Aukey Direct via Amazon offers its Aukey 12,000mAh Portable Power Bank, model no. PB-N28, for $24.99. Coupon code "45ZTSPTU" cuts it to $14.99. Plus, Amazon Prime members bag free shipping. (Non-members can spend $35 to qualify for free shipping; otherwise, it adds $6.33.) That's a buck under our June mention, $45 under list, and the lowest total price we've seen. It features up to 5-volt, 3.4-amp output and a USB charging cable.