Build your own Makita tool kit with the 18V LXT Battery and Rapid Optimum Charger Starter Pack (BL1840BDC2X). The pack includes two 18V LXT 4.0Ah batteries (BL1840B) and a Rapid Optimum Charger (DC18RC) that reaches a full charge in 40 minutes or less, providing up to 35% more run time per charge compared to BL1830. The charger's smart-charging system communicates with the battery to monitor current, voltage, and temperature, with a built-in fan for faster, more efficient charging. Compatible with Makita's Star Protection Computer Controls, which protect against overloading, over-discharging, and overheating across the 18V LXT cordless tool system.