A method for assessing a state of charge/discharge (SOC/SOD) for a secondary electrochemical cell, the cell having a first operational mode during which the cell is charged from a power supply connected to terminals of the cell, a second operational mode during which the cell is discharged into a load and a rest mode, the method comprising steps of measuring entropy and enthalpy for the electrochemical cell in the course of the first and second operational modes and during rest, and calculating a data representative of the state of charge/discharge (SOC/SOD).