Abstract
Toward the mass introduction start in 2015, Toyota continues efforts to overcome the remaining technical challenges for the commercialization of the TOYOTA FCHV. The cold start capability is one of the main issues among such challenges. An excess amount of water in fuel cells hinders the cold start, because the water turns into ice. On the other hand, when there is a lack of water in fuel cells, the initial FC output decreases. To resolve the issue of the cold start capability, the AC impedance measurement was employed for estimating the water content in the FC stack. Based on this, the water management system was developed, and it became possible to start up the FCHV at temperatures down to -30{degree sign}C.