Low battery

[Rsilva0324]

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. 

[Patrick_Caezza]

How is the Nest wired?

Does it have a C wire installed?

The batteries are not replaceable.

[Rsilva0324]

there is only a white wire hooked up to W1 only On the right side of the panel,

On the left side of the panel, Blue wire hooked up to white one yellow wire, hooked up to G and red wire, hooked up to RC

[Patrick_Caezza]

@Rsilva0324 

You need to add a C wire if an extra wire goes to the furnace from the thermostat.

If there isn't and extra wire, you can use the Nest Power Connector to solve your problem.

[Rsilva0324]

There is no C wire connected 

there is only a white wire hooked up to W1 only On the right side of the panel,

On the left side of the panel, Blue wire hooked up to white one yellow wire, hooked up to G and red wire, hooked up to RC