I purchased two replacement batteries from Ifixit and replaced in two Nest thermostats. The installation was as simple as stated above, however neither one works. The thermostats just sit on the wall and blink Green. There was a card included that said discharge to 10% to ensure battery voltage is detected properly. Does anyone know what that is about? How does one discharge to 10%,. I suppose I could leave the unit off the wall for a week and see if that fixes it, but maybe there is an explanation here? Hard to believe both batteries are defective.