The power a charger needs depends on what you are charging and at what amps. I can charge a 1s lipo at 5 amps and it only draws about 2 amps from the supply (my power supply has adjustable voltage, volt and amp meters). 4 cell NiMH at 5 amps draws about 5 amps. 6 cell at 5 amps draws about 6 amps. A 2s 300mah pack at .3 amps doesn't even move the meter