Nest Thermostat Battery

[Thomas13]

The issue: The nest thermostat will not stay charged, meaning the wifi will not connect due to lack of power, and I have to take it off the wall 3 times a day to charge it for about 2 hours at a time. Obviously, this is very inconvenient because there are several hours a day in the middle of the summer when my house isn't being cooled, and when I can finally put the thermostat back on the wall, the temps are 80+ degrees meaning my system now has to work twice as hard to cool the house.

The reason this is occurring is that I do not have a C or common wire on my system. The issue I have with this is I have had the Nest thermostat for over a year, and not once in that year did the system die or disconnect. Suddenly, around the time my warranty expires, the battery all the sudden can't stay charged for more than 6 or so hours. 

Confusing, right? How does my battery stay charged for nearly a year without a common wire, then all of a sudden can't stay charged beyond a few hours? Google support can't answer that question. The response I get is to buy a new thermostat from Google or Amazon.

I have had my Nest thermostat for about 14 months which is just outside the 12-month warranty. This problem has been going on for close to 2 months but due to work and other life issues, I just haven't had time to call, which I found out today was a mistake. 

Long story short, since I am outside my warranty, even though this issue has gone on for a while, I get no support.

I've enjoyed most of my Google products but there is no way in hell I am spending another 200-250 dollars when I can't even get an answer to my question on why the problem is occurring now, after a year of ownership.

[RnAElec]

so you need to check for correct voltage at the thermostat head, make sure nothing has happened to the supply wiring (loose connection, maybe even from diy drilling into wall etc).

if all the wiring is correct for continuity, voltage and loose connections etc, then it will be a faulty nest (in the UK they we have a seperate  'nest heatlink' that supplies the nest thermostat head, not sure how many nest parts are part of the heating system for the US.  you may still be under warranty if you used a nest pro to install - in the UK its a 3 year warranty if installed with a pro!

 



then

[TrixieCat]

This is exactly what just happened to me. My Nest thermostat, 3rd generation, worked perfectly without a C wire for 18 months. A few weeks ago it started to go offline for a few hours a day. The offline time grew until it stopped working.  I tried charging but it would only work for a few minutes. 

I bought a Google Nest thermostat power connector and had a Google approved technician come to install it. He said all Nest thermostats need a C wire despite what they advertise. It’s a known issue and that’s why they sell the power connector.  However, by the time people realize that the advertising is false and you do need a C wire, your existing unit is dead. 
I paid $30 for the power connector, $150 for the technician to install it and $245 for a new Nest thermostat. 
Great moneymaker for them. 

[zoeuvre]

Hi folks,

@Thomas13, thanks for reaching out to us, and I'm sorry to hear about the situation. Let's sort this out.

The heating and cooling wires can be used to charge the built-in battery of Google Nest Thermostats, however, as time goes by. The Nest Thermostat's battery loses its ability to charge itself using the thermostat wires, and that is when you need to connect the Nest Power Connector or a common or C wire to reliably supply power to your thermostat. The sole purpose of a common wire is to provide steady power and maintain the current flow into the thermostat; it has no control over any heating or cooling operations. If your Nest Thermostat has power problems or its battery frequently discharges, you'll need to install a C wire or a Nest Power Connector.

Learn more about the C wire and the Nest Power Connector by clicking the articles below.

• Learn about the common or C wire
• Nest Power Connector

Thanks for stopping by, @RnAElec and @TrixieCat. 

Let us know if you have any other questions. We're happy to help. 

Best,

Zoe 

[Thomas13]

Thank you for the clarification. I understand what you are talking about. I just have a hard time understanding why my system is able to keep the battery charged for a year then all the sudden a common wire is needed. If after 2 weeks this problem happens, I would understand more but nothing has changed with my system. Theoretically, if it can sustain a year, it should be able to sustain forever. I'm not an engineer or electrical expert clearly but how does the battery last for a year then all the sudden won't stay charged for more than a few hours?

[zoeuvre]

Hey Thomas13, 

Nest Thermostats are designed to work without a C wire in most homes. But some systems may require a C wire for consistent power. So, to keep itself going, the Nest recharges itself from your HVAC system's wiring. In a system with a C-wire, the Nest charges itself from the C-wire's current and all is fine. In a system without a C-wire, though, Nest recharges its battery when the heating or cooling runs.

On the other hand, we'll also take your feedback as an opportunity to learn and to be able to provide a better experience in the future. If you have questions or concerns in the future, feel free to start a new thread, and we'll be happy to help.

I appreciate the input, TrixieCat.

Regards,

Zoe 

[TrixieCat]

I was told that when your heat or A/C is running, the thermostat is pulling power from the battery. When the heat or A/C hits the desired temp and stops, the battery can recharge by pulling power from the R wire. So, with most of us having the A/C on a little more this Summer, too much power is pulled from the battery and it dies. A C wire is necessary to maintain a charge long term and stay working. What is upsetting is Google knows this but chooses to not state it upfront. It is such a well known issue that they designed a product to “fix” it(power connector).  But from everything I’ve read, by the time people get to that point, they have to replace the unit anyway. There is a 2 year limited warranty covering the unit if it dies like this but the submittal process is a nightmare.