Hi HiJony,
Thanks for reaching out to us. I can understand how this might be inconvenient to you with the low-battery warnings on your Nest Thermostat and the advice to take the screen off and charge it using a USB cable. I'd be happy to shed some light on the situation here!
The low-battery warning could be due to a few reasons. One common reason is that the power supplied to the thermostat might not be sufficient to maintain the battery charge, especially if the heating or cooling system isn't running frequently. Another possibility is that the battery itself may be aging and not holding a charge as effectively.
Regarding the advice to charge the thermostat screen separately, it helped the thermostat display speed its charging. Also, the Nest Thermostats are designed to operate with a constant power source from your home's wiring, and the battery is there as a backup in case of a power outage. If you're frequently seeing low-battery warnings, installing the Nest Power Connector or the Common Wire would help to deliver constant power in the long run.
Feel free to let us know if you have more questions in mind.
Warm regards,
Mark
