The LIPO usually have two connectors. One is for connecting and the other is for balancing. I know that some chargers can charge the pack using just the balancer connector so maybe that is how they do it. I don't have LIPO. I have lifepo4. Elitepowersolutions has a new kind lifepo4 called Next Gen or Gen II or something like that but it's about 50 % more expensive. It would be able to easily handle your 35 amp even at 15 AH capacity. You might be happier with LIPO. I have Thundersky's and they are awfully bulky. They are nice and they work very well but I'm already looking at LIPO. Not sure if I'll ever make the switch, though because my batteries probably have at least 2 more years of life left in them.

Yes, LIPO would easily work with your 9C hub motor as long as you get the right voltage for the controller. If you plan on using 48v, make sure you get a 48v compatible controller. I've heard bad things about those RC Drives. Lots of people say they spend a lot of time adjusting and re-adjusting the belts (or chain) on them and that they are a bit of a pain. Hub motors are virtually maintenance free.