Wagan Solar Car Battery Charger is the easy, maintenance-free way to keep your car battery charged and ready to use whenever you need it. This is an excellent battery maintainer that will keep the battery topped off when the vehicle is not in use. It constantly replenishes a maintenance-level charge to the battery of your vehicle. Simply plug this charger into your car's 12 volt DC power port and leave the solar panel on the dashboard or where it can absorb direct light. The solar cells will automatically charge your battery even on cloudy, overcast days. Waterproof, scratch and UV resistant, and charge indicator LED lights. The solar panel is made of high-efficiency, mono-crystalline cells embedded in transparent vinyl acetate behind tempered glass. Lighter adapter requires a lighter socket/power port that works with the key out of the vehicle (also accepts alligator clips).