can't connect Wifi f, powers off intermittently, bought new one same model same issue

[robertyu]

This is the second Nest thermostat. It can't connect to Wifi, right now powers off intermittently, after charging by USB. stay on for about a day then constant cycling. Here is a little bit history. 

We do have a C Wire.

2nd new One. 

  * As a new One, Never able to connect Wifi

 * Used for about 6-9 months, turn off during a 4 day trip

  * Nest won't start. Remove it and put on USB charger

  * restarts every 15 to 20 minutes, and batteries are drained after about 24hours. 

1st Nest. 

   * for first six months or so, works well and we can remotely control.

   * Wifi stops working, having some intermittent issue. 

   * Wife called Nest Support, Apparently you  have to pay a payment before they can't ship replacement. 

  * wait another six month and bought a new one during holiday

[CoolingWizard]

@robertyu , You need to get a Volt Ohm Multimeter(VOM) and check the voltages.  You need to se the meter to measure AC voltage. Put one test lead on the R wire and the second test lead in the C wire. Make sure you are seeing 24V AC power +/- 5VAC. If getting a VOM is problematic, then charge the display, attach it and and go to SETTINGS > TECHNICAL INFO > POWER and scroll down to Lin and see if it reports 200mA (c). 

AC Cooling Wizard

[robertyu]

Many thanks.

Here is all relevant reading: 

Battery 3.702 V

Voc 30.64 V

Vin 30.64 V

Lin 200mA(C)

Equipment Sensor On

W1-Y1-G-C-Rc

much appreciated. 

[CoolingWizard]

@robertyu , you certainly have adequate power and current to charge the battery and operate the system. As to the WiFi, you nee to make sure your access router is offering 2.4GHz and not just only 5.0GHz. Other than that, Incan see nos reason for the Nest Thermostat WiFi  module not to connect if it is within range. 

AC Cooling Wizard

[robertyu]

I just get the Google Fiber last Friday and it's on 2.4 Ghz. It is definitely within range it's 6-8 feet away from closet (google Nest) fiber.