A portable system for managing the temperature of a patient during transport includes a heater/cooler configured to be in fluid communication with a heat transfer catheter or a heat transfer surface pad; a pump for circulating heat exchange fluid; an alternating current power supply; and a processor configured to indicate if the alternating current power supply connection to the source of alternating current is interrupted. A rechargeable battery may be configured to provide power to the system when the alternating power supply is not connected to a source of alternating current. If the system is powered on and the connection to the alternating current source is interrupted, the system may automatically switch to receiving power from the rechargeable battery. The processor may alert an operator of the interruption of the connection to the alternating current source and indicate to the operator the amount of energy remaining in the battery.