This instructable shows how to create a simple aluminum air battery from a soda can and a piece of charcoal from the backyard BBQ. This instructable is being published early but I hope to combine this device with a joule thief and an LED to provide a rechargeable backyard lighting system that can be emptied and refilled.

I believe that well burned campfire charcoal could also be used. Backpackers could have an extremely lightweight, wholly renewable and non CO2 generating light source.

From Wikipedia:Aluminum Air Battery
Aluminium batteries or aluminum batteries are commonly known as aluminium-air batteries or Al-air batteries, since they produce electricity from the reaction of oxygen in the air with aluminium. They have one of the highest energy densities of all batteries, but they are not widely used because of previous problems with cost, shelf-life, start-up time and byproduct removal, which have restricted their use to mainly military applications. An electric vehicle with aluminium batteries could have potentially ten to fifteen times the range of lead-acid batteries with a far smaller total weightt.

Step 1: Bill of Materials

We'll need:

An aluminum can. I use a soda can.
A piece of sandpaper. I happen to have some sticky sandpaper for a sanding block. Very convenient. This is used to remove the surface treatments from the can. This actually may be optional. I will experiment and update the instructable appropriately.
A sponge. This will be cut to fit inside the battery. I used a cellulose sponge from a 6 pack my wife had under the sink. A natural sponge may be more conductive.
A charcoal briquet.
Several readers have suggested alternative, readily available carbon sources. The most scientific sites I've visited have recommended activated charcoal for the carbon electrode.
  • Britta disposable filters
    • Aquarium filter charcoal
1 gallon plastic garbage bag
Rolling pin or short piece of pipe for crushing charcoal
Duck Tape - That's right its called Duck Tape, not Duct Tape.

Some copper wire or copper mesh. The effectiveness of this device is directly linked to connectivity between the copper drain and the carbon cathode. Also it is not possible to solder a lead to the aluminum.

I am using copper mesh and foil from K&S Metals to obtain connectivity. In the first release I tried a simple copper mesh/carbon combination that generates power but I am working on second generation and will update the instructable when it's available.

Carbon which is used in water filters can also be used....?
<p>Yes, I believe so.</p>
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<p>You have been charged with a salt and battery!</p>
Actually aluminum can be soldered, check out this site for an easy solution www. solder-it. com they have an aluminum soldering paste that also works with soldering aluminum to dissimilar metals. There are also special brazing rods for aluminum.
How to solder some of the more difficult metals such as aluminum would make an excellent and extremely useful instructable. I don't think most of us have ready access to welding equipment unless I can make an easy arc welder from like a boatload of aluminum cans....
Here ya go. :) <a href="http://www.instructables.com/id/Quick-and-easy-brazing-aluminum-copper-and-nonfer/">Quick and easy brazing aluminum, copper and nonferrous metals</a>
Aluminum has a extremely low melting point. You can melt it over a small fire. If you had a really hot soldering iron, you could probably work with that.
The AlL "brazing" rods available only need a common simple propane torch to use, for small projects that don't sink the heat away fast. Their down side can be cost. Unless you find a motivated carnival/fair demenstrator with a large stock of the stuff to move. For most tape or alligator tips would work well enough.
Alumalloy welding rods, let you weld AL with just a propane torch. Bend-&-crimp works too.
With only 0.5 volts, you would probably only be able to get a joule thief to run if it is made with a Germanium transistor. Otherwise, you might try putting two cells in series.
Agreed. With my "Easy Carbon Electrode" I got as high as .925 mV. I'm putting together my Joule Thief this week. Will advise.
And....nothing ever happens on time or in budget....
Nice! I think Americans and Englishmen should agree on a general term that refers to an object that is spelled differently in both...... Like aluminium and aluminum and duct and duck tape. Honestly though, let's just refer to alumin(i)um to its ID in the periodic table. Back to topic of instructable, can I use homemade charcoal instead? People here don't sell charcoal briquettes (we prefer LPG). And what's the shelf-life of this battery?
This looks like a fun battery. I make potatoes get 1.8 volts, which is more than pickles, onions, celery, grapefruit, a vinegar battery, lemons, and a few others. These were in pairs of halves, except the vinegar,which there was 2. But awesome, and simple. I think the activated charcoal would work better, but this does seem a little messy. I was also wondering if it smelled bad. Pickle and onion batteries stink very bad after only an hour.
Check out my Easy Carbon Electrode instructable. That's got a much, much cleaner design. No, there are no detectable odors as far as I can tell.
What is the conductive foam you find with computer motherboards made from and could it be used instead of the carbon?<br />
I'm not familiar with a conductive foam, most electronics are packed in non-conductive materials. However I expect that any non-reactive, conductive material could work but keep in mind I'm not a scientist, I just play one on Instructables.<br /> <br /> Actually many commerical aluminum oxide devices use metal electrodes. In my projects I use carbon to ensure that no confusion arises about the operation or results.<br /> <br /> The al-oxide rig in <a href="http://www.instructables.com/id/Salt-Water-and-Aluminum-Foil-Night-Light/" rel="nofollow">Salt-Water-and-Aluminum-Foil-Night-Light/</a> might be a better test bed for that sort of experiment.<br /> <br /> I would be very pleased to hear how this experiment comes out. Don't forget to put a porous non-conductive layer ( such as paper towels or something ) between the aluminum and the carbon (or foam) electrode.<br /> <br />
Ok, thanks,<br /> My wife does a lot of craft work so we often visit art and craft shops. In one I saw some perforated plastic sheet. Next time I visit the mainland I will buy some and see how that works out as the insulator.<br />
silkscreen material, plastic screen or thin cloth can also be used.<br />
Well that's disappointing. <br /> I checked the black open cell foam, the semi transparent electronic items often come in and just to complete the checks also the pink closed cell foam. <br /> All very high resistance &gt;40Mohm over about 1/2&quot;.<br />
Don't overlook the possibilities of the foam as an insulating layer in place of the sponge. Line the can with foam and fill with the charcoal, cap with the copper grid and open cell foam. Remember that oxygen needs to get to the carbon so the top should be open, maybe some cheesecloth or a single layer of the open cell.<br /> <br /> Add some saline and you have a much tidier cell that could easily be wired in series to produce 3-6V.<br />
cool. At first I saw 2 leads, a black and red from the carbon electrode. Then I figured out that the black was a shadow. =)<br/>
The voltage is due to the reaction of the two half-cells.&nbsp; One of the leads is usually copper, the other is usually zinc.&nbsp; The vegetables contain the electrolyte to corrode the leads and generate the potential.<br /> <br /> Sadly, it is not power from potatoes.&nbsp; It is power from the metals reacting.&nbsp; But its still fun.<br />
Very cool projectIf you used the full height of the can wouldn't you get more output? For that matter what about using a 5 gal paint bucket lined with aluminum foil, or aluminum flashing? Back when I was a kid the microphones from telephone handsets used carbon somehow. I am not sure whether it changed the resistance proportionally to the sound or whether it actually generated power.
Yes, the device can be scaled up quite nicely. The only gotcha is that scaling up increases the current but not the voltage. The maximum possible voltage is 1.2V per cell (multiple cell in series for increased voltage). The carbon in older microphones was part of converting sound to electricity but I have no idea what the actual mechanism was.
The carbon produced a piezoelectric effect. Sound pressure on the carbon produced a voltage with an amplitude in proportion to the intensity of the sound waves impinging on it.
You are thinking of crystal microphone elements, the carbon mic element don't generate power.
That's right. The carbon was in the form of small granules. It was wired in series with a fixed resistor. They were fed with a fixed voltage. As it picked up sound waves the carbon compressed and relaxed in response. This varied the resistance of the carbon and so a variable voltage was generated between the junction of the fixed resistor and the carbon and ground, which of course meant it was acting as a variable resistor.<br />
Making one of those would be a cool instructable.
My guess the internal resistance has something to do with the observed voltage drop if the individual cells arranged into a battery as compared to there open circuit voltage. have measured the voltage of the cells with a load applied?
This is a primary battery. A larger physical size will only mean more total current will be available for use. As I recall the voltage that a battery can deliver has something to do with the location of the electrode materials on the periodic table of the elements. This supports my recollection, but doesn't give the &quot;why&quot; <a rel="nofollow" href=";cd=4&amp;hl=en&amp;ct=clnk&amp;gl=us">;cd=4&amp;hl=en&amp;ct=clnk&amp;gl=us</a> or <a rel="nofollow" href="http://preview.tinyurl.com/p7h83g">http://preview.tinyurl.com/p7h83g</a> The answer of why may be hidden somewhere in this search <a rel="nofollow" href="http://www.google.com/search?hl=en&amp;q=periodic+table+of+elements+battery+voltage&amp;sourceid=navclient-ff&amp;rlz=1B3MOZA_enUS323US323&amp;ie=UTF-8">http://www.google.com/search?hl=en&amp;q=periodic+table+of+elements+battery+voltage&amp;sourceid=navclient-ff&amp;rlz=1B3MOZA_enUS323US323&amp;ie=UTF-8</a> or <a rel="nofollow" href="http://preview.tinyurl.com/odtfsv">http://preview.tinyurl.com/odtfsv</a> I'm running behind with reading this weeks weekend builder so I'll let you have at it., if you wish :)<br/>
Actually, you should check out the reactivity series. For a battery, the further apart the materials are in the reactivity series, the more current generated. If I am not wrong...
Yes is the reactivity series it seems, but from what I can tell it still determines the battery voltage. I'm not to say anything for certain the topic gets pretty deep,too deep considering the point I was trying to make. That a factor other than pysical size determines output. Output was undefined in the comment I responded to. I assumed voltage because power (E x I=P) is rarely used to refer to the output of a battery.<br/>
I believe its the electrode potentials rather than the basic reactivity series alone that determine voltages from a cell. This appears to be a standard table:<br/><br/><a rel="nofollow" href="http://en.wikipedia.org/wiki/Electrochemical_series">http://en.wikipedia.org/wiki/Electrochemical_series</a><br/><br/>Now if I can just figure out what the entries mean I'll be set....<br/>
Because the electrolyte and anodes can be replenished I believe this is properly called a fuel cell. If it were sealed it would be a battery.<br/><br/>It is my understanding, from sources I can't quote offhand, that Al-Air fuel cells (replenishable) are the leading candidate to replace conventional rechargeables in netbooks and cellphones. The most common battery type used in hearing aids is Zinc-Air so this makes sense.<br/><br/>Wikipedia has the math but it doesn't explain it:<br/><a rel="nofollow" href="http://en.wikipedia.org/wiki/Aluminium_battery">http://en.wikipedia.org/wiki/Aluminium_battery</a><br/><br/>&quot;About 1.2 volts potential difference is created by these reactions&quot;<br/><br/>I'm too stupid to figure out +2.71, +.40 and -2.31 produce a potential difference of 1.2.<br/>
>This is a primary battery. A larger physical size will only mean more total current...something to do with the location...on the periodic table... Yup! As the electrons jump up/down from differing atom's electron shell sizes they release a proportional voltage and amperage...thas why to increase it you have to stack in series( + to - , for double voltage), or in parallel( -/- & +/+, for double the amperes).. most batteries are many "cells" in series, like a car battery that has 6 pairs of plates wired together to make 12 volts.. hope this clears it up least a bit :) Moto13
The carbon microphone element doesn't create electricity. The element is essentially a variable resistor, that varies the current in a circuit, so information can be transmitted using DC, varying DC to be more exact
Your wikipedia link lead to this link <a rel="nofollow" href="http://exo.net/~pauld/activities/AlAirBattery/alairbattery.html">http://exo.net/~pauld/activities/AlAirBattery/alairbattery.html</a> IMO does a good job of explaining what's going on in a AL air battery. Appears the activated charcoal would be the better choice, but you do NOT want to crush it. Crushing it would destroys it's porosity, and permeability. Both make it the better choice, because will contain more are than powder charcoal. Reads as if adding weight will make a better performing battery. My guess is that the weight increases the conductivity of the activated charcoal. I would think your addition of the copper screening against the charcoal would make for a better performing battery. In the event you are really McGuivering it a coarser grind may prove better.For the irelavent; while Duck tape is(or can be) duct tape, not all duct tape is Duck tape. Looking foward to your other AL/air battery projects to be posted<br/>
Did you see this one <a rel="nofollow" href="http://www.instructables.com/id/Easy-Carbon-Electrode/">Easy Carbon Electrode</a>. Vastly improved output and significantly improved electrode.<br/>
Possibly the sanding down of the can is required to get to a layer of 'pure' aluminium - I vaguely remember at school learning that aluminium is naturally soft and reactive, but the reason we can use it for its strength is that aluminium oxide naturally forms all around it like a protective shell and aluminium oxide is really hard.<br/>So it's like you're cleaning the rust off <sup>_</sup><br/><br/>This is just a hypothesis though, I'm no chemist!<br/>
Would it be possible to use activated carbon granules (i.e. aquarium filter carbon)? It may provide a carbon source that is more pure.
yes get the charcoal tablets from the pharmacy, it is activated charcoal, powder it and use it. i tried it with aluminium foil and managed to get around 1 volt max.
What charcoal tablets from the pharmacy? Is this a dietary supplement or an aquarium filter thing?
well this isn't a dietary supplement not its not the aquarium filter as well. It is used for treatment of food poisoning. as the activated charcoal adsorbs the "poison" from your stomach and renders it safe. so just ask them for activated charcoal. it is cheap, then you just powder it.
Thank you very much for this information. I will investigate this alternative and update the instructable if it works out. What form does in come in normally? A solid chunk of carbon would also be extremely useful.
it is in a form of a pill and you just crush it up. but you can also buy large chunks which are generally way more expensive than the equivalent weight of the tablet. the large chunks are use to deodorize rooms and purify water. P.S is it possible to use soot? like collect a lot of soot as it is very porus?
I will check this out. You may very well be able to simply hot glue the exposed wire to the tablet and use that as an electrode.<br/><br/>Soot would also work, I think. I was thinking about using this in combination with the copper mesh. If the mesh is placed where it gets covered with soot it might make a very nice electrode.<br/><br/>Did you see my other instructable &quot;<a rel="nofollow" href="http://www.instructables.com/id/Easy-Carbon-Electrode/">Easy Carbon Electrode</a>&quot;? I would expect the tablet to work about the same. I'm very interested in gathering data on various shapes and sizes of the electrodes.<br/>
yes i guess the hot glue method will work but then i am not sure if the tablet will absorb enough brine to ensure good connection.

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