[suicideneil]

Yep, run them till they dump basically- no need to worry about over discharging them; you will need a good charger though with cc/cv settings (any good lipo charger should charge A123s though I believe). You should just be able to use a Parallel Y- cable to hook the two packs together, but A123 cells are a funny size/shape, so it might require a bit of imagination to mount them securely....