New 14s6p not balanced

Hi all,

I made a pack with brand new Sanyo NCR18650GA cells: 14s6p
After my first ride 1 6p block dropped to 3.01V and i got cut off by my BMS. All the other cellblocks where at 3.7V
I cut all spot-welded connections off that block and charged and discharged cell per cell with a B6 charger and got more or less the same results for the 6 cells: 177min 2956mAh, 178min 2958mAh, ...

The complete pack is now on the charger for more than 1 day and it looks like the BMS is not balancing: C1: 4.18 C2: 4.20 ... 4.17 4.21.
I measure this with my Fluke directly on the cells.

Is this pack out of Ballance ?
What could be the problem?

Thanks

I charge with 58,8V.

is 4.18 and 4.20 out of balance ?
I have this BMS: https://bmsbattery.com/bmspcm/733-10s-16s-50a-lipo-bms-system-battery-management-system-bms-pcm.html

smurphy said:

...is 4.18 and 4.20 out of balance ?...

Click to expand...

No

Balance threshold: 4.20±0.05V
So, balance voltage can be between 4.15V and 4.25V

Over voltage protection: 4.25±0.05V
So, the protection voltage can be between 4.20V and 4.30V.

It is obvious that one cell can have balance voltage over its' protection voltage and thus it is impossible to complete the absorption phase of charging the battery; especially if inside is used different circuit for balancing than for protecting (as usually BMS has balancer on daughter board and protection circuitry is on the motherboard).

You can try to continue charging the battery pack with ~20mA bypassing the protection, but you must monitor all voltages just in order that the balancer will not allow rise of voltage on any cell above 4.25V.

±50mV difference seems to me huge for Lion or LiPo cell.

In my previous post I taught that I've seen lowest voltage 4.1V, not 4.17V.
Your measurement of cell voltages between 4.17V and 4.21V shows that the BMS is between described limits, but I suggest you to do two measurements, one measurement with charger connected and finished charging and second measurement to make after disconnecting battery from charger and resting for 24 hours.