Performance Comparison of Open-Circuit Voltage Modelling of Li-ion Batteries at Different C-Rates

Abstract

The characterization of a battery to estimate its capacity is a crucial step in open-circuit voltage modelling. The battery capacity estimation is essential to determine diagnostic details on the battery and in determining several other battery parameters. Past research has shown that a normalized open-circuit voltage characterization independent of temperature is also dependent on accurate capacity estimation. In most works, the normalized OCV characterization approaches were done at C/30 rates where the entire data collection took approximately 60 hours. The undesirably long data collection process motivated the need to determine the expected accuracy at lower C-rates in realistic conditions. However, little attention was paid in the literature to investigate capacity estimation error at various C-rates. Thus, in this paper, the battery capacity estimation is repeated at seven C-rates: C/2, C/4, C/8, C/16, C/32, C/64 and C/128, to compare their accuracy using data collected from a laboratory-based battery cycler. It was found that with a lower current rate, a maximum of 0.3 Ah error is observed in the charge capacity. An error of 0.16 Ah was observed for the discharge capacity at the lowest C-rate of C/2 A.