A method determines the value of a characteristic quantity (U1dc, U2dc) of a system for powering a load which includes M DC-DC converters, connected in series to the terminals of the load and at the output of a DC current power supply, and at least one storage capacitor and includes the measurement of a plurality of values of a first characteristic quantity (Ic) with a first high resolution, the measurement with a low resolution of a value of a second characteristic quantity (U1dc, U2dc), and a determination with a second high resolution of a value of the second characteristic quantity (U1dc, U2dc) from the plurality of values measured with the first high resolution of the first characteristic quantity (Ic) and from the value with the low resolution of the second characteristic quantity (U1dc, U2dc). The first and second high resolutions are at least 10 times greater than the low resolution.