lotec said:
doesnt a bi xenon light take up to 22 000 volts or something insane like that thus you cant just whack them in any light they need to be specially designed and have a power converter thingo etc etc etc?
Gotta be careful with the whole 'xenon' thing. can have more than one meaning.
You can buy 'xenon' replacement globes (in H4 etc) for any car. But these are just a Halogen globe (which is 99% inert gas and 1% halogen gas, usually iodine vapour) but with xenon added as the inert gas instead of argon, nitrogen or krypton. It gives a higher colour temperature (how white it looks) and slightly more brightness (only a little though) but being whiter they look brighter than an older halogen.
the other type (like on BMWs etc) are Xenon Gas Discharge. A HID (High Intensity Discharge) light just like HID bike lights! More powerful of course but exactly the same technology.
These do not have a filament like normal globes, but strike an arc to produce their light. To initially strike this arc requires anything from 6000V - 20000V. Cars generally use a 35W globe, which requires a starting voltage of at least 7kV. Because they need to start reliably and hot (ie after they have been on and get turned off) the ballasts can usually support up to 20kV.
(this is the reason you can't turn HID bike lights on and off. When the lamp has been on, and vapour pressures are high, you need a higher starting voltage. Small HID ballast systems in bike lights can only support a cold start. Still around 6kV though)
In short, XGD/HID lights are brighter, use less power and have a 'whiter' light than halogen, but are more expensive.