Hi Jack, thanks for sharing your feedback with us about the Nest Learning Thermostat. We’re sorry to learn that the battery won’t stay charged. We can imagine how hard you tried, and we appreciate the time and effort you’ve spent on this.

Nest thermostats power issues may occur when your system wires can't deliver enough power to keep the thermostats charged up. As a result, they start draining the batteries and disconnect from your Wi-Fi and sometimes cause the battery to drain faster. Your Nest thermostat uses the voltage from your system’s wires to keep its internal battery charged. If the power to your system is switched off or there’s a blackout, the battery has enough capacity to keep working for a while but will eventually run out. Your thermostat will also turn off features like Wi-Fi to preserve battery life before it must turn off completely. If your heating and cooling wires are not able to deliver the needed power for your Nest thermostat, you may need to connect a common or C wire. It helps deliver enough consistent power to your thermostat. You may contact a Nest Pro technician to check your system and help with the Common wire installation.

Or if you’d like, we can have a closer look into it and see what causes your thermostat to behave differently. Feel free to consult our dedicated team for guidance here: https://support.google.com/googlenest/gethelp