If you want a flashlight to run longer and possibly brighter, you can use a higher capacity battery. To do this, you will need the battery to be wired externally. A Techlite Lumen Master 200 flashlight was used.
Step 1: Cut Wooden Dowel
Step 2: Drill the Dowel's Ends for a Wire
Make sure that the wire can go all the way through.
Step 3: Drill One End of the Dowel for the Spring
The hole should be wide enough for the spring and shallow enough for the spring to be exposed.
Step 4: Solder the Positive Wire to the Spring
Step 5: Glue the Spring to the Dowel
Step 6: Drill the Side of the Flashlight
The screws would be used to hold the dowels inside. One of the screws would connect to the negative terminal of your battery pack. The drilled holes need to be threaded.
Step 7: Drill the Side of the Dowel
Before marking them, make sure that the spring would be depressed. Drill the dowel. Make sure that the drill bit doesn't touch the wire inside.
Step 8: Insert the Screws
The screw may need to be shortened. A ring terminal was used for the negative wire. Washers were used to keep the screws locked.