18V, 3.0AH, Lithium-ion Battery, Built In Memory Chip Memorizes The Usage History & Communicates With The Charger, Less Weight Lithium-ion Battery Weighs 40% Less Than Ni-MH Or Nickel Cadmium, Anytime Charge Lithium-ion Batteries Have No Memory Effect & Can Be Charged At Any Time, Charging Technology Controls Current, Voltage & Temperature To Maximize Battery Life.