Hey, I just realized I AM using halogen automobile driving lights and a sealed lead acid battery literally strapped to my rack. It appears that Operator's worst fears have already been realized!

VR, sorry, I forgot to address your question about using the LED light with an 18V battery. I have noticed that some of the LED lights have pretty wide operating voltage ranges, like 6 to 27 volts. However, others, like the MR16 LED replacements sold by superbrightleds.com state a 9-14 VDC range. You really have to check. If I can find any more specifics I will let you know.

Thanks for the link to scienceforums.net. That's just what I need, ANOTHER internet site to suck my time!