Make an Emergency Phone Charger - MacGyver Style!




About: Random Weekend Projects

In this video, you'll learn how to "MacGyver" a 40 Watt Electrical Generator from a cordless drill and a few household items.  Here's how to charge a phone, illuminate small lights, and make electricity in a pinch.

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Step 1: Watch the Video!

Note: This project is intended to be a "bare-bones" approach to generating electricity in a tight situation.  There are no voltage regulators, no diodes and no capacitors to smooth the current.  There may a risk of overheating and damaging equipment when operating electrical devices without a proper circuit recommended by the manufacturer. 

It worked fine for me, but if you try this on your phone make sure you understand, and are comfortable with, the risks.  Back up your data in case your phone is adversely affected and your data or equipment is damaged as a result.

Step 2: Household Items

There's no charge for this electricity! All you'll need for this project is...

1. A cordless drill
2. Anything you can find to help secure it in place and spin it by hand.

I used;

* A piece of wood 2"x4"
* Some yarn
* 1 mixing beater
* 1 salad fork
* A piece of aluminum foil
* Some Scotch tape

Step 3: One More Thing You'll Need

You'll need a way to connect the power you generate to your phone.

Look for an old phone charger you might have, and cut it in half.  We just need the piece that plugs into the phone.  You could even use a USB charger cable like the one I found.  

Inside the cable you should see 4 wires.  White, Green, Red and Black.  The Red and Black ones are the only ones we'll need for this project.

Note: For this project I used an old Blackberry Pearl.  If you are using a smart phone, the white and green wires may need to be shorted out or connected to a "dummy load" to get a successful result.  (I haven't tested this method yet but have had feedback from other viewers suggesting this is the case)

Step 4: Making a Hand-Crank Generator

Step 1: Remove the battery from the cordless drill and look up inside.  You should see 2 terminals where the battery provides power to the drill.

Step 2: Use the aluminum foil to fashion make-shift wires that connect to the terminals.  (Salvaged copper wire is even better if you can find some).

Step 3: Secure your drill to a surface like a piece of 2"x4" with the trigger pressed "on".  I used plenty of yarn to hold it down tight.  

Note:  The trigger needs to be on, and the torque setting at it's highest.

Step 4: Insert the mixing beater into the drill chuck and make sure it's tightened so the beater won't come out.

Step 5: Add the salad fork through the mixing beater to act as a crank handle, and hook up your charger cable.  Hook the red wire to the positive lead, and the black wire to the negative lead.

Note: Polarity DOES matter!  If your battery isn't charging, you've probably got the polarity reversed.  You can either switch the cables, or set your drill to reverse and crank the opposite direction.  This will reverse the polarity you generate and should fix the problem.

Step 5: We've Got Power!

Now all you have to do is twist the rotating end of the drill, and you'll be generating electricity at the contact points where the battery would normally connect. 

The little plug symbol on this phone appears at around 5 volts, and shows that it's charging.  I decided to crank just fast enough to keep the charging symbol displayed, to reduce the risk of over voltage.  On my drill, a cranking speed of 100 RPM yielded about 5 volts DC.

I used some clamps to secure the device to a desk for better leverage.  Shorting out the leads on my multimeter returned a value of 5-6 volts at 7-8 amps.  That's a 40 watt human powered hand crank generator!

The faster and harder you can crank the drill, the higher the voltage, and more amperage you can extract. 

Ideally, this could be hooked up to a bike, water power, or even a windmill to generate effortless energy.  And if done carefully, the energy could be stored in a battery for later use!

Step 6: Results

It took about 3 hours of cranking, but I got my phone fully charged.   The phone only accepts a very small current (about 94mA in my case), so it's not hard at all to crank.  But if the generator leads are shorted out, or hooked up to a re-chargable battery, the effort to crank increases quite a bit!  This is because you're pushing more current.

In retrospect, I think it would have been more efficient to spend 15 minutes cranking a larger current into a large 6 volt battery, and then charging the phone from that.  But hey, you do what you can with what you have.  

The charger illuminated an incandescent flashlight bulb, a super bright white LED, and there was even enough power to convert water into fuel with the OxyHydrogen generator made in a previous project!

Step 7: Other Projects

Well, there's a bare-bones 40 watt electrical generator that you can make in a pinch that will charge batteries, illuminate lights, and provide a little electricity in a pinch.

If you missed the video, you can still see it here!

If you liked this project, perhaps you'll like some of my others. Check them out at

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    66 Discussions


    6 years ago on Introduction

    I am contemplating using this for a "How to" project in college. I have tried three different cordless drills and am unable to get either one of them to turn by hand. Is there a particular type of cordless drill that is needed. Of the three that I attempted to use, it seemed as if something was going to "break" when I tried to forcefully rotate it to generate power.

    4 replies

    Reply 6 years ago on Introduction

    This will only work with Nimh or NiCad powered drills. LiPo or Li-Ion powered dittos have a protectioncircuit between motor and battery. Also some higher end models have PWM-circuits that does not allow for this kind of charging.
    Though I'd mention it.

    From my experience, if it feels like it will break if you force it, it usually does.

    Check the settings on the drill. Is it locked? Is the torque setting set to the drill bit setting? Is the mechanism set to one direction or the other?

    Also, are you pressing the trigger when you're turning it?

    All these factors make a big difference.

    Think of it this way .. operate it exactly as if you were drilling a piece of wood .. but do it by hand. Everything else is the same.


    4 years ago

    I would hook up the drill to a bike.


    4 years ago on Introduction

    You mentioned that there are no capacitors, So is the drill's output DC?


    6 years ago

    How much volt can i get from a toy motor?

    1 reply

    Reply 4 years ago on Introduction

    It depends which kind of toy motor... there are billions of kinds of toy motors...


    4 years ago on Introduction

    Hello. I was looking for ideas on a project on energy conversion. I was succesful on the results, but i couldn't find any explanations on how this works. i would appreciate it if you would kindly tell me how it works? the only conclusion that i came to had to do with polarity. But im not sure if i am correct.


    5 years ago on Introduction

    Hi king of random, i am trying to replicate your hand drill project but i am failing? Im using a 9v drill with a torque of 5? Do i need a higher drill to make it work? Thanks... In need of help asap...


    5 years ago on Introduction

    In your "Microwave " scrounge video you show shorting out (grounding) the terminals of the dangerous and deadly component. These things contain very high voltages that have killed a service technician that got grounded. People should be made aware of this. Especially untrained young people. Thanks, for the great ideas. Recycling and dumpster diving are my passion!


    5 years ago on Introduction

    I loved this project: It's what practical engineering is all about.

    From what I can tell the operator has to hand-crank for 3 hours at a constant speed to attain a fully charged phone. I'm reminded of an english inventor who developed a hand-cranked radio (for developing countries). I think he got it into production.

    I know there's gearing systems around that will reduce the number of "cranks" needed. (Maybe resistance could be reduced if the gearing inside the cordless drill is removed or adjusted, too?)

    Personally, I'd design a gear system and hook up the output terminals to a long-life battery. Then regulate the voltage from the battery to power phones and lights. This project really got me thinking.

    Only one question: What was the make and model of the cordless drill used, please?


    6 years ago

    Love your stuff man, ingenious

    i have an idea and a question in the same time... is it possible to use the motor from electric drill as a wind generator without the gearbox, of course?... I have 4 expired number plates made from aluminum and i want to use them as some sort of blades for a small wind turbine, but i don't have any idea where to find a proper generator that could charge few UPS batteries. :D

    1 reply

    I would sugest to add a voltage regulator, so you protect the cell phone.
    It is very cheap and easy to use.