Nest 3rd Gen BH1252 Learning Thermostat (Open Box)

I bought two Google Nest Learning Thermostats. The learning is more for me than for the thermostats. Now that they are working with my HVAC system, I love them. They replaced my old not-smart electronic thermostats which were acting erratic. But the short instructions paper and the online remarks seem to be suited for older Google Nest thermostats. They talk about replacing the AA batteries. But there are no batteries to replace. Oh, there must be an internal rechargeable battery— there is a USB port. No instruction comment about charging the thermostat up before trying to install it. That helped. My old thermostats were 4-wire. They never knew about heat pumps. I don’t have a heat pump yet. These new thermostats require 5 wires to control the AC compressor. Fortunately my house thermostat wiring had five conductors. I had my HVAC maintenance guy come to the house and connect the fifth wire from each thermostat to the proper post on the HVAC controller board. He also chose better connections for the five wires at each thermostat. Turns out one of the wires was using the heat pump terminal instead of the air conditioner terminal. Now it works. Confused? Well, so was I. The thermostat has ten terminals, but the instructions give no clues as to what each is for. They look great on the wall. I do like them. I just wish there was more information in the description about retiring requirements. The maintenance guy knew what to do. But I only install thermostats every ten years or so. Technology changes during the lifetime of my thermostats.