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Minor Versionm

by Vishal Bhatt


The Voltaic cell was one of the first batteries to be invented and the principle behind its operation is still used in some modern batteries. A simple 'wet' cell consists of two metal plates separated by a liquid, known as the electrolyte. This liquid serves as a channel for balancing the charge between the electrodes when the cell is being discharged.

Video Overview

    • Scissors have functional sharp edges. Contact may result in injury. Always keep blades away from fingers and body. Handle with care.

    • Magnesium is an active metal, people with sensitive skin should avoid direct skin contact.

    • Metal foil or tape can have sharp edges, handle with care.

  1. You have two 10 cm strips of  polished magnesium. These will serve as the negative terminals of the finished cells.
    • You have two 10 cm strips of polished magnesium. These will serve as the negative terminals of the finished cells.

    • The two 10 cm lengths of copper ribbon will be the positive terminals of our complete cells.

    • Take one filter paper and fold it in half .

    • Cut about 0.5-1 cm off the folded circumference.

    • Now unfold the paper and cut along the fold line. These two pieces will form the separators for our cells.

    • Now place one of the magnesium strips on one of the longer sides of the paper separator.

    • Take care that there is at least 1.5 cm of the strip sticking out from the rectangle; this will serve as a negative contact point later. Also make sure that the separator extends a little beyond the other end of the strip.

    • Roll the strip tightly along the rectangular piece to make a cylindrical shape.

    • Hold the bottom of the cylinder to keep it from unravelling.

    • Now place the magnesium strip wrapped in the filter paper on top of a copper strip. Make sure there is some space between the copper and magnesium electrode.

    • Now fold the copper ribbon strip around the paper to make a mostly sealed envelope of copper around the magnesium electrode separated by paper.

    • The cell is now almost complete and ready to accept the electrolyte.

    • Make another identical cell, based on the steps mentioned previously, with the remaining materials

    • Attach the positive (copper) of one cell to the negative (magnesium) terminal of the other. Leaving you with one pair of free terminals to connect the LED to. These will be the positive and negative of the battery.

    • Now wind the positive of the battery to the positive of the LED (longer leg) and the negative of the battery to the negative of the LED (shorter leg).

    • Start by taking about 10-20 ml of water in a cup.

    • Add the citric acid crystals to the water and stir till they dissolve. This solution will act as our electrolyte.

    • Our average cell voltage with this cell chemistry is 1.2 - 1.5 volts so we need at least two in series to deliver 2.4 volts, which is comfortably above our red LED's switch-on voltage (2.1 volts). If the LED is blue or white instead of red or green, it may need more cells connected in series as these have a higher turning-on potential.

    • Now dip the the cells inside the electrolyte.

    • The LED should start glowing almost instantaneously!

    • If the LED does not glow, it could be caused by either an improper connection between the cells or a short (positive and negative of the same cell are touching) on one of the cells.

    • Erroneously connecting the positive (long) lead of the LED to the magnesium electrode and the negative lead to the copper electrode.

    • Insufficient absorption of the electrolyte by separator.

    • Winding the lead of the LED to copper and magnesium could be a little tricky and not robust enough.

    • Electrolyte not concentrated enough, although typically, a dilute solution is adequate.

    • If the cells start hissing and bubbling in the electrolyte, it is too acidic, try diluting it with water for better results.

    • Make different types of batteries by changing one parameter at a time.

      • For each battery observe and record your findings in the attached table.

      • Use a multimeter (if available) to measure the voltage produced by each cell.

    • The observation table has also been appended at the end of this guide.

    • Make a battery of single cell using the same metals but, double the length i.e. 20 cm copper strip and 20 cm magnesium strip.

    • Use iron nails instead of magnesium ribbons. How many cells in series do you need now to light the LED?

    • Use a different electrolyte instead of citric acid. E.g. like copper sulphate solution or vinegar (acetic acid) or common saltwater

    • To learn and make the variations for DIY Battery, please go to DIY Battery (Variations).

Finish Line

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Kailash NR

Member since: 05/02/2017

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