Milwaukee® REDLITHIUM-ION™ batteries have sophisticated electronics(REDLINK™ Intelligence) and overload Protection which prevents the userfrom damaging their cordless power tool investment in abusivesituations. It has a temperature Management System which keeps thebattery in ideal temperature range to provide maximum life.Withindividual Cell Monitoring which ensures optimal charge and dischargefor maximum life and discharge protection which prevents cell damagefrom over-discharge. Up to 2X more run time*, 20% more power*, Up to 2X more recharges* *Comparedwith other Lithium -Ion technologies and / or with previous Milwaukee®battery technology. Results dependant on voltage, tool and application. They also feature a fuel gauge to display their remaining charge. Specifications: Battery type: Lithium-Ion. Capacity: 4.0Ah. Voltage: 12 Volt.