Supercapacitors (SCs) can handle thousands of charge/discharge cycles with high peak currents, largely due to their low equivalent series resistance (ESR). However, this can be a drawback when high charging currents are to be regulated, since DC-DC converters must work in continuous current mode (CCM). In this case a short circuit ideally occurs if the ESR is considered negligible and the input DC bus and SCs voltages are almost constant cycle by cycle. In practice, this implies that in CCM, a minimal variation in the duty cycle results in a high change in the charging current. This work proposes a practical model of a buck converter operating in CCM facilitating storing energy peaks in SCs. This model, which is based on considering the serial loss resistances of the converter parts and wires, is validated from simulation and assembly results both in open and closed loop regulating modes. So that, following the simplicity criteria, a classic discrete regulator is programmed in an 8-bit µC (microcontroller), achieving a settling time of 12 ms for a 30 A step. These results enable the rapid and stable absorption of power peaks that may appear on the DC bus.