The inner workings of the Baghdad Battery Fill the jar with an acidic liquid, such as vinegar or fermented grape juice, and you have yourself a battery capable of generating a small current. The acidic liquid permits a flow of electrons from the copper tube to the iron rod when the two metal terminals are connected. This is basically the same principle that was discovered by Galvani 2,000 years later and that Volta successfully harnessed into the first modern battery a few years later. What was it used for? Experiments with models of the Baghdad Battery have generated between 1.5 and 2 volts. Not a lot of power. So what would batteries have been used for 2,000 years ago? It’s well known that the Greeks and Romans used certain species of electric fish in the treatment of pain, they’d literally go stand on a live electric eel until their gout-pained feet went numb.(photo courtesy)