Thermostat keeps saying battery needs to be charged and to shut it down. Did that but AC only comes on for few minutes, then shuts down. Took the unit off and charged it using the usb port.
I'm sorry to hear that your Nest Thermostat doesn't hold its charge even after charging. I'm happy to shed some light on the situation here.
The built-in battery of the thermostats can be recharged over time using the heating and cooling wires. When the Nest Thermostat's battery is unable to recharge itself using the wires, you must connect the Nest Power Connector or a common wire (or C wire) in order to ensure that your thermostat is consistently powered on. A common wire serves only to maintain the current flow into the thermostat and to supply stable power; it is not responsible for any heating or cooling functions. You must set up a C-wire or a Nest Power Connector if your Nest Thermostat experiences power issues or its battery frequently drains.
Please check out these articles to see how they would help avoid power issues such as short cycling.
