Yes, and if they were (nearly) identical it is do-able with one balancer. I think there is enough variance in the packs that doing the two balancer thing is likely a safe play.

DM

I don't agree. If two packs were, and are, always used together in the same vehicle, the cells won't be any more out of balance than a single 4s pack. Two 2s packs is no different than one 4s pack, electrically speaking. If large cell voltage variances were the norm, you'd see lipos with larger balancer wires/connectors so each cell could be charged at 1C individually. The only time two seperate packs would be imbalanced is when new. During the the intial charge, I would charge and balance at 1/10C to get them equalized. After than, any large imbalances would be from a cell going bad, or a really poor cell batch IMO.