Fruit/Vegetable BATTERY

[mac11389189]

there's a school contest im joining which is about ORGANIC BATTERY. now my question is what fruit/vegetable would be the best to use? i know lemon, orange, and potato can produce good electricity but which is really the best? we're allowed to use only 10 fruits and im planning to sticking to only one fruit for this. it would be great if you can give me the average volt for one fruit/vegetable which u think is the best. u can also send me some previous projects about fruit/vegetable batteries as well.. =D

btw. the winner will be the one with the highest volt so pls mention only the fruit/vegetable that will produce the highest volt..

[theborg]

mac11389189,

Thank you for your question. I always love a good science competition. First off, let me refer you to a Science Buddies project: "Veggie Power! Making Batteries from Fruits and Vegetables" at this link:

http://www.sciencebuddies.org/science-f ... background

It provides a lot of good information for an experiment of this sort. Rather than just provide the answer of which fruit/veggie will provide the most voltage, I have a feeling that the point of the exercise assigned is to conduct some research and experiment to optimize/maximize voltage output. With that, lets discuss some of the processes involved here.

In this application, electricity is produced from a chemical reaction between two dissimilar metal electrodes immersed in an electrolyte solution. The electrolyte, in this case, is provided by the fruit/vegetable cell. You can narrow down good fruit/veggie candidates by researching ones that are high in electrolytes, such as Potassium. You can then test the candidates to find which ones are the most efficient at producing electricity.

Also, it's not just the fruit/veggie cell that contributes to the voltage output. You must also consider the type and placement of your electrodes. A) They must be two different metals, i.e. an anode and a cathode, (I'll leave the research as to which two types work best up to you) or the reaction will not work. B) Electrode orientation and distance from one other will play a factor in how efficient the circuit is (i.e. parallel, end to end, touching or not, etc...).

Some additional questions to get you thinking: Does the size of the fruit/veggie make a difference? What happens if you cut the fruit/veggie up into smaller individual cells (you said you could use up to 10 individual fruits/veggies, but you didn't say you couldn't cut them up and have 20 or more cells)? Does the circuit produce more voltage if the fruit/veggie cells are connected in series or in parallel? Does cell temperature make a difference in voltage output? Does freshness of the cell make a difference? How long before you deplete the power potential of an individual cell? I'm sure there are other questions, but these should get you started.

Please post back with additional questions or comments. I look forward to hearing how you did in the competition.

[rpedneka]

Hi,

I am doing a project for my school's science fair. My project is on fruit and vegetable battery. The question I am trying to answer is, "What fruits or vegetables will power an LED light the longest".
I went to a hardware store and they did not have any LED lights that could be powered by 2 volts. Instead, they gave me a 1 cell AAA light which should be powered by 1.5 volts. I am producing more than 1.5 volts, though.

I have tested lemons, potatoes, limes, and tomatoes, none of them have powered the bulb at all. The thing is, I have tested the bulb and it does work. The batteries are producing ample amount of voltage. One lemon battery produces about 1 volt while a lemon battery connected in a series produces almost 2 volts. I have also measured the amount of voltage an AA battery is producing and it produces the same amount as one lemon battery. I have been using alligator leads and a multimeter. I know I have connected it correctly as well. I have also watched videos and followed those.

I have tried testing it and trying many different ways. Like changing the connections, the copper wire, and the light bulb, nothing is lighting the bulb up.

I do not seem to know what the problem is. I have consulted some people at the hardware store also but they did not have an answer. They do not know why it is not lighting the bulb up.

Do you have any suggestions on what to do? Why is the Alkaline AA battery powering it but the fruit/vegetable battery not powering it? Do I need more batteries connected in series? Is there not enough current being created, if so how do I produce more current?

My rough draft for the final report is due 10/18/12.

Thanks for your help,
Rpedneka

[rmarz]

Rpedneka - A veggie or fruit based battery will generate an electro-potential (voltage and current) when electrodes of differing material are used. Typically zinc and copper are common metals. The voltage is a function or the metals chemical reaction to the electrolyte and can be over 1-2 volts, but may be producing a very small current (microamps for example). To operate an efficient LED may require over 5 milliamps to be just visible, and up to 20-30 milliamps, typically, for full brightness. Red LED's respond better to lower voltage thresholds.

The amount of current generated by one of these batteries is directly related to the surface area of the electrodes used. A small copper wire or zinc coated nail may produce a high measurable voltage, but not sufficient current to operate the device. As part of your experiment you could use a digital meter to measure output current capability of your experiment using electrode materials of different metals and surface areas. As others have suggested, individual cells connected in series will raise output voltage. Similarly, individual cells connected in parallel will provide more current.

Obviously the 1.5 V alkaline battery is capable of several hundred milliamps of current drive and may even have to be limited by a series resistor to prevent excessive currents through the LED.

Rick Marz