Just so you know...I was at Wal-Mart the other day, and noticed several different sized solar panels used to charge car batteries. They were sealed, water, and impact proof in a frame, and varied in size form about 12 inches by 4 inches, to about 12 inches by 12 inches. They seemed VERY RUGGED, and were VERY CHEAP, the most expensive being around $30.00. They also had a led, that turned on when charging. I use one of the smaller panels to trickle charge a small motorcycle battery between uses on a hovercraft that I own. For that, it keeps the battery fresh, and ready to use ALL THE TIME. Just in case anyone was looking for Large, inexpensive solar panels for a project. Kim