12 volt solar charger

Has anyone tried using one of the cheap, 12v battery solar chargers Harbor Freight sells? http://www.harborfreightusa.com/usa/itemdisplay/displayItemList.do?search.keyword=solar+charger I notice on the product description it says: "Compensates for small steady battery drains" Does that mean...

I see these 12 volt solar chargers all over now at camping and sporting good stores, and they are cheap! You can buy one anywhere from $20-$35 depending on the brand. I know they are used to charge car and boat batteries, but I was wondering what else could these be used for? Can you power...