The V20 Lithium-ion battery is ready whenever you are and wherever the job takes you, with an integral battery state of charge indicator for convenient monitoring of battery charge levels. The 18V STANLEY FATMAX V20 Cordless System batteries can be interchanged across your V20 power tools, using new and improved battery technology for longer runtime and power to get the job done. With improved battery technology, no memory effect and minimal self-discharge, the V20 lithium ion battery pack is ready to go to work. The 4Ah battery will give you twice the runtime of the equivalent 2Ah battery, allowing you to keep going to get the job done without the need to frequently charge the battery during more heavier applications. Part of the STANLEY FATMAX V20 18V Cordless System –power all your V20 tools from drills, drivers, sanders, nail guns, angle grinders, lights, multi tools and outdoor equipment, all with a common new and improved battery. 18V battery power. Battery capacity indicator. LED power light. Manufacturer’s 1 year guarantee (excludes professional use).