Lemon battery and LED question

[MJay82]

For my physics class this semester, we had a broad-ranged project to work on. Basically "anything related to physics" was the category. Initially I had wanted to build a percussion synthesizer circuit, but all I could manage to do was pick up a radio station 10 miles from my house, so I quickly switched gears so I had something to turn in.

I decided to build a lemon battery to power an LED, and do some experimentation. Out of curiosity, I picked up some limes too, and some apple cider vinegar and some balsamic vinegar. I made a few batteries and used my multimeter to measure the voltage of each battery. Then I started trying to light the LED (10 mA). In series, I added the batteries and ended up with a final voltage of 3.5 volts. I thought that this would be plenty to power an LED, but I found that it wasn't. Using my multimeter again, I measured the current produced by the batteries - 0.1 mA out of 3.5 volts! I was disappointed, but also intrigued by the discovery. I started thinking about Ohm's law, and here I get to my question:
If I were to use R = V/I, will this resistance be the internal resistance of the battery?

Also, what might be a way to increase my current with these food-related batteries? I tried V8 and Diet Coke - they both produced considerably more current than the lemons and vinegars, but still not enough to power the LED. When I added the V8 and Diet Coke batteries in series, the battery power was enough to get a flicker out of the LED.

I've got some Gatorade and wine that I hope to experiment with tonight. I would really like to get a big enough current out of these novel battery sources to brightly power the LED. Is there a way?

Additionally, my understanding of LEDs in series says that if I can power one LED, then since current will be conserved across series connections, I should be able to power a whole row of LEDs, expecting a voltage drop of about 2V across each LED.

I hope someone can help - this project is due on Wednesday and I'll have almost all day tomorrow to devote to polishing it up. Thanks in advance!

-Michael

 

[Disinterred]

These guys have made basically a short documentary on lemon batteries:



They got the LED to blink with 4 lemons, and suggested cutting up the lemons into many pieces to be used in series.

But have you tried Google? There seemed like a ton of videos on youtube for this subject.
Some research here, probably will pay off.

 

[EinsteinKillr]

I would guess that you are indeed actually lighting your led with just one lemon, just not enough that you can detect it with your eyes. The answer to a visible light just might be a capacitor, which will build up potential drawn from the battery until it reaches its total capacitance, and then it will release that potential in an avalanche across the LED. This will continue as long as the electrolytes can continue to produce current and give you a blinking LED. a 200 microfarad cap should do the trick.