This is the big brother of the little AAA Double Barrel and is for those who really want an easy mod for a big and bright light with a long running time.
The Energizer AA Double Barrel uses six AA batteries with 3 each organized in parallel in the two barrels, providing 4.5V to the lamp. This is great news, because no modification to the switch assembly is necessary, like in the mod to the little AAA brother.
First, remove the head assy and enlarge the hole in the reflector assy to 7/16" (by hand with a drill bit). This is necessary so when tightened down, it will not crush the leads on the Luxeon.
Second, locate two 1/2" washers (outside diameter 2"); these will form the heat sink. Notice how they will fit down on the switch assy tube that holds the lamp. In order to get the power to the Luxeon, the plastic tube needs to have two slots cut in it so the wires can get from the lamp socket without being crushed by the washers. Use a fine tip soldering iron to cut the two slots.
Cut a 1" to 1 1/2" round circuit card from 2oz 1/32" thick pc board. Etch or cut isolation pads for the Luxeon leads. Mount the luxeon in the center of the board with a coat of thermal compound on the Luxeon heat slug, and solder the leads to the pads.
Make a 2.5 to 2.75 ohm resistor by twisting together in parallel four 10 ohm or three 10 ohm and one 15 ohm resistors. Connect two 5 inch wires to the bulb socket and run them out the slots cut into the lamp base. Cut one of the wires in half and insert the resistor; solder in place and cover with heatshrink tubing.
Switch on the power and locate the proper +/- leads on the Luxeon. Switch off power and solder the leads to the Luxeon circuit card pads. Verify everything is working properly by switching on/off the power.
Install the two washers over the lamp bulb post, applying a coat of thermal compound between the two washers. Bend the wires and resistor back so they fit under the washers and won't interfere with anything when the light is assembled. Secure the washers in place with epoxy and spacers as shown in the photo.
Apply a coat of thermal compound to the back of the Luxeon circuit card and mount on top of the washers. Carefully center the Luxeon on top of the washers and install the head assembly; this may require several test fits. Slowly tighten the head assembly until tight.
You now have one of the most powerful LED flashlights on the planet. The beam is fairly smooth and it's pretty well defined and very bright.
Left is the DBAA against a 3D Maglite, and right is DBAA against it's little brother DB AAA