Chad

Had a little debate with a pal, that told me that my xenon kit will turn my 98 A4 headlights yellow because of the heat. Several people had told me that xenons give out less heat than a regular halogen bulb. Is that true, I'm a bit confused because I would think that if it's brighter and there is more light there will be more heat doesn't that make sense, maybe there's some scientific explanation to this. Please help!

I know this xenon issue is getting old, but one more issue wouldn't hurt and I know you are all my friends and would be more than willing to help.

DingDingDao

Okay, this is how I understand it...if there's any misinformation in what I say, please correct me with my thanks...

Normal halogen headlamps work off the same sort of principle that light bulbs in your home do. There's a filament, usually made of Tungsten (W) that is heated using electricity to give off light. In cars, where the light output is usually pretty high, this requires a fairly large amount of electricity to keep the bulb lit.

Xenons, or High Intensity Discharge (HID), headlamps have bulbs that basically consist of a sealed bulb filled with a noble gas (in this case Xenon) and two prongs spaced a short distance apart. These two prongs create an electrical arc (essentially a short piece of lightning) that excites the atoms of Xenon, causing the electrons to increase their energy a quantifiable amount (a quantum level, I believe). When these electrons return to their normal state, they release the extra energy in the form of photons, and for Xenon that light is pure white.

For HIDs, then, initially creating the arc (when you turn the lights on) requires a very large amount of electricity (something like 50,000 to 60,000 volts). Once the arc has been created, however, it takes a very small amount of energy to maintain the arc, and so during normal operation the Xenon unit actually consumes less electricity than an halogen lamp.

That's how I understand it...if I'm wrong with anything, again, please correct me. Hope this helps!

Jason Guu
98.5 A!2.8 (HMIIs, HIDs, H&RCOs)

Chad

than halogen bulbs, I'm pretty sure that it uses less energy I read it somewhere. I kind of knew how xenons work although I was unsure if it gives more heat or not, because I know that if I would replace my bulbs with a 100+ watt halogen bulb, it will turn my plastic headlight lense yellow because of the tremendous heat. That's the main reason I want to find out about the heat level comparison.

Your explanation sounds legit although I only know the general explanation of how it works not too much of that electrons and protons that you mentioned. I also know that they use xenon because it could handle tens of thousands more volts than halogen without getting blown, which is required to provide the bright light when bulb is ignited.

Just for reference I looked at my Phillips ballast it had something written 23k v max if that means anything, maybe 23000 volts maximun

I really appreciate you're feedback, but I want to know if xenons really produces less heat.

Chad

1.8TQ99.5

Magnesium, for instance, burns a blinding bright-white but is actually considered cold-burning; it produces very little heat.

The brightness of the light is determined strictly by the amount of photons in the light beam. The color is determined by where in the frequency spectrum the light wave is.

Regular bulbs get hot because they rely on light produced by the heating of the filament.

Xenon and similar lights (such as lasers) rely on exciting gas atoms into a higher energy level and focusing the emitted photons that are produced when the atoms return back down into their stable state. This does produce some excess heat, but it's negligible compared to the regular bulbs (although huge industrial lasers do require cooling.)

That's all for the physics lesson.

Chad

Thanks for the lesson, a lot learned

Peter L

Hella quotes startup discharge of the ligts at 28,000volts still alot but not 60,000 volts

ModifiedA4

In an applications sense..its about efficiency.

Lower heat = more efficient (i.e. more energy going to the desired effect..light generation)

ChrisR

Keith J

Halogens must run hot, otherwise the depositation/revaporization cycle wouldn't happen. This cycle prevents that dark film from forming on the inside of the envelop. Ordinary non-halogens run at lower temperatures to prevent the filament from vaporizing rapidly but still suffer over time.

Now, back to the original thread, higher heat alone can not turn the polycarbonate material yellow but the increased UV from HID's could. Polycarb is fairly resistant to heat, aside from thermal cycling causing partial depth cracking (crazing). If the heat is high enough to damage, it would partially melt the polymer. UV is destructive to many polymers although some like polystyrene only suffer surface effects. Non-aromatic polymers, like polycarbonate, are effected at depth.

kj