Ridgid 31013 18-volt 1.1 Ah Li-Ion Battery Lithium-Ion batteries have built-in memory chips that memorize the usage history and communicates with the charger Li-Ion batteries weigh 40-percent less than Ni-MH or Ni-Cd The anytime charge feature of Lithium-Ion batteries means that they have no memory effect and can be charged at any time Lithium Ion Charging Technology controls current, voltage & temperature to help maximize battery life Ridgid covers its products with a lifetime warranty against defects in material or workmanship for the life of the tool.