Intro: Penny Battery
I know that others have done this, but I thought that it would work good as my first instructable.
This is to make a 3 volt battery out of the following:
- 6 pennies
- Heat shrink tubing
Here we go!
Step 1: Create Cardboard Inserts
To make a battery, we will use vinegar and salt soaked cardboard inserts. Place a penny and trace the outline the penny. Cut these circles out. We will need 5 such inserts for the battery.
Step 2: Soak the Cardboard
Once the cardboard inserts are cut out, place them in a mixture of salt and vinegar. I used a 1/4 cup of white distilled vinegar and 4 tablespoons of salt. Mix it thoroughly until all of the salt is dissolved.
Allow them to soak until they are completely saturated.
Step 3: Sand the Pennies
It's necessary to remove the thin copper from one side of 5 of the pennies. I used a Dremel, but any kind of sandpaper will work for this step. Make sure that you leave one of the pennies with copper on both sides.
Step 4: Stack the Battery
Now start stacking the battery. Place a penny sanded side up. Place a soaked cardboard insert. Repeat. End with the unsanded penny on the top.
Step 5: Cover the Battery
I used 3/4" heat shrink tubing for this step. Electrical tape would work as well. Just make sure that the cardboard parts only touch the pennies that they are closest to.
Step 6: Wait for Charge
It will take a little bit of time to allow the battery to charge. The first picture was right after the battery was made. The second picture was 5 minutes later. Within 15 minutes, the battery was producing 3.2 volts.
Step 7: More Information
I decided that I wanted to measure how long the battery would hold a charge. I made a quick program and hooked it up to an Arduino.
Here is my code:
// Testing of a Penny Battery
// By Jonathon Wiggins 06-06-12
const float referenceVolts = 3.3;
const int R1 = 4600;
const int R2 = 2600;
// determine by voltage divider resistors, see text
const int resistorFactor = 361 / (R2/(R1 + R2));
const int batteryPin = 0; // analog pin battery connected to
int val = analogRead(batteryPin); // read the value from the sensor
float volts = (val / resistorFactor) * referenceVolts ; // calculate the ratio
Serial.println(volts); // print the value in volts