Fast Hysteresis Voltage Modeling of LFP Batteries for ESS Using SOC-Hysteresis Symmetry

Accurate state-of-charge (SOC) estimation for lithium iron phosphate (LFP) batteries is challenging due to their flat open-circuit voltage (OCV) plateaus and significant path-dependent voltage hysteresis. This study investigates the hysteresis characteristics of LFP batteries and proposes a time-efficient modeling method. Conventionally, characterizing hysteresis requires measuring the OCV curve across the full SOC range (0–100%) with fine steps, a process that typically consumes approximately 164.3 hours. To address this inefficiency, we propose a 'Half Range' method that exploits the symmetry of hysteresis voltage around 50% SOC. By characterizing only the 0–50% or 50–100% range, the experimental duration is reduced to approximately 44.8 hours, achieving a time saving of about 73%. Hysteresis parameters were identified using the nonlinear least squares method. Experimental validation demonstrates that the proposed method maintains modeling accuracy comparable to the conventional Full Range method (RMSE: 0.336 mV), with the Upper Half model achieving an RMSE of 0.098 mV. Consequently, the proposed method significantly reduces experimental cost and time while preserving accuracy, providing a practical and efficient tool for LFP battery analysis and SOC estimation.