Wingman 8000P -8000mAh 5V 3.1A Portable Power Bank/External Backup Battery Pack with Dual USB ports $19.89 FS Prime

Amazon.com: Etekcity Wingman 8000P -8000mAh 5V 3.1A Slim, Portable Power Bank/External Backup Battery Pack with Dual USB ports for smartphones, tablets, etc from Apple, Samsung, Blackberry, Droid, etc & almost any other rechargeable device: Cell Phon

with capacity of 8000mAh; Dual USB outputs: 5V 3.1A. High-quality Li-polymer battery cells for reliable long-term performance
Automatic shutoff function to prevent battery drainage and preserve charge & overload,over-discharge, and leakage protection
Slim & Portable size for maximum convenience - fits in a pocket or purse
LEDs indicate how much capacity is left, letting you know when the power bank needs to be recharged.
Quick-charge equipped: charges electronic devices faster than comparable power banks
for smartphones, tablets, etc from Apple, Samsung, Blackberry, Droid, etc & almost any other rechargeable device