Connected is series with 1 balancer. You just need a balance harness that will let you do that (easy to make). See the lipo wiring page in BrianG's calculator
http://www.scriptasylum.com/rc_speed/_lipo.html
Connecting a 2s pack in series with a 3s pack of the same type is electrically no different to a single 5s pack, except instead of the tabs being soldered to one another you have an extra piece of wire to join the middle cells together. Same goes for balancing