If there's one accessory category that's more popular than ever, it's external battery packs. Kinkoo's Infinite One 8000mAh Portable Backup Battery Charger ($80) is just the latest example of a new company getting in on the game. The long, flat pack holds a relatively large cell, and has a 2.1-Amp output from its single USB port. Instead of just a single Micro-USB charging cable, it comes with two of differing lengths. There's also a travel bag included.…
