My thirty cells all remain connected in one long series string, nothing is changed or disconnected.
The whole battery charges and discharges normally each day, with the BMS, balancer, and everything else still connected up.
The voltage across each cell is measured when the full normal charging cycle has completed, and charging current has ramped right back to zero. If its a horrible grey cloudy day, and this fully charged zero current condition cannot be reached, just leave it alone and hope for more sun the next day.
The particular cell with the highest measured voltage is then very slowly brought back down to the exact 3.45v average, with a one ohm discharge load connected across that particular cell.
All the other cells, some will be slightly below 3.45v, some slightly above 3.45v.
Just bring back the worst highest voltage cell to the 3.45v average each time, one cell per day, one cell at a time.
If one cell is very much lower than all the others, bring the voltage up with gentle charging, at no more than about three amps.
Very important to only correct one cell at a time doing this each day, then give the whole battery at least 24 hours to go through another full normal days charge/discharge activity to let every cell readjust and the whole string settle down to the very slightly changed conditions.
The secret to success with this is patience.
Trying to hurry the whole thing up just leads to chaos, and the voltages will be all over the place and measure different each day.
If it does go crazy inconsistent on you, just leave it alone for a week or longer and when it has all settled back down, sneak up on it.