By the fast improvement of worldwide market, the unbroken improvement of standards, there are more and more portable electronic products in the world, Such as smart phone , iphone ,iPod ,digital cameras, camcorders ,table DVD,PDA,MP3,MP4,GPS.
They all have to use batteries, but the battery for built-in battery are low, because the battery capacity cannot meet the device appears to the normal use of time.
Specially When traveling or on business, it is the peak of working of these devices, so it appears that mobile is for talking , the digital camera is taking pictures,PSP video game playing time is energetically
And at this time the battery run out of power, make you feel very helpless and powerless. And you can not put each device is equipped with a extra battery. Not only have to spend a lot of money to buy a battery for each device.