Shinny copper pennies
Wires with alligator clips on each end (2+ per battery)
and cut it in half. This will make 2 batteries. Potatoes are juicy, which is part of the reason they can be made into batteries.
Take a knife and put a slit in the potato and slip the penny into the slit. Push as much of the penny into the slit as possible, you want just a little bit sticking out of the potato. Push the nail most of the way into the potato,(at this point I cut the nails in half, so that they weren't so tall). Do not let the electrodes touch, keeping them about 1 inch apart.
Turn on the Multimeter and put it at the lowest voltage reading. Make sure the red probe is in the + slot and the black probe is in the – slot.
Use the red line to touch the penny in the potato and the black line to touch the nail. You can read how much voltage you have available in this potato battery. It reads .85 volts, not bad but not enough to do anything fun.
To increase the voltage, you will need to create more potato batteries and wire them in a series (that means to connect the + electrode of one battery to the – electrode of the next battery). So I created 3 more batteries from 3 more potato halves.
Let's take a minute and look at the LED light. It has one long leg and one shorter leg. The longer leg is the anode (+) and the shorter leg is the cathode (-). I clipped the batteries to the LED light (+ to+ and - to-), no light, therefore, not enough voltage.
I wired all four batteries together in series, and found what the total voltage is of the 4 batteries was 2.38 volts and I again wired in the LED light, again no light.