18V 5Ah Li-Ion Battery (2-Pack)(BL1850B) 

• 5.0 Ah battery offers maximum run time for prolonged, heavy-duty applications
• LED charge level indicator displays approximate remaining battery power
• 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)
• Li-Ion Batteries offer extended run time versus Ni-Cad and Ni-MH batteries
• Li-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.