It only applies to certain microcontrollers, but he provides example Arduino code showing how handy this can be for battery-powered projects.

Makers and hobbyists looking for a more substantial portable battery pack that they can make themselves, should check out this excellent DIY power bank created by Instructables user “tobychui ...

[VA3NGC] had a better idea: he built a reproduction B battery from a wooden box, some brass hardware, a nixie tube power supply, and a 9V battery (which remains hidden).

TK discusses a portable power supply module known as a Battery Shield for Raspberry Pi and Arduino.