As new methods to test degradation of c-Si single-cell PV modules, we carried out both reverse bias constant current
(RBCC) test and IV duty cycle (IVDC) test under different loading levels, that is, input power to the cell. The common
failure modes of field PV modules, such as finger electrodes discoloration, inflated back sheet, and burnt back sheet in
the modules, were observed. It was found that cell's series resistance (Rs) increases approximately linearly with testing
time, and the rate of change of Rs increased exponentially corresponding to the loading level. In the RBCC test, it was
also found that cell's shunt resistance (Rsh) decayed exponentially with time, and then it approaches to constant value.
Furthermore, threshold level for occurrence of breakdown breakage of the cells was found to be about 70 to 80 watt. The
methods presented here demonstrated the possibility of applying the reverse bias test for degradation of c-Si single-cell