Solar Battery Charger transforms sun power into electricity and maintains the car battery to be fully charged. The solar cells absorb natural light and convert it into low level electrical current to flow charge car battery. When red dot LED alights, charging is taking place; In times of sub-zero weather temperature or car is on a non-activated status, the Solar Battery Charger does the job. Installation free and self-operational. Simply place the solar panel on the dashboard (directly under the sunlight), and plug into cigarette lighter outlet or connect to a 12V DC fuse block. Rugged, dependable construction, and incorporating the latest technology for a longer lifespan.