An air cargo container temperature control system and method utilizing multiple refrigeration circuits and a controller that activates one or more of the refrigeration circuits in various modes to maintain temperature control. Each of the refrigeration circuits comprises a compressor, a condenser, and an evaporator all in fluid communication to form each refrigeration circuit. Additionally, heating elements are positioned in an evaporator cell for heating load space air and/or defrosting evaporator coils. The system is also provided with a battery pack having a transformer and battery chargers for charging corresponding battery cells by transforming power from an external source. The method compares a measured temperature to a set point temperature and activates one or more refrigeration circuits depending on the temperature difference.