15C is the max disharge rate and has nothing to do with how fast you can charge.
1C is generally the highest accepted rate so no matter what charger you use it will take at least 1 full hour PLUS.
Why do I say PLUS? most lipo chargers will charge to about 90% or so of the batteries capacity then it will slow down for the last 10% to prevent heating and possible fire.
I personally use the Bantam Estation charger on my lipos and it does balance charge.
http://www.bantam301.20m.com/BC-5.htm