I ordered this battery pack https://www.adafruit.com/product/1565. 

I am nervous because it needs to power the board, the screen, and the speakers. 

If it does not accomplish those tasks, I will have to spend $39 on the 10000 mAh version. It was a risk to get the cheaper 4000 mAh version, but I want to be as economical with power as possible so I want to try the smaller battery first!

If I ever take this thing to mass market, I will need an EE for sure to help me figure out stuff like power consumption!