Will a Nest power connector help low battery issues?

[Chipsy64]

Our Nest thermostat(s) is loosing Wi-Fi connection in low temps, while I'm away. All three thermostats we have are set to eco mode, at about 43F. 

We do not have a C wire, and our hearing tech wrote me

C" wires are not required as your system is TWO-wire conductors

After USB charging of the thermostats battery, I have the connection again through the app. The volt is now up at 3.73V

To avoid this trouble in the future, I consider a power connector.

The question is, will one power connector be enough to handle three different thermostats in three different zones? 

Is a power connector the best solution. 

Any other recommendations? Thanks

[CoolingWizard]

@Chipsy64 

a power connector is only paired with a single thermostat so if all three thermostats are having problems, you will have to have three separate power adapters. 

AC Cooling Wizard

[Chipsy64]

Ok. Noted about power connector. Thank you.

And you think power connectors are the best option? Our maintenance guy suggested to move the thermostats to the boiler room and have sensors in the original location. But those sensors are also on battery, so I worry we will run into the same issue.

Any other options?