Balance condition will not make a charger refuse to charge a lipo, its low voltage and your buddys are running either no lvc or using one that's set too low. Needless to say, this is not good for the lipo as far as cycle life is concerned and I'm surprised you have seen several puff in response to this kind of mistreatment.

If you have to provide this as a service, get a charger than charges thru the balance conn - this one is cheap and will do multiple lipos, at least it won't tie up your Duo -

http://www.hobbycity.com/hobbycity/s...idProduct=2055