The 51-620 Charges 6 & 12 volt batteries, deep cycle marine batteries and provides reverse connection protection. Built tough, has features of other automatic chargers but built with a rotary selector switch in stead of slide switches for durability in rugged work environments. No more lost knobs or broken unreplaceable switches. Features automatic 12-volt settings to shut output OFF at full charge, but resumes charging if the battery discharges for any reason. Battery Type Selector ensures full charge for deep cycle and conventional batteries. Powerful 100 amp engine start helps start stubborn cars in cold weather. Charges 6 & 12 volt maintenance free and deep cycle batteries used in cars, trucks, farm equipment, RV and applications. Charges automotive batteries in 2 to 4 hours. 2 amp setting is ideal for charging 12 volt motorcycle and lawn mower batteries. Reverse connection warning light and charge complete indicator. Large clamps deliver solid connections. 1 year limited warranty.