The 40 V max XGT® 4 Ah battery is engineered to outlast the competition. XGT batteries feature an advanced design with an impact-resistant outer case and shock-absorbing inner-liner that are engineered to protect the battery in harsh jobsite environments. XGT batteries also feature rigid rails with impact-resistant construction to secure the battery to the tool during high-demand applications. 40 V max XGT batteries are equipped with smart technology. The digital communication within XGT batteries optimizes performance to provide up to 2X longer sustained power under heavy-load applications. The digital communication within XGT batteries and chargers (sold separately) actively monitors and protects against overload, over-discharge and overheating. This advanced charging technology helps optimize battery life and deliver a faster charge. The battery reaches a full charge in only 45 min or less.