Take power to measure voltage?

I would like to have a warning or error if my RTC clock battery gets low, does it take power to “T” off that line and go to an analog input?

Basically I don’t want to have it die sooner because the positive line is being read.

Thanks!

You've included no information about your RTC. Let us know at least which RTC it is, and better yet, a link to its datasheet.

Just replace the battery every 3 to 4 years.

Sooner if there are lots of power failures.