In this article you will find step-by-step instructions on how to build a battery charger from wood scraps that will allow you to charge a NiCd (ni'-cad) cordless drill battery.
** WARNING ** only NiCd (Nickel Cadmium) batteries may be charged using this method. The pack type is usually written on them. Many newer drills use other types of batteries (Li-Ion, NiMh) that WILL EXPLODE IF YOU USE THIS PROCEDURE. If you are unsure, do not attempt this instructable. Also, improper construction or calculation of component values can cause the batteries to CATCH FIRE or EXPLODE.
Step 1: Cut two wooden blocks to hold the battery pack in place.
First measure the thickness of the stem on the battery pack and rip two wooden blocks to the same thickness. Then, make a v shaped groove to accept the rounded part of the battery pack. Make the second block with grooves to accept any keying bosses (ribs) the manufacturer may have added to the pack. I found it was easy to press the wood hard against the battery pack and use the dents as a guide for putting the slots in with my table saw. The two block can then be held in place and traced on a thin piece of wood that will become the side. Screw the side to the two blocks and test fit them.
Step 2: Cut a second side for your battery holder
Cut a second side from a thin piece of wood. The thinner, the better. It will be flexed when the battery pack is inserted. Cut a relief or leave out two of the screws so that the wood will bend a little when the contacts slide in. The puzzle piece shape isn't required, but it makes it easier to cut on a bandsaw. It does allow prongs of material to come from both sides that can flex out of the way as the pack is inserted.