Compact Stud Size. Two stage 3 amp charger keeps batteries in a full charged cOuter Diametertion. Unlike a trickle charger, the float circuit design senses when battery is fully charged and reduces current flow. Automatic safety shutoff lets you leave it on Hose I.D.efinitely without damage to batteries. Maintains 12 Volt flooded or gel cell batteries rated between 5 and 250 amp hours and charge/maintain any 12 volt battery for storage. 2 year warranty.