Nest Thermostat randomly says batteries are dead, then hours later says they're fine again

[tllado]

I installed a Nest Thermostat a little over one year ago. For the first ~year it was fine, then one day it started displaying error messages saying the batteries were dead. It said the battery voltage was something absurd like 0.05V and impedance was N/A. I took the batteries out and checked them with my multimeter and they were about 1.4V each. I put in new batteries that were 1.55V each and the indicated battery voltage slowly rose over the course of several days back to the normal/actual range. A month later, all of a sudden one day with no warning once again the thermostat said battery voltage was <0.1V and batteries needed to be replaced. And once again, my multimeter said actual battery voltage is ~3.0V combined. And again a few days ago, about another month later, it said the batteries were dead again when in fact they're just fine. Over the course of 24hrs it will switch between saying batteries are <1.0V and batteries are ~3.0V several times. I've removed batteries and factory reset everything multiple times. I've swapped out batteries multiple times. The RWGC are all connected properly and haven't changed since the system was installed a year ago. R/C show 28.5VAC differential. What gives? I can't imagine any explanation except the thermostat is broken after one year.

[CoolingWizard]

@tllado , First of all if you have a Nest Thermostat that uses AA batteries, that thermostat does not have an internal battery. The AA batteries are used as a backup in case the HVAC transformer fails.  Your Nest Thermostat receives its operating power from the HVAC air handler.  You say that the system voltage is 28.5Vac, then there should be ample power to operate the Nest and the HVAC system.  Now when you check your AA batteries, use a battery tester that checks the battery under load.  

AC Cooling Wizard

[tllado · Accepted solution]

I spent a while chatting with Nest tech support and they acknowledged that my thermostat is just defective. It started misbehaving after only 8months, but I didn't complain about it until after the warranty had expired so there's no solution for me. A $100 thermostat that breaks after 8months is pathetic (the previous one cost $30 and lasted thirty years) and that's inline with my experiences with other google hardware products. I won't be buying any more hardware from Google. I interviewed for jobs with two google hardware programs and I'm glad I didn't accept either because they both imploded. Google doesn't understand or aren't willing to acknowledge that hardware is not software and needs to be developed and supported differently. Their product management is narcissistic and irresponsible.

[Jenelyn_O]

Hi there,

I appreciate your help, @CoolingWizard.

@tllado, thanks for reaching out and for sharing your experiences. I'm sorry for the delay and for the trouble this has caused you — I understand how frustrating it can be. We’re always looking for ways to improve and we’ll take this as feedback. Let me know if you still have questions and concerns. Otherwise, I'll be locking this thread after 24 hours.

Best,

Jenelyn