Where I live, we frequently go without power 3-8 hours at a time. It can get annoying and expensive running down batteries for light and burning candles is simply a bad idea. Rummaging through Instructables I found MooseTooths project, and though I liked it, it seemed the efficiency could be greatly improved with an LED replacement, but who wants to struggle with getting the polarity of an LED right in the dark? We'll take care of that.

Step 1: The Polarity Problem

The problem of polarity was solved by building a bridge rectifier. We usually think of rectifiers in the sense of converting AC to DC, but they can also be used if the polarity of the source is unknown.

I already had one assembled from an old project ,however the wikipedia page contains more than sufficient information in this case.

One source of diodes, indeed the source I used is CFL's, instructions for disassembly have been posted by Westfw.

Step 2: Attachments

The springclips on a lantern battery can be frustrating to attach things to. I decided alligator clips were the best solution. They are imply soldered onto the inputs of the diode bridge and bent to fit the battery.

Step 3: Voltage Drop

If you want to be accurate at this point, you can measure the voltage drop caused by the bridge to accurately compute the resistor you will need. I didn't and simply put two 68 ohms in parallel to get 34 ohms.

Step 4: The LED

I have these lovely little 10 mm LEDs from Alan Parekh, which are very bright, but I didn't just want a spot on the ceiling so following guyfrom7up's instructions I diffused the LED.

Step 5: Finally

I attached the LED resistor combo to the bridge, remember, here polarity matters. Now we have a circuit that we can clip onto the battery, in the dark without regard for the polarity and that will provide somewhere between 10-15 days of light.