Convert a Battery Drill to Wall Power

Intro: Convert a Battery Drill to Wall Power

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


[Edit]
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
https://www.instructables.com/id/EQ3VVA5ZVKEYF7HZ0W/
or
Reuse "Wallwart" transformers
https://www.instructables.com/id/EC1BYG2K40EWPKHAGV/
in a perminant way.

How to solder
https://www.instructables.com/id/E30LR180T4EWP872BS/
or
Soldering to large metal objects
https://www.instructables.com/id/EYUBQBN818EWZMIAYA/
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
https://www.instructables.com/id/EZO32EAKLOEXCFECUK/
for screws.

and, yes, i screwed up the batteries before i had a chance to use
Revive Nicad Batteries by Zapping with a Welder
https://www.instructables.com/id/EPV474YLF3EV2Z8V9V/
or
Hot Rodding a Power Drill Battery
https://www.instructables.com/id/EZOAB2A75XEV2ZHAQP/

STEP 2: 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)
Screwdriver
Sandpaper
Soldering equipment
-butane torch
-solder
-flux
wire cutter (and stripper, if you want)

STEP 3: 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

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

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.

Comments

[NelsonI2]

Eu acredito que o transformador não irá funcionar pois motor de furadeira consome muita corrente principalmente partida, minha fura deira consome em media 4 amperes sem forçar

[Myself]

A note about transformer sizing: The battery rated at 1400mAh will theoretically put out 1400mA for 1 hour, or 700mA for 2 hours, or 2800mA for half an hour, etc. (Not really, look up "Peukert's effect", but rough numbers will do for now.)

Electric motors draw lots of current when they start, or when they're pushing against a load. Spinning freely, they draw almost nothing. So even if the 1400mAh battery pack would run the drill for a solid hour, there were still some moments in there when it was supplying well over 1400mA of current.

That's why a 1200mA wallwart has such a tough time here. You should consider adding some batteries or capacitors to supply the motor's momentary demands for power, which could be replenished during idle time. There was a long thread about exactly this subject over at toolmonger some months ago.

It's funny, I have an ancient 7.2v Black & Decker drill, with a built-in battery and a jack on the bottom for the wallwart. It's premade for this mode of operation! Somewhere along the line, interchangeable batteries did away with the on-tool charging jack, and we lost the ability. (Traded it, really, for smarter chargers and more powerful batteries.)

[ac-dc]

I still have one of those 7.2V B&D drills. The charging jack has a switch built in that cuts the power from battery to motor so it's not "premade for this mode of operation".

Further it was a terrible design, that is two speeds but to achieve the lower speed, it tapes into the middle of the series of cells to get lower voltage, which discharges them more than the rest, and risks causing a reverse charge state damaging them as the voltage drops lower.

[jtobako]

using the battery info was an easy way to make sure i wasn't going to short the motor out. that and i didn't have a bigger wall wart : ) since i'm not using it as a driver, the motor will start at no-load or nearly so.

[lennyb]

i wonder what would happen if you put a 12volt lighter plug on ot and plugged into the car? be handy to have if you need a drill while on the road

[ac-dc]

1) It would pull too much current and burn out the motor under load because it's a 9.6V, not 12v drill.

2) While doing so, it would pull too much current through the lighter outlet fuse and blow that too. The question is which blows first, but it won't work unless you limit it below the max possible output to the motor whether through the trigger or a resistor or motor controller in series.

[csnyder]

This has been done many times, and you cannot hurt the drill by doing this. The fuse in the lighter plug will protect the wiring in the car. Just think, if this was a worry you could not use low power devices on hydro because you have all those amps from Niagara/6 mile island/whatever on tap. A friend built an entire Zenith 601 airplane with a 9.6 volt drill run off his 12 volt truck battery. Drill still works fine.

[jtobako]

probably work even better, but i'd worry about too many amps-not nessisarily for the motor, but for the speed control burning out.

[mccord]

A couple of comments- Most cordless drills and other items do have motors that work on AC and DC. They have electromagnetic field windings, so the field polarity changes with the armature polarity, thus keeping the motor going in the same direction during the AC polarity change. However, some portable equipment has permanent magnet motors, so the field does not change polarity during the AC cycles, but the armature does. If this is the case, AC will just make the drill buzz rather uselessly at 60 hz. Usually, if the equipment has a permanent magnet motor, the magnets are visible or the side of the motor will attract a screwdriver tip or a nail. You also might find still filings sticking to it. Secondly, on the current issue. Commenters are correct. Higher current will supply higher torque. The reason the drill doesn't have much power is that the voltage from the power supply goes down as the current use goes up. The lower the voltage, the lower the speed of a DC motor. The rating on the power supply is a certain voltage at a certain current draw. If less current is being used, the voltage (and motor speed) might be considerably higher. If higher current is used, the voltage will be lower. For those who don't work much with electricity, it might be useful to think of a water analogy. The voltage is similar to water pressure. The amperage, or current, is similar to water flow in gallons per minute. If high pressure is available, but the pipe is very small, there will not be many gallons per minute and the work done by a waterwheel won't be very much. On the other hand, if the pressure is low but the pipe is big, a lot of current is available, but with very little pressure. An underrated power source is like a pump without much power driving it. If the pipe is small (a motor not needing much current) the voltage (Pressure) will be high. If the pipe is bigger (a motor under load, the voltage will be lower because the pump cannot supply water fast enough to keep the pressure up. Finally. If you happen to still have the old (dead) batteries and have access to a variable power supply that can supply 2 amperes or so, you might want to try hooking the battery up to the power supply (be sure to check polarity. Most packs are marked. If there are three terminals, the center terminal is probably a center tap on the batteries. Only connect to the outside terminals. Start at 0 volts and slowly increase voltage until the current is about 2 amps. (Sorry, you need to be able to read meters. If you are lucky, the power supply will have a voltmeter and current meter. At first the current will quickly decrease, so you will have to slowly crank up the volts. As the voltage gets higher, it will take longer for the amps to decrease. Eventually, you will reach a voltage about 20% above the rated battery pack volts and the current will remain fairly steady. After half an hour or so, disconnect the battery from the power supply and stick it in the regular charger. If you are lucky, it will operate about as well as it did when it was new. I did this with two 16.8 Sears battery packs that indicated bad in their charger after 3 years of heavy use. They sat around collecting dust for 2 years (I loved the drill and couldn't stand to throw it away.) Surprisingly, the power and operation time is as long as it was when the batteries were new! No guarantees, but it works for me. BTW, the charging method will also work if your charger is bad or, er, lost. Just leave the battery pack on the power supply for an hour or two once you hit the peak voltage. David W. McCord, BSEE, MSIE, PE (Impressed? I didn't think so.)

[ac-dc]

No. There are very few (almost none) cordless drills that work on AC, because they all use permanent magnet DC motors. Please don't guess, take some drills apart and educate yourself about it before putting incorrect info out there.

[ewilhelm]

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!

[ac-dc]

That is a reckless and uninformed bad guess. I am 100% sure the motor will burn out immediately, because I know this is a 9.6V DC motor. Please, don't suggest things involving potentially lethal voltages without more knowledge about which you write.

[carpespasm]

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]

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]

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]

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.

[ewilhelm]

That was one of Tim's:
https://www.instructables.com/id/EBLN6A48CVERIE1R92/

[Protractor]

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

[ac-dc]

"Maybe". Since the computer power supply probably has low voltage protection, it may shut off if the load becomes too high. The odds are that your Dewalt 12V drill draws more than 10A at high load, and you will probably need to put a dummy load on the 5V rail to keep it regulating correctly. Lastly, you don't need a rectifier between the PSU and the drill.

[sam.russek.9]

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