NKTECH Mini E4s Adjustable 1A/2.1A LCD External Power Bank 18650 Battery USB Charger Box For iPad MP3 Tablet iPhone Samsung SONY Android Cell Phone This is a DIY 18650 Mobile Power Bank Box. You can put 1 to 2 18650 batteries into the slot. Therefore, you can determine the capacity of the mobile power bank. Adjustable Output DC 5V 1A/2.1A. Provides extra backup power to all devices that supports USB charging. E.g. For iPhone, Android (Such as Samsung, HuaWei), tablets, MP3 players, GPS units, etc. Intelligent power manage IC, overcharge protection, short circuit protection. Charging-in with bundled USB cord, or by charging the batteries with other chargers. Built in protection against over-charge of batteries, short circuti and battery reverse polarity protection. LCD display Current Voltage Capacity Time. Charge and discharge at same time. Can use 6V 5W solar panels.