PowerBoost 1000 Charger - Rechargeable 5V Lipo USB Boost @ 1A is the perfect power supply for your portable project. With a built-in load-sharing battery charger circuit, you'll be able to keep your project running even while recharging the battery. This little DC/DC boost converter module can be powered by any 3.7V LiIon/LiPoly battery, and convert the battery output to 5.2V DC for running your 5V projects.
The output of the Powerboost 1000C is tweaked to be 5,2V instead of 5Vto create headroom for long cables, high draw or the addition of a diode on the output. 5,2V is still safe for 5V powered electronics like Arduino, Raspberry Pi or Beagle Bone.
PowerBoost 1000 Charger - Rechargeable 5V Lipo USB Boost @ 1A is based on TPS61090 boost converter from TI. This boost converter chip has some really nice extras such as low battery detection, 2A internal switch, synchronous conversion, excellent efficiency, and 700KHz high-frequency operation. These specs are:
To make this even more useful, Adafruit stuck a smart load-sharing Lipoly charger 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 1000mA max rate.
Since the built-in battery charger has load-sharing, it will automatically switch over to the USB power when available, instead of continuously charging/draining the battery. This is more efficient, and lets you charge-and-boost at the same time without any interruption on the output so it is fine for use as a "UPS" (un-interruptable power supply).
Note: Be aware that the charge rate is 1000mA max, and there's some inefficiency during the boosting stage, so make super sure that the USB adapter you're using to charge with is high quality, can supply 2A and has thick power wires.
TPS61090 Datasheet: http://www.ti.com/product/tps61090
Adafruit Product Page: https://www.adafruit.com/products/2465