It’s very likely the cells have been damaged, but in any case to bring it back to normal you need a new BMS, preferably with an 84mA or higher balance function. Bestech D140 will do, 10S flavor. Be advised that this battery may be permanently bad though before you decide to spend any money on it. Also, I don’t even know if it’s a good idea to use the D140 or another BMS in bypass mode for these cells. Probably would need to discharge through the BMS which means a big heavy expensive BMS, not the D140.
Do not charge it or discharge it (by running motors) until this is fixed
Trying to discharge packs individually to get 3.6V on each pack. I got a thinner BMS on charge only (like the old BMS on the raptor). GOnna plug everything after to see if it charge more than 55%.
Last results:
10S4P : Voltage mesured: 42V
Pack 1 : 3,62V
Pack 2 : 3,63v
Pack 3 : 3,65
Pack 4 : 3,66
Pack 5 : 3,85
Pack 6 : 4,79
Pack 7 : 4,83
Pack 8 : 4,81
Pack 9 : 4,78
Pack 10 :4,8
If you have cell groups over 4.25V, this is an immediate fire hazard and dangerous. Place this battery gently on a concrete surface and don’t try to charge it more or discharge it until you understand what is wrong.
Using the fan like that should discharge the P groups, but maybe connecting a BMS would be a safer way to do it. I don’t know how much current that fan is drawing.
You have 5 groups (20 cells) at around 4.80v and not a single cell caught fire? Impressive!
But for real, like Brian said, carefully put that battery somewhere outside on concrete, try to discharge it to safe voltage and think about new battery. @Acido did some overcharging experiments, maybe he could give some data
Well, thanks for your answers guys. My last hope is to discharge this battery with the fan but it’s freaking long. Otherwise, I will rebuild a new battery. Gonna put that operation on the balcony just in case but on 4 month, it never get hot so… I suppose I’m lucky.
Last thing, I misplaced the Bluetooth recepter I think, I gonna reopen the box and check that because It seem I got some connection issue with the remote.
I have a similar issue. I have a Samsung 30Q / 10s3p pack. I noticed that it only charges to 94% or so. I decided to take it apart and test each group of cells. I found that group #2, which should read 4.1v only reads 3.5 volts. What is the recommended solution here?
Should i discharge all cells down to 3.6 then hook up charger and see if it fixes issue?
Should I try to charge just that group of cells that are low? If so, how do i just charge that one group?
Should I just convert my pack to 10s2p and just take out a bunch of batteries? (i dont have spot welder)
Here is a video i made testing the battery: youtu.be/HzaxFkAk_dY
@danp You could either discharge them all to be equal (variance of 0.05v or less) or simply do a supervised charge on that specific pgroup to bring it up to the same level then do a power cycle to see if it follows with the others
When you say discharge all to equal. How would I do so?
Hook up some sort of load to each grouping? (run a load that requires 3.6volts and run positive to where i was testing each pack and ground to ground?)
Supervised charged seems a little easier and less time consuming. but how do i supervise charge just that one grouping? Same way, just positive to the positive lead and ground to main ground… but what do i use to charge it?
