This paper is the second in a series of two papers focusing on the applicability of highly variable direct current (DC) for the production of high quality cathodes by electrowinning. Different current profiles were simulated from solar irradiance data and then applied to electrowinning cell using a precision programmable power supply. The simulated DC current was applied to the zinc electrowinning process, which was chosen as a case study due to its intensive energy consumption. The present work discusses the combined effect of highly variable current with the concentration of magnesium ions (Mg2+) in the zinc sulfate electrolyte. The impact of this impurity is relevant due to the complex mineralogy of the zinc ores available for processing (i.e., magnesium is one of the major elements contained in low-grade silicate ores). The results showed that even over a wide range of applied current densities (highest average value = 697 A m−2; highest peak value = 1486 A m−2), the average values of current efficiency calculated for the process, according to the different types of solar irradiance variability, are comparable. The lowest value (90.3% for intermittent day) could be explained by high amplitude variations in the intensity of the current density, which enhances the hydrogen evolution rate. The average values of current efficiency decreased with increasing impurity concentration in the electrolyte; decreases of 0.8–2.0% units in the average value of current efficiency were calculated at 15 g L−1 Mg2+. At this concentration, an increase of 2.1–6.8% in the average values of specific energy consumption was calculated, which was explained by the observed decrease in current efficiency and a slight increase in the cell voltage due to a decrease in the electrolyte conductivity. The deposits formed in the presence of 15 g L−1 and 30 g L−1 Mg2+ in the electrolyte showed a relatively greater number of pores, which, however, did not cause them to fracture or break during stripping.