Mophie makes some of the best power banks, but at a cost. Anker is a solid line at lower prices. My goal was to be able to fully charge two phones each day from one power bank on our trip. Never needed to fully charge our phones but the bank let us go without worrying about anything. If you have
Amazon check out the Anker Portable Charger, PowerCore Slim 10000 Power Bank for about $24