Soshine Portable Smart Power Bank for 2X 18650 External Batteries, with LED Indicator and Micro USB Cable (YM-E4C) This is a Smart Power Bank 2X 18650 Battery Charger Box for mobile devices It takes 1-2 replaceable UNPROTECTED 18650 li-ion batteries to power and recharge your USB devices It has LED indicator lights to show the status of battery cell inside It will cut off the circuit automatically if any battery cell is wrongly installed or become defective. It will cut off circuit if data cable or mobile device become short-circuited It provides extra backup power to all devices that supports USB charging. E.g. iPhone, Android, tablets, MP3 players, GPS units, etc