Nest Thermostat Low Battery (Easy To Follow Guide)

The Nest Thermostat is a smart thermostat that can be controlled through your phone. It allows you to change the temperature from anywhere through your phone and is a touch screen. They have various features such as eco mode which allows you to use less power but still feel comfortable with the temperature in your home.

Fixing a Nest Thermostat’s low battery can come in many forms from adding new batteries or charging the thermostat. To do any of these you would need either a screwdriver, AAA batteries, or a USB charger.

There are a few ways to fix a low battery on a Nest Thermostat. Some are easier than others and it is likely that you just need to charge the battier or change them but there is a possibility that the Nest Thermostat could need more attention. 

7 Easy Fixes For A Low Battery on The Nest Thermostat 

A Nest Thermostat can have a low battery for several reasons. There are seven main reasons that your Nest Thermostat could have a low battery. Each of these issues has easy fixes if you follow the guide correctly you’ll be able to easily get your Nest Thermostat up and running again in no time.

Reconnect The Thermostat To Its Base

The first easy fix you can do is to reconnect the thermostat to its base. To do this you will want to remove the thermostat from the base by taking it off of the wall. You should be able to just take it off since the wires are connected to the base. 

Reconnect the thermostat to its base

You should try to make the wires as flat as possible so they are not sticking out and are messy. After you ensure that the wires are flat you will want to put the Nest Thermostat back so that the display is placed properly. If you take these steps and there are still issues you will want to continue down this list.

Replace The Batteries

It’s possible that the batteries of the Nest Thermostat have gone bad and need to be replaced. The tools you will need for this are a screwdriver and AAA batteries. Some newer versions of Nest Thermostats have different batteries so checking which ones you need may be best.

Start by taking the thermostat off the wall and powering it off. The Nest Thermostat should just come off. You will then want to use the screwdriver to take the backing off which reveals the wires and batteries inside. 

Changing the Batteries

Remove the batteries and try to not mess with any other wires. Place the AAA batteries or other batteries it may take in the correct way. After that close the Nest Thermostat up and screw the back on using the screws and screwdriver. Then place it back on the wall properly and dispose of the batteries in the most eco-friendly way possible.

Charge The Built-In Battery 

There are two ways that you can charge a Nest Thermostat. One is with a USB and one is with a C wire. The Nest should have a USB charge port in the back. If you have a C wire you can connect the C wire and have constant power running through.

Charge It With A USB 

Charging a Nest with a USB is an easy process but may take a few hours. Somewhere between 1.5 to 3 hours which is not too long. To start you will need to get a USB charger and box. You should read the instructions before purchasing the USB charger to make sure it’s the correct one.

Charging with USB Nest

To charge it you need to take the Nest Thermostat off the wall. You should be able to just pop it off the wall and then plug it into the USB. It should start blinking indicating that it is charging. 

Charge It With A C Wire

Charging a Nest Thermostat with a C wire means that your Nest Thermostat will have constant power with a C wire connected. Connecting a C wire is a little more difficult than using a USB wire. You may need to get professional help but it is possible to do it on your own.

Charge with A C-Wire

When you get a C wire you will need to connect it to your electrical panel and connect specific wires to the C wire to get it up and running. To do this you will need the instructions and a screwdriver. Some C wires require being run all the way to the thermostat and so it may be easier to call a professional. 

Check That It’s Connected To The HVAC System 

Sometimes the Nest Thermostat will get disconnected from the HVAC system. To fix this it is a two-step process. First, you should find any loose connections with the tech info diagram. It will tell you if there are any issues with connections. Then reconnect any loose connections. 

Find Any Loose Connections With The “Tech Info Diagram”

Loose connections will cause the Nest Thermostat to display “Tech Info Diagram” and is accompanied by a title saying wiring report. Two possible reasons are a loose connection to the HVAC system or wiring.

To find any loose connection you are going to have to go to your HVAC system so you can see if anything seems to be loose or check the wiring to see if a wire is loose. Make sure you take a few safety precautions and follow a few steps before reconnecting the loose connections.

Reconnect Loose Connections

When there are any loose connections to the HVAC system you should be able to push whatever is loose back in. If there are loose wires or broken wires that appear to be the main issue then you will need to reconnect them.

To reconnect a wire you need a wire stripper to expose a certain portion of the wires. After that, you can use electrical tape or special sleeves for the wires to connect them together. Once you have connected them you should put them back into place and put back the thermostat.

Check That The Wires Are Compatible 

To check that the wires are compatible you will want to turn off the power supply to your thermostat. Then you should take it off the wall and see if there is a spot for a C wire to go. If there is a spot for it you will be able to add a C wire. 

Thermostat Wire

Check for the G and Y wires where there is not a C wire. You can connect an adapter to those. If you do not have a C, G, or Y spot then it will not be compatible. You will have to attach the wires to your furnace as well.

Another way to see if your Nest is compatible is by using the compatibility checker on the Nest Thermostat app. Most Nest thermostats come with a spot to put a C wire or adapter so you should have compatible wires.

Check For a Blown Fuse

Another reason your Nest thermostat could be malfunctioning is that there could be a blown fuse. To check for a blown fuse you need to go to the electrical panel. 

Blown Fuse

When you get to the electrical panel you’ll want to take off the panel. You can do this by using a screwdriver to open the panel or some can just be opened with a latch. After you open the panel it is best to use a flashlight to check for the blown fuse.

A blown fuse will look brown or have a black spot inside of the fuse.

Replace Blown Fuse

To replace a blown fuse you need to turn off the power so that you will not electrocute yourself. Then use a screwdriver to unscrew the blown fuse and take it out. Before putting a new fuse in you need to be sure that it is the same size and amperage.

Once you are sure that you have the correct fuse, place it back into the fuse socket and screw the fuse back in. Turn your electricity back on and check that the fuse is working properly. This may be a difficult task so calling a professional for help would be advised. 

Replace The Built-In Battery

To replace the built-in batter for a Nest you need to take the Nest off the wall and unscrew the back. Gently lift the back off because it is connected to the Nest. once the back is off there is another layer to move up. Get both of those out of the way and you should see a square battery.

There is a wire that attaches the Nest battery to the Nest itself. You will want to detach that and take the battery out. Put in the new batteries and close backtrack closing the Nest back up.

How Can You Detect A Faulty Battery?

A faulty battery can be such an annoyance. Luckily there are several easy ways you can detect a faulty battery in a Nest Thermostat. The first way would be by looking at your Nest Thermostat app. This app will give you a warning that the battery is low or the Nest is disconnected. 

It is recommended that you download the app so you can easily control your Nest Thermostat along with telling if there is anything wrong.

The Nest way is by going and looking at the best itself. If the screen displays that the battery is low or the Nest is completely off then the battery could be faulty. Especially if you had just charged the battery or the Nest is new. 

The Types Of Nest Thermostat Batteries 

Depending on which model version you got, your Nest Thermostat either has a built-in battery or 2 AAA batteries inside. Batteries can be harmful to the environment so when you dispose of the batteries you should take them to a hazardous waste site. There should be one in your city.

Built-In Battery

The built-in battery of a Nest is a small square battery with a high capacity. It can be recharged with a USB or constantly charged with a C wire. This type of battery is the more advanced type of the two. 

The built-in battery is meant to last the whole lifetime of your thermostat so long you recharge it. You won’t have to go out and buy batteries or keep a stash in your kitchen drawer with the built-in battery.  

Triple-A Batteries 

The AAA batteries in a Nest mean that your Nest may be a little bit older but still works as well as the built-in battery. These batteries can be bought anywhere and need replacement ever so often. They’re reliable and will keep your Nest running perfectly fine.

They cant be left in the Nest for too long after they go dead or the battery may become corrupt and ooze out into your Nest. Make sure to replace them when your Nest tells you to.


The Nest Thermostat is a technological advancement that can sometimes fail due to technological bottlenecks. If your Nest is not working properly it is likely to be a battery issue and you should follow this guide to see what you need to do when your Nest Thermostat is saying low battery.

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