Nest 3rd gen Thermostat low battery issue after several years

[ErnieC6720]

After about 4 years, my NEST is now going to low battery and disconnecting from WiFi.  I can recharge with usb but doesn't seem to be charging on the wall.  Nothing has changed in my home.  Can these rechargeable batteries be replaced?  Could it be something else?  It hasn't happen before.  Maybe once after a power outage but never again.  Any suggestions would be greatly appreciated. 

[pstreicher]

Where can on go to see if any, results from testing this theory? If this is proved true, is there a way to downgrade the firmware to the previous working version?

Seems that if I am no longer having this problem, either the firmware was updated to correct the so called bugged version or taking the unit off the wall and charging overnight with a phone charger, fixed my issue.

C wire is 'ground' wire. Any circuit to work requires a positive and a ground. I don't know any other way around this. Color or wires can be different depending on the installer, whether amateur or professional is all I can say.

[MikeK_]

Mine didn't work ("low battery", and won't hold a USB recharge for more than a few hours) upon initial installation (admittedly, however, with a unit that sat (new/unused) in a box for a year because of the problems I had read (and feared) regarding a "2 wire" installation.  MADDENING that the only 'help' I can get now is reading through 175 other "Replies" with same problem.  Where's the actual Google help/support?  Is there a person/submittable link where I can actually get some remedy for this $200 device!!!!!!

[pstreicher]

Have you tried here?  https://support.google.com/store/answer/13026601?hl=en&ref_topic=3380791

[Chrsprc]

Once I purchased a new unit, everything went back to normal. Meaning, it wasn’t the c wire at all. C wire power seemed to be operating perfectly but the unit wasn’t recognizing that. My Ecobee product is nearly 10 years old in several other properties and still working as prescribed. it is a better unit and has lasted much longer problem free. 

[rjp123]

After nearly a year of "low battery" issues I have resolved the issue with my Nest 3rd Gen thermostat.

Recap:  I have had the Nest 3rd Gen thermostat installed for nearly 5 years.  My Nest 3rd Gen was wired via 4 wires (Y, G, Rc, W) as it was advertised to work without the C wire and my thermostat only had 4 wires running to it.  It worked perfectly from day one until April 2022 when all of the sudden it would drop off from wifi and say "low battery" when looking at the settings details on the device.  The battery would hover around 3.60 to 3.75v and the device would not connect to wifi or take data from the sensors (of which I have 4 around the house).  By running the AC or furnace the Nest would charge up the battery a bit and then it would be fine for a few days/weeks (depending on how often AC or heat was on). I was able to "extend" the time between having issues by turning off the auto schedule and the screen of the device (so it was off unless I physically interacted with it). Doing these two things reduced electrical demand on the device.

Issue: I believe this problem is caused by a firmware update pushed by Google at some point a year or so ago (Q1 2022).  Prior to the firmware update the device was able to keep itself charged enough (without a C wire) to work with wifi/full features.  The update changed something where the battery would draw down unless AC/heat was running through the device (offering a trickle charge on the battery).  Long periods without AC/heat would draw the battery down below 3.8v and the device would turn off/limit features until it was able to charge up again slightly via AC/heat (or via manual charging with USB).  Without a C wire the device draws 20-40 mA. Previous to the firmware update this 20-40 mA was significant enough to keep the battery above 3.8v (and prevent it from turning off).  After the firmware update this trickle of current was insufficient.  Running AC/heat keeps the current high enough (without the C) to recharge the battery slightly, which is why this issue seems intermittent for some people.

Solution: Due to the firmware update, the Nest 3rd Gen now requires a C wire to operate correctly.  You have three options to resolve: (1) Rewire your thermostat with minimum 18/5 wire so that you can connect the C with via having 5 wires, (2) Get rid of the Nest and leave the ecosystem, or (3) Use a device to "add" a 5th wire so you can have the C connected.

I opted for #3 and just installed the Venstar ACC0410 Add-A-Wire device.  It took me about 20 minutes to install and the Nest Gen 3 now shows 200 mA current and the battery is at 3.95v (well above the 3.8v threshold which causes the Nest to have issues).

There are 2 devices on the market which allow you to "add" a 5th wire without actually changing the hard wiring:  Venstar ACC0410 Add-A-Wire and Fast-Stat 1000.  You can find them online and they are easy to install yourself (YouTube for install instructions).

I hope this helps everybody as this clearly is a major issue on these devices.  Good luck.

[EdB]

The Venstar ACC0410 Add-A-Wire says not to be used to add a C wire. So doesn't seem like a good solution.

[rjp123]

I installed it and it works fine. The video instructions produced by Venstar specifically show them using it for the C wire. 

https://youtu.be/FjkPh1_I40A

[EdB]

Interesting as the unit for sale on Amazon specifically says not for C wire. Did notice in the comments that if you every use fan only this no longer works, that in fact it turns on the AC compressor.

[EdB]

Just found another video that provides three solutions to this problem. One of the solutions is the one you provided. He also provided a was to get the Common by using the fan wire (G) by moving it to the common and adding a jumper on the controller to always turn on the fan when the AC is turned on. See the video for details:

https://www.youtube.com/watch?v=nki-65gtvac

[rjp123]

Just follow the official install video and everything works fine (including the fan).

https://youtu.be/FjkPh1_I40A

[EdB]

Thanks for the info. Was just looking at getting the Google device to add the 5th wire. Will look at these two and compare prices.

[EdB]

just found this article from January 2016: https://gizmodo.com/nest-thermostats-are-having-battery-problems-and-theres-1751800309

Basically says turn if off and on again, seems like an episode of The IT Crowd.

[J_Dubb]

Our Gen 3 has started reporting this issue and won’t hold a charge.  Nest Support was unhelpful and suggested we purchase a new device.  Really?! Disposable smart devices?

[bumkin1216]

Well All - after months of searching for a solution, trying Nest Support, swapping out one of the T-Stats for a new 3rd Gen, nothing worked and i was tired of having my Nest go off line constantly.  As much as it pained me to do it, I called an electrician and he ran new wire to both of my Nests so that I now have a dedicated C Wire connected to both supplying a constant 24v power source.  Each Nest has been holding at around 3.92/3.93 battery since then and has not dropped WiFi once.  Not the route I was looking to take as the electrician cost more then the two T-Stats combined but at least now I have a C Wire and no more issues.  

[ashfaqshaik11]

I have a 2.5-year-old nest thermostat, unfortunately, same charging issue. Spoke to the agent and was advised to trash it and buy a new one.  I had invested into nest assuming it to be worthy, and now I am learning that the life of the nest product is only 2 years (i.e. warranty) and anything more than 2 is a bonus. Then, I would advise people not to make such a huge investment for a thermostat. there are alternate products. Please use them. A disappointed Google Customer .... 😞

[rrobster]

These units should have a more than 2-year usable life. I know that you can replace the internal lithium battery, but I haven't tried it yet.

[mjd]

I had the battery issue also and this appears to have fixed it..good luck.https://www.amazon.com/gp/product/B08TWDT4J2/ref=ppx_yo_dt_b_asin_title_o08_s00?ie=UTF8&psc=1

[Shabellabu]

Did it worked ?

[BN231]

Yes haven’t had a problem since then. 

[Markjosephp]

Hello there,

I know it has been a while, but I wanted to ensure that everything was covered here.

Thanks for assisting the users here, Zoe.

For everyone, the built-in battery of Google Nest Thermostats can be charged via the heating and cooling wires. In order to reliably power your thermostat, you must connect the Nest Power Connector or a common or C wire, as the Nest Thermostat's battery loses the ability to charge itself using the thermostat wires over time. A common wire has no influence over any heating or cooling processes; its only function is to supply constant electricity and maintain the current flow into the thermostat. You'll need to install a C-wire or a Nest Power Connector if your Nest Thermostat experiences power issues or its battery discharges frequently.

Lastly, Wi-Fi connection issues also add up and drain the battery quickly. Try disconnecting your thermostats for 24 hours and letting us know if they still drain their batteries.

Regards,

Mark

[Chrsprc]

Yea, the internal battery is fused into a micro plate. It didn’t work well for me trying to replace it myself. Was a waste and as a few here have noted, with the battery not replaceable, the unit has a 2-3 year life span. Anything more than that is beyond life expectancy. Not so satisfied customer here on the quality. 

[WisconsiNate]

Same issue for the past few months!  Nothing has changed I've had the nest for years and now all of a sudden it's having low battery issues.  In charge it... 1-2 days later same issue.  After charging..  3.9v.  voc 39.05 vin 27.92

Wats the deal?

[J_Dubb]

We ended up paying an Electrician to run a C-wire to our Gen3 Nest Thermostat, and the problem has gone away.

Google has been completely unsupportive in this domain and we have decided against purchasing all Google products moving forward.

Telling people to re-purchase a 300 dollar piece of electronics that your support teams aren't trained adequately to support, is bad for all consumers.  If Google hadn't of bought NEST, this wouldn't be an issue, but in today's capitalist world, players like Google get away with things like this all the time.

It's in your best interest to vote with your wallets, people.

[ashfaqshaik11]

I would never buy or recommend anyone to buy Nest going forward. It is not worth the money you spend and have to replace it after 2+ years. 

[BN231]

I’m having the exact same issue after 2years of working fine. Now all of a sudden keeps disconnecting from wifi and from my 2 temp sensors and is annoying as hell to say the least. How do you fix this?  Help! 

[trafsta]

I am having the same issue with my Nest Learning Thermostat 3rd gen. It worked great for 6ish years until the last few weeks and it's even worse today (won't connect to wifi at all). For the first while it just lost connection to 1 or 2 of my best sensors throughout my house here and there but they would come ask after a while. 20ma power coming in but it has always been that much (no C wire) and there was a firmware update on it on May 3rd which looks sketchy... I did a factory reset but it's too low to reconnect to wifi or my Google account so it is going to run as a dumb-thermostat for now since it's 30C outside and we need the AC running!

Not sure if I should try this?

Google Nest Power Connector - Nest Thermostat C Wire Adapter - C-Wire Adaptor for Smart Thermostat - Nest Thermostat Accessories, Snow https://a.co/d/0tflzKk
Read hundreds of posts in here but still not sure what the best solution is.... I ordered the above C wire adapter and may try to figure out how to wire it up to my thermos in a few days if the issue does not rectify itself... Otherwise I'll return the adapter. Guessing maybe us Canadians got the 2022 firmware update that everyone else is mentioning just this current May or something... Cause all was fine prior to May!

Crazy stuff!

[trafsta]

Just an update. I did a factory reset on the thermostat and turned off the fancy features like sensing when you are passing by an showing the current temperature and weather etc and overnight it has charge back to over 3.8v (20ma input still). I then added it back to wifi and the 3 sensor pods I have are working also. I will report back if it drops below 3.6v again and drops off wifi again 

[MikeJeffries]

Here we go again. Around April 4th they sent my RMA unit out - worked fine until TODAY june 23, 2023.

The battery issue is back. It seems that they say they dont need a c-wire, but they actually need it because the batteries inside them are so cheap they dont last 10 years like they should.

[MikeJeffries]

So just as a heads up, the unit started to show w5 code. The instructions online say to try and restart it but if its still not working, call support. Support told me the unit is faulty if thats the code, and here comes RMA#2 - device #3 (within 7-8 months)

[-MBS]

I've attached the C-wire and mine still won't charge...

[zoeuvre]

Hi folks, 

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

@MikeJeffries, don't give up on us yet. We'd like to further check on this. Could you fill out this form and let me know once you're done? 

@geneswain, do you have any questions or concerns with your thermostat that we can also settle? 

@-MBS, can you help me with your Nest Thermostat’s power reading?  

1. To open the Quick View menu, press the thermostat’s ring.
2. Choose Settings.
3. Turn the ring to highlight Technical Info then press the ring to select it.
4. Select Power.
   • Battey
   • VOC
   • VIN 
   • IIN

I’ll look forward to your responses. 

Best,

Zoe

[Mark63]

Buy a Honeywell T6 Pro and be time and money ahead, I did no more issues.

[MikeJeffries]

done but i just replied below. 3rd unit came as the 2nd RMA, and immediately started to discharge and no wifi again, a few min later and it reconnected which was strange, but without paying too much attention to it, it ended up happening again discharging.  I called customer service again. The representative said if it's anything below 3.9 volts in the settings that means it is discharging and mine was showing around 3.6 to 3.7 volts so I must have one of those systems that cannot power itself without the C wire I'll report back in a couple of days once I get this power connector and see if that works. Thanks for all the help guys 

[Shabellabu]

Can you help me I have the same problem!! Don’t know what else to do ? It’s doesn’t charge in the wall, it does charge in the usb it’s very annoying  it turns off every 30 minutes 

[MikeJeffries]

ANDDDD GUESS WHAT??? Nest Learning unit 3 immediately starts with low battery and no wifi. the power shows it's at like 3.6-3.7 Volts. The rep today said it has to show either close or more than 3.9.v - anything less is showing that it is just discharging.

[BN231]

I already had a 5th spare wire in furnace and thermostat not connected so I connected it to the opposite side of the transformer and in the c wire spot and no more issues everyday with disconnecting temp sensors disconnecting and thermostat shutting down. 

[MikeJeffries]

So here's the final resolution after a 2nd RMA = i must install a C-wire.

I have 4 wires. W G Y and R in the thermostat side.

W G and R all match the control board terminals, EXCEPT the Y on the thermostat side, goes into C on the controller board.

I tried Y to Y, the AC wouldnt work. I didnt bother doing C to C, because the AC definitely wouldnt work that way. 

I have a forced air system so A/C probably got added after the furnace (especially since when i moved in a year ago i saw one ac unit still located in a bedroom wall from years ago). When they added the A/c they probably had no way to get power to the Y wire except by plugging it into the C terminal = just my guess...

So my only solution = schedule OnSite tech for $150 and install c-wire.

[krroller]

I have 4 Nest Thermostats and have the issue of the thermostat not holding a charge any longer on 3 of the units that are 5+ years old.  The one thermostat that still has a good battery is one in a garage where the HVAC is system is not used often and the system is usually off.   

I've never had a C wire connection in the many years I've had these units.   Google tech support was adamant that I needed a C wire, which seems to be a band-aid approach for keeping an old battery trickle charged. 

I tried to replace the battery with an aftermarket battery but the header for the pin connection is so delicate that the slightest movements can and will break off.  So after rendering that thermostat useless except for parts, I put in a new thermostat using the old wire base without changing the wiring and still not using a C wire, and everything is working like new again.  

So, the real issue here seems to be the internal battery goes bad on the thermostat and there is no easy way to replace it.   Future designs should be permit for a replaceable battery in the same way that Nest Protects have replaceable batteries.   

Google tech support agents seem to be trained to not comment on the life of the battery and to always suggest that use a C wire to deal with this issue.   

Unfortunately, I now have to have spend $$ to replace 3 more thermostats because the units do not have replaceable batteries and it's quite clear that the batteries simple won't hold a charge.  From what I can tell, these old batteries either need the trickle charge that a C-wire provides or the thermostat needs complete replacement because there is no easy way to just replace the battery in an otherwise perfectly functional thermostat.