PowerBoost 1000 Basic - 5V USB Boost @ 1000mA from 1.8V+ is the perfect power supply for your power-hungry portable project! This small DC/DC boost converter module can run from 1.8V batteries or higher, and convert that voltage to 5.2V DC for running your 5V projects. With a 4A DC/DC converter, it can give you 1A+ from as low as 2V.
The output of PowerBoost 1000 Basic - 5V USB Boost @ 1000mA from 1.8V+ is tweaked to be 5.2V instead of a straight-up 5.0V so that there's a little bit of 'headroom' long cables, high draw, the addition of a diode on the output if you wish, etc. The 5.2V is safe for all 5V-powered electronics like Arduino, Raspberry Pi, or Beagle Bone while preventing icky brown-outs during high current draw because of USB cable resistance.
PowerBoost 1000 Basic - 5V USB Boost @ 1000mA from 1.8V+ has at the heart a TPS61030 boost converter from TI. This boost converter chip has some really nice extras such as low battery detection, 4A internal switch, synchronous conversion, excellent efficiency, and 700KHz high-frequency operation.
Adafruit Web Site: https://www.adafruit.com/product/2030