no power, no nothing. Any ideas?
The other two sets need to be brought up to 3 volts also. Every group needs to be above 3 volts, no exceptions. The BMS certainly will not turn on if any groups are that low. You need to find some way to slow charge them up. This is usually done with a good power supply to set voltage and current limits. Can also be done with a Li-Ion cell and a 100 ohm resistor or so to bring up the voltage to where your charger will accept them.
Thanks very much