Fuel cell stack with improved discharge of condensed water

A cell assembly (10) has reactant gas passages connected in series in first and second unit cells (14, 16), and oxygen-containing gas inlets (46), intermediate oxygen-containing gas inlets (42), oxygen-containing gas outlets (54), intermediate oxygen-containing gas outlets (40) which are defined in the first and second unit cells (14, 16). The oxygen-containing gas inlets (46) and the intermediate oxygen-containing gas inlets (42) are disposed upwardly of the oxygen-containing gas outlets (54) and the intermediate oxygen-containing gas outlets (40). The oxygen-containing gas outlets (54) and the intermediate oxygen-containing gas outlets (40) are disposed at least partly below electric energy generating surfaces of the first and second unit cells (14, 16).