The fully automatic Battery Tender 4 Amp battery charger and maintainer is a top-of-the-line 12V or 6V switchable battery charger, perfect for cars, trucks, SUVs, and boats. This battery versatile and powerful charger is equipped with a simplified 4-Step Automatic charge process used with lead acid and lithium batteries. Qualification (making sure the battery is ready for charge), bulk charge (getting your battery to the right charge level), absorption (the final 20% of charge), and float (maintaining charge without overcharging your battery, perfect for storage). All Battery Tender chargers automatically switch from full charge to float charge mode once the battery reaches optimum charge levels. Reverse hook-up protection makes connecting your charger safe and easy to do. LED light indicators make selecting your charge mode simple and straightforward.