Human Powered Emergency Cell Phone Charger


Power outage? For the average citizen it’s very easy to take electricity for granted. Go a few hours or more without it though, and you’ll suddenly be reminded just what a luxury it is. During an emergency situation, sometimes you have to come up with alternative methods to get the job done. This human powered cell phone charger is a great example.

Using just a few ordinary around the house items, [The King of Random] turned a cordless electric drill into a human powered electrical generator. If the drill is run in reverse and cranked by hand, the generated energy can be transferred through the battery terminals to a connected device.  So, he cut a USB charger cable in half and wired it up to the terminals to be able to charge his cell phone. Some yarn, a salad fork, a mixing beater, a scrap 2″x4″, some aluminum foil, and scotch tape were the only other materials he used. Using this technique, a totally dead phone battery was charged in around 3 hours.

Remember that this method is only intended to be used in an emergency, not as every day practice. Using these methods could potentially overheat or damage your gear, so be careful.

Check out the MacGyver worthy video tutorial after the break.

[via Neatorama]

36 thoughts on “Human Powered Emergency Cell Phone Charger

  1. Oh jeeze, no voltage regulator, no current regulator. Not good for a sensitive phone. Moreover, the phone is going to take a long time to charge, as he mentions. Charging a battery and using the battery to properly charge other devices is the way to go, not jury-rigging a cordless drill.

  2. Better to open the phone and make the connection directly to the DC motor inside.
    A 78xx type regulator could be used in current mode to limit charge current to whatever seems sensible.

    Better to charge a lead-acid type battery and then use that battery and a regulator to charge
    cellphones or whatever.

    This will come in handy when Kim Jong Un sends over the EMP device :-/
    (at least it will if you have your electronics tucked away in a suitable metal container)

    I did this once but I just stuck a piece of small rebar into a vice and made two
    bends in it to form a crank…then used a short piece of small PVC pipe to make
    a slip handle that went over the crank part so you could crank easily.

    1. It’s not a stupid question. The answer is no. As others have noted on the thread, there’s a lot more to changing a battery than just hitting it with some juice. You drill’s efficient with current moving in one direction. It’s nothing near that way in reverse (remember we’re talking about current to the motor REGARDLESS of the direction it’s turning).

      1. Motors and alternators are practically the same thing. Most electric vehicles use regenerative braking to recharge the battery pack. Lithium batteries are a more sensitive chemistry to over-voltage and under-voltage conditions than most. They also have a maximum discharge rate which is largely determined by internal resistance.

        Battery Management Systems serve to limit voltage and current within these constraints. If you can keep a multimeter on the contacts and monitor the voltage, you can do as good of a job as a Linear Technologies, Analog Devices, Texas Instruments, or ON Semiconductor BMS Chip.

        Practically speaking, your arm is going to get tired twisting on your cordless drill chuck way before you manage to bring the SoC high enough to damage the cells. If you want to be funny you can say “Coulomb 1… Coulomb 2” while you’re doing this. The effectiveness is probably going to depend on the drill, with the cheaper drills being less likely to have internal circuits to interfere. Variable speed would be a feature to avoid for instance.

        The recommendation to use a Lead Acid as an intermediary is because you cannot exceed the “C” rating of the cells doing things this way. The charger will source a constant current constant voltage. Realistically, unless you’re Quagmire from family guy, I wouldn’t worry about it too much. The good drills should self protect, and the bad ones are too cheap to care.

        The planetary gear set is bidirectional by design and is usually well lubricated enough with lithium grease to where you don’t need to worry about it.

    2. Well, it would be a lot of cranking for a short burst buy yes you should be able to recharge
      the batteries in the drills pack. They are usually a collection of AA size Ni-Cads.
      You could also break apart the cells into smaller groups and charge them to create a 5v
      pack for the phone. I’d think you could just crank away at full speed on a small 5v pack
      made from the cells…just watch that they don’t overheat.
      BTW: Harbor Freight has 18v cordless drills in their current sales sheet for 16.99
      They would also have probably 14 AA Ni-Cads in the included battery packs.
      Not bad for a drill, charger, and battery pack :-)

      In case of the zombie apocalypse or an EMP I’d start collecting drills and scavenged car batteries…. a car battery would soak up any amperage you could crank into it. A deep-cycle battery would be even better. And several cheap Chinese ebay dc-dc switching up/down convertors would be a nice addition.

      1. If your drill loses its charge after the zombie apocalypse you could remove the battery charging step and just attach the chuck to your rebar crank, and there you have it…. a brace and bit for drilling holes….

        Plus, if you do become a zombie, it will be good for getting at brains…..

    3. Yes, after a lot of time eventually and only if it doesn’t have any electronic regulation in place which probably restricts the possibility to a few older models, certainly not the newer ones using Lithium cells.
      If it worked, you would also heavily wear the motor brushes and reduction gears.

    4. Some of these answers seem mis-informed.. Yes you could, but not by simply having the battery installed like it normally is. In order to charge the battery you need a current path to it, and that would mean having the drill set to ‘on’ it’s going to fight you every step of the way, you charge it up, it immediately fights you and tries to turn opposite. And you will probably strip the gears in no time.

      The battery pack would need to go through some additional circuitry, one being DC rectification then possibly through some extra power conditioning and finally the battery. Keep in mind some batteries have very specific charging curves.

  3. This is about as sophisticated as the Lego creations I made when I was three. Who uses string in place of a zip tie? No voltage regulator? No current protection? FOIL?

    Solder a resistor and a 7805 right up to the motor, bypassing the trigger, and ditch 70% of the bulky casing and you have something only worthy of half a joke.

    1. Mmm it’s meant to be an emergency situation where you use only what you use. The “average” person at home isn’t likely to have resistors and voltage/current regulators just laying around. But most people have a drill. It may not be the best way of doing it but if the zombies are beating on your door and you want to play one more game of snake on your Nokia then this could do the job.

    2. Yeah, when the power goes out just grab that soldering iron and… oh… Well, pass the foil please.

      If he had enough power to solder, he could just charge his cell phone normally. This is an “emergency last resort” kind of idea, not “vacation resort” where you get to optimize everything.

  4. If you’re sensible you’ve already got one ready made. You can pick one up for about £5 from Maplin. I’m guessing it includes a regulator and definitely includes gearing so that a reasonable crank speed generates a decent voltage. I know I’ve got one, no idea where it went though.
    Anyone who assumes they can have mains voltage and only a zombie apocalypse is going to stop that needs a dose of reality.

    1. Interesting ideas.
      Just imagine the worst actually happening and then no power for years.

      And even worse…imagine not being a hackaday type person but a member of the clueless masses! :-( Just OMG!

      1. I dont think reading Hackaday makes you less clueless, its just that most of the people reading hackaday already have knowledge of voltage regulation

        also which device with a motor buyable in a hardware store is most suited for hand cranked charging of stuff (minor modifications included ofcourse)

      2. Electricity really is not all that important. Adjust your sleep cycle for the sun and spend more time outdoors. Stuff takes more physical effort and planning, but that is it. Living without electricity on tap isn’t scary or hard.

        Go backpacking some time. It is a really fun way of learning what matters and what doesn’t. (hint, in order: people, heat, potable water, shelter, sanitation)

  5. The problem with charging batteries is that it takes a long time to charge a battery according to the battery specs.
    Normal LIPOs can charge at “1C” which means you can charge them in an hour (In theory, in practise 20% longer).

    A human can deliver 40W easily, Pedaling a bike 70-100W, no problem. So with a 4Wh battery, you need to pedal the bike for about 1/25th of an hour, or close to two minutes to deliver the energy to charge the cellphone. THAT is an entirely reasonable amount of effort to put in to charging your cellphone.

    So the solution would be to charge a big battery for 2-3 minutes to get enough energy to charge the cellphone for an hour. This means you need a battery that can charge at about 100W.

    For example, I have a 3000mAh 3S 40C-discharge RC-flying LIPO. It can charge at 5C or 15A. At 11.1V, that comes to over 150W of charging capacity.

    So… to do this properly we’d need to charge the big LIPO with a DCDC converter from the generator. Preferably in a way such that we can adjust the load/charging current. Some people rather put in 7 minutes of 50W effort while others prefer 5 minutes of 70W effort. A simple voltmeter will do as the charging circuit: “Don’t ever let this come above 4.2V”. And then a step-down to provide 5V for the phone.

    1. I have one of these exact “rechargeable” torches. It contains 3 alkaline button cells. After being charged three times they immediately regurgitated their guts all over each other… not the best design really.

  6. Last time I popped open a drill (a nice Panasonic one), it had a great big flippin’ mosfet/transistor attached to a heatsink on the back end to control the drill speed. Methinks this wouldn’t exactly work with current being driven back in to the batteries.

    1. That thing is for the speed control, most cheap drills just bypass the controller and connect the motor directly to the batteries when the button is fully pressed (which is why he says the button has to be fully pressed in the video)

      Note that this only applies to simple NiMh or NiCd powered drills (not Li-Ion or LiPo), and probably won’t work on expensive machines with proper regulation, breaking and ramping.

  7. You’d want some kind of gearing to really make good use of your power. Rotating load X 5000 times is a lot more tiring than rotating load 5*X for 1000 times. Within reason.

  8. 50 cents worth of 1982+ year pennies with lemon juice in between each will do the same thing. I say 50 cents because it will probably take two penny batteries to give you a full charge.
    Interesting hack and the comments about charging the drill’s battery first are great ideas :)

    I have also used a bag of potatoes to charge a phone but it seems to take longer. I thought it would be a cool party trick and teach my niece a lil something but it took waaay too long for a 5 year old’s attention span lol. She enjoyed getting the pocket change to play “grocery store” more than the hack lol.

  9. I’m on the fence about this one. I never approve of Kipkay-type hacks. He’s the kind of guy who will show you how easy it is to wirelessly transmit power using an incandescent bulb, a solar cell, and two lenses. But never goes into any real details, like how terribly inefficient it is, giving people the entirely wrong impression. Who will then run around telling people it’s ridiculous we’re still using power lines.

    I suppose claiming it’s MacGuyver-esque forgives the fact that there’s no voltage regulator, or intermediate battery. It’s true, you might not have such things in a situation where you’re forced to improvise. But this:

    “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!”

    Is vague and suspect enough that I think he may have measured incorrectly, overstating the real power output. The cell phone limits charging current, so he tries to demonstrate the power output other ways:

    “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!”

    But neither the bulb or the LED is a particularly large load, or anywhere near 40W. Converting water into fuel? It doesn’t take a lot of power to get a result from that, albeit a small result. And there’s already so many misconceptions and crackpots surrounding that topic, that by merely mentioning it, it’s a nosedive into Kipkay territory by association.

    1. It’s 3 years later but, yes, always worth reiterating that Kipkay is a dick. If he put more effort into learning basic science, and less into talking like an infomercial, well, he probably wouldn’t have as many Youtube views. It’s depressing though, just the large amount of wrong that he spreads.

  10. Valid points raised, about protection devices, but does raise awareness on emergency applications.

    I would also suggest using a bicycle with gearing, such is done at many outdoor events nowadays where people can recharge their phone by cycling. :)

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