Development of Water Content Control System for Fuel Cell Hybrid Vehicles Based on AC Impedance

Toyota has been developing fuel cell hybrid vehicles (FCHV) since 1992 and is currently working to resolve issues that remain for commercialization. This research focused on one of the main issues for fuel cells (FC), namely water content of the electrolyte membrane, to develop a FC water content control system based on AC impedance measurement. Adopting this control system in the FCHV resolved the issue of reduced efficiency caused by FC membrane dry-out, and makes it possible to start up the FCHV in temperatures down to -30°C by performing appropriate water content control for freezing environments.