New Life for Old 12 Volt Cordless Drill




About: Computer geek since 1983. I didn't invent the Internet, but I helped it grow.

Like many of you, I have a collection of old cordless drills with dead batteries. It seems like every year the batteries get more powerful, so people upgrade when their old batteries stop working. That's a shame, since the drill itself still has lots of life left in it. I had some old 12 volt Sears drills with bad batteries and I decided to reuse one. The natural choice was a 12 volt corded conversion so I could use them on the road. My truck is 12 volt, so this works perfectly. Here are the steps for giving life back to your old drill.


Step 1: Grab Your Old Drill and Some Tools.

You will need the following:

1. Your old 12 volt cordless drill and dead battery

2. A screwdrive to take the battery compartment apart (and remove the old batteries)

3. Two wires to connect the drill motor to the 12 volt automotive plug

4. Wire spade connectors (female) to attach the wires to the battery terminals in the drill handle

5. A drill or some way to make a hole in the battery compartment

6. A small saw to cut off the top part of the battery compartment

7. An automotive plug and cable (12 volt accessory cord)

The first thing is to remove the battery battery compartment and open it up. Mine only had a few screws holding it together, but some have clips you have to pry apart. Once it's open; yank out the batteries and any cables. We just need to compartment, so pull it all out. In this picture, you can see my battery compartment is empty and already has the hole drilled into it to accommodate the automotive accessory cord.

Step 2: Simple Wiring

My drill had two metal strips in the handle that would make contact with the sides of the battery compartment. This would enable the current to flow from the battery to the drill motor. To convert the drill to corded, I just used two female spade connectors on two wires. The connectors fit perfectly on the ends of the metal contact strips. The connection was tight enough that I didn't have to solder anything.

Step 3: A Little Surgery to the Battery Compartment

Now that your battery compartment is empty, it's time to torture it even more. Start by drilling a small hole in the bottom, so you can feed in the automotive accessory cord. I tied a small knot on the cord inside, so it could not be pulled out of the hole. Next the two wires from the drill motor are soldered to the end of my automotive accessory cord. Red is positive, black is negative. You may want to test the drill at this point before you put it back together.

Step 4: And More Surgery to the Battery Compartment

You will notice that the battery compartment fits snugly into the drill handle. This is great normally, but it would now be too tight with the power wires in the way. So, we are going to cut off the top of the battery compartment. You can use a saw or just snip around the top using wire cutters. Once the compartment is modified correctly, you should be able to insert it back into the drill handle.

Step 5: And That's It!

You just created a drill that requires a connection to a large motor vehicle in order to operate!

Great, Eh?

Actually, this a perfect tool for those unexpected projects. Sometimes I am working on my truck and need to drill or grind a plastic part. Instead of running back in the house for my cordless, I just grab this drill and finish the task. It's also great as a mixer/blender when tailgating. Need a fan? Just put a small propellor on the drill. There are probably more uses, but those are just a few of mine. The best part is that I am still using this drill instead of just throwing it away. If you have more ideas, please post them, and please remember to vote for me in the contest. Thanks!



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    8 Discussions


    1 year ago

    I did this years ago. I found it helpful to have battery charger type clips on the cord, and often power the drill and saw from my garden tractor battery. They do sell adaptors with clips on one end and a lighter socket on the other end, or you could rig it up like those 1 & 2 watt solar collectors with swappable ends.

    Also wondering what gauge wire you used to avoid a voltage drop to the drill.

    2 replies

    Reply 1 year ago

    Yup, I also did this a few years ago. I had the pictures laying around and decided it would make a good Instructable. I love the idea of a clip-on version for a lawn tractor. I would have to have the engine running, but the idea is great.
    I believe I sized the internal wiring to be the same size as the wire that came with the accessory plug. I want to say 14 gauge, but I forget now. Maybe 12, lol.


    Reply 1 year ago

    I used 12 gauge speaker wire I had laying around.

    Following the rules for the solar PV I use a volt meter on the tractor battery, when it drops to a resting voltage of 12.0 volts I start the tractor recharge the battery. My fully charged battery rests at 12.6 volts. But my Simplicity use's a small car battery (stock), not those little batteries with the bolt on terminals.


    1 year ago

    Plug it in to a jump starter (a battery pack with jumper cables - mine has an accessory socket) and your converted drill is vehicle-free again!

    1 reply

    2 years ago

    Good idea, I have several "dead" drills and this would be perfect for working in the paddocks/driveway rather than running 1/4 mile of extension leads (like I sometimes do!!!) The car even has 4 power points (front and rear cigarette and 2 aux in boot)

    1 reply

    Reply 2 years ago

    Thanks Buck, glad you liked my instructable.


    2 years ago

    This type of conversion works great, I have an old Makita I found roadside with a clapped out battery pack that I converted in this manner too, although I do use it in the shop at my bench, it was worthy enough to make a fresh custom power pack for it (not a rebuild of the original). With just enough "zip"cord, it reaches where I need it to for routine drilling tasks.