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Get this K3 Power Backpack with a Removable 4500 mAh Battery for $49.99 at Woot. Shipping is$5. This is the lowest price we found by at $60! It has a padded compartment that holds laptops up to 15.6" and has two pass-through portals for cords. The battery can charge micro USB devices or Apple 30-pin devices. Other size bags with batteries of larger capacity are also on sale. Sales tax is not charged in most states.