In this article, I will show you how to replace the typical 3 AAA battery pack in common cheap LED flashlights with pocket change to power the flashlight in a pinch. The battery created will even fit right inside where the normal battery pack should go! We've all seen these cheap little multi-LED flashlights at gas stations, convenience stores, dollar stores; you probably have one or more lying around. Let's get hacking!
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:
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.
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.
Be sure to vote for this Instructable in the Make It Glow contest!
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.
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Signing UpStep 1: Preparing the Barriers
We must prepare the barriers which will sit between the nickels and pennies in our pile. With a sharp knife, like an X-Acto knife, carefully cut some thin cardboard or similar material to the size of a penny. How many wafers you must prepare depends on how many coins you end up needing. This amount may vary due to a number of factors. If you end up needing too few to make your battery long enough for the flashlight, simply stack nickels without barriers on the end to fill the space. I chose the backing of an old notepad for my material. Select something thin, stiff, and absorbent. These wafers will hold our electrolyte and keep space between our metals to prevent short circuits which will reduce efficiency. Even blotter or filter paper works, but I've had better luck with cardboard.
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.
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.
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