Hey all, first post here and first LiFePo4 pack was just made! I already reached out to the shop I bought these from on Amazon but I figured I'd ask you guys while I wait for a response.
So I bought a set of matched Sinopoly cells from Amazon, and when I got them in I checked that they were all matched and that their voltages were within 50mv, which they were. However, and here is where I may have messed up, one of the cell terminals had some strange blue powdery residue on it, almost like a dab of white paint got on it. It didnt smell and it wiped off easily, so I didnt think anything of it. Anyway, I dont have a DC power supply, so I didnt top balance them (perhaps second mistake), but I figured they seemed well enough that I'd try playing around with them. They discharged down to ~15% great and when I got my solar delivered, I decided to then charge the battery. They seemed to charge great, nothing heated up, and they stayed within .07V of each other the whole time, up until I got up to around 3.4v per cell. Suddenly one of the cells started shooting up in voltage until the BMS tripped the overvoltage protection, going from 3.45ish to around 3.6+V in probably less than a minute. Turns out this was the cell that had the residue on the terminal.
Did I get a bad cell? Or is it more likely because I didnt top balance it? Sorry if I'm a bit rambly!
So I bought a set of matched Sinopoly cells from Amazon, and when I got them in I checked that they were all matched and that their voltages were within 50mv, which they were. However, and here is where I may have messed up, one of the cell terminals had some strange blue powdery residue on it, almost like a dab of white paint got on it. It didnt smell and it wiped off easily, so I didnt think anything of it. Anyway, I dont have a DC power supply, so I didnt top balance them (perhaps second mistake), but I figured they seemed well enough that I'd try playing around with them. They discharged down to ~15% great and when I got my solar delivered, I decided to then charge the battery. They seemed to charge great, nothing heated up, and they stayed within .07V of each other the whole time, up until I got up to around 3.4v per cell. Suddenly one of the cells started shooting up in voltage until the BMS tripped the overvoltage protection, going from 3.45ish to around 3.6+V in probably less than a minute. Turns out this was the cell that had the residue on the terminal.
Did I get a bad cell? Or is it more likely because I didnt top balance it? Sorry if I'm a bit rambly!