This document is a science fair project report from Colegio San Patricio in Monterrey, Mexico. The project was conducted by 5th grade students Jesus Carvajal, Ma. Fernanda Corona, Felipe Cuellar, Jesús Carmona and Fidel Cantú, under the guidance of their teacher Ms. Claudia Vilchis. The students tested different battery brands to determine which lasts the longest, with their hypothesis being that Duracell Ultra batteries would last the longest due to their higher cost. They used various materials and methods to conduct their experiment and recorded their results and observations.