your #1 cell does not hold it's voltage for 50 hours.
this means there is a leak either internal to the cell or externally.
If its internal replace cell.
if it,s external removing the cell will stop the leak.
I am interested in building a 30 cell BMS
Could you provide me with a schematic for your 16 cell board.
And where can I buy a raw PCB
any info will help.