It only charges. It should be able to do both packs at 9.9 amps. It is pretty close to the single version except it can do two packs. It has 3 charge modes. Peak, Yokomo Charge (pulse type charge) and temperature charging.
I have two of the single charger versions and really like them. I bought mine from SpeedTech. My new chargers draw alot of attention from other racers. They do work well. Programming is not really too hard but the directions are a little rough but good enough to figure them out without too many problems.
I think they work great.