I didnt know the pinball machine had batteries? Yes, that is correct! Most modern pinball machines have batteries located on their circuit boards. Why? These provide a constant stream of power to the memory so the game can retain its settings as well as high scores.
Cool - but why should we care?
Well, batteries deteriorate over time. If the batteries are not removed every 1-2 years, they can begin to leak acid. That acid can leak on circuit components and destroy the CPU. Some CPUs cannot be fixed and replacements cost anywhere from $150 bucks to $450 depending on the game.
So - lesson of the day - replace those batteries! When selling a game, most collectors will want to see the batteries. If there is bad damage, expect a lower asking price.