CellularFactory offers this 2,100mAh External Battery in White (pictured) or Black for $15.29. With free shipping via coupon code "T4ZQWT", that's $14 under the lowest total price we could find for a similar device. It's compatible with Apple, Samsung, Motorola, LG, and Nokia phones as well as most GPS models. Deal ends July 27 at 3 am ET.