Wireless power is taking its sweet time becoming a reality, but did you know that with a few household items you can light your Christmas tree without having to deal with a tangled mess of cords? It not only makes decorating and undecorating a tree much easier, this tutorial can even help drain that giant bowl of change on your dresser.
As Popular Science points out, U.S. pennies minted after 1982 feature a zinc core covered in an outer layer of copper that can easily be removed with a little bit of sanding. Revealing this core, and exposing it to an acid like lemon juice, causes the zinc to dissolve and release electrons like a battery. And that's exactly what you end up with after this tutorial; a crude battery with enough juice to run a low-power LED.
And we're not just talking about a few minutes of battery life, either. Believe it or not, a ten-penny version of this battery kept an LED glowing for almost two weeks. At just over ten cents per light, that sounds like the best deal you're going to find this holiday season. [Popular Science]