Hub dynamo connectable to a wheel of a bicycle, comprising: - an electric machine capable of alternatively operating as a generator and as a motor; - one or more batteries connected to said electric machine in order to be capable of exchanging energy with the latter; - a closure body rotatively integrally connected to said bicycle wheel, adapted to receive inside the means necessary to operate the dynamo itself and housing the electric machine and said one of more batteries; said closure body being devoid of connectors for connecting the batteries to external energy sources so that said batteries are only rechargeable by the electric machine acting as a generator due to the rotation of the bicycle wheel; - a control unit configured for commanding the electric machine; - a sensor for detecting the charge state of said one or more batteries, connected to the control unit and suitable for generating a signal representative of said charge state of the one or more batteries; wherein the control unit is configured to command the electric machine: - according to a first mode, wherein the electric machine acts as a generator and is capable of converting the rotation mechanical energy of the wheel into electric energy to be stored in the one or more batteries, said first mode being further configurable by the control unit according to a first and second recovered energy levels, wherein the recovered power according to the first level is less than the recovered power according the second level under the same motion conditions of the bicycle; - according to a second mode wherein the electric machine acts as a motor and is capable of delivering additional power to the bicycle wheel by withdrawing energy from said one or more batteries; wherein the selection between the first and second modes, and/or between the first and second energy recovery levels, can be performed at least partially automatically by the control unit, based on signals from suitable sensors and/or - one or more command members are connected to the control unit and commandable by an user for selecting between first and second operative modes and/or between said first and second levels of the first operative mode, and wherein said control unit is configured for commanding said electric machine according to the first mode such that, under the same motion conditions of the bicycle, the recovered power increases as the charge level of the one or more batteries decreases. - an electric machine capable of alternatively operating as a generator and as a motor; - one or more batteries connected to said electric machine in order to be capable of exchanging energy with the latter; - a closure body rotatively integrally connected to said bicycle wheel, adapted to receive inside the means necessary to operate the dynamo itself and housing the electric machine and said one of more batteries; said closure body being devoid of connectors for connecting the batteries to external energy sources so that said batteries are only rechargeable by the electric machine acting as a generator due to the rotation of the bicycle wheel; - a control unit configured for commanding the electric machine; - a sensor for detecting the charge state of said one or more batteries, connected to the control unit and suitable for generating a signal representative of said charge state of the one or more batteries; - according to a first mode, wherein the electric machine acts as a generator and is capable of converting the rotation mechanical energy of the wheel into electric energy to be stored in the one or more batteries, said first mode being further configurable by the control unit according to a first and second recovered energy levels, wherein the recovered power according to the first level is less than the recovered power according the second level under the same motion conditions of the bicycle; - according to a second mode wherein the electric machine acts as a motor and is capable of delivering additional power to the bicycle wheel by withdrawing energy from said one or more batteries; - one or more command members are connected to the control unit and commandable by an user for selecting between first and second operative modes and/or between said first and second levels of the first operative mode,