TOMO&reg; 10400mAh Dual USB Charing Port Smart Power Bank for 4X 18650 External Batteries, with Large LCD Display (YM-V8-4) This is a dual USB Smart Power Bank 4X 18650 Battery Charger Box for mobile devices It takes 1-4 replaceable UNPROTECTED 18650 li-ion batteries to power and recharge your USB devices It has a large green LCD display to show the status of each 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