This 2,000-Year-Old Battery Actually Works—And One Craftsman Found the Hidden Detail That Proved It
This 2,000-Year-Old Battery Actually Works—And One Craftsman Found the Hidden Detail That Proved It
His recreation suggests that ancient people may have been harnessing electricity millennia earlier than we thought.
Here’s what you’ll learn when you read this story:
- Archeologists have long contested the idea that the “Baghdad Battery” was meant to generate electricity. Recreations have had mixed results at best.
- However, an interested knife craftsman used his design and research experience to notice some details missing from modern experiments. He published a paper supporting the idea that this device could indeed have been used as an electrical power source.
- His recreation showed how the design would likely have worked as two batteries connected in series, increasing the total voltage of the device.
In 2005, knife craftsman Alexander Bazes was watching a rerun of MythBusters that attempted to reconstruct a mysterious ancient artifact—purported to be a kind of battery developed 2,000 years ago. But the experimenters’ method did not make sense to him.
What is now known as the Baghdad Battery is a ceramic jar containing a copper cylinder with a vertical iron rod inside. Several of these supposed proto-batteries were discovered near Baghdad and dated to about 300 BCE, though their exact use has been lost to time. Since its finding in 1936, nobody has been able to recreate it in a way that supports the idea of the design capable of generating a practical electrochemical response.
After the Discovery series episode, Bazes, who moonlights as an independent researcher, was inspired to do his own investigation. Something seemed to be missing in the TV recreation of this object, he thought. He then recalled his training in Japan, seeing how some seemingly irrational features of his teachers’ knives had in fact been incorporated into the design for valid reasons.
It was then that Bazes realized that what may appear unnecessary might actually end up being surprisingly useful.
“I decided to approach my experiment instead from the perspective of looking at something crafted by a master,” he says. “If this artifact had once truly functioned as a battery, then I assumed it probably would not have been the first device of its kind to have been made. The language of the artifact’s design should therefore tell a history of trial and error whereby its makers found the best way for them—2,000 years ago—to get the results they wanted. Nothing should be superfluous or needlessly inconvenient.”
Previous experiments recreating the Baghdad Battery involved filling the jar with vinegar and measuring electrical output. At only two volts, the output was weak, but Bazes suspected these attempts had overlooked an important piece of design. He created his own Baghdad Battery and recently published his findings in the journal Sino-Platonic Papers.
Concept drawing of the Baghdad Battery, with the three main component pieces found together in 1936: a ceramic pot, a tube of copper, and a rod of iron, sealed with bitumen for insulation; plus the inner cell with a liquid electrolyte.
Detailed cross-section of the Baghdad Battery illustrating the soldered copper vessel, iron rod, bitumen seal, and electrolyte integration (central to Bazes' higher-voltage recreation).
Bazes thinks the failure of other experiments to produce enough volts to power anything now—or in antiquity—comes down to neglecting certain elements of the battery’s design. This is probably the source of doubts surrounding the artifact being an actual battery. Bazes decided to include the solder MythBusters forgot at the top of the ceramic jar in his reconstruction, then reassessed the function of the jar itself.
“MythBusters’ experiment ignored that the copper vessel inside the ceramic jar was originally soldered to be watertight,” he says. “Instead, the experimenters chose to use plain copper tubing, open at both ends. This gave their devices only one compartment to hold liquid, the clay jar, whereas the original clearly had two compartments. The experimenters then had to awkwardly attach wires to the copper tubes in order to access the batteries’ positive terminals. It just didn’t feel believable to me that ancient craftspeople would have made something so clumsy to use for so little effect.”
In the end, the MythBusters battery could only generate 0.4 volts per cell, which can hardly be called useful. Bazes found that combining the solder and unglazed ceramic jar created an aqueous metal-air battery (tin being the metal in question).
The soldered ceramic jar functions as the outer cell of the battery, which integrates with the copper and iron that make up the inner cell. When an electrolyte such as salt water or lemon juice, both of which were available to ancient craftsmen, was poured into this recreation, it generated over 1.4 volts.
This amount of voltage can power electrochemical reactions such as electroplating and electrolysis, which are important for a number of reasons. For example, these processes are used to refine metals and prevent corrosion today. The inner cell is what gives the voltage (the difference in electric potential between two points) a boost. Bazes’ recreation shows that the type of liquid in the clay jar affects the voltage.
Adding liquid “creates an additional voltage between the solder on the outside of the copper vessel and the outside of the clay jar, which is the new positive terminal,” says Bazes. “This significantly increases the total voltage of the device, which now becomes two batteries connected in series, and it also makes it convenient to use, since now the positive terminal is on the outside of the device instead of being buried inside it.”
The MythBusters version of the battery only had one cell–the ceramic vessel–instead of two. Using copper tubing open at both ends and then attaching wires to it, as the experimenters did on that episode, would make it difficult to access the cathode terminal, the negatively charged electrode where electrons enter. With only an unsealed copper component and no iron, the setup would produce no effect while immersed in a liquid electrolyte.
Unglazed ceramic is also problematic because it is so porous. Any liquid in this vessel would soon drain the battery’s power, due to the saturated ceramic becoming conductive. The galvanic corrosion, caused by exposing the tin and lead solder to a corrosive liquid, would lead to more energy drainage, and the solder itself would be degraded.
Bazes managed to avoid these problems.
“If you recreate this artifact faithfully to how it was made, and if you put in electrolytes that were readily available 2,000 years ago, it ends up working as a much better battery than previously thought,” he says. “You get a big boost in voltage, and the battery’s two terminals are now convenient to access. I find this recreation more believable, at least, as something an ancient craftsperson might have made.”
The Baghdad Battery’s demonstrable voltage difference between the copper and iron components brings an understanding of voltage onto the scene thousands of years before Alessandro Volta would be considered the progenitor of modern electricity research. Ancient craftsmen had no idea that the principles behind these types of batteries would someday be used for applications such as electric vehicles and even power plants.