One thing I have noticed is that sometimes I catch a wrong cell voltage on one of my older packs after plugging in the balance plug before the charge. It reads on the low side of reality which is bad. Good thing is my Ultima seems to catch it. It wont charge if it thinks the pack is so unbalanced. I plug it in again, check the voltage to make sure it reads similar to the other cells.

I guess if I really do have a pack that is so far unbalanced, this charger will not accept it making it unusable. Maybe thats a good thing and time for the pack to be retired.