Batteries have mah and voltage ratings. They also have a C rating. If you mtiply the mah by C that gives you the max amp draw te battery an deliver. A 2C 5000mah battery can deliver 10Amps.
They also have a charging C figure. If a battery is 5000mah and rated at 1C charge (default c number) it can be charged at up to 5amps. A 2C battery coul be charge at 10amps.
The higher the amps the faster it will charge. To charge a 11.1v 5000mah at 1C you will need a charger that can deliver 5amps and about 60w. Pretty cheap an easy. If however you want to charge same battery at 2c you will need a charger that deliver 10amps and about 100w.
If you start using higher voltage and mah batteries and want to charge them in less than an hour you will need more like 200w and 10amp charger.