In the present invention there is a power adaptor with backup rechargeable battery comprising a power adaptor body with a plug for receiving power from an electrical outlet, a battery charger for charging a battery with power, and a power supply outlet to deliver power to an external device from the electrical outlet or the backup battery when the plug is not receiving power. The present invention also comprises this power adaptor with backup rechargeable battery with an external device with which it communicates, such as a fire detector. The present invention further comprises a power adaptor outlet with backup rechargeable battery, having at least one electrical outlet.