Can a cordless drill be repurposed as a generator?

[Rich Engelhardt]

I have two 18V B&D cordless drills that the batteries are no longer any good.
I got to thinking ( I know - a dangerous thing ;))..
All these things are are DC motors. A DC motor can be used as a generator.
If that hold true, then I should be able to use the drill to generate an 18V DC source, right?

I've been looking at some of the internet plans for DIY wind generators, and it seems doable to make one and use the one drill as a generator to power the other 18V drill.

[Gary Curtis]

Not all DC motors function alike. Smaller machines have what is called a Universal motor, and these have brushes and a commutator. It won't work. Bigger devices like table saws use an induction motor. I believe these can generate electricity.

If were lucky and had one of 3 models sold by Festool that have 3-phase brushless motor, I think they act as generators if you spin the chuck. I'm not Festools come from Germany and are quite expensive. Ask an electrician to be sure.

[Ronald Blue]

I am no expert on this but I don't know why it couldn't work but unsure it's worth the trouble on such a small scale. Years ago many garden tractors with Kohler and Wisconsin engines used a combination starter/generator unit before the change over to a conventional gear drive starter and ring gear on the fly wheel.

[ray hampton]

a GENERATOR produce electric because of the permanent magnets that surround the commutator, a magneto produce high voltage by the same means, my lawn tractor use the generator to start the engine and use the starter to produce electric to charge the battery,I am the proud owner of a couple of D C MOTORS and have been thinking about making smaller windmill power supply myself or using a steam engine to power the generator

[Chip Lindley]

Rich, spend your time and resources building a "battery zapper!" Bring your ni-cad batteries back to life! Time well-spent as opposed to contemplating such a tiny DC generator.

[Rod Sheridan]

Yes you can convert a series wound motor to a generator.

You need to use the stator windings as the field, and the rotor windings as the armature.

By varying the field current with a voltage regulator you can control the output voltage.

I expect that the brush lead angle won't be optimum for use as a generator, however nothing else (brushes, gears, bearings) will be optimum rated for long term use under load either.

I wouldn't expect that a drill would even be rated at 100 watts continuous so you're not going to have much return on your investment..........Rod.

[Clarence Miller]

Rich, spend your time and resources building a "battery zapper!" Bring your ni-cad batteries back to life! Time well-spent as opposed to contemplating such a tiny DC generator.

battery zapper????

[Stephen Cherry]

Sounds like you're on to something. The first thing I would ask is if they are really dc motors. when I start my drill, I hear a high pitched sound, the first question would be if this is just varying the duty cycle of a dc signal, or if it is also modulating the output into ac. The easy thing to do is to take the drill apart, spin it with another drill, and see if it gives off any juice.

People used to mess around with things all of the time, before complexity set in. If you are interested in learning a little about electronice, a good book is Horowitz and Hill, "the art of electronics". Not too much on motors, but a lot of everything else.

[Jack Pinkham]

Rebuild the battery packs. I rebuilt my Bosch 24 volt batteries using cells from two $9 Harbor Freight batteries. Works great. I also rebuilt my Metabo 4.8 volt screwdriver & flashlight batteries using cells from EBAY, $14 delivered.

[Mike Gregory]

Why don't you chuck a round rod to this drill and another and run the other drill (driving this one) and put a meter on the contacts that the battery connects to? Let us know if you get voltage.

Mike Gregory

[Mark Eisen]

battery zapper????

I would like to know more of this as well.

[Rich Engelhardt]

I am the proud owner of a couple of D C MOTORS and have been thinking about making smaller windmill power supply myself or using a steam engine to power the generator
That's sort of what I had in mind.
Instead of a steam engine though, I'm considering using a Tesla turbine and the exhaust from the shop vac or DC to power it.
I have some old computer hard drives I can take apart and use the platters for the turbine.

I also found a lot of info on making a DIY windmill.


+1 to wanting to know more about a battery zapper.


Why don't you chuck a round rod to this drill and another and run the other drill (driving this one) and put a meter on the contacts that the battery connects to? Let us know if you get voltage.


Excellent idea! I'll try that first off before I go anywhere else with the idea.
I did find some info on the web that says it can be done - use a cordless drill as a generator - but - it has to be the right type of drill.
The one I stumbled across said to use a HF single speed that has no electronics.

[Ronald Blue]

Interesting that you mention using a mini turbine to possibly be a power source. Most if not all EOT (End of Train) devices or at least ours have a small turbine generator as a power source that operates off train line air pressure. So there are some mini turbines out there. Sounds like a science project to me. Have fun.

[Matt Meiser]

Got anything you want to power? I have one sitting around to use to spin the shaft on a push-type fertilizer spreader that I want to build a bracket to mount on the back of the tractor for use as a salt spreader. But I've never gotten a round tuit which I of course need...

[John Coloccia]

re: high pitched noise
That's probably the variable speed control PWM'ing the drive to the motor.

re: everything else
It almost certainly won't be enough to spin and measure contacts. The batteries are going through the drive electronics. Even a simple variable resister would require squeezing the trigger before anything got to the batteries, but in this case it won't be so simple. You will be back driving unknown circuitry. If the designers thought it through, everything will be protected and nothing will happen. You can potentially fry the electronics, though, as it may not be expecting to see that kind of power supply at that point.

The thing to do would be to go right to the motor itself.

[Curt Harms]

What you're thinking about doing is done on a larger scale with small aircraft gas turbine engines. The same spinning copper parts function as both starter & generator. The starter/generator is controlled by a GCU (generator control unit). That's where the magic happens :cool:. I expect any similar device would require similar exciting/regulating circuitry. It'd be a fun "Mr. Wizard" project but not terribly practical.

[JohnT Fitzgerald]

I don't think so Rich. To generate electricity, you need movement of a wire winding through a magnetic field. Unless the drill motor has permanent magnets, it won't work. Most of those motors have a winding to create a magnetic field and run current through to make the motor work - no permanent magnets.

I think a better alternative (if you're looking at experimenting) would be an alternator from a car.

[Rod Sheridan]

As I indicated in my earlier post, a series wound motor can be reconnected as a generator by using the stator winding as the field winding. This produces the madnetic flux for the generator.

Your car alternator or old generator worked that way, they don't have permanent magnets because you can't control the output with a permanent magnet machine.

Regards, Rod.