Fuel cell system

Abstract

The object is to suppress degradation of the durability of an electrolyte membrane caused by deformation by expansion and contraction of the electrolyte membrane. A controllercalculates a humidity P of an electrolyte membranebased on a cell resistance value (step S) and determines whether the humidity P of the electrolyte membraneis less than a humidity threshold A (step S). When the humidity P is less than the humidity threshold A, the controllerdetermines that a dimensional change rate of the electrolyte membrane is not greater than a predetermined value and performs a process of increasing the humidity of the electrolyte membrane(step S). The predetermined value is a dimensional change rate that is unlikely to have damage by drying stress. This enables the electrolyte membraneto be humidified before the electrolyte membraneis excessively dried and thereby suppresses tensile stress from being applied to the electrolyte membraneby drying of the electrolyte membrane. Accordingly this suppresses cracking and thinning of the electrolyte membraneand improves the durability of the electrolyte membrane