New to the boards and had a question. I posted this in the charger section as well, but this section appears to be more active.

I bought an EZ Peak charger and the dual 3S charger expansion. I have two 3s 8400mah Traxxas packs. What rate should I charge these packs with the dual board? My LHS suggested charging a single pack at 3 a, even though the charger will go to 6. Any feedback and suggestions are much appreciated.