Pete's right, and the way you have it wired makes it impossible to tell which pack is #1 when viewed from the balancing circuit.

As Pete said, the pack who's negative lead is connected to the charger must be plugged into the A or first connection on the balancer board, otherwise you short it out. This is the same for every type of charger I have used, I don't think yours would be any different.

I would suggest wiring it different so you can clearly see which pack negative lead is going to the charger.

I have done it a few times, never really seemed to hurt anything though.