About twenty years ago, I sprang for a state of the art, best that money could buy, a Porter Cable 12 volt cordless drill. (the highest voltage then). It came with a charger, steel carrying case and two nicad battery packs. I got a lot of good use out of it over the years. About eight years ago, the battery packs started to die. I bought one new one for $50 or so, which has since died. At that point, I ended up with three dead batteries and a really nice drill that I couldn't use.
I intend to rebuild two of the batteries with new NiMH cells eventually, but for now, I decided that as long as it is a 12 volt drill, it can run from a 12 volt battery pack, of which I have several. This battery case was fairly easy to convert. Some of them may be harder or easier than mine.
You will have to open it up and engineer it to hold the contact plates firmly in place with the wires attached. If you want to do this with a drill that is less than 12 volts, you will have to determine a way to drop the voltage to a safe level. Putting a resistor in line is the simplest way. If your drill is a higher voltage, I don't know of any simple way to provide a higher voltage.
At every step of the wiring, it is a good idea to check the wiring with a continuity tester or ohmmeter to determine that the connections are complete and that there are no opens or shorts.
Before chopping, cutting, drilling, examine the components to determine the best path for the wires. It is a good idea to mark the ends of the base and top of the case to prevent confusion.
If you have problems with my instructions, drill a hole through your hand, set your hair on fire or burn down your house, all correspondence regarding these issues should be made to my attorney. You will be promptly awarded 16.4 million dollars after sending the appropriate handling fees to his PO Box in Nigeria.)
Step 1: Parts and Tools
- One old battery pack
- One cigarette lighter plug and cord, the heavier the better. Mine looks like about 14 gauge and holds a replaceable fuse in the plug. The cord
is about seven feet long. Try to find a cord that is long enough to comfortable reach the battery pack from where you will be working.
- Short length of rubber hose for strain relief that the cord will fit snugly through, about four inches.
- Fuse - fuse size is not critical. It is mainly to prevent a short circuit from causing a fire or meltdown. Probably a 5 amp would work. If it blows,
- inline fuse holder (if your cord does not have one built in.)
- 2 or 3 tie wraps to secure the cord and strain relief
- electrical tester for checking polarity, voltage, continuity.
- Soldering iron
- Diagonal cutters
Step 2: Prepare battery case
Open up one of the batteries and extract the cell assembly. Clip off the lower cells that fill up the main body. Throw them away. No, don't throw them away. Rechargeable and button batteries should be disposed at authorized battery collection sites. Take them down to your local Radio Shack and make them throw them away.
Remove the thermal sensor, the small metal thing tucked between the cells that is wired to the third contact plate(or leave it in if it isn't in the way). This leaves two dead cells, that hopefully are not too nasty and corroded, that fit into the "tower" that have the contact plates attached. If your cells are not usable, or the case is a different shape, you might be able to carve a block of wood that fits the case and can hold the contact plates. Silicone caulk, Friendly Plastic or Fimo might also work.
Drill a hole that the hose will fit through in the base of the case. Thread the wire into the hose and thread both through the hole. A knot can be tied in the cord, or tie wraps added to be tightened later to prevent the cord from pulling out and straining the soldered connections.
Step 3: Wiring
Step 4: Preparing case
Step 5: Final assembly
(note: There is no next step. Do not click on that button. Don't say I didn't warn you.)