In this work, a commercially available membrane electrode assembly from Advent Technology Inc., developed for use in high-temperature proton exchange membrane fuel cells, was tested under various operating conditions (OCs) according to a sensibility study with three OCs varying on three levels: hydrogen gas over-stoichiometry (1.05, 1.2, 1.35), air gas over-stoichiometry (1.5, 2, 2.5), and temperature (140 °C, 160 °C, 180 °C). A polarization curve (V-I curve) was performed for each set of operating conditions (27 V-I curves in total). A semi-empirical and macroscopic (0D) model of the cell voltage was developed in steady-state conditions to model these experimental data. With the proposed parameterization approach, only one set of parameters is used in order to model all the experimental curves (simultaneous optimization with 27 curves). Thus, an air over-stoichiometry-dependent model was developed. The obtained results are promising between 0.2 and 0.8 A·cm−2: an average error less than 1.5% and a maximum error around 7% between modeled and measured voltages with only 9 parameters to identify. The obtained parameters appear consistent, regardless of the OCs. The proposed approach with only one set of parameters seems to be an interesting way to converge towards the uniqueness of consistent parameters.