The LET-10i is a portable charger for your iPhone or IPod device, including the iPhone 3Gs. The unit itself is a portable battery, which charges using the solar panel, or an electrical outlet via USB. The charged battery is then plugged into your iPhone / iPod for when you run out of power. The device can recharge with a USB cable or with the solar panel, however the solar panel takes a long time, and it is recommended to use the AC/DC power charge option, and the solar panels only in an emergency situation. If you like this product let us know, leave a message and we will relay the good ideas to the manufacturers.