This automatic onboard battery charger is a high output portable charger, is completely automatic, and great for professional mechanics as they can be used for deep cycle batteries. Its 75-amps helps engines for emergency starting and the 12-amp fast charge helps to charge a battery in 2-5 hours. The 2-amp trickle charge charges a small 12-volt battery in 2-12 hours. It includes 2 LEDs which light up when the battery is fully charged and a 6 function rotary switch prevents overcharging of batteries.