Update 24th Auguest 2010. The headlights (drawing 110W total) were becoming a pain. A pain especially to the small 12V battery I have for running the car electrics (turn signals/horn etc). So I have changed the headlights to use standard household Compact Fluorescent Bulbs. I chose the 9W bulbs (light output of an incandescent 40W).

My battery pack runs at 96V nominally and so I tested to see if CFLs (normally working at 110V AC) would light with 96V DC - well, they work just fine. I checked to see if they would dim a bit as the pack voltage sags during acceleration but they dont dim and more importantly, they dont flicker out either.

Since the CFLs work on 96V DC it means that I can use the whole pack to power the lights (not that 18W @ 96V is drawing a lot of current). In this way I still dont have to have a DC-DC converter - I can just wire up a circuit using the whole pack. The stress of running the headlights is evenly distributed over the whole battery pack.

The next stage was to wire up a 96V DC supply and a socket to plug the wires from the headlights (plus an inline switch, of course).

Next I took out the old headlight (a sealed beam standard 7" round unit) and carefully ground out the internal bulb components. With a diamond 4" angle grinder attachment this was much easier than I had expected - it only took 2 minutes to produce a ragged but mostly circular hole. Rather fortunately, this hole is pretty much the perfect size for a CFL curly bulb.

Next was to mount the bulb holder in the shell of the light housing. The housing is made of metal so a couple of holes and some self-tapping screws made this job easy too. Another hole drilled and grommetted for the wires to come through from the 'engine' bay and a bit of soldering to join the wires together and the job was practically done.