A system for monitoring power supply to a refrigeration unit of a container, the system comprising: one or more cargo sensors located within the container configured to detect a cargo within the container; a power connector configured to receive power from a power supply, the power connector operably connected to the refrigeration unit to supply power thereto; a power supply sensor operably connected to the power connector, the power supply sensor configured to detect a lack of power supplied through the power connector; and a controller in communication with the one or more cargo sensors and the power supply sensor, the controller configured to: store predetermined information related to power requirements of the refrigeration unit, wherein the predetermined information includes a maximum time period of a powered-off state; receive data from the one or more cargo sensors; receive data from the power supply sensor; and when the data from the one or more cargo sensors indicates the presence of cargo within the container and the data from the power supply sensor indicates a lack of power for a duration that exceeds the maximum time period, the controller is configured to provide an indicator that the refrigeration unit does not have power; wherein the power supply sensor is configured to detect a voltage or current across the power connector; and wherein the power supply sensor and the controller are powered by an auxiliary power source. one or more cargo sensors located within the container configured to detect a cargo within the container; a power connector configured to receive power from a power supply, the power connector operably connected to the refrigeration unit to supply power thereto; a power supply sensor operably connected to the power connector, the power supply sensor configured to detect a lack of power supplied through the power connector; and a controller in communication with the one or more cargo sensors and the power supply sensor, the controller configured to: store predetermined information related to power requirements of the refrigeration unit, wherein the predetermined information includes a maximum time period of a powered-off state; receive data from the one or more cargo sensors; receive data from the power supply sensor; and when the data from the one or more cargo sensors indicates the presence of cargo within the container and the data from the power supply sensor indicates a lack of power for a duration that exceeds the maximum time period, the controller is configured to provide an indicator that the refrigeration unit does not have power; store predetermined information related to power requirements of the refrigeration unit, wherein the predetermined information includes a maximum time period of a powered-off state; receive data from the one or more cargo sensors; receive data from the power supply sensor; and when the data from the one or more cargo sensors indicates the presence of cargo within the container and the data from the power supply sensor indicates a lack of power for a duration that exceeds the maximum time period, the controller is configured to provide an indicator that the refrigeration unit does not have power; wherein the power supply sensor is configured to detect a voltage or current across the power connector; and wherein the power supply sensor and the controller are powered by an auxiliary power source.