Device for the electric power supply of a load, comprising: - at least two energy storage elements (13, 14) connected to said load, said energy storage elements (13, 14) comprising a maximum specified discharge current (Ibat.max) and a minimum specified voltage (Vbat.min) guaranteeing a life of said energy storage elements (13, 14), - means for determining the power needs (Pchg(t)) of said load, - means (Cbat(t), Csc(t)) for controlling each energy storage element (13, 14) which are able to define a power (Pbat(t), Psc(t)) delivered by said energy storage element (13, 14), and - means (16, 17) for monitoring each energy storage element (13, 14) which are able to provide information about a maximum instantaneous power (Pbat.max(t)) that can be requested of said energy storage element (13, 14), characterized in that: - said monitoring means (16, 17) are able to provide information about an electromotive force (Ebat(t)) and a resistance (Rbat(t)) of the Thévenin equivalent model of each energy storage element reflecting the internal state and the state of health of each energy storage element (13, 14), in that: - the device comprises a calculation body able to determine, for each energy storage element (13, 14), a maximum secured power (Pbat.max.spec(t)) according to the electromotive force (Ebat(t)) and to the resistance (Rbat(t)), according to the maximum specified current (Ibat.max) and to the minimum specified voltage (Vbat.min), and in that: - said control means (Cbat(t), Csc(t)) are adjusted over time (t) according to the power needs (Pchg(t)) of said load and to the maximum secured power (Pbat.max.spec(t)) of each energy storage element (13, 14). - at least two energy storage elements (13, 14) connected to said load, said energy storage elements (13, 14) comprising a maximum specified discharge current (Ibat.max) and a minimum specified voltage (Vbat.min) guaranteeing a life of said energy storage elements (13, 14), - means for determining the power needs (Pchg(t)) of said load, - means (Cbat(t), Csc(t)) for controlling each energy storage element (13, 14) which are able to define a power (Pbat(t), Psc(t)) delivered by said energy storage element (13, 14), and - means (16, 17) for monitoring each energy storage element (13, 14) which are able to provide information about a maximum instantaneous power (Pbat.max(t)) that can be requested of said energy storage element (13, 14), - said monitoring means (16, 17) are able to provide information about an electromotive force (Ebat(t)) and a resistance (Rbat(t)) of the Thévenin equivalent model of each energy storage element reflecting the internal state and the state of health of each energy storage element (13, 14), in that: - the device comprises a calculation body able to determine, for each energy storage element (13, 14), a maximum secured power (Pbat.max.spec(t)) according to the electromotive force (Ebat(t)) and to the resistance (Rbat(t)), according to the maximum specified current (Ibat.max) and to the minimum specified voltage (Vbat.min), and in that: - said control means (Cbat(t), Csc(t)) are adjusted over time (t) according to the power needs (Pchg(t)) of said load and to the maximum secured power (Pbat.max.spec(t)) of each energy storage element (13, 14). - the device comprises a calculation body able to determine, for each energy storage element (13, 14), a maximum secured power (Pbat.max.spec(t)) according to the electromotive force (Ebat(t)) and to the resistance (Rbat(t)), according to the maximum specified current (Ibat.max) and to the minimum specified voltage (Vbat.min), and in that: - said control means (Cbat(t), Csc(t)) are adjusted over time (t) according to the power needs (Pchg(t)) of said load and to the maximum secured power (Pbat.max.spec(t)) of each energy storage element (13, 14).