Amazon via Anker direct, is offering the Anker Astro Slim2 4500mAh portable battery charger for $20 shipped when you enter coupon code SLIM2AST at checkout. That is the lowest price ever by $8 for this popular power bank. It hoards enough power to completely recharge a smartphone two to three times. Features include the ability to charge two devices at once (1A each), a built-in micro USB for convenient power fill-ups (AC adapter also available), and a slim design perfect for traveling. Amazon reviewers give it a nearly perfect rating.