Aluminum Can, Saltwater and Charcoal Battery

Step 4 Assembling the battery..

Okay Macgyver we're off and running.

Place the sponge inside the aluminum can and pour in the salt water gradually allowing the sponge to expand. When the water just comes to the top of the sponge place the copper mesh on top of the sponge making sure it lays flat.

Now carefully pour the crushed carbon onto the copper grid.

Attach one lead from the voltmeter to the can, attach the other to the copper mesh. In this particular shot you can see the multimeter showing 3.6 mA, the intro shot shows the .5V reading.

If I've been reading everything correctly I believe this can be hooked up to a "Joule Thief" to power an LED.

Look for continuing updates to this project to reflect the Mark II design.

Comments

[Dick Cappels]

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.

[egbertfitzwilly]

Agreed. With my "Easy Carbon Electrode" I got as high as .925 mV. I'm putting together my Joule Thief this week. Will advise.

[Dick Cappels]

And...

[egbertfitzwilly]

And....nothing ever happens on time or in budget....

[msw100]

Warning to everyone do not install the free fish screensav'er advertised on this page it is spyware

[Wareagle]

 i thought it was common knowledge that ads almost always contain spyware/viruses.

[LiquidLightning]

 I believe that the ads on the page change every time you refresh, and btw almost all of those are viruses. =)

[samnew]

There's a product called alumaloy that you could use to braze aluminum to a copper wire. I used it on my thin-walled aluminum bike frame when i poked a hole in it in a crash.

[jayhalase]

Yes you can solder aluminium. You need a special solder that you can usually find for sale at car shows. It comes in long thin rods. Using a small torch you can solder aluminium and even white metal the stuff is incredible. I think bernzomatic has a similar product.

[rhackenb]

From the photo I can't quite see how you connect to the copper mesh. I'm not sure where to get copper mesh but what would it look like if I used just copper wire? Do I strip the insulation from several inches of braided copper wire and lay it on top of the sponge? You show a .5 volt output. That's not enough to light up an LED. Is .5 volt the most you can get out of such a battery? What if the can was deeper and you used a thicker sponge. Would that increase the voltage? If not, do you have to build a series of batteries? Nice instructable.

[bill14224]

rhackenb, the voltage is determined by the materials used in the battery, in this case aluminum, air, and charcoal. You probably noticed that alkaline batteries are 1.5 volts whether they're AAA-size, D-size, or anywhere in-between. A larger battery could produce more current but the voltage would be the same. The example here makes such a small amount of current at only half a Volt so it's practically useless. This experiment shows just how impractical aluminum-air batteries are. Terminal voltage is too low and you can't make a reliable electrical connection to the cathode because it's aluminum. Also, who cares if it produces no CO2? How does that matter? We're men of science, not global warming kooks, aren't we? I like how he digresses and explains more about Duck Tape than the battery he's making. First he says add enough salt so it won't dissolve, then he says stir it so it will. Huh? He shows none of his work, and doesn't say exactly how to make the anode either. Soldering a wire to a copper screen would do the trick, but he doesn't show anything, and since that's the most important part of this project, it stood out to me that this information is missing. There's lots of detail however, albeit out of order, on how to crush charcoal. I was wondering how to accomplish that tricky and technically demanding part of the project. I'm still glad I read this. Now I'm an expert on the history of Duck Tape!

[macrumpton]

Somebody got up on the wrong side of the bed today...

[egbertfitzwilly]

Actually with a higher energy density than lead/acid batteries the metal oxide battery a far safer and more practical solution. That's why they use metal oxide batteries for hearing aids, nothing else packs as much energy into as small a space. They are also used in space travel and military applications for the same reason. Most of "men of science" would understand that "adding salt until it won't dissolve" means a saturated solution. Achieving full saturation frequently involves both heat and agitation. Sorry for the confusion. Perhaps you didn't notice the alligator clips attached to the multimeter which is used to connect to both the copper and the alumuminum can. As was noted by other readers mechanical attachment to the aluminum via a crimp connector as well as properly fluxed solder offers multiple solutions.

[egbertfitzwilly]

Absolutely copper wire will work. Just strip the end and place it in the carbon. The keys are small particle size of the carbon (to get good conductivity) and good connectivity between the carbon and the copper lead(s). One could also use graphite powder which is extremely fine. You can get this at your local hardware store, Home Depot had only a small tube while Ace carried a larger jar.

Check out my Easy Carbon Electrode instructable. I got 900+ mV with a sponge, a piece of aluminum foil and a replacement brush for a Black & Decker power tool.

The theoretical maximum is 1.2V, I believe that scaling up increases the amps but not the volts. You are correct that higher voltages are obtained by using multiple cells in series.

[lorenrad]

I suggest you repeat the experiment without the carbon powder. If the copper mesh is already wetted by the salt water, you have an electrolytic cell with the aluminum and the copper. The carbon is superfluous. If you want to use the copper as a collector it should be dry and on top of the heap of carbon.

[egbertfitzwilly]

I agree, another reader made the same point. In the original design (shown) the carbon was on top of the powder.

You'll probably prefer this design:
Easy Carbon Electrode