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For lithium iron phosphate batteries (LFP) in aerospace applications, impedance spectroscopy is applicable in the flat region of the voltage-charge curve. The frequency-dependent pseudocapacitance at 0.15 Hz is presented as useful state-of-charge (SOC) and state-of-health (SOH) indicator. For the same battery type, the prediction error of pseudocapacitance is better than 1% for a quadratic calibration curve, and less than 36% for a linear model. An approximately linear correlation between pseudocapacitance and Ah battery capacity is observed as long as overcharge and deep discharge are avoided. We verify the impedance method in comparison to the classical constant-current discharge measurements. In the case of five examined lithium-ion chemistries, the linear trend of impedance and SOC is lost if the slope of the discharge voltage curve versus SOC changes. With nickel manganese cobalt (NMC), high impedance modulus correlates with high SOC above 70%.
Peter Kurzweil; Wolfgang Scheuerpflug. State-of-Charge Monitoring and Battery Diagnosis of Different Lithium Ion Chemistries Using Impedance Spectroscopy. Batteries 2021, 7, 17 .
AMA StylePeter Kurzweil, Wolfgang Scheuerpflug. State-of-Charge Monitoring and Battery Diagnosis of Different Lithium Ion Chemistries Using Impedance Spectroscopy. Batteries. 2021; 7 (1):17.
Chicago/Turabian StylePeter Kurzweil; Wolfgang Scheuerpflug. 2021. "State-of-Charge Monitoring and Battery Diagnosis of Different Lithium Ion Chemistries Using Impedance Spectroscopy." Batteries 7, no. 1: 17.
With respect to aeronautical applications, the state-of-charge (SOC) and state-of-health (SOH) of rechargeable nickel–cadmium batteries was investigated with the help of the frequency-dependent reactance Im Z(ω) and the pseudo-capacitance C(ω) in the frequency range between 1 kHz and 0.1 Hz. The method of SOC monitoring using impedance spectroscopy is evaluated with the example of 1.5-year long-term measurements of commercial devices. A linear correlation between voltage and capacitance is observed as long as overcharge and deep discharge are avoided. Pseudo-charge Q(ω) = C(ω)⋅U at 1 Hz with respect to the rated capacity is proposed as a reliable SOH indicator for rapid measurements. The benefit of different evaluation methods and diagram types for impedance data is outlined.
Peter Kurzweil; Wolfgang Scheuerpflug. State-of-Charge Monitoring and Battery Diagnosis of NiCd Cells Using Impedance Spectroscopy. Batteries 2020, 6, 4 .
AMA StylePeter Kurzweil, Wolfgang Scheuerpflug. State-of-Charge Monitoring and Battery Diagnosis of NiCd Cells Using Impedance Spectroscopy. Batteries. 2020; 6 (1):4.
Chicago/Turabian StylePeter Kurzweil; Wolfgang Scheuerpflug. 2020. "State-of-Charge Monitoring and Battery Diagnosis of NiCd Cells Using Impedance Spectroscopy." Batteries 6, no. 1: 4.