Thermal Monitoring of LiFePO4 Batteries Using Switching Harmonics

Thermal monitoring is of high relevance for safe operation and degradation management of batteries. Direct measurement of battery temperature has drawbacks due to both cost and reliability issues. To overcome these limitations, the development of temperature estimation methods has received significant research attention. Most of the existing estimation methods are based on the injection of an additional signal, which can produce additional losses. This article proposes a temperature estimation method for LiFePO4 batteries using the switching harmonics of the converter feeding the battery. Temperature changes are estimated from the variation of the battery impedance at the switching frequency. The method operates online and without interfering with the normal operation of battery and power converter, and does not therefore introduce additional losses or any other adverse effect in the batteries.