An autonomous cardiac implant of the leadless capsule type, comprising: - a tubular body; - surface electrodes (70, 72) carried by the tubular body; - an energy harvesting module adapted to convert external stresses applied to the implant into electrical energy, comprising an inertial pendular unit including an elastically deformable element coupled to an inertial mass; - a rechargeable battery adapted to be charged by the energy harvesting module, the battery being previously charged to an initial charge level; and - an interface circuit adapted to selectively couple the surface electrodes (70, 72) to the rechargeable battery, said implant being characterized in that the interface circuit comprises a switching circuit (88-94; 88-100) adapted to operate a switching between:. a transport and storage configuration in which, before implantation of the implant, the surface electrodes (70, 72) are connected (66, 68) to a link (78, 80) coupling to an external source forming an electrical energy reserve, the external source being physically separated from the implant, the interface circuit being adapted, in said transport and storage configuration, to receive a power supply from the external source and to provide said power supply to the rechargeable battery, and. a functional configuration, in which the surface electrodes (70, 72) are decoupled from the external source after the implant has been implanted, and in that the implant further comprises: - a data transmitter circuit adapted, in the transport and storage configuration, to send communication signals (IMP_TX), via the surface electrodes (70, 72), on the link (78, 80) coupling to the external source, and/or - a data receiver circuit adapted, in the transport and storage configuration, to receive, via the surface electrodes (70, 72), communication signals (EXT TX) transmitted on the link (78, 80) coupling to the external source. - a tubular body; - surface electrodes (70, 72) carried by the tubular body; - an energy harvesting module adapted to convert external stresses applied to the implant into electrical energy, comprising an inertial pendular unit including an elastically deformable element coupled to an inertial mass; - a rechargeable battery adapted to be charged by the energy harvesting module, the battery being previously charged to an initial charge level; and - an interface circuit adapted to selectively couple the surface electrodes (70, 72) to the rechargeable battery, said implant being characterized in that the interface circuit comprises a switching circuit (88-94; 88-100) adapted to operate a switching between:. a transport and storage configuration in which, before implantation of the implant, the surface electrodes (70, 72) are connected (66, 68) to a link (78, 80) coupling to an external source forming an electrical energy reserve, the external source being physically separated from the implant, the interface circuit being adapted, in said transport and storage configuration, to receive a power supply from the external source and to provide said power supply to the rechargeable battery, and. a functional configuration, in which the surface electrodes (70, 72) are decoupled from the external source after the implant has been implanted,. a transport and storage configuration in which, before implantation of the implant, the surface electrodes (70, 72) are connected (66, 68) to a link (78, 80) coupling to an external source forming an electrical energy reserve, the external source being physically separated from the implant, the interface circuit being adapted, in said transport and storage configuration, to receive a power supply from the external source and to provide said power supply to the rechargeable battery, and. a functional configuration, in which the surface electrodes (70, 72) are decoupled from the external source after the implant has been implanted, - a data transmitter circuit adapted, in the transport and storage configuration, to send communication signals (IMP_TX), via the surface electrodes (70, 72), on the link (78, 80) coupling to the external source, and/or - a data receiver circuit adapted, in the transport and storage configuration, to receive, via the surface electrodes (70, 72), communication signals (EXT TX) transmitted on the link (78, 80) coupling to the external source.