The impedance-based methods, also referred to as sensorless methods, have the advantage of measuring the average internal battery temperature without using external or internal hardware temperature sensors and cables. In addition, as the temperature is measured through the impedance, thermal measurement delays are very short.
Although these measurements are useful for quantifying the internal temperature, either specially designed batteries with integrated sensors must be made, or a hole must be drilled into an existing (commercial) battery to insert a sensor.
Forgez et al. measured the internal temperature of a LiFePO 4 /graphite lithium-ion battery (26650 cylindrical cell) by destructively inserting a commercial thermocouple with a junction of 1 mm in diameter into the cell in an argon protected atmosphere .
Temperature measurements of Li-ion batteries are important for assisting Battery Management Systems in controlling highly relevant states, such as State-of-Charge and State-of-Health. In addition, temperature measurements are essential to prevent dangerous situations and to maximize the performance and cycle life of batteries.
Sensor assembly process is minimally intrusive and semi-automated. Method presented hold promise to be implemented in battery management systems. Temperature monitoring is important for improving the safety and performance of Lithium Ion Batteries (LIB).
Therefore, measurement details partly remain unknown, making it impossible to accurately reproduce the measurement results reported in the literature. As with thermistors and RTD, commercial (micro) thermocouples are also used to measure the internal battery temperature , , , , , , , , , , .