Its a little more involved than that. The cells are constructed diff - the pos is the full metal end and the end with the blue insulator is neg. They make special bars for these (I've only seen them in a plane shop out of Japan) due to the way the cell ends are made, but most use soldering braid. The cells do need to be balanced - the Dewalt pacs I harvested had a balancer builtin to the pac.

Most modern chargers will charge a123s - they usually call it LiFePO4 or LiFe - its the same thing.