Makita BL1840B-2 18V LXT Lithium-Ion 4.0Ah Battery Twin Pack Integrated L.E.D. battery charge level indicator allows user to monitor battery charge 18V LXT Lithium-Ion 4.0Ah battery BL1840B provides up to 35% more run time per charge compared to BL1830 18V LXT Lithium-Ion 4.0Ah battery BL1840B reaches full charge in 40 minutes or less 18V LXT Lithium-Ion 4.0Ah battery BL1840B is compatible with 18V LXT Tools Compatible only with Star Protection tools, indicated by the Star Symbol and/or Yellow Battery Receiver under the tool