It was in 1938, while working in Khujut Rabu, just outside
Baghdad in modern day Iraq, that German archaeologist Wilhelm Konig
unearthed a five-inch-long (13 cm) clay jar containing a copper cylinder
that encased an iron rod.
The vessel showed signs of corrosion, and early tests
revealed that an acidic agent, such as vinegar or wine had been present.
In the early 1900s, many European archaeologists were
excavating ancient Mesopotamian sites, looking for evidence of Biblical
tales like the Tree of Knowledge and Noah's flood.
Konig did not waste his time finding alternative explanations
for his discovery. To him, it had to have been a battery.
Though this was hard to explain, and did not sit comfortably
with the religious ideology of the time, he published his conclusions.
But soon the world was at war, and his discovery was forgotten.
More than 60 years after their discovery, the batteries of
Baghdad - as there are perhaps a dozen of them - are shrouded in myth.
"The batteries have always attracted interest as
curios," says Dr Paul Craddock, a metallurgy expert of the ancient
Near East from the British Museum.
"They are a one-off. As far as we know, nobody else
has found anything like these. They are odd things; they are one of
No two accounts of them are the same. Some say the batteries
were excavated, others that Konig found them in the basement of the
Baghdad Museum when he took over as director. There is no definite figure
on how many have been found, and their age is disputed.
Most sources date the batteries to around 200 BC - in
the Parthian era, circa 250 BC to AD 225. Skilled warriors, the Parthians
were not noted for their scientific achievements.
"Although this collection of objects is usually dated
as Parthian, the grounds for this are unclear," says Dr St John
Simpson, also from the department of the ancient Near East at the British
"The pot itself is Sassanian. This discrepancy presumably
lies either in a misidentification of the age of the ceramic vessel,
or the site at which they were found."
In the history of the Middle East, the Sassanian period
(circa AD 225 - 640) marks the end of the ancient and the beginning
of the more scientific medieval era.
Though most archaeologists agree the devices were batteries,
there is much conjecture as to how they could have been discovered,
and what they were used for.
How could ancient Persian science have grasped the principles
of electricity and arrived at this knowledge?
Perhaps they did not. Many inventions are conceived before
the underlying principles are properly understood.
The Chinese invented gunpowder long before the principles
of combustion were deduced, and the rediscovery of old herbal medicines
is now a common occurrence.
You do not always have to understand why something works
- just that it does.
It is certain the Baghdad batteries could conduct an electric
current because many replicas have been made, including by students
of ancient history under the direction of Dr Marjorie Senechal, professor
of the history of science and technology, Smith College, US.
"I don't think anyone can say for sure what they
were used for, but they may have been batteries because they do work,"
she says. Replicas can produce voltages from 0.8 to nearly two volts.
Making an electric current requires two metals with different
electro potentials and an ion carrying solution, known as an electrolyte,
to ferry the electrons between them.
Connected in series, a set of batteries could theoretically
produce a much higher voltage, though no wires have ever been found
that would prove this had been the case.
"It's a pity we have not found any wires," says
Dr Craddock. "It means our interpretation of them could be completely
But he is sure the objects are batteries and that there
could be more of them to discover. "Other examples may exist that
lie in museums elsewhere unrecognised".
He says this is especially possible if any items are missing,
as the objects only look like batteries when all the pieces are in place.
Some have suggested the batteries may have been used medicinally.
The ancient Greeks wrote of the pain killing effect of
electric fish when applied to the soles of the feet.
The Chinese had developed acupuncture by this time, and
still use acupuncture combined with an electric current. This may explain
the presence of needle-like objects found with some of the batteries.
But this tiny voltage would surely have been ineffective
against real pain, considering the well-recorded use of other painkillers
in the ancient world like cannabis, opium and wine.
Other scientists believe the batteries were used for electroplating
- transferring a thin layer of metal on to another metal surface - a
technique still used today and a common classroom experiment.
This idea is appealing because at its core lies the mother
of many inventions: money.
In the making of jewellery, for example, a layer of gold
or silver is often applied to enhance its beauty in a process called
Two main techniques of gilding were used at the time and
are still in use today: hammering the precious metal into thin strips
using brute force, or mixing it with a mercury base which is then pasted
over the article.
These techniques are effective, but wasteful compared
with the addition of a small but consistent layer of metal by electro-deposition.
The ability to mysteriously electroplate gold or silver on to such objects
would not only save precious resources and money, but could also win
you important friends at court.
A palace, kingdom, or even the sultan's daughter may
have been the reward for such knowledge - and motivation to keep it
Testing this idea in the late seventies, Dr Arne Eggebrecht,
then director of Roemer and Pelizaeus Museum in Hildesheim, connected
many replica Baghdad batteries together using grape juice as an electrolyte,
and claimed to have deposited a thin layer of silver on to another surface,
just one ten thousandth of a millimetre thick.
Other researchers though, have disputed these results
and have been unable to replicate them.
"There does not exist any written documentation of
the experiments which took place here in 1978," says Dr Bettina
Schmitz, currently a researcher based at the same Roemer and Pelizaeus
"The experiments weren't even documented by photos,
which really is a pity," she says. "I have searched through
the archives of this museum and I talked to everyone involved in 1978
with no results."
Although a larger voltage can be obtained by connecting
more than one battery together, it is the ampage which is the real limiting
factor, and many doubt whether a high enough power could ever have been
obtained, even from tens of Baghdad batteries.
One serious flaw with the electroplating hypothesis is
the lack of items from this place and time that have been treated in
"The examples we see from this region and era are
conventional gild plating and mercury gilding," says Dr Craddock.
"There's never been any untouchable evidence to support the electroplating
He suggests a cluster of the batteries, connected in parallel,
may have been hidden inside a metal statue or idol.
He thinks that anyone touching this statue may have received
a tiny but noticeable electric shock, something akin to the static discharge
that can infect offices, equipment and children's parties.
"I have always suspected you would get tricks done
in the temple," says Dr Craddock. "The statue of a god could
be wired up and then the priest would ask you questions.
"If you gave the wrong answer, you'd touch the statue
and would get a minor shock along with perhaps a small mysterious blue
flash of light. Get the answer right, and the trickster or priest could
disconnect the batteries and no shock would arrive - the person would
then be convinced of the power of the statue, priest and the religion."
It is said that to the uninitiated, science cannot be
distinguished from magic. "In Egypt we know this sort of thing
happened with Hero's engine," Dr Craddock says.
Hero's engine was a primitive steam-driven machine, and
like the battery of Baghdad, no one is quite sure what it was used for,
but are convinced it could work.
If this idol could be found, it would be strong evidence
to support the new theory. With the batteries inside, was this object
once revered, like the Oracle of Delphi in Greece, and "charged"
with godly powers?
Even if the current were insufficient to provide a genuine
shock, it may have felt warm, a bizarre tingle to the touch of the unsuspecting
At the very least, it could have just been the container
of these articles, to keep their secret safe.
Perhaps it is too early to say the battery has been convincingly
demonstrated to be part of a magical ritual. Further examination, including
accurate dating, of the batteries' components are needed to really answer
No one knows if such an idol or statue that could have
hidden the batteries really exists, but perhaps the opportunity to look
is not too far away - if the items survive the looming war in the Middle