Estimation of membrane hydration status for standby proton exchange membrane fuel cell systems by impedance measurement: First impedance measurement circuit

Fuel cells are getting growing interest in both backup systems and electric vehicles. Although these systems are characterized by long periods of inactivity, they must be able to start at any instant in the shortest time. However, the membrane of which PEMFCs are made tends to dry out when not in use. This increases the time required to start the system and could lead to the destruction of the fuel cell. In this article an impedance measurement circuit is presented, which is part of a humidity status estimator for monitoring the humidity status of a fuel cell stack during standby. The impedance measurement circuit has been connected to a fuel cell stack and the operation of estimating the relative humidity has been demonstrated.