To charge a 6s battery that is 5600mAh, you will need a charger with at around 200 watts output (150 watts minimum) to charge at 1c. If you need to charge higher capacity batteries or higher c-rating, the power requirement will be even greater. Hyperion makes some good chargers that are AC/DC that fit that bill.

It is unfortunate, but DC chargers on a good power supply do a better job on large capacity high voltage batteries.