Bi-Xenon headlights become less bright over time?

[c4s jim]

I have a 2002 C4S that I've owned for about 7 months. It has the bi-xenon headlights, but from the beginning I've found them to be far less bright (how far directly in front they'll effectively illuminate) then I would have expected. When driving at speed at night on a curvy road, it's far too easy to "outdrive" the headlights and not have enough advance notice of which way the road is curving.

Does anybody know if the bi-xenons can become less effective with age? (could the bulbs themselves slowly be depleting the xenon gas, or could it be the ignighters maybe?)

My previous car was a 2001 Audi TT with xenon headlights; when new, they lit up the night just like it was daytime and they were effective over a very long distance. After 4 years and 90,000 miles I swear that they became far less bright (or was it just my imagination?).

Edited January 20, 2006 by c4s jim

[nycebo]

You're right: it happens. Though oddly enough, my 2000 cab xenons still seem good though in truth, the lights aren't often used since the car only has 8000 miles. So, perhaps instead of age, it has more to do with usage. How many miles does your car have?

[c4s jim]

You're right: it happens. Though oddly enough, my 2000 cab xenons still seem good though in truth, the lights aren't often used since the car only has 8000 miles. So, perhaps instead of age, it has more to do with usage. How many miles does your car have?

About 35,000.

[wingless]

Yes, the intensity of Xenon lamps drops with usage. Internal to the lamp, the electrodes erode, the arc moves and deposits form on the optics, all contributing to the decrease in intensity.

[Costa]

The intensity will decrease over time somewhat - but mainly due to spectral drift of the light outbut towards the shorter wavelengths (Towards the blue/purple end which to the human eye looks less intense).

The number of cold and hot starts the lamps are made to cycle through affects the lamps ageing more than anything else.

[rcg412]

The intensity will decrease over time somewhat - but mainly due to spectral drift of the light outbut towards the shorter wavelengths (Towards the blue/purple end which to the human eye looks less intense).

The number of cold and hot starts the lamps are made to cycle through affects the lamps ageing more than anything else.

Can you replace the lamps? is this a RTFM I have a 01 996 with litronics.

[Costa]

Yes the lamps can be easily replaced - refer to your owners manual on replacing the lamps.

The lamps are just a simple one piece affair and to the casual observer they almost look like a normal halogen type lamp.

[wingless]

The intensity will decrease over time somewhat - but mainly due to spectral drift of the light outbut towards the shorter wavelengths (Towards the blue/purple end which to the human eye looks less intense).

The number of cold and hot starts the lamps are made to cycle through affects the lamps ageing more than anything else.

As defined in the PerkinElmer Cermax Lamp Engineering Guide, page 7, there are almost imperceptible shifts in the color temperature throughout the life of this Xenon lamp.

However, the decrease in intensity, is documented and measurable. The deposition of electrode material onto the internal reflector and window is described on page 31.

The movement of the arc is shown on page 10. Small changes at this location in the optics translates to large changes where the lamp illuminates.

[Costa]

Automotive Gas discharge lamps usually have a slightly different mix of gases and composition compared to other dischrge lamps.

This is mainly to allow repeated hot and cold starts etc which the lamps may have to put up with during their use in vehicles. Another factor is the requirement of having full output after switch-on in a short time. Note that when you turn your Xenons on they appear to be not very bright and also appear to have a purply/blue cast to them. After approx 30 secs or so they are reasonably white and when they have been running for 5 minutes or more they seem even brighter again.

Material deposition on the electrodes is what tends to reduce the life of Xenon lamps in automotive uses, but you will find that most of the current range of automotive lamps have a life of around a few thousand hours.

[wingless]

The intensity will decrease over time somewhat - but mainly due to spectral drift of the light outbut towards the shorter wavelengths (Towards the blue/purple end which to the human eye looks less intense).

The number of cold and hot starts the lamps are made to cycle through affects the lamps ageing more than anything else.

Automotive Gas discharge lamps usually have a slightly different mix of gases and composition compared to other dischrge lamps.

This is mainly to allow repeated hot and cold starts etc which the lamps may have to put up with during their use in vehicles. Another factor is the requirement of having full output after switch-on in a short time. Note that when you turn your Xenons on they appear to be not very bright and also appear to have a purply/blue cast to them. After approx 30 secs or so they are reasonably white and when they have been running for 5 minutes or more they seem even brighter again.

Material deposition on the electrodes is what tends to reduce the life of Xenon lamps in automotive uses, but you will find that most of the current range of automotive lamps have a life of around a few thousand hours.

Is there any documentation that supports this information?

[wwest]

There is NO reflector integral to HID lamps/"bulbs" for automotive use.

The "ignitor"/ballast module maintains the arc current flow at a constant level throughout the life of the bulb so there is no brightness variation due to the arc itself. Yes, the arc may move over the life of the bulb but not even 10% of that of an equivalent incandescent filamant bulb.

Any deposition of material, assuming there is some, on the inside of the glass encapulation would quickly result in failure of the bulb due to the level of heat then trapped within the encapsulation.

[wingless]

The "ignitor"/ballast module maintains the arc current flow at a constant level throughout the life of the bulb so there is no brightness variation due to the arc itself. Yes, the arc may move over the life of the bulb but not even 10% of that of an equivalent incandescent filamant bulb.

Any deposition of material, assuming there is some, on the inside of the glass encapulation would quickly result in failure of the bulb due to the level of heat then trapped within the encapsulation.

Is there any documentation that supports this information?

[Q-Ship986]

Is there any documentation that supports this information?

You might try here...Philips Automotive Lighting Forum

--Brian

[wingless]

Is there any documentation that supports this information?

You might try here...Philips Automotive Lighting Forum

--Brian

Thanks, on that web site, or somewhere else on the Internet, is there any documentation that supports this information?

Is there a specific link to an engineering design guide or a manufacturer's data sheet, or any other technical document that supports this information?

[Costa]

Is there a specific link to an engineering design guide or a manufacturer's data sheet, or any other technical document that supports this information?

Yes there is documentation right in front of me actually. An article appeared in an electronics magazine here in Australia (Silicon Chip) May 2003 edition which described in-depth how HID (High Intensity Discharge) lamps operate.

It covered the Bosch and Hella Reflector + Projector systems and the Philips bulbs (D2S, D2R, D1S and D1R).

Excerpt from one paragraph talking about the life of the lamps: "Tungsten from the electrodes gradually blackens the inside of the globe, a process that is greatly accelerated during cold starts. Manufacturers specify lamp life at up to 3000 Hours, which includes a 'typical' number of cold starts."

The article covers the operating/controlling igniter (ballast) operations in depth.

I assume the article is copyrighted so they would not be too happy if we placed it on Renntech.....

(but I could probably scan a copy for your private email address)

Edited January 24, 2006 by ZX7R

[wingless]

Please send me the document. Thanks.

[wingless]

Yes there is documentation right in front of me actually. An article appeared in an electronics magazine here in Australia (Silicon Chip) May 2003 edition which described in-depth how HID (High Intensity Discharge) lamps operate.

I assume the article is copyrighted so they would not be too happy if we placed it on Renntech.....

(but I could probably scan a copy for your private email address)

Please send me the document. Thanks.

Could I please get this document?

[Costa]

Please send me the document. Thanks.

I was away from home the last couple of days so I did not get a chance to scan it in etc..

Anyway I have just scanned it in and forwarded onto your email address supplied - There should be 7 pages in total approx. 300Kb each in jpg format.

[wingless]

I assume the article is copyrighted so they would not be too happy if we placed it on Renntech.....

(but I could probably scan a copy for your private email address)

Please send me the document. Thanks.

I was away from home the last couple of days so I did not get a chance to scan it in etc..

Anyway I have just scanned it in and forwarded onto your email address supplied - There should be 7 pages in total approx. 300Kb each in jpg format.

Thank you very much for sending me the document. It contains lots of useful information.

This document, titled: “HID Headlights – how they work” may be purchased from the publisher, Silicon Chip. I requested permission from the publisher to post that article here, but they declined.

This is mainly to allow repeated hot and cold starts etc which the lamps may have to put up with during their use in vehicles. Another factor is the requirement of having full output after switch-on in a short time. Note that when you turn your Xenons on they appear to be not very bright and also appear to have a purply/blue cast to them. After approx 30 secs or so they are reasonably white and when they have been running for 5 minutes or more they seem even brighter again.

That is correct for the metal halide lamp, not the Xenon. According to the article, in the metal halide section, “Initially, the tube emits a dull bluish discharge but as heat from the arc vaporizes the mercury (and other metals) and the pressure increases, it changes to a brilliant white.”

Yes, the intensity of Xenon lamps drops with usage. Internal to the lamp, the electrodes erode, the arc moves and deposits form on the optics, all contributing to the decrease in intensity.

Any deposition of material, assuming there is some, on the inside of the glass encapulation would quickly result in failure of the bulb due to the level of heat then trapped within the encapsulation.

As previously stated, this does not agree with the PerkinElmer Cermax Lamp Engineering Guide, page 31.

This also disagrees with the article which states the Xenon lamp blackens, “In particular, tungsten from the electrodes gradually blackens the inside of the tube”.

Of particular interest to me was that the lamp drive is not unipolar, with a specific polarity, with the lamp having an anode and a cathode. Instead, the lamp has a bipolar drive, with the electrode polarity being reversed using an H bridge.

The Cermax and XBO lamps that I have used both have unipolar drives.

[Costa]

Of particular interest to me was that the lamp drive is not unipolar, with a specific polarity, with the lamp having an anode and a cathode. Instead, the lamp has a bipolar drive, with the electrode polarity being reversed using an H bridge.

The Cermax and XBO lamps that I have used both have unipolar drives.

Driving lamps etc with AC rather than is quite common in preventing problems with material deposition etc. Valves, CRTs, and various other electron tube devices driven off DC suffer from these issues over time. Mainly due to the buildup or removal of electrons from a particular surface (eg Anode/Cathode/ plates and even heater filaments in valve assemblies etc). This problem is much worse for higher current devices (more electron flow). Using AC drive (where possible in the design) can alleviate the issue to some degree as you do not have continuous high electric fields present between metals etc in one direction only.