UPDATE: MAXOAK has a high capacity 36000mAh powerbank with 4 output ports. ChargeTech takes this one step further by supplying a universal adapter which meant you can charge virtually anything. This meant you can simply plug your laptop Power Adapter to it like you would to a wall socket and charge your laptop that way. Of the 5 portable external battery chargers in our line-up, only two offers AC power outlet, ChargeTech and ChugPlug. There are two types of power banks as you will see in our list below, ones with AC power outlet or DC power outlet. Give or take, that is nearly 50 hours of battery life without needing a single wall socket. The highest capacity backup battery packs listed below lets you charge a MacBook Air up to 4 times. You won’t be left without power for MacBook or other USB devices. If you do a lot of field work, work away from the office, take daily commutes that can last for an hour or more, a frequent flyer or look to take that long vacation with several hops this summer, then an external battery charger is going to be a life saver. Most of you have seen this and some of you might have been there too, sitting on the floor in the mall or at the airport, next to a wall socket, charging your laptop for the connecting flight or some extra work hours.