There is described a method for establishing an NFC connection between a subscriber identity module (SIM) and an NFC device (RDR). The subscriber identity module (SIM) is connected to a telecommunications system (CELL_P) through contacts (VCC, RST, CLK, D+, GND, SWP, IO, D−) of the telecommunications system (CELL_P). The telecommunications system (CELL_P) comprises a chipset (CHP) and an NFC circuit (NFCC). The method comprises measuring the level of charge of a battery (BATT) powering the telecommunications system (CELL_P) with a battery gauge. Based on the measurement, the method selects the source for supplying power to the subscriber identity module (SIM) and configures the wiring of the subscriber identity module (SIM). The disclosure also relates, in particular, to a telecommunications system, to a computer program, and to a storage medium.