6Pac - the 9v lit the lights but they were dim, so I will need a little more power. I may try the 12V idea as Hoozie mentioned.

Hoozie - I looked for another set of lights, it seems only the higher end (20 a string) have the rectifier. I will keep looking. I contacted that company you linked the video from. They won't help as I didn't buy the lights from them and can't give advice on a product they didn't sell. I will try the car battery - I have some lawnmower batteries around and try that. I'll keep the link to the rectifier in mind next. I don't know why I can't find the simple inline rectifier as that is used in all these light sets... it is like a trade secret or something!