> After much research, my conclusion is that my HVAC system didn't have one of the wires connected, Common, C. This was not a problem until some update that caused the rest of the wires to be insufficient to recharge completely.
My Ecobee doesn't have a battery at all, so that's something I had to deal with immediately upon installation. Luckily, I had an unused wire going to my own thermostat that I could repurpose. I believe it also came with a kit that would allow it to use a nonstandard signaling protocol so it could get needed power even if I didn't have an extra wire.
I'm kind of puzzled why a Nest would even have a battery. Just a kludge to allow unreliable installation in places that don't have the proper wiring?
One of the things I hate about modern software/product engineering is the over-reliance on updates and the mindset that aggressively obsoleting "old" versions. It creates a huge amount of unreliability and wasted time. IMHO, updates break things as much as they fix them.
> Who knows though. It was fine for the first few years, aside from when my power company overrode my settings on hot days and my kid had a life threatening fever.
Could they do that through the Nest, or did they have a separate cutout on the AC?
My home has a remote operated cutout, which I'd assumed wad inactive until I randomly read by bill very carefully and realized it was active even though I never signed up for it (apparently the previous homeowner had it active, and that carried forward to my account).