Rechargeable electrical power supply unit for an electronic device of a bicycle

A rechargeable electrical power supply unit (1) for an electronic device (2) of a bicycle, comprising three battery elements (5, 6, 7) with a positive pole (5a, 6a, 7a) and a negative pole (5b, 6b, 7b). The battery elements (5, 6, 7) are arranged in such a way that through switching means (9; 23, 24; 31, 32; 51, 52) it is possible to realise a first operating configuration wherein the battery elements (5, 6, 7) are connected in series for the delivery of energy to the electronic device (2), and a second operating configuration wherein the battery elements (5, 6, 7) are individually recharged by a respective source of a recharging device (3).