DROK Ultra Small Mini DC Power Module DC 3V to 5V 1A USB Battery Converter Step Up Module Charge for MP3/MP4/Phone Samsung Galaxy S3 iPad iPhone 4S 5 6/6 Plus Electronic circuit requires no electrolytic capacitors and tantalum and it adopt ceramic capacitor Small ripple brings little damage to the board Undervoltage indicator: when battery voltage below 2.7V in load, the LED will not light up; when battery voltage less than 2.7V in load, LED will light off; when battery voltage is more than 2.7V without load, LED will in dim light Simple wiring connection: connect the IN+ to positive pole of power supply and connect IN- to negative pole of power supply Efficiency: Up to 96% (the higher the input voltage, the higher the efficiency)