A method for correcting the variation in open-circuit voltage due to ageing of at least one electrochemical cell of a battery, the method comprising a step of obtaining measurements of the voltage and current of the at least one electrochemical cell during a charge or discharge comprising the planar portion, the method being characterised: in that the at least one electrochemical cell has a state of charge - open-circuit voltage characteristic with a planar portion, a planar portion being a portion wherein the variation in open-circuit voltage is less than 30 mV for a variation of at least 10% in the state of charge, the planar portion comprising at least one reference point, each reference point having a reference state of charge (SOC REF) and a reference open-circuit voltage (OCV REF), the method being implemented by a computer, the computer storing a calibration function (f) which gives, on the basis of an open-circuit voltage value of the at least one electrochemical cell, the value of the state of charge of the at least one electrochemical cell, and characterised in that the method comprises the steps of: - calculating an overvoltage parameter by solving an equation obtained by calculating the value of the state of charge according to a first technique for estimating the state of charge and a second technique for estimating the state of charge, wherein only the first estimation technique involves the application of the calibration function (f) stored by the computer, the overvoltage of the at least one electrochemical cell being the difference between the voltage of the at least one electrochemical cell and the open-circuit voltage of the at least one electrochemical cell, - determining the measured value of the reference open-circuit voltage (OCV REF MES) of the at least one electrochemical cell for each reference point using the calculated overvoltage parameter, and - estimating the variation in open-circuit voltage related to ageing by comparing, for each reference point, the value of the reference open-circuit voltage (OCV REF) and the measured value of the reference open-circuit voltage (OCV REF MES). in that the at least one electrochemical cell has a state of charge - open-circuit voltage characteristic with a planar portion, a planar portion being a portion wherein the variation in open-circuit voltage is less than 30 mV for a variation of at least 10% in the state of charge, the planar portion comprising at least one reference point, each reference point having a reference state of charge (SOC REF) and a reference open-circuit voltage (OCV REF), the method being implemented by a computer, the computer storing a calibration function (f) which gives, on the basis of an open-circuit voltage value of the at least one electrochemical cell, the value of the state of charge of the at least one electrochemical cell, and characterised in that the method comprises the steps of: - calculating an overvoltage parameter by solving an equation obtained by calculating the value of the state of charge according to a first technique for estimating the state of charge and a second technique for estimating the state of charge, wherein only the first estimation technique involves the application of the calibration function (f) stored by the computer, the overvoltage of the at least one electrochemical cell being the difference between the voltage of the at least one electrochemical cell and the open-circuit voltage of the at least one electrochemical cell, - determining the measured value of the reference open-circuit voltage (OCV REF MES) of the at least one electrochemical cell for each reference point using the calculated overvoltage parameter, and - estimating the variation in open-circuit voltage related to ageing by comparing, for each reference point, the value of the reference open-circuit voltage (OCV REF) and the measured value of the reference open-circuit voltage (OCV REF MES). - calculating an overvoltage parameter by solving an equation obtained by calculating the value of the state of charge according to a first technique for estimating the state of charge and a second technique for estimating the state of charge, wherein only the first estimation technique involves the application of the calibration function (f) stored by the computer, the overvoltage of the at least one electrochemical cell being the difference between the voltage of the at least one electrochemical cell and the open-circuit voltage of the at least one electrochemical cell, - determining the measured value of the reference open-circuit voltage (OCV REF MES) of the at least one electrochemical cell for each reference point using the calculated overvoltage parameter, and - estimating the variation in open-circuit voltage related to ageing by comparing, for each reference point, the value of the reference open-circuit voltage (OCV REF) and the measured value of the reference open-circuit voltage (OCV REF MES).