@4994james or just use internal vcc measurement as described on the same page. That saves you the voltage divider.
I wrote a convenient library to measure vcc internally : https://github.com/Yveaux/Arduino_Vcc
@nekitoss
I used 3.3V pro mini with regulator removed and powered by Vin pin. Also removed leds from the pro mini.
I used minicore bootloader.
I used the small pir sensors and again removed the regulator to power directly from the pro mini outputs.
After that sleep the node and trigger on interrupt.
Send battery level once a day.
Use inbuilt battery level monitor and not external components that constantly drain power to get battery level.
1.8V is 0% on the graph (not visible yet!) but I have had nodes working below 1.7V It's a matter of luck with that it seems.
Hope this helps you on the right track. I'll try and help if you want.
This is the latest image and still going strong after 18 months. Voltage is at 2.903V
Here is photo of the test example - I need to make a case and produce more of them over winter.....
Here is the same build/code of a window sensor. Similar time frame but hardly triggered.....
@bisschopsr I now have the schematics posted for all of my boards. I also posted another board for my in-wall scene controller line. Is there any other pics or information that you think might be useful to others for any of these boards?
