RE: THE Official Traxxas E-REVO Thread
I got my revo used and the chassis was dyed when I got it. You'll need one balancer to balance the two packs in any configuration. If you hook up one balancer to each pack, you may have all the cells in one pack at 4.12v and all the cells in anoter pack at 4.22v, which would make the final 4s pack very unbalanced.