The Bosch 18V 4.0Ah Li-ion Coolpack battery that uses a passive cell cooling system. Passive cell cooling allows for better performance and a greatly improved run time, so you only need to stop when the job is done. The interchangeable battery is compatible with any 18V Bosch Li-ion power tool, allowing for added flexibility while you work. These Bosch 18V 4.0Ah batteries are also easy to pack and carry thanks to their lightweight and compact design.