This type of battery is exactly as its name suggests. It was developed in the 18th century as a method of storing usable energy based on the belief that electricity was generated solely by living creatures. An Italian physicist discovered that the muscles in the legs of dead frogs would twitch on the application of an electrical charge. He also found that the legs would also convulse if he pressed the hooks attached to the spinal cord against the iron rail on which they were hung. From this, he deduced that electricity was produced by animals.
A frog battery required a chain of dead frogs’ thighs to be strung together with the inner surface of one in contact with the outer surface of the next. At either end were two cups of water which acted as the terminals. This produced ‘the current of injury’. Its uses were mainly confined to laboratory experiments.
The idea of ‘animal electricity’ and the gruesome process of making a frog battery was overtaken by the work of another Italian, Alessandro Volta, after whom the ‘volt’ is named. He created the voltaic pile, which was the first step away from the use of animals towards the technology we know today.