Abstract: It is described an electronic system (50) to drive an electric device (5) of a bicycle assisted electrically (1) by means of a rechargeable battery (6). In case of detecting that the calculated human power is greater than or equal to the bicycle estimated friction power and in case of detecting that the state of charge of the battery (6) is greater than or equal to a first threshold, the processor is such to generate a driving current value for driving the electric device (5) operating as an electric motor (5) supplied from the battery (6). In case of detecting that the calculated human power is smaller than the estimated bicycle friction power, the processor is such to convert at least part of the human power into electric power by means of the electric device (5) operating as an electric generator (5), and generate therefrom another driving current value for charging the battery (6) from the electric device operating as electric generator.