Automatic method for estimating the state of charge of a cell of a battery, this method including: - reiterating the following steps at instants k: a) acquiring, at the instant k, the measured value y k of the voltage across the terminals of the cell, and the measured intensity i k of the current charging or discharging the cell; b) estimating the state of charge SOC k of the cell, at the instant k, from the measured value y k, from the measured intensity i k and from a capacity C n,k3 of the cell; this capacity C n,k3, which is expressed in Ah, representing the maximum amount of electrical energy storable in the cell at the instant k3, the instant k3 being the instant at which the capacity C n,k3 has been estimated closest the instant k; and - fully executing (166; 246), with an electronic processor, an algorithm for estimating the capacity C n,k3 from the intensity i k3 measured at the instant k3, the instants k3 being less frequent than the instants k, characterized in that: - full execution of the algorithm for estimating the capacity C n,k3 is inhibited (164; 244) provided that the value of a parameter has not crossed a first preset threshold, this parameter being chosen from the group composed of the measured value y k, of the estimated state of charge SOC k and of an amount Q k of current passed by the cell between the instant k and a preceding instant; then - full execution of the algorithm for estimating the capacity C n,k3 is triggered (164; 244) in response to the fact that this parameter has dropped below the first preset threshold if the parameter is the measured value y k or the estimation of the state of charge SOC k, or has risen above the first preset threshold if this parameter is the amount Q k of current passed. - reiterating the following steps at instants k: a) acquiring, at the instant k, the measured value y k of the voltage across the terminals of the cell, and the measured intensity i k of the current charging or discharging the cell; b) estimating the state of charge SOC k of the cell, at the instant k, from the measured value y k, from the measured intensity i k and from a capacity C n,k3 of the cell; this capacity C n,k3, which is expressed in Ah, representing the maximum amount of electrical energy storable in the cell at the instant k3, the instant k3 being the instant at which the capacity C n,k3 has been estimated closest the instant k; and a) acquiring, at the instant k, the measured value y k of the voltage across the terminals of the cell, and the measured intensity i k of the current charging or discharging the cell; b) estimating the state of charge SOC k of the cell, at the instant k, from the measured value y k, from the measured intensity i k and from a capacity C n,k3 of the cell; this capacity C n,k3, which is expressed in Ah, representing the maximum amount of electrical energy storable in the cell at the instant k3, the instant k3 being the instant at which the capacity C n,k3 has been estimated closest the instant k; and - fully executing (166; 246), with an electronic processor, an algorithm for estimating the capacity C n,k3 from the intensity i k3 measured at the instant k3, the instants k3 being less frequent than the instants k, - full execution of the algorithm for estimating the capacity C n,k3 is inhibited (164; 244) provided that the value of a parameter has not crossed a first preset threshold, this parameter being chosen from the group composed of the measured value y k, of the estimated state of charge SOC k and of an amount Q k of current passed by the cell between the instant k and a preceding instant; then - full execution of the algorithm for estimating the capacity C n,k3 is triggered (164; 244) in response to the fact that this parameter has dropped below the first preset threshold if the parameter is the measured value y k or the estimation of the state of charge SOC k, or has risen above the first preset threshold if this parameter is the amount Q k of current passed.