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To improve the life performance of Polymer Electrolyte Fuel Cell (PEFC), the degradation behavior of the cell is diagnosed at the early stage, and an appropriate treatment should be applied to the cell. Our proposal diagnostics evaluates the transient response which includes the resistance polarization, the activation polarization and the diffusion polarization. The obtained diagnostic parameters from this transient response should include the degradation factors. This paper aims the establishment of diagnostics by clarifying the correlation of diagnostic parameter and each polarization. Because the anode polarization is considerably small compared with the cathode polarization and most fuel cells are controlled by the cathode reaction, the diagnostic parameter focused on the cathode polarization and resistance polarization of the membrane. As a result, the diagnostic parameters can judge each degradation factor, and the degradation factor distribution under the standard operating condition can be measured by applying this diagnostics to the quadrisection electrode.

Our proposal diagnostics evaluates the PEFC’s transient response with a resistance polarization, an activation polarization and a diffusion polarization, and derives diagnostics parameters by analyzing this transient response. Because we have already clarified that this diagnostics system was able to diagnose the 25cm2 PEFC single cell, we tried to elucidate the degradation factor distribution in the same electrode by applying it to the quadrisection separator. As a result, our diagnostics was able to judge the difference of the degradation factor in each section in the same electrode such as the resistance polarization is the highest at the gas upper stream, the activation polarization is the lowest at the middle section and the diffusion polarization is the highest at the gas downstream.

If the degradation of the Polymer Electrolyte Fuel Cell (PEFC) was able to be diagnosed at the early stage, the life performance could be improved by applying appropriate processing to PEFC. We are proposing the PEFC Performance Diagnose System (PPDS) which diagnoses the state of each polarization (the resistance polarization, the activation polarization and the diffusion polarization) by analyzing transient response. The application of the PPDS to the PEFC-stack was tried because it was able to diagnose each degradation factor of a single PEFC. As a result, the PPDS was able to find the unit with the deteriorated cell when it diagnoses each unit composed of four cells in the stack. Moreover, the PPDS was able to diagnose the degradation factor of the deteriorated cell instantaneously. Because we confirmed that the PPDS can diagnose a PEFC-stack, we propose the application of the PPDS to FCV as the diagnosing unit.

The cost reduction and the improvement of a life performance are necessary for the dissemination of Polymer Electrolyte Fuel Cell (PEFC). If the degradation of the fuel cell was able to be diagnosed at the early stage, the life performance can be improved by applying appropriate processing to PEFC. We have been proposing the PEFC Performance Diagnose System (PPDS) which diagnoses the state of each polarization (the resistance polarization, the activation polarization and the diffusion polarization) by analyzing transient response with Turuga Electric Corporation since 2002. Since 2014, the application of our PPDS to a PEFC short stack was tried because it was able to diagnose each degradation factor of a PEFC single cell. As a result, the PPDS not only found out a degradation cell in the four cells short stack but also was able to diagnose the degradation factor of this deteriorated cell. Therefore, this paper aims to grasp the correlation between the degradation factor and the cell position of the PEFC Short Stack using our PPDS, and the PPDS was able to find the unit with the deteriorated cell when it diagnoses each unit composed of four cells in the stack. As a result, because we elucidated the correlation between the degradation factor and the cell position of a stack, we can propose the structure of a PEFC stack where deteriorating is not caused easily. Moreover, we can apply our PPDS as a maintenance device for a fuel cell vehicle and a domestic use fuel cell.