Sunvalley Brands via Amazon offers the RavPower 20,000mAh Dual-USB Portable Battery Pack in Black for $36.99. Coupon code "K3WG53C6" cuts that to $27.99. With free shipping, that's $9 off, a buck less than our mention from three weeks ago, and the lowest price we could find. It features two iSmart USB 2.0 ports with 2.4-amp output. Deal ends January 20.