5.0 Ah battery offers 33% increased run time versus 3.0 Ah batteries with no added weight or bulk. NEW Battery Protection System provides Over-Discharge, Temperature and Current Protection for enhanced performance, battery cycle life and overall battery life (when used with STAR marked tool). Lithium-Ion Batteries offer extended run time versus Ni-Cad and Ni-MH batteries. Lithium-Ion Batteries offer more cycles over the life of the battery versus Ni-Cad and Ni-MH batteries. Optimum Charging System utilizes 3 Active Controls (Current, Voltage Temperature) to maximize battery life. Built-In Memory Chip communicates with Charger CPU to optimize the charging process based on the unique conditions of each battery.