I will show you how to properly supply power to a Raspberry Pi or Pi 2 with a battery pack or any voltage between 2.9 -32 volts DC. I will be using a efficient Pololu Step-Up/Step-Down Voltage Regulator and a toggle switch.
This can be done with any Raspberry pi version. Using a DC-DC converter allows us to have around a 90 percent efficiency in converting the power of the battery into power for the pi. You can substitute out for a fixed output DC to DC regulator but its nice to have a adjustable one if you want to use it for other projects. Its a dollar cheaper and available here (Pololu fixed 5v regulator). This will also allow to skip the steps on adjusting the above regulator.
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