This is a twin pack of the Makita 18v LXT Star Batteries includes 1 x BL1850 5.0ah and 1 x BL1830 3.0ah Batteries. LXT Lithium-Ion battery and optimum charging system produces 280 percent total lifetime work with 2x more cycles. 5x Lower self-discharge keeps battery cells active and ready for use, even after long periods of storage. Charging at any time will have no effect on the battery. Built-in shock absorbing features protect the battery. Sixteen firm holding contact terminals reduce the risk of power loss/fluctuation in high vibration work environments. Battery's built-in Memory Chip communicates with the charger to maximize battery life using 3 Active Controls (Current, Voltage Thermal). Battery suitable for all Makita li-ion LXT 18 volt machines. Star Protected Makita Battery The demanding applications you take on every day are also demanding on your cordless tools and batteries. You rely on your tools, so Makita created STAR Protection Computer Controls . STAR Protection is communication technology that allows the tool and battery to monitor conditions and exchange data in real time to protect against Overloading, Over-Discharging and Over-heating. Look for Makita tools and batteries with the STAR and get these protection features. Makita Star Battery - Overload Protection High-drain applications require maximum battery power. Makita tools and batteries are engineered for industrial applications, but sustained peak demand can overload the tool. Makita s STAR Protection Computer Controls allow the battery and tool to communicate and protect your tool and battery from overload by cutting power when put under abnormally high current draw. Makita Star Battery - Overcharge Discharge Protection Lithium-ion batteries are engineered for longer, sustained performance. But running a battery until it s dead empty can damage the cells. Makita STAR Protection Computer Controls monitor battery charge capacity, and if the battery is too low to compl