Power management for portable Raspberry Pi projects

The Raspberry Pi is a low cost, single board computer with reasonable performance and relatively low power consumption, typically a version of the Linux operating system, often Raspbian. The Pi family of boards have turned out to be very useful machines for standalone and/or portable projects such as remote environment monitoring, cameras, etc. But to be truly portable, a system needs to include a power source and a way to control that power - such as a rechargeable battery, a charger, an on/off switch and some way to monitor battery status.”