With a good number of batteries now popping up in the 10,000mAh to 15,000mAh range, iBattz has decided to outdo them with the largest capacity external battery pack we've ever covered: Mojo Battstation Optimus ($160) weighs in at a staggering 20,400mAh. The power cells are held inside a relatively small 5.5" by 2.8" by 0.87" plastic package, with 2.1A and 1A USB outputs. It recharges using micro-USB, which may be one of the big downsides to the capacity;…