Battery issues with 2nd Gen Thermostat

[billwesty]

**Subject: Low Battery Message on Thermostat Despite Battery Reading 3.57 Volts**

Dear Google Nest Support Team,

I hope this message finds you well. I am writing to seek assistance with an issue I am experiencing with my Google Nest Thermostat. Recently, I have been receiving a low battery warning on my Gen 2 thermostat. However, when I check the battery status on the device, it shows that the battery is at 3.57 volts. It has worked for years but now cannot connect to the wifi for a low battery condition. I have charged it using USB but that doesn't help

Given that 3.57 volts is within the normal operating range and should not typically trigger a low battery warning, I am concerned that there might be an issue with either the battery sensor or the software. I kindly request your guidance on how to resolve this discrepancy to ensure that my thermostat continues to function properly.

Thank you for your attention to this matter and for providing support.

Best regards,

Bill Westheimer

[Patrick_Caezza]

@billwesty 

3.57 V is not within the normal operating range.

Here is a helpful article that will explain it better.

Nest thermostat information menu 

If the battery reading is below 3.8V it will shut the WiFi off.

Is a C wire installed?

[billwesty]

@Patrick_Caezza

No, there is no C wire. It has worked for years without a C wire. But now even when I charge the display with a USB cord it does not increase the voltage appreciably.  I suspect the battery is failing and the battery is not replaceable. (this is a Gen2 thermostat I think)  I went to install a new Nest thermostat but the app says my wiring is not compatible. I am at the limit of my skills and understanding.  I have swapped out many thermostats over the years, but I don't know how to proceed.

Unfortunately I have a very old house and the wiring in the basement is very old and hard to find.

[Patrick_Caezza]

@billwesty 

Nest thermostats are known to work fine for a long time without a C wire and then out of the blue they start to have battery problems. It has to do with the way they steal power to keep the battery charged. Simply put the power stealing can't keep up with keeping the battery fully charged.

The Nest Power Connecter will solve the no C wire issue but you'll have to replace your 2nd Gen to one newer to use it.

[billwesty]

@Patrick_CaezzaLots has happened since the last post. I discovered the USB charging cable didn't work so I charged with a new cable. Then my neighbor, a HVAC contractor came over to get things working again but we had a power failure due to high winds. But we have a generator. We got a C wire hooked up (from the boiler side) and when we tried to start the A/C (which IS powered by the generator) it was surging so we turned it off. The next morning the power was back on but the thermostat was dead. I charged it for 5 hours and put it on the base and the compressor was surging. So he figured out how to hook up the replacement Nest thermostat that I got from our utility company. It won't do both heating and cooling but for now it will run the A/C. I will have to buy a new thermostat to run both heating and A/C. But at least the A/C is running, it is connected to the wifi and all is good.  Good neighbors are a true gift. Thanks for your help too.