One of the requirements for riding off-road at night is a good set of lights. The definition of "good" varies but more light is always better. Good battery life is also very important; there's no point having lights that die on you when you're two hours from home.
I can't afford, and cannot justify spending up to £1000 on a set of bike lights, so I looked at a DIY/homebrew solution. I wanted a small(ish) system with good runtimes and good light. I have no complicated multicharger, so off-the-shelve AAs were a good choice. There are plenty of websites detailing DIY halogen lights, but halogens are more power hungry and so need bigger, heavier batteries to get the required runtime.
Using a couple of 5 watt Luxeons, Downboy Converters and some small torches from eBay, I was able to make a very reasonable twin lamp system: one bar mounted and one helmet mounted. The battery holder was from Maplin. Handlebar QR clamp was £3.99 from CRC.
I used the lights in the Dusk Til Dawn race and apart from a focusing problem, caused through lack of pre-race testing, they performed well. I have since sorted the focus. I ran both lamps (on a local ride) off the same partially