Your pacj should be charged at 2.1 amps or less. 1C is one times the capacity in mAh. So theoretically if it is discaharged you shoudl charge in for one hour at 2100 mA. Most chargers will taper the charge so it will actually take more than one hour and the rate will drop off at the end.

If a battery says it can be charged at 3C and it is a 2100 mAh pack, you can charge it a 6.3 amps.

I have never messed with any balancer and think they are unnecessary.