Fun with Less Kilowatts —Build an Aluminum Air Battery

By Vernon Trollinger, September 11, 2017, Family

Welcome to Fun with Less Kilowatts! We believe that science experiments at home can be a creative way to engage kids in learning while having fun. They can be educational AND great activities to keep your kids busy and away from the television. Each month, we’ll feature a new science experiment that can be a great resource for parents and teachers.

How to Make an Aluminum Air Battery

Fun with Less Kilowatts —Build an Aluminum Air Battery

Yes! You can make electricity from a damp pile of charcoal, a paper towel, and a piece of aluminum foil!

While many batteries work by being immersed and bathed in some sort of solution, an air battery is a battery cell that works when a pure metal reacts with oxygen (that is, the metal oxidizes) in the open air.

All batteries have a positive side (anode), a negative side (cathode), and an electrolyte. In metal air batteries, the pure metal is the anode, the oxygen in the air is the cathode, and there’s an electrolyte which is usually water-based.

The great thing about metal air batteries is that since they aren’t completely sealed boxes of liquid and metal, they’re very lightweight. Plus, the products of the chemical reaction (called “redox”) that makes the electricity are more environmentally friendly than, say, the typical lead-acid car battery.

That’s why electric car manufacturers and utilities that want to develop grid-battery systems to store electricity from wind turbines and solar arrays are interested in metal air batteries. There are still problems with metal air batteries, but there are lots of combinations of metals and other materials that engineers might one day use to create a long-lasting battery that is cheaper to use than gasoline.

The Materials

Fun with Less Kilowatts —Build an Aluminum Air Battery

  • One pair of alligator test leads
  • A small 2.5 volt incandescent Christmas light bulb
  • Table salt
  • Activated charcoal Use fish tank filter carbon, available from pet stores for under $5. Smaller pieces work best. Crush any pieces bigger than a pencil eraser.
  • A paper towel
  • About 12 inches of aluminum foil
  • Cup of water and a spoon

The Directions

  1. Make the saturated salt solution. To do this, dissolve some salt in a warm cup of water. Keep adding salt until you start seeing undissolved salt at the bottom of the cup —that’s when the water can’t hold anymore and has become saturated.
  2. Cut a 6”x 6” square from the foil (having extra is always handy).
  3. Fold the paper towel into a square to fit onto the foil. Spoon some of the saturated salt solution onto the towel to make it damp. NOT SOGGY.
  4. Pour a generous pile of the charcoal onto the damp paper towel. Be sure to keep it from touching the foil.
  5. Add more saltwater to the charcoal to wet it thoroughly – again, damp but not soggy.
  6. Clip one lead to each bulb wire. Clip one lead to the aluminum foil.
  7. Gently press the other lead onto the carbon pile.

The Result

Fun with Less Kilowatts —Build an Aluminum Air Battery

The light should light up!

The Science

All batteries have a positive side, a negative side, and an electrolyte. For our air battery, the aluminum foil is the positive (anode) side, the charcoal is the negative (cathode) side, and the salt water is the electrolyte.

As mentioned at the beginning, positive and negative sides are separated by an insulator but the electrolyte provides a way for charged atoms (called ions) to pass through through the insulator. Ions flow from the aluminum side through the saltwater to the charcoal side and drop off an electron. The places where the test leads are connected are call “electrodes”. The electrons flow through the negative electrode and leave the air cell, becoming electrical current. They flow down the wire, light the light bulb and return to the positive electrode. Here, they’re picked up by atoms and form ions again.

If the bulb doesn’t light, you might not have enough of the salt-water-soaked carbon making contact with the lead. You can get around this by scrunching the carbon close together or tightly or attaching the lead to a loop of bare wire and burying it in the charcoal. I used a handy old steel bolt.

Do you have any fun and kid-friendly science experiments you’d like to see us try for Fun with Less Kilowatts? Share with us in the comments!

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