Vktech ENB 3x18650 1A 18650 Li-ion Battery USB Emergency Charger Power Bank Provides extra backup power to all devices that supports USB charging. E.g. iPhone, Android, tablets, MP3 players, GPS units, etc This unit takes 3 replaceable protected 18650 li-ion batteries to power and recharge your USB devices Power bank can be recharged via micro USB port with LED capacity indicator Over current and over charge protection built-in After place or replace batteries, please charge the power bank to activate the output circuit