I received and assembled my battery a couple of months ago (with new cells) and everything seemed fine. I charged it to 50% (cells at 3.75v) but left it there as I didn’t have my wheel as yet (Grin All-axle + baserunner).
Yesterday I finally got all the parts, assembled the bike, went for a 10 minute test ride (up and down some very steep hills) and it all worked well under power, but the battery shut down several times under regen. Each time it did this it automatically restarted after about 10 seconds and then worked normally. The cutoff under regen is not the problem I want solved just now - I will come back to that later.
When I got off the bike the display showed 27% so I removed the battery and plugged it into the charger. I connected to it with the app and everything seemed to be working normally (charging). Some cells were switching between red and green and I assumed this was normal.
About 2 hours later I noticed the 4 LEDs were all pink and when I connected with my phone I saw this…
I left it for 12 hours and tried again - same thing. I then disassembed the battery and tested all cells with my multimeter and they were all normal, around 3.84v (±0.01). I then reassembled the battery and the error was still there. I tried switching all the cells around to different locations but no difference. I checked the contactors for cells 4 and 5 and there does not appear to be any problem. When I tension up the 2 halves the gap in the middle is about 1mm and I can see all the cell contactors are slightly flexed out. I also tried cleaning the contactors by wiping gently with a small flat blade screw driver but no change. I am almost certain the problem is NOT related to the contactors making a good connection to the cells.
I have tried pressing the reset button on the BMS multiple times but it makes no difference.
Any help would be appreciated as I don’t know what else to try.
So after a bit more investigation I believe I have found the problem. Using the multimeter with the battery seperated and the BMS removed I discovered I could measure the cell voltages between each cell and its corresponding pin where the BMS plugs in. On the right side every cell measured 3.84v, but on the left side cells 4 & 5 measured 0v. I then unscrewed the outer cover and determined there is a component that I assume is a fuse labelled F204 that is connected to cells 4 & 5 and appears to be blown. All the other fuses on the board have no resistance but this one is open circuit. I’m surprised this happened during charging. Awaiting your advice on what to do to resolve this.
Thanks Alex, I suspect this fuse was already defective when I received the battery. If you recall I posted a problem when the battery was first assembled and I attempted to charge it. One of cells connected to this fuse was low which makes me think the fuse was already limiting the charge current. Then on the first ride the battery kept cutting out when I applied regen brake, even though the power was not very high. And then finally the fuse failed completely during a normal charge with the supplied charger. Is it possible to send me a new left side board? The idea of soldering over the fuse worries me, and I do not have the skills to solder a new fuse in.
the fuse as triggered on the first assembly because you plugged a low cell: what happens when you do this, is that the other cells of the group create an inrush current to the lower cell and that is what triggered the fuse.
the subsequent issues are all related to the fact you have one level that has only 2 cells connected compared to the 3 in normal usage.
