Battery life on 3rd Gen Learning Thermostat

[Magnus1]

Persistent problem with internal battery of this device. Dumb of me possibly but I delicately disassembled after reading they used a couple of AAAs but that must be another model because all I found was what looked like a permanent fixture. Anyway keeps going flat despite my leaving it constantly plugged into a wall (i.e. mains socket) USB. Did I do wrong? Does leaving it connected on a permanent basis destroy the battery? Alternative is to let it go flat when I'm away from home (long periods) then recharge when I get back?

[zoeuvre]

Hi Magnus1, 

Yikes! I'm sorry to hear that your Nest Learning Thermostat is not charging. Let's sort this out. A few questions: 

1. Are you located in North America or Europe?
2. When did the issue first occur?
3. If the thermostat was recently installed, what is the make and model of your heating, ventilation, and air conditioning (HVAC) equipment?
4. Are the power breakers on, and do you receive power to your home?
5. Is the thermostat's display seated properly?
6. Are all the wires of your thermostat seated firmly in its terminals (with no loose or exposed wires)?
7. Did you use a micro-USB cable to charge the thermostat display? Is it working with other devices?
8. Did you plug the thermostat into a working power outlet?
9. For how long did you charge the thermostat display?
10. Does the thermostat have a C-wire?

Also, gather the power readouts of your Nest Learning Thermostat's Battery, VOC, VIN, and lIN under Settings > Technical Info > Power. 

Keep us posted. We're happy to help.

Best,

Zoe