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A simple classroom (no soldering) project to show aluminum air batteries in use. In this instructable I will show you how to create a simple 3 cell aluminum air fuel cell using household aluminum foil and saltwater. You can use this to drive a small light or possibly a motor. This device will function for extended periods as long as the fuell cell is periodically recharged with electrolyte and the aluminum foil is replaced when power output drops below acceptable levels.
To simplify construction I used one of those solar yard lights available from OSH, Home Depot or Lowe's for about $5. These contain a simple circuit to recharge a battery along with a Joule thief type circuit and use that to drive a super bright LED after dark. Sundown is detected by a photocell located on the face of the device.
This circuit has many drawbacks but it eliminates the need to build a circuit or run down to Radio Shack, although obviously for a science fair project one would presumably build a simple joule thief/recharger circuit.
The design can be scaled up with additional cells wired in series or in parallel to increase power output and the output power can be fed to any suitable low voltage circuit. Do a web search for "solar powered light circuit" and substitute the appropriate al/air fuel cell array for the solar panel(s).
Now let's take a look at what we're going to need for this project.
To simplify construction I used one of those solar yard lights available from OSH, Home Depot or Lowe's for about $5. These contain a simple circuit to recharge a battery along with a Joule thief type circuit and use that to drive a super bright LED after dark. Sundown is detected by a photocell located on the face of the device.
This circuit has many drawbacks but it eliminates the need to build a circuit or run down to Radio Shack, although obviously for a science fair project one would presumably build a simple joule thief/recharger circuit.
The design can be scaled up with additional cells wired in series or in parallel to increase power output and the output power can be fed to any suitable low voltage circuit. Do a web search for "solar powered light circuit" and substitute the appropriate al/air fuel cell array for the solar panel(s).
Now let's take a look at what we're going to need for this project.
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The basic construction of this device is extremely simple. We're going to use some non-conductive trays and make a sandwich of aluminum foil, paper towels and a carbon brush electrode which begins its life as an aquarium filter.
You're going to need some non-conductive tray containers. I used some carryout containers from a local rib joint but almost any tray may be used. Since there only two dinners I used two bases and one lid. The common glass 9X11 glass cooking trays would be perfect.
3 paper towels to act as the porous layer.
A box of carbon aquarium filters. I used the Fluval brand of carbon pad replacement filters available at PetSmart for about $4. These come 4 to a box, I used the "4 Plus" size. These are used as the carbon electrodes in our assembly and function in this role quite nicely.
Some salt to use as an electrolyte. Ordinary table salt is fine, you'll need about 5g to start with. That's approximately 1/2 TBSP. In a liter of water that should produce approximately a 5% solution. Feel free to vary electrolyte strength.
A solar yard light. (see picture). These are available at most hardware stores for about $4. This is a self contained solar powered light with a rechargeable battery. it works by using a joule thief type circuit to maximize energy stored in the battery, the difference being that this circuit uses a capacitor rather than a traditional toroid so it doesn't provide the power amplification normally associated with a joule thief. NOTE: In the joule thief circuit the toroid provides both power amplification and capacitance.
4 electrical leads with clips, these are available from Radio Shack in a package of 12. These are used to make all connections.
A scissors, ruler and ball point pen along with a small screwdriver for dissassembling the solar light.
Now let's get started...
You're going to need some non-conductive tray containers. I used some carryout containers from a local rib joint but almost any tray may be used. Since there only two dinners I used two bases and one lid. The common glass 9X11 glass cooking trays would be perfect.
3 paper towels to act as the porous layer.
A box of carbon aquarium filters. I used the Fluval brand of carbon pad replacement filters available at PetSmart for about $4. These come 4 to a box, I used the "4 Plus" size. These are used as the carbon electrodes in our assembly and function in this role quite nicely.
Some salt to use as an electrolyte. Ordinary table salt is fine, you'll need about 5g to start with. That's approximately 1/2 TBSP. In a liter of water that should produce approximately a 5% solution. Feel free to vary electrolyte strength.
A solar yard light. (see picture). These are available at most hardware stores for about $4. This is a self contained solar powered light with a rechargeable battery. it works by using a joule thief type circuit to maximize energy stored in the battery, the difference being that this circuit uses a capacitor rather than a traditional toroid so it doesn't provide the power amplification normally associated with a joule thief. NOTE: In the joule thief circuit the toroid provides both power amplification and capacitance.
4 electrical leads with clips, these are available from Radio Shack in a package of 12. These are used to make all connections.
A scissors, ruler and ball point pen along with a small screwdriver for dissassembling the solar light.
Now let's get started...
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http://en.wikipedia.org/wiki/Aluminum-air_battery
Run some water through wood ash to get a mild sodium hydroxide solution and I think you've pretty much MacGyver'ed yourself out....I believe with a little experimentation in advance you can drive an LED directly from such a device but you'll probably need multiple cells.
And let's face it, showing them how to make light from a campfire and a soda can pretty much rocks....
By the way, if you've got a camp fire you dont really need the light do you... :D
but i still think its a great idea and would do the very same thing on a camping trip :)
If you ask at a store for 'carbon pads' they cannot help you, try a pet store and ask for aquarium filters.
There are also carbon electrodes available at your local ACE (or other) hardware store, tell them you're looking for a replacement brush for an electric motor.
www.instructables.com/id/Making-a-Saline-or-Hydroxide-Solution/
More layers of aluminum will probably increase your current. You might try with and without layers of paper towel between each layer of aluminum.
It might interersting to soak the towels in a saturated solution and allow them to dry partially then assembling the cell. This should eliminate the surface oxidation that occurs while the towel is drying and may give a better overall performance curve.
Also zinc may work better then aluminum.
anyway, 4.5 for the rating.
The number of things I don't like about this circuit would only just about fill the Grand Canyon. The next project will probably a battery pack charger with a more sophisticated circuit and a toroid for power amplification.
If the electrolyte is refreshed it should run for a week to 10 days per sheet.
Yes, you are correct, the difference between a fuel cell and a battery is that a fuel cell can be refueled ( as opposed to being single use or recharged ). It's not that a battery doesn't need a fillup, its that it cannot be filled up even if one wants too.
"Fuel cells are different from conventional electrochemical cell batteries in that they consume reactant from an external source, which must be replenished"
http://en.wikipedia.org/wiki/Fuel_cell
in this cell it remains a closed system replacing the anode isn't the same as having an external supply of fuel.
as for your question if I have something useful to do. this is my break. and despite your Monty Python clip I'm not here for an argument. I read your instructable and comment, left some of my own and then was going to leave.