This article presents a nonlinear approach to characterize a solar battery charging system with a single photovoltaic (PV) module. It proposes a linear classical control method to test the system under different operating conditions. A buck converter reduces the voltage of a 330 W PV module (typically from 20 to 50 V) to charge a 12 V battery. It manages the energy flow between the photovoltaic module and the battery, ensuring maximum power point tracking (MPPT) and proper battery charging. The nonlinearity stems from switching the converter’s active device and considering the device’s nonidealities. The nonlinear behavior of PVs is a function of environmental conditions that directly impact the energy produced. A linear controller designed from the linearization of the model at a standard point is proposed, and the MPPT technique used is modified incremental conductance (INC) with variable increment. The control obtained a satisfactory dynamic response with correct tracking at the maximum power point (MPP).