Battery Pal's big brother, the Magnum, is perfect for storage or for small boat and personal watercraft charging. Its unique circuit senses when the battery is fully charged and automatically reduces current flow to supply only a maintenance charge to keep batteries fresh. It has an automatic safety shutoff; you can leave it on indefinitely without damage to your batteries. Battery PalTM Magnum is designed for charging 12 volt flooded or gel cell batteries rated between 5 and 250 amp hours, and for storage of any 12 volt battery, including motorcycles, tractors, personal watercraft, etc. It's waterproof and has an LED indicator to assure you of proper operation. Full one year warranty.