Solar backpack bag is an eco-friendly mobile phone charger,collect power from sun, then converts sunlight into electricity and charging electronic devices such as mobile phone,power bank,camera etc. the backpack is very good for your outing,can put your different gadget inside,make your traveling life so easy and comfortable. Product Description Material: Oxford fabric with strong metal buckle and anti theft zipper Size：29*17*48 cm/11.4*6.6*18.8 inch weight:0.8kg Capacity of Bag:23L Size of solar panel:23*16.5cm Solar conversion rate:20% Max. power:4.3W Voltage:5V Current:1A ※please note that only solar bag with USB voltage controller,it can charge mobile phone directly under sunshine,if no voltage controller for the solar bag,it is need to use the power bank store solar power,than charging mobile phone devices. Backpack Bag contents -1*Solar backpack bag -1*Power bank battery -1*USB charging cable -1*Anti-theft Coded Lock. We’ve done all we can to enable your gadgets to tap into the sun’s unlimited(and free)power. but we can’t control the weather,cloudy weather and indirect sunlight may cause fluctuations in the current output that percent your devices from charging. in this event,try-placing the solar charger in more direct sunlight or wait for the weather to clear.