The Baghdad Battery or Parthian Battery is a set of three artifacts which were found together: a ceramic pot, a tube of one metal, and a rod of another. The current interpretation  of their purpose is as a storage vessel for sacred scrolls such as those from nearbySeleucia on the Tigris. Although the Seleucia vessels do not have the outermost clay jar, they are otherwise almost identical.

Wilhelm König was a professional painter  who was an assistant at the National Museum of Iraq in the 1930s. In 1938 he authored a paper ] offering the hypothesis that they may have formed a galvanic cell, perhaps used for electroplating gold onto silverobjects.  This interpretation is generally rejected today.
While some researchers refer to the object as a battery, the origin and purpose of the object remains unclear. In March 2012, Professor Elizabeth Stone, of Stony Brook University, an expert on Iraqi archaeology, returning from the first archaeological expedition in Iraq after 20 years, stated that she does not know a single archaeologist who believed that these were batteries
The artifacts consist of terracotta pots approximately 130 mm (5 in) tall (with a one-and-a-half-inch mouth) containing a cylinder made of a rolled copper sheet, which houses a single iron rod. At the top, the iron rod is isolated from the copper by bitumen, which plugs or stoppers, and both rod and cylinder fit snugly inside the opening of the jar. The copper cylinder is not watertight, so if the jar were filled with a liquid, this would surround the iron rod as well. The artifact had been exposed to the weather and had suffered corrosion.
König thought the objects might date to the Parthian period, between 250 BC and AD 224, but according to St John Simpson of the Near Eastern department of the British Museum, their original excavation and context were not well-recorded, and evidence for this date range is very weak. Furthermore, the style of the pottery is Sassanid (224-640).
Most of the components of the objects are not particularly amenable to advanced dating methods. The ceramic pots could be analysed by thermoluminescence dating, but this has not yet been done; in any case, it would only date the firing of the pots, which is not necessarily that of the complete artifact.
Some believe that wine, lemon juice, grape juice, or vinegar was used as an acidic electrolyte solution to generate an electric current from the difference between the electrode potentials of the copper and iron electrodes.
König had observed a number of very fine silver objects from ancient Iraq, plated with very thin layers of gold, and speculated that they were electroplated using batteries with these as the cells.
Supporting experiments
After the Second World War, a man named Willard Gray demonstrated current production by a reconstruction of the inferred battery design when filled with grape juice.[4] W. Jansen experimented

with benzoquinone (some beetles produce quinones) and vinegar in a cell and got satisfactory performance.
In 1978, Arne Eggebrecht reportedly reproduced the electroplating of gold onto a small statue. There are no (direct) written or photographic records of this experiment.   The only records are segments of a television show
The idea that the terracotta jars in certain circumstances could have been used to produce usable levels of electricity has been put to the test at least twice. On the 1980 British Television series Arthur C. Clarke's Mysterious World, Egyptologist Arne Eggebrecht created a voltaic cell using a jar filled with grape juice, to produce half a volt of electricity, demonstrating for the programme that jars used this way could electroplate a silver statuette in two hours, using a gold cyanide solution. Eggebrecht speculated that museums could contain many items mislabelled as gold when they are merely electroplated.
The Discovery Channel program MythBusters built replicas of the jars to see if it was indeed possible for them to have been used for electroplating or electrostimulation. OnMythBusters' 29th episode (March 23, 2005), ten hand-made terracotta jars were fitted to act as batteries. Lemon juice was chosen as the electrolyte to activate the electrochemical reaction between the copper and iron. Connected in series, the batteries produced 4 volts of electricity. When linked in series the cells had sufficient power to electroplate a small token.
Archaeologist Ken Feder commented on the show noting that no archaeological evidence has been found either for connections between the jars (which were necessary to produce the required voltage) or for their use for electroplating.  In fact, plating of the era in which the batteries are claimed to have been used, have been found to be fire-gilded (with mercury).
In 2016, a team of researchers from Vanderbilt University developed a low-cost rechargeable "junkyard battery" using scrap steel and brass, by converting the surface of these metals into iron oxide and copper oxide nano structured architectures using an anodization process. The team drew inspiration from the simple design of the Baghdad battery
 
https://en.wikipedia.org/wiki/Baghdad_Battery