Hello!
This is a great idea which I have also implemented for my outdoor temperature sensor:
One thing that has happening is that even with this new battery setup, the sensor is still draining within 20 days as can be seen below:
I am using 2 AA batteries R6L4B AA penlite from Philips which are advertised as having being long life.
I have two sonoff sensors indoors and those have been running off of their original cells, while this outdoor sensor has gone through 2 cells, and almost 4 batteries.
Is there something wrong with my setup, or is the sensor broken ?