The Common Sense RC Ultra-Balancer is the simplest method for keeping your Lipo packs balanced.  It can be used for packs up to 22.2 volts (6S).  Works as a stand-alone balancer before charging or simultaneously with your charger doing it's balancing function at the same time that your pack is being charged.  2.5mm spacing on pin connection allows over 90% of the packs in the market to be used without any adapter required.  There is also an available adapter to facilitate the balancing of Thunder Power packs.