Abstract: Apparatus 10 uses presently existing, conventional extension cord(s) 40 to couple a power tool 20, which normally operates using an internal direct current power source (i.e. battery cartridge), to an external direct current power source 90. The apparatus 10 has a power tool adapter or coupler 30 that couples to the power tool 20 and that further couples to a plug end of the extension cord(s) 40. The apparatus 10 also has an external source adapter or coupler 50 that couples to the other plug end of the extension cord(s) 40 and that further couples to the external direct current power source 90. The power tool adapter or coupler 30 has a tool adapter housing/casing 32 or battery cartridge housing/casing 32 that is conformed to slidingly insert, fit, and couple into a power source receptacle 22 of the power tool 20. A safety trip mechanism or fuse 70 is integrated into the power tool adapter or coupler 30 to prevent damage and injury when a power overload or surge occurs.