Aukey Direct via Amazon offers the Aukey Quick Charge 2.0 10000mAh External Battery
, model no. PB-T1, for $29.99. Coupon code "3QXBUPPC" cuts the price to $24.99
. Plus, Prime members qualify for free shipping
. (Non-members can spend $35 to qualify; otherwise, it adds $6.55.) That's $25 off list and the lowest total price we could find. It's compatible with several smartphone models, including the Samsung Galaxy S6, Note 4, Sony Xperia Z4, HTC One M9, Motorola Droid Turbo, and LG G Flex2.