Adafruit PowerBoost 1000 Charger - Rechargeable 5V Lipo USB Boost @ 1A - 1000C

Perfect power supply for your portable project, Safe for all 5V-powered electronics like Arduino, Raspberry Pi, or Beagle Bone, Boost converter chip extras: synchronous conversion, excellent efficiency, and 700KHz high-frequency operation, 2A internal switch means you can get 1000mA+ from a 3.7V LiPoly/LiIon battery., Low battery indicator LED lights up when the voltage dips below 3.2V, optimized for LiPo/LiIon battery usage