Introduction: Convert a Battery Drill to Wall Power

Picture of Convert a Battery Drill to Wall Power

Turn an old battery powered drill into a wall power unit.

In the spirt of Instuctables, I'm adding some of the sugestions for improvement and why I didn't do things that way in the first place. Some I had considered, others i had not.

Q. Why not just put in new batteries?
A. Too expensive. The drill was $5 (with case, extra drill and 2 battery packs) and worked for a while. The wall wart was free at another garage sale. Brand new unit would be about $20 and be ready 'out of the box.' A new set of batteries and a charger for them would not be worth the time or money. If it was a good brand name on the other hand...
A. While trying to find out which cells in the battery were live and which were dead, I lost the parts. Thus, no battery shell to reload : )

Q Use a Zener transorb/5 f. capacitor/ect.
A Aint got one. Too expensive to go out and get some just to play with. I don't feel comfortable enough with electronics to risk the parts.

Q Use a more powerful transformer.
A Aint got one. That and i don't know how much I can pump threw the motor before it burns out. I may end up finding a bigger transformer, or trying it on AC current-but not untill I don't need this one any longer.

You may notice a theme here-this is a cheep fix with what I had on hand. Nothing fancy, not a lot of pre-planning to get in the way of getting something finished. Are there better ways to do this? Absolutely : )

Step 1: Research!

wall transformer for project power supply
Reuse "Wallwart" transformers
in a perminant way.

How to solder
Soldering to large metal objects
if you are lazy like me and decide to solder onto the large battery clips rather than fiddle with the wires inside the case. or, you can't find your soldering gun but can find your butane torch...

you could even use
Handy box from scratch paper
for screws.

and, yes, i screwed up the batteries before i had a chance to use
Revive Nicad Batteries by Zapping with a Welder
Hot Rodding a Power Drill Battery

Step 2: Gather Your Parts (and Tools)

Picture of Gather Your Parts (and Tools)

First, look at the drill. On the side it will (hopefully) have a description of the battery pack. If it doesn't, look up what a replacement would be. In this case, an old craftsman drill used a 9.6 v, 1400 mAh battery pack. Then find an old, unused wall wart that might work-in this case, i found a 12 v, 1.2 A unit. I figure higher voltage will give a higher rpm, and the lower amperage means less power.

(1 A = 1000 mA)

What I used:

Craftsman Drill/Driver ($5 at a garage sale)
Wall wart (12 v, 1.2 A)
Soldering equipment
-butane torch
wire cutter (and stripper, if you want)

Step 3: Void Your Warrenty

Picture of Void Your Warrenty

Open up the drill.

It's useful to figure out which leads on the drill and power supply are which. If you don't, and the drill doesn't work, try switching leads around. It turns out that the speed control needs to be biased correctly. Who woulda thunk?

Step 4: Playing With Fire

Picture of Playing With Fire

Cut the end off the power supply. If I had the parts, I might have put a jack in the drill. Instead, it's perminent.

Strip and tin the ends of the wire. Sand, flux and tin the battery conecter. If you prefer, you could remove the battery clip and solder wire to wire instead.

Solder the power supply wires to the battery clips. Try and figure out why it doesn't work. Test power supply with multi-meter. Re-solder wires the other way...

Sorry, no picture of me soldering. It takes me two hands to solder and two more to hold the camera.

Step 5: Conclusions

Picture of Conclusions

Put it all back together.

It works!

Well, it works as a drill, which is what i needed. It only overpowers the first setting on the clutch, otherwise I can stop the motor with my hand.


ΧωρίςΌ (author)2015-11-04

The most critical step is to find the power-tool's maximum current draw in Amps (amperes).

You do that by disassembling the drill, looking inside, and reading off of the motor's casing it's power characteristics.

If you are lucky it will say exactly how many Amps the motor will draw under (full) load. If it does not list the Amps then it should probably say how much power it needs in Watts, at which point you use the "Power (Watts) = Current (Amps) x Voltage (Volts)" equation (or simply P = I x V) to solve for Current and find out how many Amps the motor will draw.

Then you need to find a GOOD AC to DC power converter which will provide the proper Voltage AND Current (e.g. Amps) to the motor. Remember (!), the Amps figure is the MOST critical component. If you provide less Amps the motor will be underpowered eventually burning out the power converter, possibly itself as well. If this happens that will definitely create a fire hazard. Be cautious.

Ideally the supplied current should be at least 25% more than the motor's requirements, if I were you I'd go as high as 50% to be on the safe side.

If you do the math, you will see that the Amperage required is too high for the power converter (transformer) you are using. Eventually, you will wear out the motor and ultimately (if used for harder/longer jobs) you will risk the power supply overheating, metling possibly cacthing fire.

Remember DC does not travel well over long cable runs, especially if the Amp draw is high. You need a heavy duty AC to DC transformer capable of providing high Amps, with heavy gauge cables, which will make the transformer big, heavy, cumbersome to use and above all expensive.

This is a nice attempt but it won't work in the long run. Plus you are exposing your self to some degree of danger. Battery operated power tools are getting more affordable by the day while becoming more powerful, efficient and safer with LiPo battery technology.

I say, throw this old tool away (I mean dispose it responsibly) and get yourself a new one, altogether.

jtobako (author)ΧωρίςΌ2015-11-20

Don't just read the techno-babble - if you aren't sending a check, an upgrade isn't going to happen. That's the basis for the article.

"More affordable" doesn't mean a drop in price from $150 to 'only' $125. See above : )

TylerL41 (author)jtobako2016-04-30

"More affordable" cannot also mean "causing a fire". That wall-wart is running way over its maximum limits, it IS overheating, and it WILL fail. How it will fail is up to debate, likely the transformer magnet wire insulation will melt, short itself out and pop an internal fuse (non-replaceable), but it may also simply catch fire. This type of project should not be attempted by those who do not know the risks involved. I urge you to edit your instructions to say something to that effect.

jtobako (author)TylerL412016-05-02

Current limited. Did not run hot. Did not pop circuit breaker. If you read the article, it didn't pull enough current to keep me from stopping it with my hand.

Think about it-if it had a dead short on the output side, how hot would the designer allow it to get?

Right now my motto is if you deserve a Darwin award, you should get one and I'm not going to stop you or hold your beer (I don't like beer).

sdsu builder (author)2015-12-02

Looks like the guys at have built an industrial unit that actually provides more power than a battery. Only the dewalt 20v is available now, but it looks like Milwaukee and Makita versions will be available soon. Can't wait to get my hands on one of these!

!Andrew_Modder! (author)2007-12-16

i tried this and it didnt work for some reason!!! (i used 1000mah, dc AND ac...).... errg... (yes i had the right polarity.) lahh

jtobako (author)!Andrew_Modder!2007-12-17

What, exactly, does the power supply say-and are you sure the power supply and drill worked to start with?

ShaunHill (author)jtobako2012-12-29

I have a 12v drill:

What do I need to change it to wall powered, whilst being able to use all torque settings without burning it out but using its full power?

ΧωρίςΌ (author)ShaunHill2015-11-04

You can't, just dispose of it properly and buy a new one with lithium technology power pack.

DFIII (author)ShaunHill2014-12-25

The motors in drills are power hungry. My dewalt just took out a 20A rectifier (The part that makes AC to DC). It's gonna take a high power power pack to work efficiently.

!Andrew_Modder! (author)jtobako2007-12-18

9.6v dc (w ac switch), 1000mah. i used it in a 9.6v cordless drill (used aligator clips for contacts in the drill handle). and i no the power supply works, because i use it a lot for random things, lol, and also tested it with a multimeter. And for the drill, ya it works cause i took the battery out and tried it w dc (batterys are dc), then tried it with ac, did not work, so i put the battery back in and it works w battery still, but no addapter...... :-|....

jtobako (author)!Andrew_Modder!2007-12-18

Mah would be milli-amp-hours, odd for a power supply but normal for a battery. I suppose there could be some kind of switch (mechanical or electrical-checking the status of the battery if it runs on Li-ion or something) on the drill. Other than that, I don't know without seeing it : ) Might be as simple as the clips not making good contact or as complicated as the electronics in the drill and power supply fighting it out over power requirements.

!Andrew_Modder! (author)jtobako2007-12-18

its a power adapter like this

except it is 9.6 volt, 1000mah, and AC/DC capable.. :-\? oh ya also i put semi new copper plated steel aligator clips on instead of the plug at the end. :-|......

jtobako (author)!Andrew_Modder!2007-12-18

So, except for being completely different, it's the same power supply? Which drill? And how do you know that the clips are making good contact?

!Andrew_Modder! (author)jtobako2007-12-19

errrg.... no i showed you that because it is the same type of power source im using, just i dont know what thos are called, so i showed you a pic! lol.... :-(.... What drill, umm it is a offbrand no namer i think? but it works, and i no it makes good contact because i opened the drill up once to see the motor, and see how it works :-), but i put it all back together, and it works the same with batterys as it did b4 i opened it.. and the contacts are thick bars, witch nicely got cliped onto by my aligator clips :-D

jtobako (author)!Andrew_Modder!2007-12-19

I'm guessing not enough amps. At 1.2 amps, mine was a bit anemic : )

!Andrew_Modder! (author)jtobako2007-12-20


I think you mean you used a wall wort rated for 1,000mA.

Power tools use a lot more than 1,000mA. Drills use around 3A (3,000mA.) Saws can easily pull 18-25A.

IhsenS (author)2015-08-20


I Convert a battery of Cordless drill to ATX power supply

farhad.bijan (author)2014-12-29

I have a full set of dewalt 18v, would this work?

sam.russek.9 (author)2014-08-30

Does anyone know how to convert a wall powered drill to 12/24 volt batteries

DFIII (author)sam.russek.92014-12-25

The easiest way is to use a DC to AC inverter but they are not very efficient. I've seen people use car or Marine batteries (marine is way better and last longer) with an inverter to be able to use AC to power the drill. I have also seen instructables where a guy successfully used DC power to power the drill but it was something like 90v. Hope this helps get a little understanding.

DFIII (author)2014-12-25

I love it. I am so for using what you have to solve a current problem. I do have some electronics experience and took this idea to another level. I used an old microwave transformer and converted it to a 20v transformer to run my 18v dewalt tools. the batteries were 92 bucks each so this was much more cost effective. Even though I now have 2 new batteries I still use the power pack. If I'm near a plug why burn up my batteries when I have to do a lot of drilling. If you want I will share my information considering I need to rebuild the AC to DC converter that I put inside a battery housing from a dead battery. Have to use a stronger rectifier and maybe add a small fan to keep it from burning out under high stress.

pj63 (author)2013-03-27

Very informative instructable............................

ShaunHill (author)2012-12-29

I have a 12v drill:

What do I need to change it to wall powered, whilst being able to use all torque settings without burning it out but using its full power?

RangerJ (author)2012-11-24

Good idea. I probably have a wall wart that is beefy enough.

codongolev (author)2010-11-26

I think that after christmas, I'm going to go to Big lots (if you don't know, it's a big cheap stuff store) and get a crappy cordless drill set for 25 dollars. I've had a crappy drill, so I know that the batteries go first, and therefore I am going to convert it to wall power. I'm going to use an 18v power supply for my laptop that died (it has an 18 volt battery- perfect!). as for the battery, I'm going to repurpose it as a battery for a really ghetto electric scooter that I made from an old razor scooter, some lumber, and parts from a power wheels car someone was throwing away. I was able to wire the scooter in parallel, not series so that it goes faster, but it still doesn't go fast, maybe just a little faster than a walk. if I added an 18v battery, though..... (I think I might just add it as a speed boost type thing, like wire it in parallel with some diodes and add a switch... that way the battery won't run out in four seconds).

the reason I say after christmas is because I don't have money currently (well, I do, but I kind of need it for gas and insurance) so I need to get a job and get money. that, and my mom told me I couldn't go in my dad's workshop for the rest of the year because I cannot keep anything clean (cruel and unusual!) so I really can't do anything anyway.

and thus ends the rant of codongolev. have a nice day.

jtobako (author)codongolev2010-11-27

I've found that the key for power isn't voltage, it's amps. So use the biggest amperage transformer that you can.

codongolev (author)jtobako2010-11-28

yeah, the computer power supply is 3.9 amps or something ridiculous like that. I think it'll work.

unasimple (author)2010-09-24

I've done two drills like this.
One a 12v craftsman drill where I used the 12V 750 mA adapter for the charger that came with it. This one seems underpowered.

For the second one a black and decker 18V I used the biggest adapter (physically as well as voltage) that I could find a 30V 500mA and this one seems to work great. Not sure about longevity though but it hasn't melted yet. :)

Protractor (author)2009-12-09

This is a cool project.  I am thinking of doing similar thing to my old Dewalt 12V drill.  I don't have a "wall-wart," but I have an old computer power supply that has a 12V rail and can supply up to 10 A on that rail.  It's rated at 350 Watts max power.  Would using this power supply with a rectifier work?

Crude schematic below:

Wall jack---PC power supply---rectifier---drill

TheGoodLife (author)2009-03-25

Thank you for supporting my work through your daily visits to my instructable.

jtobako (author)TheGoodLife2009-03-25

You're welcome. But I just have the 'e-mail me' option activated and visit when commented on.

Oh, and the argument was here. Not the first time this has been tried : )

ewilhelm (author)2007-03-08

If you really want to tempt fate, try connecting the drill motor directly to AC. There are some permanent magnet motors I've seen in drills that run either on DC or AC at 60 Hz. When you do the test, make sure to use a circuit breaker!

carpespasm (author)ewilhelm2008-10-20

For a little more safety you could also throw it on a dimmer switch to drop the voltage. You might still burn up the dimmer though, they're not usually rated for high-draw conditions. It would drop the voltage though.

csnyder (author)ewilhelm2007-06-20

You definitely need a rectifier on a permanent magnet drill motor, and if variable speed the controller will fry. Also DEFINITELY need to reduce the voltage. 110 will let the "magic smoke" out of a 14 volt motor in an instant.

ewilhelm (author)csnyder2007-06-21

For a run-of-the-mill DC motor, that is true. However, the motors in hand-held drills are often designed to run on either 12 volts DC or 120 volts AC, and as jtobako points out are called "universal motors."

jtobako (author)ewilhelm2007-03-08

universal motors (ones with brushes i believe) can be run with AC or DC. i saw somewhere that someone was running things like (AC) angle grinders off 3-4 car batteries to get enough voltage instead of springing for an inverter.

ccconsulting (author)2007-03-09

I like it.... Now, can it be set up so a dead battery shell can be retro-fitted with an adaptor and a cord to keep the cordless function by switching to a normal battery?

stone3408 (author)ccconsulting2008-10-20

Yes that is the way mine is set up. Its a 18 volt ryobi. It runs on two 12v batteries in a series, the battery that it came with, or my car. It is a great idea to retro fit a dead battery pack with power jack. Just be careful when you take the pack apart. The batteries usually hold some of the contacts in place inside the pack. A bit of epoxy will solve that problem.

jtobako (author)ccconsulting2007-03-09

same idea, just one step removed. you might be able to put the transformer inside the battery shell to retain the original balance.

gzusphish (author)2007-03-08

Hmmm....I've got an old Chicago Power Tools drill with a dead battery this would be perfect for.

By the way...if you want to do this instructable but you want a drill which will function at full power you'll have to get an AC adapter (wall-wart) which can at least match if not surpass the original battery's current capability. The one in this instructable was probably trying to draw more current than the wall-wart was capable of providing. Extended peak usage like that may overheat the transformer in the wall-wart and throw a breaker or make a bunch of nice smoke.

As the author said in step one
more voltage with less current = more RPMs with less power
more current with less voltage = more power with less RPMs
also: more voltage AND more current = more RPMs AND more power And overheated drill.

So depending on which power supply you choose you could end up with a really big dremel moto-tool, a really small winch, a pile of molten, smoking slag, or a functioning drill.

The best bet is to stick with a PS that supplies the original battery's voltage and matches or surpasses its current capabilities.

stone3408 (author)gzusphish2008-10-20

Yup, I just smoked a wall wart. Two twelve volt batteries from an upc in a series works great though and still portable! It runs great off the car as well.

eviloverlord (author)gzusphish2007-03-09

...Or you could just open the battery unit up and replace the cells with shiny new ones.

jtobako (author)eviloverlord2007-03-09

IF you have batteries avalible. this is a 'make-do'. if i had the money for new batteries, i'd rather have a newer, more powerful drill : )

eviloverlord (author)jtobako2007-03-16

I've just replaces my old 1200maH NiCad drill cells with 2700maH AA cells. While I was at it, I added 2 more to up the voltage from the rated 12V to 14.4V. It now has more than twice the battery life, is more powerful because of the voltage increase and so far seems to have suffered no ill effects from overvolting it slightly. Oh, and the batteries from ebay worked out much cheaper than a new drill, which would still have used nicads and had a poor battery life.

jtobako (author)eviloverlord2007-03-16

what did the new charger cost?

Possum Living (author)2008-06-17

I would recommend either running it off a car battery, or adding a 12 volt gelcell battery or a pack of cheap AA nicads (I solder them together with short pieces of wire, then wrap duck tape around them to make a pack) and use the wallwart to charge the batteries. That will work much better; even a small 12 volt drill motor can easily draw over 30 amps under load.

jtobako (author)Possum Living2008-06-18

Sounds great. Tell you what, I'll send you my address and you can mail me whichever you prefer : ) I didn't have an extra set of batteries, I did have a wall wart. This is about making do. Best would have been to go out and buy a $300 Makitta rechargable-but that aint gunna happen : (

About This Instructable




More by jtobako:Forge a KnifeConvert a battery drill to wall power
Add instructable to: