Pete,
Glad to hear the lamp arrived. Let me know what you think. I put in the 36 degree flood version of the same lamp. I like it better than the 8 degree spot. I have always preferred spots because they concentrate the light from lower wattage bulbs. With the 35W equivalent lamp the flood works great.

Here is a progress report. I made my battery box and tried it out yesterday. It seems to work quite well. The box is a 6x6x4 weather resistant electrical box. It is light but quite sturdy plastic with walls a little over 1/8" thick. The brand is Carlson (or Carlton). I got it at Lowe's. I knew my 5 AH battery would fit easily, and I was hoping I might even be able to get my 7 AH in there, but it doesn't quite make it. If the walls didn't taper slightly it would work. Nor will two 5AH batteries fit. Oh, well. I installed a regular lighter type socket and a push button switch with weather resistant boot. So what I now have is basically a universal 12V 5AH power center that I can plug anything into - lights, cell phone, etc. I glued a piece of mouse pad in the bottom of the box and laid the battery on its back. I also put a large patch of industrial on one side to secure the side of the battery to a box wall. Then I took an old mouse pad and folded it enough times to get a snug pressure on top of the battery when the top is screwed down. Lemme tell ya, I don't think that battery is ever going to move from bumps in the road! I shook it as hard as I could in ever direction, and it never budged. Keeping everything snugly in place is an obsession with me.

To mount the box to my rack I first glued two layers of mousepad together face to face for a shock absorber then made a simple but effective system of innertubes tight enough that, again, nothing is going to budge. I went through some pretty bumpy spots last night and and everything stayed firmly in place.

Another benefit of using the standard 12V socket is, as Pete knows, you can unplug the lights and plug the charger right in. For those concerned about my charging the battery in a sealed box, have no fear. I drilled several small holes, angled upward, just under the lip of the lid. They should provide ventilation without allowing water to enter. Since the socket and plug don't look as weather resistant as I would like, I am going to make a little cover out of cordura to wrap over the box. This will serve two purposes, it will provide all the weather resistance I need and have the added benefit of camouflaging the box somewhat so that it just looks like a little rack trunk or something.

Now that my power unit is done I can move on to experimenting with taillight arrangements. I still want to develop a little more sophisticated mounting system for the box. The inner tube arrangement works fine, but lacks elegance. Hey, I may be a geek, but I have some pride!