During the application process of the solar cell, due to the voltage drop, it may be reversely charged by other cell strings. If the reverse charging current has not reached the protection current of the cell string fuse, it may cause the module to be reversely charged for a long time, resulting in the temperature continues to rise, which can damage module. This test is to provide a reverse power supply, reverse charge the solar cell, simulate the actual working condition, and test the ability of the component to withstand the reverse current. Conform to the MST26 clause in the IEC61730 standard.