Couldn't you use the 5V pin instead?

Alright, I'll look into getting some NiMH batteries. But why did you step the voltage down to 3.14V? Is it necessary to do that?

Sweet! That means I don't need any sort of internet connection for this, right? I'm currently working on a project for school using the Raspberry Pi, and I need to monitor the level by percentage. I know in your configuration, you used 8 Lithium Ion batteries. I'm planning to use this: http://www.am...

Is it necessary to have a SIGFOX module connected for the PiCheckVoltage to work.

I have an additional question. In connecting an I2C or SPI, how do you read/extract the voltage value? I'm trying to monitor the battery life via a percentage and am wondering if it's possible to get the value and convert it to a percentage to output on a display.