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
- Cardboard
- Vinegar
- Salt
- Heat shrink tubing

Here we go!

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.

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.

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.

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.

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.

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.

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

void setup()
{
Serial.begin(9600);
}

void loop()
{
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
}