This economical 12 volt charger can be used two ways: manual or fully automatic. No overcharging worries when in fully automatic mode. 10 amp fast charge for everyday charging needs - charges in 3 to 5 hours. 2 amp trickle charge - charges a small 12 volt battery in 2 to 12 hours. LED light signals Fully Charged. Fully automatic - will not overcharge batteries.