We study a set of 47 nightside inverted-V events using the Freja F7 (Two-dimensional Electron Spectrometer; TESP) electron detector. For each data point, we determine the peak potential, the source plasma density and temperature, and the field-aligned current density. We show that the temperature and peak potential are correlated, which is in line with previous studies: the temperature is on the average 3.3 times smaller than eV, where V is the peak potential. On the contrary, the current density is statistically quite independent of the potential. Thus, based on Freja F7 data, the observational current-voltage relationship is that the current is constant with respect to the voltage in an average sense. The formation of a parallel electric field, represented by the voltage, is more related to the source plasma density and temperature and density than the current. Our results concern energies up to 8.7 keV.