Battery was simply a battery.
It was a temporary part on the The Krusty the Clown Show, along with Stingy. Krusty used them to replace Itchy & Scratchy. They have a theme song similar to the Itchy and Scratchy theme. "They bite and light and bite and light and bite! Bite bite bite, light light light...yadda yadda yadda." Krusty then drops Stingy, causing him to itch.