If you had to total up the number of AA batteries in your house, you’d probably end up with a pretty decent number. Rechargeable batteries are great, as they have a longer life than their disposable counterparts. However, some devices such as TV remotes don’t use enough power to really justify spending the extra money for rechargeables. So what do you do when it’s time to throw away those old AA’s? Well, you might be surprised to know that even though they appear dead, most still have a bit of juice left in them, just not enough to power the gadget you had them in.

If you want to feel like you’ve really gotten your money’s worth with your batteries, you can build one of these Joule Thieves. So what exactly is this strange little contraption? It’s a small circuit that does little more than light up an LED. With the low power consumption of an LED, it will be able to suck the last little drops of juice from your AA battery. Sure, it isn’t exactly useful, but at least you know that you’re not throwing away a battery that could still serve some purpose (even if it is a silly one).