The device includes a set of electronic switches having a common structure and forming modules for converting electrical energy and a power DC bus onto which the modules are connected in parallel. These modules are controlled by a control circuit so as to supply electrical energy originating from external sources of energy over the power DC bus or to extract electrical energy over this bus to recharge batteries. The device includes at least one AC-DC conversion module configured for carrying out the rectification of an AC line supply and for powering the DC bus, a DC-DC conversion module configured for charging a user battery from the DC bus and a DC-DC conversion module configured for alternatively allowing the recharging of a storage battery from the DC bus or the discharge of the same battery over the latter. The various modules are mounted onto an accommodation structure forming a heat dissipator.