When you do not have when the outdoors the power source supplies, the handset does not have the electricity? The digital camera does not have the electricity? GPS does not have the electricity? MP3, MP4 does not have the electricity? PDA does not have the electricity? This product provides by the solar energy of light power source,even if also needs not to worry the electricity question in outside The solar energy charge knapsack can provide you five charges ways: A, the solar energy charges B, in the room charges (110-230V) C, the vehicle carries charges D, computer USB charges E, disposable battery power supply Solar cell board 0.75w &2w voltage 5.5v & 5.5v-24v