The BL1815 Makita battery with five times lower self-discharge keeps battery cells active and ready to use after a long period of storage. Charging at any time will have no effect on the battery. Battery's built-in memory chip communicates with the charger (sold separately) to maximize battery life. For use only with Makita chargers DC18RA, DC18SC, DC24SA (sold separately). The Makita DC18SD 240V Li-ion 9.6v - 18v 30-60 Minute Charger uses a CPU to communicate with the batteries built in memory chip during a charge cycle, which analyses the data stored in the battery chip to decide on the best charging method at that time. This innovative technology results in longer battery life. This charger is suitable of charging up to 3.0ah Batteries only. Built in sounds on the DC18SD let you know charging status and completion. Makita Forced Air Cooling Fan technology cools the battery during charging by forcing cool air through the battery' s built-in air vents prolonging the life of the battery.