Method for determining a state-of-health (SOH) indicator for an electric accumulator, this method comprising the following steps: - determining the nominal energy capacity (Enom) of the electric accumulator; - acquiring measurements of parameters representing the voltage across the terminals of the electric accumulator, the current delivered by the electric accumulator, and the state of charge (SOC) of the electric accumulator, this acquisition being carried out over a measurement period (PM) comprising a set of charging and discharging operations of the electric accumulator; this method being characterized in that it comprises the following steps: - a) converting the set of charging and discharging operations in the measurement period (PM) into an equivalent set of symmetrical reconstructed cycles, each symmetrical reconstructed cycle comprising one charging operation and one discharging operation having the same state-of-charge amplitude; - b) selecting the symmetrical reconstructed cycles in which the state-of-charge amplitude is greater than a predetermined value; - c) for each selected symmetrical reconstructed cycle: determining the rate of energy supplied by the electric accumulator during the discharge phase, by unit of state-of-charge amplitude of the electric accumulator; and determining a total equivalent energy value for a full charge of the electric accumulator; - d) determining an average value from the total equivalent energy values relating to a plurality of selected symmetrical reconstructed cycles, and determining the state-of-health (SOH) indicator of the electric accumulator by dividing this average value by the nominal energy capacity (Enom) value of the electric accumulator. - determining the nominal energy capacity (Enom) of the electric accumulator; - acquiring measurements of parameters representing the voltage across the terminals of the electric accumulator, the current delivered by the electric accumulator, and the state of charge (SOC) of the electric accumulator, this acquisition being carried out over a measurement period (PM) comprising a set of charging and discharging operations of the electric accumulator; - a) converting the set of charging and discharging operations in the measurement period (PM) into an equivalent set of symmetrical reconstructed cycles, each symmetrical reconstructed cycle comprising one charging operation and one discharging operation having the same state-of-charge amplitude; - b) selecting the symmetrical reconstructed cycles in which the state-of-charge amplitude is greater than a predetermined value; - c) for each selected symmetrical reconstructed cycle: determining the rate of energy supplied by the electric accumulator during the discharge phase, by unit of state-of-charge amplitude of the electric accumulator; and determining a total equivalent energy value for a full charge of the electric accumulator; - d) determining an average value from the total equivalent energy values relating to a plurality of selected symmetrical reconstructed cycles, and determining the state-of-health (SOH) indicator of the electric accumulator by dividing this average value by the nominal energy capacity (Enom) value of the electric accumulator. <EOS>