why does my fruit powered battery not work

[lmmullen01]

we have created a lemon and grapefruit powered battery using copper wire, zinc (galvanized nails), jumper cables with alligator clips. We know it creates 3 volts maximum when we connected multiple fruits in series and ran it to a voltmeter. When we connect it to a clock or buzzer or small bulb that requires 1.5 volts (AA battery), why is it not getting teh clock, buzzer or small bulb to operate? Is there one more connection needed between the + and - area where the battery goes? That is hard to do in the small space - using copper wire (tried it). ANy other ideas to get things to work or power something? Thank you.

[deleted-71827]

Hi!
I would first check if the circuit is closed (so that no wires are left hanging out in the open). In any case, here is a bit of a twist on a similar project that you could probably use to help you-
http://www.sciencefairadventure.com/Pro ... jectID=154
http://www.energyquest.ca.gov/projects/lemon.html
Hope this helps, good luck!

[deleted-71785]

Immullen01,

I am very new to the forum but I may have an idea. I suspect the problem is you are not creating enough current.

One solution that may or may not be too technical is to get a current meter (from your local hardware store, RadioShack, or a friend who knows electronics). I have seen them for around $20 at various hardware stores. Connect this in your circuit (in place of the bulb) with the lowest setting and read what current you are producing.

It is probably low enough that it is in fact working but not producing light.

Regards,

-Vince

[lmmullen01]

Thanks Vince, I had hooked the fruit up to a voltmeter and found that we had created an effective circuit with 1.5 volts one time and even 3.0 volts another time. So we proved that we were generating as much current as a 1.5 volt AA battery (or even over/double the amount). IF the voltmeter reads the same for the battery and the fruit, why does one (the battery) light/run the object but the fruit does not?

[kgudger]

Please understand that there is a difference between current (I) and voltage (V). When you use the voltmeter to measure the voltage on the "battery", you are not drawing much current. If you were to continue to measure the voltage while you put a "load" on the battery, you will see that the voltage drops quickly as the load increases. (Here load is defined as current draw.) This is because "fruit batteries" have a very high internal resistance.

You need a load that draws very little current from your "battery". Have you looked at the Science Buddies project? (https://www.sciencebuddies.org/mentorin ... p029.shtml) In the project is suggests that you need a load that draws less than 0.5 mA (500 μA). The project gives some ideas for this.

I would suggest you include a vocabulary section in your project. Make sure you know what these words mean, e.g. Voltage, Current, Resistance. Best wishes!

Keith

[lmmullen01]

We have actually shown on a voltmeter that the fruit battery generates the same current as a 1.5 volt AA battery.
So, after the fruit battery was disconnected from the voltmeter and the exact same setup was connected to a number of things requiring a 1.5 volt AA battery we assumed they would turn on, buzz, light up, move. There was no response - even though the voltmeter showed the full voltage we knew we needed.

[deleted-71704]

Hello,

Did you try the suggestions which kgudger posted? The fruit battery may have the same voltage as a manufactured battery, but it is not nearly as reliable. That's why we make batteries in factories--we need them to be reliable and have low internal resistances.

Try doing what kgudger said to do: use a device which draws less than 0.5 mA (500 μA). Be sure to visit the science project link in kgudger's post as well.

Good luck,
AerospaceGuy

[lmmullen01]

Good news!!
2 grapefruit plus 2 lemons = 3 volts
I went to radio shack and got a low amp red LED (tiniest light bulb) (specs: 15mA max forward current and 3.0 forward volt)
and a low amp buzzer (specs: 5mA max current consumption at 12 VDC, voltage rnge 3.0-28VDC).

Both items worked and the 3 girls in 4th and 5th grade were so excited that their science fair project can demo something cool!!!
They learned a lot about current, voltage, and resistance!!! Lots to write up on the science fair notebook and display board.

Thanks all!!!

[deleted-71704]

Excellent! I am glad that you were able to overcome your difficulty and get something out of this project.