Our LED light-sensing experiments lead to an interesting observation: When these loggers are left running overnight they still produce readings because reverse-bias ‘leakage-current’ eventually triggers the Interrupt Capture Unit (ICU) – in the absence of any light. The speed of this self-discharge depends on the ambient temperature. If you deliberately cover an rgb LED with heat shrink, the different color channels have different rates of thermal decay
This application note is based on the analog output MCP9700/MCP9701 and serial output MCP9800 temperature sensors. Link (PDF) here
Microchip Technology Inc. provides a number of analog and serial output Integrated Circuit (IC) temperature sensors. Typically, these sensors are accurate at room temperature within one degree Celsius (±1°C). However, at hot or cold temperature extremes, the accuracy decreases nonlinearly. Normally, that nonlinearity has a parabolic shape.
Low current consumption temperature battery monitoring TMP303 from Texas Instruments. Link here (PDF)
Charging a battery cannot be independent of temperature. In fact, most batteries specify a range of temperatures where charging is permitted. Charging outside these bounds risks damage, failure or worse. To prevent charging when the temperature is too hot or too cold, a temperature sensor and corresponding circuitry are required to disable the charging circuit accordingly. Some temperature sensors like TMP303 already incorporate this functionality. TMP303 monitors the local temperature and asserts its output when the temperature rises above or falls below factory-programmed trip points. This output signal is used to disable the charging circuit.