BTemp
From CPKB - Cell Phone Knowledge Base
It is used to measure the battery temperature.
It stops the charging, if the battery is starting to overheating. In case of NTC thermistor, if the temperature increasing, the resistance decreasing. The temperature of the battery make the resistance beetween the GND and the BTemp change.
There are batteries which don't have BTemp connector. In this case, the phone has a temperature meter close to the battery.
