Bi-Xenon headlights

[david480]

Apparently my newly acquisitioned C30 has bi-xenon headlights which was supposedly quite a desirable option back in the day, although I am sure most new cars have them now. This is the first car I have ever owned with this feature and there does seem to be a substantial improvement over std halogen ones. I was just wondering what exactly is the technology used in these lights, is there an actual filement bulb somewhere in there or is it completely different altogether?

[Tannaton]

Originally Posted by david480

Apparently my newly acquisitioned C30 has bi-xenon headlights which was supposedly quite a desirable option back in the day, although I am sure most new cars have them now. This is the first car I have ever owned with this feature and there does seem to be a substantial improvement over std halogen ones. I was just wondering what exactly is the technology used in these lights, is there an actual filement bulb somewhere in there or is it completely different altogether?

The Xenon bit means it is a gas discharge bulb - so no filament - just a tube of gas that glows when it is energised.

The "bi" bit means that there is only one lamp which does both the high and low beam - a mechanical baffle moves in the light fitting to change the beam when you switch between the two.

Have a look on wikipedia#

[theshadow27]

Bi-xenon uses a type of Gas Discharge Lamp (GDL) called High Intensity Discharge (HID) to differentiate them from the sodium vapor street lamps.

The HID bulb is a type of arc lamp which means there is no filament, but instead two tungsten contacts within a quartz envelope filled with xenon gas and a small amount of mercury and metal halides.

An electronic controller called a "ballast" converts the 12V DC electrical power in the car into voltages appropriate for this bulb. First, it strikes an arc across the electrodes, like an ignition coil, to create a plasma within the capsule. Then, it uses constant-current control at ~85V AC to keep the bulb lit.

The bi-xenon bit refers to the electromagnetic actuator that moves the shield out of the way when you engage the main beams. This allows more light out of the projector.


The main advantage is increased efficiency, 35W of power in HID puts the same light as 100W or so in a Halogen incandescent bulb. They also have a much whiter spectrum that is closer to daylight. They also last much longer, e.g. 2000hrs in D1S vs 600hrs of an H7 bulb, which reduces "overall emissions" metrics for manufacturers.

Pretty cool stuff

[phil1968]

It's a bit like having a spark plug inside your headlamp, except that the spark is constant, like an arc welder. Similar voltages too, circa 30,000 volts to the electrodes, 12 volts from the car battery gets stepped up to high voltage in the ballast. If you fit aftermarket HIDs to a car that previously didn't have them you'll notice that there is what looks like an ignition HT lead connected between the ballast box & bulb -well that's exactly what it is

[Bonefishblues]

Magic Pixies live in a special little house under your bonnet, and on command they use special pixie dust to light the way. Presumably yours also has the "make a wish" button on the lighting panel - that's them too.

...or what the others said.

[Tannaton]

Originally Posted by phil1968

It's a bit like having a spark plug inside your headlamp, except that the spark is constant, like an arc welder. Similar voltages too, circa 30,000 volts to the electrodes, 12 volts from the car battery gets stepped up to high voltage in the ballast. If you fit aftermarket HIDs to a car that previously didn't have them you'll notice that there is what looks like an ignition HT lead connected between the ballast box & bulb -well that's exactly what it is

20kV to 30kV is the "strike" voltage for the lamps - i.e. the voltage needed to initiate the arc in a cold lamp. Once the arc is established and the lamp warmed up the running voltage is circa 85v. AC current is used so that both electrodes wear evenly. The point to note is that the "open circuit" output from the ballasts is very high - just like the ignition circuit on a petrol car - not something you would want to experience.

[Tannaton]

Originally Posted by Bonefishblues

Magic Pixies live in a special little house under your bonnet, and on command they use special pixie dust to light the way. Presumably yours also has the "make a wish" button on the lighting panel - that's them too.

...or what the others said.

I prefer this explanation actually.... because you can now get different colours of pixie dust (i.e. white dust is 5000k, blue dust is 8000k etc.)

[Nmack]

Are these bi xenon headlights or bulbs expensive to replace when there blown

[Bonefishblues]

https://www.powerbulbs.com/store/cat...1r/fitting/d1s

As an example. Lots of fakes around AIUI so be careful where you purchase.

[Tannaton]

Originally Posted by Nmack

Are these bi xenon headlights or bulbs expensive to replace when there blown

If you go to the dealer - yes - if you use the website above - not so much...