Charging wise, when I was using A123s I used a lipodapter

http://www.slkelectronics.com/lipodapter/

Not sure if they still make them but you can use a cheap high charging nimh or nicad charger. I used an old astroflight charger with it that could give a good 10amps charging a pack in no time at all. Never bothered balancing A123s and the cells were never out of balance voltage wise.