You need to charge each battery individually up to 14.6V, in order to properly balance each cell and reset the SOC.
I'm in this exercise with some batteries sitting for a few months and which need to be properly balanced before being connected in parallel.
You could also connect all batteries together in parallel and charge up to 14.6, but be careful if one cell is too heavily unbalance in regards of the 3 others internal cells, it may lead to overcharge other cells.
Better to closely watch battery and charge up to 14.6 by monitoring them, increasing voltage step by step.
For one of the battery with a severe internal unbalance, it appears only when 3 of the cells reach over 3.4V, where the last cell was still at around 3.35V.
3 cells were almost charged while the last one was few Ah behind... I add to lower the amp around 1A and decrease top voltage to remain below 3.65V/cell for the 3 charged...Internal balancing kicked in, but I believe it is limited to something around 2 or 300 mA...It tooks hours for the last cell to reach the level of the 3 others...
On one battery, the unbalance was so heavy that I opened the case and charge the individual cell via the balance plug.
These batteries are now performing perfectly well, used in a serie of 7 in an electrical car. I have some peak power at around 270A and all 7 batteries remains perfectly balanced!