Review on Adafruit PowerBoost 1000 Charger - High Capacity 5V Lipo USB Boost @ 1A - Rechargeable 1000C by Alexandria Richmond

By far the best solution to power your Pi from a single 3.7V battery, but it does have a few quirks. It's going to be hot, but that's to be expected. Pros: * Can power the Pi with a single cell (3.7V) LiPo or Li-Ion battery * Can connect an external 5V power supply to power the Pi and charge the battery at the same time * Small package Cons: * Only 1000 ma left when turning on the Pi and charging the battery. So if you are using 750mA with the Pi, you are only charging the battery with a maximum current of 250mA, which takes a very long time to charge large capacities. For 2 hours of battery life while powering my project, it takes 3.5 hours to charge before the indicator turns green. * Conflicting information about the LBO chain. There are posts in the adafruit admin's support forums that contradict what the manual says.