When it comes to battery packs, Anker is among the best you can get. Their packs are high quality, sleek, and they offer plenty of options. This particular Anker battery pack (the 2nd gen Astro E3) is on sale on Amazon right now for just $21.99 and it boasts Anker's PowerIQ technology that can detect your device and deliver as fast of a charge as your device will support, up to 3amps. The pack comes with two USB ports so it can charge two devices at once, and you can keep tabs on how much power the pack itself has left with the four LED indicators on the front. The pack does come with its own microUSB cable for recharging though you'll need another if you want to charge two devices simultaneously, and it also comes with a travel pouch for storage if you take it with you places.