Battery-Temperature Sensing Nicad Charger

Two simple circuits enable NiCad battery charging based on the temperature differences between the battery pack and the ambient temperature. This method allows for fast charging by sensing the temperature rise that occurs after charging is complete when the battery under charge is producing heat instead of accumulating charge.

The described circuits utilize thermistors or temperature sensors to monitor the temperature of the battery pack relative to the surrounding environment. When the battery is charging, it generates heat, and this heat is detected by the temperature sensing component. The circuit is designed to initiate charging based on a predetermined temperature differential, ensuring that the charging process is efficient and safe.

In the first circuit, a thermistor is placed in close proximity to the battery pack. As the battery charges, the thermistor detects the increase in temperature. The circuit includes a comparator that compares the voltage output from the thermistor with a reference voltage. When the temperature exceeds a specific threshold, the comparator triggers a relay or a switching transistor that engages the charging circuit, allowing current to flow into the battery pack.

The second circuit functions similarly but incorporates a microcontroller for more precise temperature monitoring and control. The microcontroller can be programmed to interpret temperature readings and adjust the charging current accordingly. This feature enhances the charging efficiency and extends the battery's lifespan by preventing overcharging and excessive heat generation.

Both circuits include safety features such as over-temperature protection, which disconnects the charging circuit if the temperature exceeds safe limits, and a feedback loop that continuously monitors the battery temperature throughout the charging process. These mechanisms ensure that the charging is not only efficient but also adheres to safety standards, preventing potential hazards associated with battery charging.

Overall, the integration of temperature-based charging circuits for NiCad batteries represents an innovative approach to battery management, optimizing charging times while maintaining safety and battery health. Two simple circuits permit Nicad charging of a battery based on temperature differences between t he battery pack and the ambient temperature. This method has the advantage of allowing fast charging because the circuit senses the temperature rise that occurs after charging is complete and the battery under charge is producing heat, not accumulating charge.