Adafruit PowerBoost 500 Charger - Rechargeable 5V Lipo USB Boost @ 500mA+ is the perfect power supply for your portable project! With a built-in battery charger circuit, you'll be able to keep your project running even while recharging the battery! Adafruit PowerBoost 500 Charger - Rechargeable 5V Lipo USB Boost @ 500mA+ can be powered by any 3.7V Li-Ion/LiPoly battery, and convert the battery output to 5.2V DC for running your 5V projects.
To make this even more useful, a MicroLipo charger is added on the other side. The charger circuitry is powered from a microUSB jack, and will recharge any 3.7V/4.2V LiIon or LiPoly battery at 500mA max rate. There are two LEDs for monitoring the charge rate, a yellow one tells you its working, a green one lights up when it’s done. You can charge and boost at the same time no problem, without any interruption on the output so its fine for use as a "UPS" (un-interruptable power supply) for a low-current draw device. Just be aware that the charge rate is 500mA max, so if you're drawing more than ~300mA continuously from the 5V output side, the battery will slowly drain since the charge rate is less than the dis-charge rate.
Adafruit PowerBoost 500 Charger - Rechargeable 5V Lipo USB Boost @ 500mA+ is great for powering your robot, Arduino project, single-board-computer such as Raspberry Pi or BeagleBone! Each order comes with one fully assembled and tested PCB and a loose USB A jack.
Adafruit Website: https://www.adafruit.com/product/1944