Bosch BAT838 36V 4.0 Ah Lithium-Ion FatPack Battery Bosch BAT838 offers 50 percent more runtime over previous generation of Bosch 36V batteries Maintains the same footprint as previous generation 2.6Ah 36V batteries Maximizes battery runtime on the jobsite and eliminates user frustration in looking for charged battery Longer battery runtime increases productivity for critical system tools like rotary hammers, drill/drivers and saws