This WA3004-G1 Quad Battery Charger charges up to four spare High-Capacity or Super High-Capacity battery packs. It is designed to charge up to four Lithium Ion batteries at one time. A fully discharged battery can take up to 4 hours to charge. The quad battery charger stops applying power to the battery when it is fully charged-there is no risk of overcharge if the battery remains in the charge well.