Why does my C wired Nest Thermostat need batteries

[Sbm872]

I’m gone  for 6 months. What happens if I get a low battery message when I’m gone. Will the AC still work?

[David_K]

Yes, as long as your thermostat is receiving enough power. Normally, your thermostat gets power from your HVAC system, sounds like you also know about the common wire. It has 2 AAA alkaline batteries as a backup, or to supplement if your system can’t deliver enough power.

You can check if your thermostat is getting enough power:

1. Go to Settings > Technical Info > Power.
2. If the Voc, Vin or lin values are not within the specific ranges listed here, you may have a wiring or system issue. Expand the "Power" section of the article, and see the "Voc Vin lin" section.

[Sbm872]

My screen under thermostat settings does not have a “power “ subject under Technical info. The wiring shows all wires including the common are hooked up. The battery voltage is at 3.1.  The original batteries lasted about a year, but we had a 4 day power outage and since we all electric the AC was out. 

[Markjosephp]

Hello folks,

I wanted to stop by and see how I could help.

Thanks for the input, @David_K.

@Sbm872, in addition to what was mentioned by davidking, the Nest Thermostat comes with a pair of backup Google private-label AAA alkaline batteries. Unlike the previous versions of Nest thermostats, these batteries aren’t rechargeable and need to be replaced when their power runs low.

In the event of a power loss, the thermostat’s batteries will power your thermostat. So when the thermostat doesn't receive power through any of the power wires and only relies on the batteries for power, the battery life becomes shorter, and you'll receive a "low battery" message. Could you please check your thermostat's battery status?

Let us know how it goes.

Regards,
Mark

[Jenelyn_O]

Hi there,

Chiming in — I hope you get the answer you're looking for. Were you able to check your Nest Thermostat battery status? Let us know what it is.

Best,

Jenelyn

[Sbm872]

Battery status now is 3.1, good for two 1.5 AAA batteries. The concern I have is that I am gone for 6 months. If the batteries become low when I am not here will the thermostat still work. The original batteries lasted about 1 year. We did have a 5 day power outage as a result of the hurricane so that probably depleted the batteries quite a bit.

[Markjosephp]

Hello everyone

Thank you for your help. Jenelyn.

Got it. Thank you @Sbm87 for letting me know. There is a possibility that the thermostat won't be able to maintain the power it requires to function if there is a five-day power outage. If a schedule has been set up, your system may still operate as intended, but if the thermostat goes offline, you might not be able to control it remotely because of low power.

Have a look at this article and let us know if you need more help.

Regards,

Mark

[Sbm872]

Since our hvac system is electric it won’t make a difference, but when the power returns will the thermostat work as normal. We are retired and don’t have a regular schedule so we can’t set a schedule. I just want the thermostat to hold the temp at 78* when we are not here in Florida in the summer. All I really want is to be able to check the temp when I am not here.

[Jake]

Hey Sbm872,

I wanted to follow up with you. Once the power has been returned, your device will then try to reconnect to everything such as the Wi-Fi on its own. Once the device has reconnected to the internet, you will then be able to control it and check the temperature using your mobile device. Let me know if you have any other questions from here, as I would be happy to take a closer look.

Best regards,

Jake

[Dan_A]

Hey there,

I wanted to follow up and see if you still need help. Please let me know if you are still having any concerns or questions from here, as I would be happy to take a closer look and assist you further.

Thanks,

Dan

[Sbm872]

I believe the thermostat will function when power returns if we have a power outage. If the batteries weaken to the point of needing replacement my house sitter should be able to replace them and I believe we won’t have to reset the Wi-Fi connection. Is that right?

[Jake]

Hi Sbm872,

That is correct. If you need to replace the batteries on your device, it will still hold all the information. The only time you would need to enter in the Wi-Fi connection is if you factory reset your device. Let me know if you have any further questions from here, as I would be happy to help.

Best regards,

Jake

[Jake]

Hey there,

I wanted to check in and see if you are still in need of any help. Please let me know, as I would be happy to assist, and answer any questions you may have.

Best regards,
Jake

[EmersonB]

Hello everybody,

@Sbm872, just one quick final check in here since activity has slowed down. We'll be locking the thread in the next 24 hours, but if you still need help, we would be happy to keep it open. If there's more we can do, just let us know.

Thanks for lending a hand, davidking, Mark, Jenelyn, Jake and Dan.

Best,
Emerson