Concrete mixer truck comprising: - a vehicle provided at least with a heat engine equipped with a drive shaft, a movement unit with drive wheels, a clutch and a gearbox to selectively transmit the mechanical energy of said heat engine to said movement unit; - a concrete mixer mounted on said vehicle and having a rotating drum; - an auxiliary device comprising at least a unit for generating electric energy and an electric motor selectively fed by said electric energy generating unit and mechanically connected to said rotating drum in order to make it selectively rotate; wherein said electric energy generating unit comprises: - at least an electric energy accumulator; - connection means between said accumulator and an external electric network to selectively recharge said accumulator by means of said external electric network, characterized in that said electric energy generating unit further comprises: - an alternator selectively connectable to said heat engine and to said movement unit by means of said gearbox using a power take-off comprising a drive shaft and a possible speed reducer connected to said drive shaft by means of a connection joint positioned between said clutch and said gearbox, said alternator being configured to convert mechanical energy produced by the rotation of said drive shaft into alternate electric energy and vice versa; - reversible electric energy conversion means, made with a plurality of semiconductor switches, connected to said at least one accumulator and to said alternator to selectively either take continuous electric energy from the at least one accumulator and to supply alternate electric energy to said alternator when said clutch is disengaged and said drive wheels are disconnected from said heat engine, in order to selectively move the drive wheels of said movement unit, or to convert the alternate electric energy produced by said alternator into continuous electric energy to be transferred to said at least one accumulator in order to selectively recharge said at least one accumulator; - connection means between said accumulator and a kinetic/mechanical energy recovery device produced by said movement unit in order to selectively recharge said accumulator by means of said kinetic/mechanical energy recovery device. - a vehicle provided at least with a heat engine equipped with a drive shaft, a movement unit with drive wheels, a clutch and a gearbox to selectively transmit the mechanical energy of said heat engine to said movement unit; - a concrete mixer mounted on said vehicle and having a rotating drum; - an auxiliary device comprising at least a unit for generating electric energy and an electric motor selectively fed by said electric energy generating unit and mechanically connected to said rotating drum in order to make it selectively rotate; - at least an electric energy accumulator; - connection means between said accumulator and an external electric network to selectively recharge said accumulator by means of said external electric network, characterized in that said electric energy generating unit further comprises: - an alternator selectively connectable to said heat engine and to said movement unit by means of said gearbox using a power take-off comprising a drive shaft and a possible speed reducer connected to said drive shaft by means of a connection joint positioned between said clutch and said gearbox, said alternator being configured to convert mechanical energy produced by the rotation of said drive shaft into alternate electric energy and vice versa; - reversible electric energy conversion means, made with a plurality of semiconductor switches, connected to said at least one accumulator and to said alternator to selectively either take continuous electric energy from the at least one accumulator and to supply alternate electric energy to said alternator when said clutch is disengaged and said drive wheels are disconnected from said heat engine, in order to selectively move the drive wheels of said movement unit, or to convert the alternate electric energy produced by said alternator into continuous electric energy to be transferred to said at least one accumulator in order to selectively recharge said at least one accumulator; - connection means between said accumulator and a kinetic/mechanical energy recovery device produced by said movement unit in order to selectively recharge said accumulator by means of said kinetic/mechanical energy recovery device.