Lemon and salt water batteries

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Our lemon tree, two of our munchkin cats who love the lemon tree and 5 lemons.

A 5 cell lemon battery was built and tested running a blue LED.
You need lots of lemons to make it a success.
I used 5 lemons in series but to really make it go well, you need at least 20 or 30 lemons in series parrallel strings of 5 at a time, to get a current of about 15 mA.
Each lemon supplies about 0.9 volts between a copper electrode (positive) and a plated steel screw (negative). Total 4.5 Volts.
It drops rapidly to the zenervoltage of the blue LED at around 2.5 Volts and a current of below 1 mA.
For a red LED 4 lemons in series will suffice.

The saltwater test has a better current and with 4 cells in series gave 3 Volts open circuit and 1 to 2 mA for the LED.
Open circuit Voltage 3 Volts, loaded 2.4 Volts.

It definitly proves the fact that a large surface area is needed for the electrodes to be in contact with the acid or salt to give a reasonable current.
The internal resistance of the path of the electrons through the conducting medium is relatively high.

Compare for example a 12 Volt car battery in size with a 12 Volt truck battery. Same voltage but for the truck battery a very large current compared with that for a car required for starting the engine.

LED data:
Red led 1.7 Volts 15 mA for good brightness
Blue led 3.1 Volts 15 mA for good brightness
( most led's are rated for 20mA continuous )

The reason I put this experiment up on YouTube is that my 10 y.o. daughter wanted to know it for a school project, that if you could get power out of a lemon.


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