Going LED or HID will dramatically reduce the size and weight and cost requirements of a battery system. 2-4X the efficiency per lumen means 1/2-1/4 the energy storage needed.
However, there is something to be said for good ole incandescent lighting, which many people prefer as it seems to really bring out the "3Dness" of your surroundings better, which can be important when you are in motion
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Here's some things to consider:
I assume you are thinking about using track-lighting style bulbs, like MR-8, MR-11, and MR-16 options. Which are primary available in 12V long-life halogen options. If you can come up with a simple housing for them with a ceramic socket in the base, (something already made, or made yourself), then you're all set. The cost of the actual light itself would be pretty low.... So then we have to figure out how it's going to be powered...
The tricky part is that, most 12V long-life halogens you are going to find at the hardware store, are not very efficient, and really not even very bright when driven to spec ay 12V. They are designed with long term installation in mind, with minimal bulb failures, (usually they are rated anywhere from 2000-6000 hours life). In order to boost the efficiency of the bulb, and make it worth running in a portable application, you need to crank up the voltage, and get the estimated bulb life down under ~100 hours. For most of these bulbs, this requires getting up around or over 18V. In the case of NIMH cells, that's 15 or more cells. When we overdrive the bulb, the current flowing through the bulb also increases, and the total wattage increases quite a bit overall, so you need lower wattage bulbs to start with, to overdrive, to get where you want to be....
Anyways... here's some ideas:
Have a high output and low output housing, one with a 10W, the other with a 20W bulb. These will be overdriven to almost exactly double that wattage on the higher voltage pack. The 10W bulb may not be available at your local store, so you might consider ordering from bulb-connection.com, or 1000bulbs, or one of the many other bulb suppliers online. It doesn't really matter much if you go with MR-11 or MR-16 or whatever, just depends on what you decide you think you'll like best, some of the "spot" versions of the MR-16s are going to have some more throw, so that might be worth taking into consideration if you travel at high speed a lot and need to reach out with that light.
The exact bulb and battery combination you choose is ultimately up to you, but just keep in mind that for any long-life bulbs, you will need more input voltage for them to work well...
If it were me, I think I would build a triple MR-11 setup. Using 6V 2000 hour MR-11 bulbs. I think I'd just use either 7 or 8 cell NIMH packs (would need to test the bulb's and see what they can handle).. I'd have a 5W, 10W, and 20W bulb on the bars, with a toggle switch on each, the ability to run any single light or combination of lights. I'd probably build the pack from F size cells. (14AH capacity). That would be enough to run the 10W bulb (overdriven to ~20W) for over 6 hours. Or the 20W bulb (overdriven to 40W) for about 3 hours. Might consider a spare pack mounted somewhere else that the cord could be switched over to of needed.
Eric
