The Milwaukee M12 B REDLITHIUM-ION Battery Packs are fitted with sophisticated electronics (REDLINK Intelligence) and overload protection which prevents the user from damaging their cordless power tool investment in abusive situations. It has a temperature Management System that keeps the battery within an ideal temperature range to provide maximum life. Individual Cell Monitoring ensures optimal charge and discharge for maximum life, and discharge protection prevents cell damage from over-discharge. Delivers up to 2x more run time, 20% more power and up to 2x more battery life compared to other Lithium-ion technologies and/or with previous Milwaukee battery technology. Results depend on tool and application.The Milwaukee M12 B4 REDLITHIUM-ION Battery Pack has the following specification: Battery Capacity: 4.0Ah.Battery Chemistry: Li-ion.Voltage: 12 Volt.