The Makita 18-Volt 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 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 LED charge level indicator to monitor battery charge. The 18-Volt LXT 4.0Ah battery (BL1840) is compatible only with Star Protection tools, indicated by the Star Symbol and/or Yellow Battery Receiver under the tool. Makita 18-Volt 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. This promotion also comes with a BL1840B 18V LXT Lithium-Ion 4.0Ah Battery and a bonus BL1840B 18V LXT Lithium-Ion 4.0Ah Battery.