Electric power supply system

An electric power supply system for an item of electrical equipment, the system comprising:

• a DC power supply bus,
• a first battery configured to deliver a first DC voltage on said DC power supply bus, said first battery comprising first cells, each of which is configured to be switched between an active state and an inactive state,
• an auxiliary battery configured to deliver a second DC voltage, which is distinct from the first DC voltage,
• control circuitry,
• a second battery configured to deliver said first DC voltage on said DC power supply bus, said second battery being connected in parallel with said first battery, said second battery comprising second cells, each of which may be switched between an active state and an inactive state,
• first switches configured to connect or disconnect the first battery from the DC power supply bus,
• second switches configured to connect or disconnect the second battery from the DC power supply bus, and
• third switches configured to connect or disconnect the auxiliary battery in series with the first battery and/or in series with the second battery,
• wherein said control circuitry is configured to:
• select at least one battery from among the first battery and the second battery in order to set said first DC voltage on the DC power supply bus by connecting the selected at least one battery to the DC power supply bus, and
• order the unselected battery to be connected to the DC power supply bus, and said auxiliary battery to be charged by placing the auxiliary battery in series with the unselected battery and by switching the cells of said unselected battery in order to control a charge current for said auxiliary battery.