Just keep in mind: The charger is designed to charge a pack 2S2P. The more 2S cells you add in parallel the more the input current has to divide for each parallel 2S. ( example: suppose the input current from the charger is 1A. Split between each parallel 2 series , each channel will get 500ma. Add another 2S in parallel and each will get 333ma....etc, etc.) It will still work only the charge current will be lower to each 2S link that you add. Therefore it will take longer to charge the pack. No matter what you do with the batteries the input current from the charger will remain the same ( unless you have an adjustable charger of course ).Vancbiker said:You can use to charge only 7.4V packs. 2 or 4 or 6 cells is fine as long as the voltage is 7.4V.