The high negative amplitude rapid-charging events (RCEs), which were observed by the floating potential measurement unit (FPMU) on the International Space Station (ISS) and occurred at the eclipse exit, have attracted a lot of attention recently and are not yet understood. The RCEs are most serious of all types of ISS charging phenomena. Compared with the normal-charging events (NCEs) which occurred on morning sector, the RCEs are characteristic of rapid rise time (<10 seconds) and higher amplitude (30—70 V). In particular, their occurrence at the morning terminator indicates that they are related to the solar panel excitation process at the moment of receiving solar illumination. In this paper, an electric circuit model for the charging of the ISS structure and solar panel is established, based on which a differential equation is developed, with the different charging mechanisms included and also the way of solar panel excitation considered. The calculation results for the RCEs agree well with the typical waveforms.