Proton Exchange Membrane Fuel Cell (PEMFC) is a complex multi-physical system in which phenomenon from several fields are coupled (e.g. electro-chemical, electrical, thermal, and hydraulic). This promising energy converter needs to be optimized to become competitive. This is the reason why many researches have been conducted for its modeling. The optimization of such a converter requires the study of the whole system through simulation. Thus the Bond Graph theory is well suited. In this paper, a dynamical model of a PEMFC stack using the Bond Graph formalism is presented and a procedure to estimate the model parameters is proposed. The global model is validated thanks to experimental data from an 8-cell fuel cell stack.