Batteries are quite amazing if you stop and think about it. Little cylinders of power that allow people to do everything from controlling a television set, to create artificial light in the darkest of places. In days gone by, they were also widely used to power pocket calculators.
One such model is the Casio College FX-100. This scientific calculator was used in the 1980's by students all over the world and its descendents are still used today. I had a FX-100, as did my wife. When my wife showed me her FX-100, the other day, she pointed out that she still had the original batteries that came with the device over 30 years ago. Still powering strong with no signs of leakage.