You can use a regular five to ten watt solar panel and a car usb charger to charge your smart device. First you take the positive and negative lines from the solar panel and hook them up to the positive and negative terminals on the replacement 12v socket. Then you plug the usb car charger into the socket and plug your smart device into the charger. Point your solar panel at the sun and enjoy the advantages of charging purely off of the sun! If done right, you can even use this method to charge your laptop too.