measure full battery voltage

[Saxin]

Just a friendly suggestion that full battery voltage can be measured by using simple resistor divider, it will be x2 more resistors but I think will be better overall.

[Dakkaron]

Thanks for the suggestion!
You are absolutely right with that, and it would be the better solution. I might add an option for that in the code.

The reason why I didn't do that (along with a few other things that might improve the design) is, that I wanted to keep it as minimal as possible. This way there is less need for soldering, additional boards, buying components, etc.

Also, full battery voltage might not actually be as useful as Cell 1 battery voltage, since Cell 1 has a higher drain than the other cells, due to the Arduino being plugged into it. So even if the difference in drain is not that much, measuring when Cell 1 is empty should be just what is needed.