But does that warning need to give the user a week's notice? a day? an hour?
Also, you'll probably want a separate level to save important info and stop...
Indeed.
But beware that a voltage divider permanently connected across the battery will be permanently drawing current ...
Did you forget your anti-nitpick pill this morning 
That is simply not true. I gave all of the information I later had to repeat, in the OP. The only thing I missed was to specify that the battery I am using right now is an alkaline battery. But tomorrow I may use a lithium battery and still want to know its charge, so I didn't see that as being as important as finding out the principals of measuring the actual charge of the supply battery.
I will get to the bottom of this and when I do I will post the answer on this forum.
You also didn't say which sketch you were talking about.
They were the only 2 things you were asked to clarify.
As you've hopefully now seen, the type of battery does make big difference, in practice, in what can be achieved.
Good point, fortunately the input resistance of an analog port is extremely high, so you could use a couple of 10M ohm resistors. Also, presumably it won't be connected when power is switched off.
1 Like
OK. So you don't like any of the answers given so far?
Simple solution: use a voltage divider to A0, use that battery capacity vs voltage curve. If you use the internal reference, use voltage divider values to bring the voltage down to an appropriate level.
1 Like
This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.