The Makita 18V LXT® Lithium-Ion battery charges faster and works longer than standard lithium-ion batteries, giving you and your cordless tools unmatched performance and productivity to take on the most demanding applications. The Makita 4.0Ah battery, model BL1840B, combines more run time (35% more run time per charge than the Makita BL1830 battery) with a category-leading charge time of only 40 minutes so it spends more time working and less time sitting on the charger. For added convenience, it also features an on-board L.E.D. charge level indicator to monitor battery charge.Makita 18V Lithium-Ion batteries resist self-discharge so they're ready for use even after long periods of storage. The Makita Rapid Optimum Charger (sold separately) is a smart-charging system that communicates with the battery during the charging process to monitor current, voltage and temperature. This advanced charging technology helps optimize battery life and deliver a faster charge. In addition, the Charger has a built-in fan to cool the battery for faster and more efficient charging, even in hot weather conditions.For improved tool performance and extended battery life, Makita created STAR Protection Computer Controls™. STAR Protection is communication technology that allows the tool and battery to exchange data in real time and monitor conditions during use to protect against overloading, over-discharging and overheating. Makita, the innovation leader in cordless tool technology, has the world's largest cordless tool line-up powered by 18V lithium-ion slide-style batteries.