Introduction: Convert a Perfectly Good Cordless Drill to a Corded One

Picture of Convert a Perfectly Good Cordless Drill to a Corded One

Convert a cordless drill to plug into a 12 volt battery pack when your battery packs die.

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

Parts List
Main Components:
- 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,

go larger.
- 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
- Screwdriver
- Diagonal cutters
- Drill

Step 2: Prepare Battery Case

Picture of Prepare Battery Case

Determine the polarity of the contact plates. Fortunately mine was marked on the outside of the case. If your battery pack has any capacity at all, you can read the polarity with an electrical tester. If you get it wrong, it will probably still work but the direction switch will work backward. Worse case is if there is a diode that prevents it from working at all. It is a good idea to mark the polarity with tape or a sharpie to prevent confusion. (I am an expert on confusion and can supply references)
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

Picture of Wiring

Solder the wires to the remaining cell assembly, either to the connection wires, contact plates, or the body of the cells (Not really desirable if you can avoid it. If you do this, be advised that applying high heat to a battery cell may have unpredictable results. At least wear protective glasses and clothes. Performing work using electrical tools naked is generally not a good idea. Same with cooking bacon.)

Step 4: Preparing Case

Picture of Preparing Case

Make a spacer block that will fit snugly in the space left by the removed cells to hold the remaining cell/contact assembly firmly in the tower. I made mine from assorted blocks of wood with a tunnel carved in one to allow passage of one wire to the other side. This can be made from a single block of wood, friendly plastic, paper mache, etc. Just be sure it is hard enough to resist the pressure of inserting the case.

Step 5: Final Assembly

Picture of Final Assembly

Pull the wire out through the hose and tighten tie wraps. Assemble parts, carefully juggling the block, wires and screws. Be sure screws don't poke into the wires. As you put all the parts together , Close case and screw together.

(note: There is no next step. Do not click on that button. Don't say I didn't warn you.)


Excoriator (author)2016-08-25

I went a step further than this. One doesn't always have a a car handy, and a 12V battery is a bit heavy to lug about. So I made a much smaller lightweight replacement using six 500 Farad supercaps wired in series. This will happily keep you going with a hundred or so medium sized screws into pine before requiring to be recharged.

This is where supercapacitors really come into their own. If you use a constant current charger capable of supplying 20 Amps, it takes about 30 seconds to charge.(I built my own. Two transistors, a handful of resistors and a fan cooled PC processor's heat sink I had hanging around) and off you go for more happy trouble free screwing! My charger will work from a car battery or a mains supply (I bought a mains 20Amp 12v supply from the internet for about £15 and tweaked it a bit to supply 17v)

Supercapacitors make lousy batteries. They hold a much smaller charge, and have a high self discharge rate. But they can supply current at up to 1,000A or more and be charged in seconds rather than hours. They are a fraction of the weight and size too and this makes up for it in this application. The high current capability makes the screwdriver able to supply MUCH higher torque than the original batteries too, should you want need it.

My supercapacitors are mounted in a plastic box and weighs a bit more than a pound. It is about 6" by 4" by 3" and was manufactured by Messrs Tupperware. I added a cheap digital voltmeter to it as a sort of fuel gauge. The energy it contains is proportional to the square of the voltage so it is not exactly linear, but it gives you an idea of when to go charge it up again with experience.

PKM (author)2008-12-10

(Not to be condescending, but if you don't know what "VOM" stands for, you probably should not be doing this.)

Erm... sorry, but you are being condescending. I didn't know what VOM stood for (although given context and the letters I took a shot in the dark that proved to be right) but I've never heard those called VOMs, only multimeters.

Saying "if you don't know what this is for then you shouldn't be doing this" is OK if you are talking about a pair of scissors or a marker or something equally obvious, but using it on terminology that otherwise-well-informed people might not have heard just alienates people. Someone asked me what "flex" meant on one of my Instructables- I had to tell them it meant wire, and if you dont know what wire is for then stay the hell away from electrical projects, but it was just a difference in terminology.

Ranting aside, this looks like a good project. Now we just need an Instructable on how to deal with the people who say "hurf durf why did you attach a wire to a cordless drill now it's not cordless any more hurr".

Rbrbr (author)PKM2016-05-02

Lol at a small power supply able to supply 200 amps...That's a HUGE 12 volt supply.

sharpstick (author)PKM2008-12-10

Okay, I took out the condescending comment. I assumed that VOM was a well known term with anyone who would be doing this. I do think that if anyone is not familiar with basic tools used for this project, they may have a - shall I say - less than positive experience. Maybe there should be a site-wide disclaimer indicating that if anyone is attempting a project that is beyond his skills, it may turn out to be more entertaining than she expected and let them have their fun. I've had many entertaining hours exploring my limitations that way! I explained why I attached a wire. For all I care, they can look stupid publicly and don't deserve any response.

jumpfroggy (author)sharpstick2011-02-24

True, if someone isn't familiar with these things already, it'd be hard to learn them all at once. That being said, I've used a multimeter quite a bit but have never heard of a VOM before now :)

sharpstick (author)jumpfroggy2011-02-24

Sorry for my inconsideration and rudeness. I've now removed all mention of the offensive "VOM" term. Anyone who reads any of this are now responsible for their own safety. If anyone still has problems with my originally well intentioned desire to share a good idea, please let me know and I'll delete the entire post and immediately commit seppuku (and try really hard not to bleed on anyone).

mossDboss (author)sharpstick2009-01-18

Thank you very much for this instructable. I have a battery drill that holds a charge long enough to drill through a sheet of plywood. I would much prefer to have a cord on it, so thank you.

sunvip99 (author)2013-12-19

If you do this mod properly you can power your drill off of anything that supplies 18 volts of power. I modded my drill's dead battery pack to accept power from anything, whether it be wall power, or a car battery for when you are on the road, to solar power when you are just away from normal power sources. TNKs, and it's a great job! About more informations

sharpstick (author)sunvip992013-12-19

By "properly" do you mean putting a voltage regulator in? Otherwise, it's probably not a good idea to feed 18 volts to a device that's designed for 12.

captainj954 (author)2012-11-24

How would one bypass the 12 volt lithium ion batteries temp sensor output signal which drill requires?

Ian01 (author)captainj9542013-01-13

I would keep the temperature sensor as long as it's not inside the cells or something. Just remove the cells from the battery pack and leave the temperature sensor in there.

sharpstick (author)captainj9542012-11-25

Good question. But this one was a NiCad drill and the third contact is only for charging. The drill itself only has two contacts.
Someone familiar with LIon devices might know.

RangerJ (author)2012-11-24

This is a good idea - I hadn't thought of using a battery jumper box.

blkhawk (author)2012-10-18

I came up with an Instructable with the same idea ( It's true!). I stumbled with your 'ible after I published mine. Great minds think alike!

thatmanagain (author)2012-09-22

I have adapted a ridgid jobmax multitool....(add smiley here)
the samsung lithium batteries are notoriously poor quality and can die after 6 charge cycles!!
I used a laptop charger!
Straightforward procedure and it appears to work well.

adus123 (author)2012-01-28

I am interested in doing this to as i have a good 12v drill and 2 Batteries just sometimes when i down my allotment and the Batteries go flat i have no way to charge them.

But I do have lots of car 12v Batteries whic i us as a power source for lights and stuff.

just need a old Battery to play with now lol as i dont wont to f up a good one.

retrotimelord (author)2011-07-28

Nice idea Great idea but turn a perfectly good cordless into a corded one well i would not do this unless it was totaly screwed

rgarman (author)retrotimelord2011-10-26

Ok it's pretty simple. I have a 12 volt battery charger. I BARED the wires and clamped the teeth on them. Works fine. What's the problem???? Just take the battery apart and yank the terminals away.
I have the charger set on 12 volt. Amps can differ, I just get more rpms. I used this set-up to power a grain mill for 23 pounds of , malted barley for a beer that I'm brewing tomorrow. In the bag quit whining

retrotimelord (author)rgarman2011-11-06

fu*ked nicad battery you can fix with a welder

It didn't affect the drill at all, just an old dead nicad battery pack.

rgarman (author)retrotimelord2011-10-26

Duh Mr. dagger of tomato juice, Let me make this simple for a monkey. If your battery and drill are fine, skip this tip. Ignore it. Don't comment. you are ok.

rgarman (author)retrotimelord2011-10-26

not understanding your complaint. No problems on my end. real simple. I don't have to spend $70 on another battery that is non-rechargeable ( that is the whole point here Dexter). Chord is fine. Just bare the wires and hook up. DUH!!!!

Andale_The_Great (author)2011-04-10

I tried this, but with all the batteries still there i got nothing but a tiny spark (connection not attached permanently yet), tried with only 2 then 1 left and got nothing but that same connection spark. I tried hooking it directly to the 12 volt source but when i hit the trigger it not only made a bigger spark on BOTH + & - AND the wires got VERY hot instantly.

(I'm not sure what you mean by "with all the batteries still there")
Hard to tell, but sounds like you either have a short or incorrect wiring somewhere.
I would take it apart and check continuity at every point with a continuity tester. There should be continuity between each plug contact and the other end at the battery contacts, but no continuity between the two.
Compare your wiring with how the circuit is supposed to be. If your battery has three contact terminals, make sure you are using the right two. Temporarily touch 12 volts to the terminals inside the drill to make sure you're using the right one.

the battery (original) had still worked, though only for 5 minutes. I thought i knew the polarity (busted my tester the other day) and tried it with the cells (inside the battery pack) inline because that was the first howto i found. I tried with just 2 and then 1 of the original cells because i read another which stated that you could have a dead cell. Even connected straight to the 12v source it still didn't work.

Can I run a cord from the charger directly to the drill? Does it have the oomph to power it well? Will it even work with a DeWalt charger (since it has the different modes)?
I've wondered (when the batteries were decent) if the batteries could be connected in series (based on the fact the inner cells are series) to the charger so more than one could be charging at the same time.

NOTE: APPARENTLY THE SWITCH HAS STOPPED WORKING. The motor still works when attached directly to power, but the trigger has stopped working.

Note the title of this instructable includes the phrase: "perfectly good". You have to have a functioning unit. You are replacing the power source and the drill has to work first.
If the switch is broken or the internal circuitry of the drill is otherwise damaged, it will not work. There is no way anyone can diagnose this problem without testing the circuit.
I suggest that you get a good battery pack and get it to work with that first. You can also use a tester to check for polarity and the proper contacts. Most battery packs have three contacts. I think the third one is for a thermal probe so the charger will know when to turn off or regulate the charging current.
If your polarity is reversed, it should still work but backwards and your direction switch will just be reversed.
As for using the charger itself to run the drill, I doubt that it has enough current. Chargers are designed to trickle charge with a low current, typically 1/10 of the normal run current. I see no advantage in doing that. It would require taking it apart and rewiring everything anyway. If you do want to use an AC adapter for your drill, it will require a DC output that supplies enough current to match what the battery has.

I did find a dc adapter to run it that 1.8 Amps so I'll probably just use that.

As for 'perfectly good', it was. Until I hooked it to my power source which was actually outputting closer to 14v (my fault, should have checked settings) it was still working just fine with batteries. I had just had that particular battery on the charger before starting this experiment.
The source I use is a little homemade power supply that handle a 200 amp draw. I assumed this would be okay because the power drawn from it should have been based on the need of the drill. I believe that whatever system the trigger uses to control speed is the problem. Going to see about a replacement trigger today.

fazgard (author)2009-05-26

Thanks man, I've got a great Dewalt Hammer Drill that I've used for years - and same old story, bad batteries and not wanting to buy new, blah blah blah.... Replaced it with a coupla other drills, but it's an old favorite... Been looking for a way to rebuild it as corded (but most 12v PS don't have the apms to drive it, and the ones that do cost more then a new drill), and never occurred to me that I could use one of my 12v boosters to cord it up! Thanks for the Idea!

wdwrkr1 (author)2009-04-11

Cool; A few months ago my son gave me an old rusty B&D; cordless without a battery. I loosened it up with a lot of Power Blaster and added 2 14 ga. wires 10 feet long. I put a little cap over the end where the wires came out. I put battery clips on the ends so I can hook directly to the battery in my truck or hook up to a booster. The other day I needed it to work on a trailer, so I hooked up my jumper cables and hooked the drill to them. So then I had 22 feet of cord.

klee27x (author)2008-12-10

Terminology aside, I agree that most people who are familiar with DMM/VOMs would certainly be the type to do something like this. But most of them will know what you did by the time they've finished reading the title. Keep in mind that this could be a nice Instructable for opening the doors to the "non-VOM people." :)

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