Groupon offers the Mota 2600mAh Smartphone Backup Battery Stick in four colors (Blue pictured) for $19.99 with free shipping. That's $5 under the lowest total price we could find for a comparable 2600mAh backup battery stick in any color elsewhere. It includes an iPhone/iPod 30-pin connector, mini USB connector, micro USB connector, 2.5mm adapter, 3.0mm adapter, and charging cable. Deal ends June 4 at 12:59 am ET.