I use Orion advantage 6A charge 3 mv d peak, and a few IB 4200 batteries can charge to at least 4600 mah.
However, I also have a pack IB of 4200 mah who had low voltage and dead after just 1 to 2 charge. And another pack who deteriorate rapidly after a few charge. I think there is a QC problem in some batch of IB 4200 battery.