I have two objectives. Add more amp hours and use rechargeable lithium batteries.
Originally, I thought I could get AA rechargeable lithium batteries, but I now believe that to be a mistake.
From what I am reading, the Arduino pro mini RAW input can be powered from 3.4 volts to 12 volts.
Using 18650 cells wired in parallel connected to the RAW input may be the best way for me to go.
Also, the 18650 cells seem to come in a range Amp Hours.
Should I choose the ones with the most?