Empirical Model of a High-Temperature Proton Exchange Membrane Fuel Cell for Diagnostics Based on Test Without Active Gases Procedure

Abstract This paper presents a static electrical model developed to analyze results from the Test Without Active Gases (TWAG) procedure, which characterizes fuel cell behavior in the absence of electrochemically active gases. The model topology is inspired by electric double-layer supercapacitor circuits and was derived from first principles using Lagrangian formalism. It was validated using five experimental TWAG discharge curves recorded at temperatures between 40°C and 120°C. Despite its simplicity and low computational cost, the model achieved satisfactory accuracy. The extracted parameters indicate potential for further refinement, such as introducing temperature-dependent components. The approach provides insight into the intrinsic electrochemical properties of high-temperature proton exchange membrane fuel cells in states without active gases and may serve as a foundation for broader diagnostic and modeling applications. Future developments may include extending the RC circuit, incorporating nonlinear elements, or applying the model to other fuel cell technologies. Testing on deliberately degraded cells could also help correlate model parameters with cell health.