Christmas lights are good for more than just decorating your tree. You could make a sparkleball with them. But what if you want to hang it from your ceiling? You would have to plug the lights into an outlet and I don't know about you but I don't have outlets in my ceiling. So why not make them battery powered?
I've only tried this with one type of Christmas lights so if you try it with other types and it doesn't work... Well then that sucks.
Anyway this is really simple and won't take long at all. Maybe like ten minutes tops if you include searching through drawers for stuff like batteries and cleaning up a broken lightbulb.

Step 1: Stuff

There aren't many things you need for this. Just a set of LED Christmas lights, two AA batteries, and a battery case that you can connect to the Christmas lights. A pair of scissors might help too, as well as duct tape or heat shrink tubing.

Step 2: What to Do

Cut off the plug and strip about an inch or less of the insulation stuff off the wire. Then connect the wires to the battery case by either soldering them or twisting them together. If you twist them together use duct tape to put tape around both of the wires separately and then put tape around both of them. And there you have it! Battery powered LED Christmas lights!

Step 3: All Done :D

Think of all the possibilities for these lights! :D
Just a word of warning, once you cut off the plug do not connect the lights to it again and try plugging it in. My mom told me that