PROJECT TITLE :

Non-Zero Intercept Frequency: An Accurate Method to Determine the Integral Temperature of Li-Ion Batteries

ABSTRACT:

A brand new impedance-based approach is introduced in which the integral battery temperature is connected to alternative frequencies than the recently developed zero-intercept frequency (ZIF). The advantage of the proposed non-ZIF (NZIF) method is that measurement interferences, ensuing from the current flowing through the battery (pack), will be avoided at these frequencies. This gives higher signal-to-noise ratios (SNRs) and, consequently, a lot of accurate temperature measurements. A theoretical analysis, using identical circuit model of a Li-ion battery, shows that NZIFs are temperature dependent during a manner almost like the ZIF and will so additionally be used as a battery temperature indicator. To validate the proposed technique, impedance measurements are performed with individual LiFePO4 batteries and with large LiFePO4 battery packs tested in a full electric vehicle under driving conditions. The measurement results show that the NZIF is clearly smitten by the integral battery temperature and divulges the same behavior to that of the ZIF technique. This makes it doable to optimally alter the NZIF technique to frequencies with the highest SNR.