A climate controlled vehicle comprising: a prime mover ; a transport climate control unit ; a vehicle power network comprising: an alternator configured to be driven by the prime mover when the prime mover is active, a primary battery electrically connected to the alternator for charging; a secondary battery electrically connected to the alternator for charging; power supply terminals connecting the vehicle power network to the transport climate control unit ; a switch having a closed configuration in which the primary battery and the secondary battery are electrically coupled to the alternator for charging and an open configuration in which the secondary battery and the power supply terminals are isolated from the primary battery to prevent power supply from the primary battery to the transport climate control unit ; characterised in that the transport climate control unit is connected to the power supply terminals of the vehicle power network to receive power from the alternator when the prime mover is active and the switch is closed, and to receive power from the secondary battery when the prime mover is inactive and the switch is open; and wherein a controller is configured to determine whether to maintain operation of the transport climate control unit or to deactivate the transport climate control unit , based on a power setting for the transport climate control unit (740. a prime mover ; a transport climate control unit ; a vehicle power network comprising: an alternator configured to be driven by the prime mover when the prime mover is active, a primary battery electrically connected to the alternator for charging; a secondary battery electrically connected to the alternator for charging; power supply terminals connecting the vehicle power network to the transport climate control unit ; a switch having a closed configuration in which the primary battery and the secondary battery are electrically coupled to the alternator for charging and an open configuration in which the secondary battery and the power supply terminals are isolated from the primary battery to prevent power supply from the primary battery to the transport climate control unit ; an alternator configured to be driven by the prime mover when the prime mover is active, a primary battery electrically connected to the alternator for charging; a secondary battery electrically connected to the alternator for charging; power supply terminals connecting the vehicle power network to the transport climate control unit ; a switch having a closed configuration in which the primary battery and the secondary battery are electrically coupled to the alternator for charging and an open configuration in which the secondary battery and the power supply terminals are isolated from the primary battery to prevent power supply from the primary battery to the transport climate control unit ; characterised in that the transport climate control unit is connected to the power supply terminals of the vehicle power network to receive power from the alternator when the prime mover is active and the switch is closed, and to receive power from the secondary battery when the prime mover is inactive and the switch is open; and wherein a controller is configured to determine whether to maintain operation of the transport climate control unit or to deactivate the transport climate control unit , based on a power setting for the transport climate control unit (740. <EOS>