Method of determining, for each cell of a battery comprising a plurality of series-coupled cells (Ci), of an indicator QCi representative of the charge stored in the cell (Ci), this method comprising the steps of: a) at the end of a phase of partial discharge or charge of the battery, measuring the voltage Ui across each cell (Ci) of the battery; b) calculating , for each cell (Ci), an interpolation coefficient Xi from a value C_rate representative of the battery discharge or charge rate during said partial discharge or charge phase , and from the voltages Ui measured at step a); and c) determining , for each cell (Ci), from the interpolation coefficient Xi calculated for the cell at step b) and from a quantity Qcm representative of the charge stored in the battery, said indicator QCi representative of the charge stored in the cell (Ci), wherein for each cell (Ci), the interpolation coefficient Xi calculated at step b) is a function of the voltage Ui of the cell measured at step a), of value C_rate, of a value Umin defined as being the lowest value of the voltages Ui measured at step a), of a value Umax defined as being the highest voltage of the voltages Ui measured at step b), and of a value Umoy defined as being the average of the voltages Ui measured at step b), and wherein, for each cell (Ci), the interpolation coefficient Xi calculated at step b) is defined as follows: Xi = K + B ∗ D ∗ C + B ∗ D ∗ E − B ∗ A / K where A, B, C, D, E, and K are parameters defined as follows: K = Umoy 2 ∗ 1 + S ∗ C _ rate / 2 ∗ C _ rate A = Umax − Ui B = Ui − Umin C = Ui / Umin D = Ui / Umax E = Umax − Umin / Ui where S designates the sign of the discharge or charge current applied to the battery at step a). a) at the end of a phase of partial discharge or charge of the battery, measuring the voltage Ui across each cell (Ci) of the battery; b) calculating , for each cell (Ci), an interpolation coefficient Xi from a value C_rate representative of the battery discharge or charge rate during said partial discharge or charge phase , and from the voltages Ui measured at step a); and c) determining , for each cell (Ci), from the interpolation coefficient Xi calculated for the cell at step b) and from a quantity Qcm representative of the charge stored in the battery, said indicator QCi representative of the charge stored in the cell (Ci), wherein for each cell (Ci), the interpolation coefficient Xi calculated at step b) is a function of the voltage Ui of the cell measured at step a), of value C_rate, of a value Umin defined as being the lowest value of the voltages Ui measured at step a), of a value Umax defined as being the highest voltage of the voltages Ui measured at step b), and of a value Umoy defined as being the average of the voltages Ui measured at step b), and wherein, for each cell (Ci), the interpolation coefficient Xi calculated at step b) is defined as follows: Xi = K + B ∗ D ∗ C + B ∗ D ∗ E − B ∗ A / K where A, B, C, D, E, and K are parameters defined as follows: K = Umoy 2 ∗ 1 + S ∗ C _ rate / 2 ∗ C _ rate A = Umax − Ui B = Ui − Umin C = Ui / Umin D = Ui / Umax E = Umax − Umin / Ui where S designates the sign of the discharge or charge current applied to the battery at step a). <EOS>