What we will be creating is a voltaic pile, named for its inventor, Alessandro Volta in 1800. Our pile battery will consist of cells created from a US penny, cardboard, a US nickel, lemon juice, and salt (not shown in images). Another item not shown was a piece of glossy card cut from an advertising mailer. I didn't think of it while shooting the images, but used it to encase the battery and make it fit the flashlight better. I chose coated, glossy card for this as it will not readily absorb our electrolyte.
The lemon juice is an acid which acts as a catalyst to enhance the reaction, to it we add sodium chloride (table salt) to reduce the internal resistance of the battery. We will cut thin cardboard pieces to the size of a penny, soak them in the acidic electrolyte, and sandwich them between nickels and pennies. It just so happens that the 3 AA battery packs common in cheap LED flashlights are just a tiny bit smaller than a US nickel, which is why I chose this arrangement.
For those who want more chemistry information:
A galvanic voltaic cell contains two metals which are dissimilar in electrical potential, separated by a thin barrier. To this cell we then add an electrolyte which causes the electrochemical reaction to occur. The metal contains cations, ions heavy with protons; cations react with water containing anions (electron heavy). While one metal causes the reduction of oxidation in the other, the reaction of anions and cations create an exchange of electrons - an electric current.
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On with the show!
What you need:
- US Pennies (copper plated zinc - we want the copper here)
- US Nickels (25% nickel, 75% copper - we are utilizing the nickel content)
- Lemon juice or another acid such as strong acetic acid for cleaning coffee pots
- Table salt (sodium chloride)
- A sharp knife
- Thin cardboard or similar material
- Electrical tape (vinyl)
- Multimeter or another device to measure output voltage
Note: the number of coins and spacers needed will vary depending on many factors, you will need to adjust them depending on what the output of your cell measures. Just remember they should be dissimilar and alternating. If you are not in the US, check to see what metals your coins are made out of and use two with a different electrical potential such as zinc and copper.
Step 1: Preparing the Barriers
If you're young, clumsy, or for any other reason think you might have problems then please do this with supervision or ask for help. It is far less embarrassing to ask for help than to cut yourself badly and have to explain to a trauma physician how you managed to hurt yourself. Cost of this project will rise exponentially if medical expenses are incurred.