Instructables
Picture of Pumpkin Battery
Here is a fun food hack I did over the weekend that is a useful alternative to lighting jack o' lanterns with candles or traditional batteries on Halloween. It could also double as a center piece for the fall and is easily made with common household items.

You'll need miniature pumpkins (I used Baby Boo), unflavored gelatin, salt, vinegar and oil from the grocery store. You'll also need 18 gauge copper and aluminum wire, an LED (preferably one that runs on 1.5 volts- I used one that I had candied in an earlier project), wire cutters, pliers, a ruler and multimeter. In the kitchen you'll need a medium sized bowl, small bowl, small pot, cookie sheet, pairing knife and mellon baller (or spoon). If you already have the tools and kitchen stuff the project should cost about $20.

Update: One week later and the pumpkin battery is still generating 1.5 volts! My follow up post on it is here.
 
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Step 1: Cut and Gore the Pumpkins

Picture of Cut and Gore the Pumpkins
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Start by cutting the top off a pumpkin in a circle and scooping out the seeds and innards. You will only need seven pumpkins, six to make the battery and one to house the light so choose the battery pumpkins to be slightly flatter and the center pumpkin to be slightly larger so you can cut a decent face into it. Keep the guts and seeds for later!

Step 2: Cut and Bend the Wire

Picture of Cut and Bend the Wire
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Cut 6 pieces of both aluminum and copper wire into 8 inch strips and take one piece of aluminum wire and wrap it around itself three times. Flatten the swirl, making sure none of the wire touches the inner curves of the swirl (this increases surface area for the electrochemical reaction) and bend the straight part up.
I like this!!! Great idea!!!
flodato3 years ago
I started this project last night, but chickened out on the electrolyte because it looked completely different than yours. Tried just salt water and generated 2.5 volts with 6 pots. For some reason my light would not illuminate. I used 22 gauge aluminum wire and 20 gauge copper. I doubled up the thickness of each wire by using 16 inches of aluminum, folding the wire in half, and twisting it together with my cordless drill. So now I have nice, thick 8 inch copper and aluminum wires.

The light, I sanded the aluminum that I used because it was blue. I thought the color would be a nice contrast to teach the kids about what I was doing. However, after roughing up the surface the light still did not illuminate. I got the LED off of some Christmas lights... not sure what the voltage/amps of it is, but it worked with my cell phone battery. I will keep you posted. Please provide some pointers if you have any! Thanks - Frank
LED- Light Emitting Diode. Diode. Diode. (I repeat diode because sometimes I forget...and I work with stuff like this frequently.). Diode.

A diode only allows current flow in one direction- check to make sure you have the wires on the correct lead. IIRC, the longer of the two is the positive.
Also, thin gauge wire like that is usually covered with a kind of varnish for insulation- you'll have to burn it off for that wire you twisted together to actually be one stranded wire. What you probably have now is just one really long wire that's wrapped around itself a bunch. Good luck! If it weren't already 6 in the evening, I'd try this one. Definitely keeping it in mind for next year, and I'm going to incorporate a huge Frankenstein switch and glam it up to look all mad scientist-y.
emdaniels (author)  flodato3 years ago
Ok- what is the blue coating on the aluminum? Did you sand down the coating where the aluminum is immersed in the electrolyte and where it is wrapped around the copper wire? The LED I used generated a lot of lumens for low voltage- it typically runs on 1.5 V. LED voltage requirements span 1.5 to 3.7 or so, depending on the chemical composition. Radioshack would probably carry a wider selection, or you could order them, but your best bet would be to look for red LEDs as they tend to require less energy to light. Definitely keep me posted!
The aluminum wire was offfered in blue, yellow, red, etc. colors. I will try adding orange juice or vinegar to the solution to see what happens. I purchased 2 1.8V, 20mA LEDs at Radio Shack. I don't think that is the problem though. I think it's the connection and the solution that I made. Gonna mess with it tonight. Thanks! Having a blast with this.
Kasm2793 years ago
I cannot put into words how epic this project is.
emdaniels (author)  Kasm2793 years ago
Thanks! I hope you have fun making it.
Really,really neat. But isn't it possible that the punkins themselves could act as an electrolite? Like a potato battery? Did you try that?
I had the same thought when I first saw this... But I'm not sure how you would do it. It doesn't seem like plugging wires into the meat of the pumpkins would generate enough energy.
emdaniels (author)  TJSonOfAnder3 years ago
What would probably work is a salt water solution poured into the pumpkins (with guts and seeds in place) around the wires. I'd be willing to bet it would give off roughly the same energy (1.5 volts) as my experiment, but then you'd be wasting the seeds you could be eating! :)
tromano3 years ago
Great project... make yourself a "Jewel Theif" and you will get longer brighter runtime out of the pumpkins or even use less of them... check it out
Great idea!
emdaniels (author)  tromano3 years ago
Good idea- for those interested I found this link on instructables: http://www.instructables.com/id/Make-a-Joule-Thief/
randofo3 years ago
This is entirely awesome. You should enter this into The Mad Science Fair contest!
emdaniels (author)  randofo3 years ago
Thanks! Good idea- I think I'll do that. :)
This is really cute. And the metal you use to connect them gives it a real Frankenstein-likeness to it :)
emdaniels (author)  Penolopy Bulnick3 years ago
Thanks Penolopy!