a first mode for example the controller 26 directs the refrigeration unit 10 to operate the fan 24 only to circulate air to and from the control region the power to drive the fan 24 is provided by the battery 36 and the motor 32 and generator 34 of the power package 14 are maintained in non operational mode the other components of the refrigeration unit 10 e g the compressor 16 etc are also maintained in non operational mode in a second mode the controller 26 directs the refrigeration unit 10 to operate the fan 24 to circulate air to and from the control region and to operate at least one of the other components e g the compressor 16 etc of the refrigeration unit 10 the power to drive the fan 24 and the other component is provided by the battery 36 and not by the motor 32 and generator 34 of the power package 14 in a third mode the controller 26 directs the refrigeration unit 10 to operate the fan 24 to circulate air to and from the control region and operate at least one of the other components e g the compressor 16 etc of the refrigeration unit 10 the power to drive the fan 24 and the other component is provided by motor 32 and generator 34 of the.