Does the Nest thermostat require batteries when on a Nest power connector?

[ncoig]

The post title says most of it. I bought this thermostat so I could monitor a vacation home to minimize the chances of the home freezing in winter. Originally, I had to commandeer the fan wire as a C wire in order to ensure that the power stayed on to the thermostat when the furnace was energized... Or so I thought.

This spring when I opened the home again, I installed a Nest power connector and restored my fan wire to its original place. Everything seemed fine, until it wasn't.  On a whim, I removed the thermostat from the wall and took out the batteries and placed it back in its cradle. The thermostat would not power up. I would think that the Nest power adapter would provide power to the thermostat in that case, but it doesn't appear to be doing so. Am I missing something about how this Nest power adapter works?

I've received no error messages, the Nest power connector shows "enabled", and I have voltage showing in the power menu on the thermostat.

Any insight would be appreciated.

[ncoig · Accepted solution]

Answering, at least in part, my own question: I went back to the substituted C wire method, removed the batteries and snapped the thermostat in place.  Booted right up.  Evidently, the Nest must be powered up with batteries for it to be able to discern the faux C wire setup using the adapter, which, in my view, renders the device mostly useless as a means to ensure a space is properly heated. 

I must assume then than the Nest power connector is only useful to extend the life of the batteries by drawing some juice from the control board.  While in and of itself not a crime to have this setup as such, this should be WELL-advertised for those of us who would have relied upon this to heat our homes when away to help prevent catastrophic damage.

I chose instead to relocate the thermostat and run a proper 5 conductor cable to it, and Google can have this silly device back via Amazon on their nickel.  What seemed too good to be true, was.

-N