Features:  Durable, water-resistant and long lifespan.  Light and thin, easy to use and carry.  High conversion rate, high efficiency output, excellent weak light effect.  Overcharge protection, reverse protection, DIY your backpack and teaching use.  Little noise, high efficacy and low malfunction and suitable for outdoor activities like camping, fishing, hiking, etc.     Specification:  Bulb Wattage: 3W.  Bulb Voltage: DC12V.  Solar Panel Voltage: 18V.  Solar Panel Wattage: 20W.  Solar Panel Material: Monocrystalline solar panel.  Application: Car, boat, caravans, camping, fishing, hiking, etc.     Controller Specifications:  Buck charge: 28.8V.  Float charge: 27.4V.  USB output: 5V/3A.  Working current: 10A.  Self-consume: <10mA.  Discharge stop: 21.4V.  Voltage: DC 12V/24V.  Max solar input: <50V.  Rated working current: ≤20A.  Discharge reconnect: 25.2V.  Working temperature: -35℃~60℃.  Output voltage: 12V/24V Automatically distinguish voltage.     Package Included:  1X 20W Solar Panel.  1X 10A Controller.  2X 3W Light Bulb