The Battery Tender Solar Charger 021-1175 is a solar-powered battery charger designed to maintain and charge 12-volt lead-acid batteries. It features a built-in solar panel that converts sunlight into electricity to charge the battery. The charger also has a microcontroller that monitors the battery's voltage and adjusts the charging output accordingly to prevent overcharging. This product is compact, lightweight, and weatherproof, making it suitable for outdoor use. It also comes with a built-in charge controller and a 3-step charging program for optimal battery health. The Battery Tender Solar Charger 021-1175 is an efficient and eco-friendly way to keep your batteries charged and ready for use.