Make an AA Battery

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• published: 20 Dec 2014
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In this video we’ll show how to make an AA battery. Warning: Potassium hydroxide is corrosive, zinc is a heavy metal, and manganese dioxide is an irritant. Wear gloves when handling them. Get a 5 mL plastic syringe (the one i got was from a company called “BD” and the catalogue number was 309603). Discard the plunger and cut off the tip. Also cut the back up to the 5 mL mark. Get a 5 by 3 cm sheet of zinc metal about 0.5 mm thick. Cut into the 3 cm side a series of cuts about half a centimetre long. Roll the sheet so it fits into the syringe tube. Don’t roll it too tight so it falls out. It should be big enough that it stays in by friction. Once you have the right diameter, pull it out and bend inward the tabs we cut earlier.This should now form a zinc can. Prepare the cathode powder by mixing 8 grams of manganese dioxide and 3 grams of carbon powder. This will provide enough cathode powder to make about ten batteries. The carbon is just a conductor for the oxidant which is the manganese dioxide. The best manganese dioxide to use has the gamma type crystalline structure. The more common beta type crystalline structure will still work but will give lower current. So try and get the gamma type if you can. If you make your manganese dioxide electrochemically then it will be of the gamma form. While manganese dioxide made pyrolytically is usually of the beta form. Now get some filter paper or a coffee filter and cut a rectangle, about 5 by 10 centimetres. To that pour a five centimetre line of about one gram of the cathode powder. Also insert a 7 centimetre length of 2 mm thick pencil lead into powder. Roll that into the paper and fold over one side so it doesn't spill out. The paper serves as a separator between the zinc and the manganese dioxide. If they came in contact the battery would short out. Now get the zinc can we made earlier and insert the cathode roll into it. Cut off or tear any excess paper. If there is too much cathode powder that it doesn't fit then you’ll need to pour some off. If there is too little then you’ll need to take it out and add more. Now insert the assembly pencil end first into the syringe container from earlier. Make sure the pencil lead goes through the hole in the tip. Then break off the exposed pencil lead and leave 2 mm for electrical contact. Fill the battery with electrolyte by dropping the whole thing in solution of 30 g of potassium hydroxide in 50 mL of water. Leave it for several minutes to soak in and then take it out and leave it on some tissue for another several minutes to drain out any excess. And that’s your battery. Mine had an open circuit voltage of about 1.412 volts and two of them could power a cheap digital clock. Now I know some of you are wondering what the electrochemistry is behind the alkaline battery. Under load the zinc anode reacts with the potassium hydroxide electrolyte to give zinc oxide and two electrons. These electrons then go through the load and at cathode they travel through the carbon to the manganese dioxide. The manganese dioxide reacts with water to produce manganese (III) oxide and hydroxide ions. The reactions stops and the batteries dies when either the zinc or the manganese dioxide is consumed, or when the waste products build up and block further chemistry.