OK.
The 3S 2200 mAh batteries should be charged at about 2.2A (C-10 or 1/10 battery capacity)
The Accucel 6 is a 6A charger so you could charge at most (at C-10 or 2.2A in this case) is 2 batteries at a time. To balance them you need to charge separately or they could be charged in a series but to balance you would have to make up a balance port connector for each battery that both connect to a 6S balance plug then it to your charger. This would charge and balance both batteries.
The charger has the capacity for the 3S 500 mAh batteries but you have the limitation that the charger can only monitor 6S as a max so you are still limited to 2 at a time in series with the balance plug configuration described above.
The dual balance plug adapter (2X 3s to 6S) is the key and may have to be built from parts.
Thurmond