Arduino and Iteaduino can be powered by USB or external power supply, but both of them need to connect with a cable. When you want to put board far way from the power suopply you need a long cable and it's inconvenient.
So here we bring you a power shield, it has the high-efficiency DC-DC boost circuit and you can use two AAA batteries to offer 5V/350mA for the Arduino board and shields under it. When your Arduino project need a portable offline power supply, this shield should be a good choice.
There is a USB socket in board, and you can use this USB interface for outputing power as well. And the switch on board can turn on or turn off the power supply for Arduino board, when you turn on the battery power supply, the PWR LED will light on.
