FUEL CELL SYSTEM AND METHOD OF ESTIMATING CONTENT OF METAL IONS

A fuel cell system includes: a fuel cell including an MEA including an electrolyte membrane and anode and cathode catalyst layers sandwiching the electrolyte membrane; an impedance measuring device measuring AC impedance of the fuel cell when AC voltage is applied to the fuel cell; an impedance acquisition unit configured to obtain a first imaginary part value of the AC impedance measured when AC voltage with a fixed frequency satisfying Fixed frequency [Hz]×(Thickness of the electrolyte membrane [μm])≤500 [Hz×μm] is applied in a state where a relative humidity of the MEA is 20% or greater, and a fuel gas is present and an oxidant gas is absent in the anode and cathode catalyst layers; and a metal ion estimation unit configured to estimate a content of metal ions in the electrolyte membrane based on the first imaginary part value of the AC impedance.