For one reason or another reading the Arduino power source (battery usually) voltage seems like a common thing. There are lots of posts, and it seems a few different options.
Me, I want to do it do I can test different batteries, and confirm under which conditions, how long they all last and their rate of decent.
I presume there are two scenarios. Those that have a source over 5v and those that have a source under 5v. Are we able to come to a conclusion on what is the best practice method for each scenario? And confirm wiring/code.
Some links I have been through:
http://provideyourown.com/2012/secret-arduino-voltmeter-measure-battery-voltage/