C.H.I.P. Pro uses the AXP209 IC to manage battery charging. Pin 7 marked BATTEMP or BTS is directly connected to the TS pin on the AXP209. This pin supports a thermistor to monitor the battery temperature when the battery is charging or discharging. Find out how to disable or use this pin in the Battery Charging + BTS Pin section of the C.H.I.P. Pro docs.