[suicideneil]

You need to make the balancer see the 2 lipos as one big one, and that wont work without the balancer being part of the charger (same effect as wiring a pair of lipos in series to the charger and using the built in balancer). There needs to be a ground/black wire from both lipos connected to the balancer in this instance, and you cant do it without wiring both lipos to the balancer in parallel; not advisable as the balancing wont be accurate due to small differences in cell voltage between the two lipo packs.

In short, wont work. You need to buy another lipo balancer if you want to use both charge circuits on the charger, have a balancer for each lipo.