Earth batteries were used extensively around the end of the 19th and beginning of the 20th century to power telegraph lines. They were buried in convenient locations along the power lines and supplied free current for that infrastructure. The technology was discarded and replaced with hydroelectric because hydro was a measurable, finite resource that industry could use to make money. Much like oil.
The earth battery bears a resemblance to the common chemical/acid battery you may be familiar with, if you’ve ever torn apart a battery or done science experiments. Basically, the battery consists of two metal sheets or rods: one copper or carbon, and the other zinc or aluminum (galvanized steel is a zinc surface), each with wires running from them.
These are negative (-) and positive (+) terminals of the battery. Once these metals are buried in soil (at a distance of 1-10 feet), you will have measurable current between your terminals.
Single earth battery
Earth batteries in series
The average single earth battery produces about 0.8 volts.
Some say that to obtain the best current, the rods/sheets should be positioned in a North (copper) to South (zinc) alignment, but it actually doesn’t matter.
There are a few ways to increase your available current with an earth battery setup:
Size and number
This is basically the ‘more is better’ principle – you vary the size of your rods/sheets, and how many of them you decide to bury in series. Using a larger surface of metal, and planting several of them in series, will deliver more telluric current.
Passing your current through a circuit and capacitor can improve the output and reliability of your voltage. A great example that is easy to set up is called the ‘joule thief’. This takes your direct current and oscillates it so that it actually delivers more usable energy than is actually available in the form of a direct stream.
Current can be amplified by a number of salvaged devices and standalone equipment such as the common 12v-110v inverters used with car batteries and solar panels.