With lithium batteries, a few mv can be important.
Ever wonder how well your tool box meter is holding up?
$10 and a 9v battery connector gets you a 4.096 volt precision source.
Connect voltmeter. It’s that easy.
Then either calibrate meter or mark it, as I did mine.
Ie. reads .01 volts low at 5 volts.
One of mine was spot on, reading 4.10. Only reads to .01v on 20v scale.
Can’t wait to get my 7s volt monitors that read to 1mv.