720 is a 7s lipo charger right? I believe you probably bought that balancing adaptor for the 2-6s hyperion chargers, this item:
http://www.allerc.com/product_info.php?products_id=3162 correct?
hence its too small and wont fit the cable coming from the charger. What you need is this I believe:
http://www.allerc.com/product_info.p...oducts_id=4308 for 2-7s.