As stated above, running the backlight, even on battery power, will elevate this temperature. On battery power, it turns back off by itself, which usually prevents the heat from building up in such a short time. If the light is turned on frequently during the period you are monitoring, it may have an effect. Also, I see you have the IP cable unplugged. If you have the datalogger connected to the console, it may be feeding off the console batteries to generate this heat. The latest firmware update for the IP datalogger includes an offset to counter the heat buildup when the IP datalogger is in use.