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.