Among the new innovations we saw a handful of times at the 2014 CES were stackable batteries. Executed in different ways, the core concept is the same with all of them: start with a small, low capacity pack, and add on more when you need extra juice. That's what Lepow's ADD Power Bank ($50) is all about. Its base is a 4500mAh rectangular battery with standard micro-USB and USB ports, plus charge indicator lights. Also included is a second cell with…
