Creating electricity is surprisingly easy. Copper and Zinc were widely available for centuries before electricity and the only other item you need is an acid. Nitric acid was being made back in the 13th century. Arrange a copper bar and a zinc bar separated from one another with an insulator (glass, ceramic, or even wood) in a glass or ceramic jar. Pour in the acid submerging most of the bars with some expose above the acid. You now have a battery with the anode and cathode (positive and negative terminals) being the top of the bars.

Barely slightly more sophisticated batteries than this powered telegraph offices for powering Morse code sending keys.