Lithium-ion Battery Open-Circuit Voltage Analysis for Extreme Temperature Applications^†

Accurate estimation of the open-circuit voltage (OCV) as a function of state of charge (SOC) is fundamental for reliable battery management system (BMS) design in lithium-ion battery applications. However, at low temperatures, traditional low-rate OCV testing methods suffer from polarization-induced voltage drops that truncate the measured voltage range. This results in capacity underestimation and distorted OCV–SOC profiles, directly impacting SOC estimation accuracy. In this paper, we demonstrate how low-temperature conditions can severely distort the OCV-SOC models due to elevated polarization leading to premature voltage cutoffs. This paper presents a novel offsetting based correction method that extrapolates the charge/discharge curves beyond polarization-induced cutoff points to recover the full OCV span that otherwise would be lost at low temperatures. The approach is demonstrated using experimental low-rate OCV characterization data collected from Samsung EB575152 Li-ion cells from negative −25°C to 50°C. Results show that the proposed method significantly restores the usable OCV-SOC profile without requiring any modifications to the standard low-rate test protocol. By preserving complete voltage curves across a wide temperature range, this technique significantly improves the SOC estimation accuracy for battery management system.