General Question: Why is HID so expensive?

[alecmuffett]

Hi All,

A general question from my observations: Why is it that all HID lighting systems are so expensive? I am motiviated to find out having learned that this goes for both Motorbike and Bicycle systems, that as soon as you move out of the realm of LEDs and incandescent bulbs then something magical happens which multiplies the cost tenfold.

For instance browse

http://www.rei.com/online/store/Search?vcat=REI_SEARCH&storeId=8000&query=hid

- bicycle lights start at USD20 through 70+, and then skyrocket to 500+ when HID is mentioned !

I am beginning to wonder what's the deal? Do they contain compact nuclear reactors? Do the circuits carry several thousand volts? Are computers required to drive them? Are they made from purest platinum, and lined with panda intestine?

Or perhaps is it just a rip-off/"what the market will bear" situation?

 

[Droopy Dick]

Hi All,

A general question from my observations: Why is it that all HID lighting systems are so expensive? I am motiviated to find out having learned that this goes for both Motorbike and Bicycle systems, that as soon as you move out of the realm of LEDs and incandescent bulbs then something magical happens which multiplies the cost tenfold.

For instance browse

http://www.rei.com/online/store/Search?vcat=REI_SEARCH&storeId=8000&query=hid

- bicycle lights start at USD20 through 70+, and then skyrocket to 500+ when HID is mentioned !

I am beginning to wonder what's the deal? Do they contain compact nuclear reactors? Do the circuits carry several thousand volts? Are computers required to drive them? Are they made from purest platinum, and lined with panda intestine?

Or perhaps is it just a rip-off/"what the market will bear" situation?

They do indeed work with very high voltages, in the order of 20,000 or so.

But they draw very little current.

The lamps seem to retail for around £60-70 or so.

Goodness knows what's in the ballast units..

But you can buy a single unit from hids4u.com for around £100.

 

[dirtydog]

The lamps are expensive due to the use of Halide gas. We were messing about with some big HID lamps at colloge last night, impressive stuff!

 

[birdseye]

Biggest influence - they are the latest "must have". And if you "must have" you "must pay"!

Bling = wodge.

P.S. If halogen gas is so expensive, why are neon lights, fluorescent lights, quartz halogen etc so cheap?

 

[Yoda]

The lamps are expensive due to the use of Halide gas. We were messing about with some big HID lamps at colloge last night, impressive stuff!

Does it make you speak like Joe Pasquale when you inhale?

Or does it kill you.

 

[unshift]

The lamps are expensive due to the use of Halide gas. We were messing about with some big HID lamps at colloge last night, impressive stuff!

i thought the expensive bit was the special startup controller that is needed to turn the "lamp" on almost instantaneously as opposed to it taking a while like say the streetlamps do

 

[Deleted account W]

I found this, interesting if you want to know what your buying, boring if you just like to think of electrickery as a magic that just happens

Whats in a HID Lamp?

Description of the Lamp / Bulb
This sort of lamp consists of a tubular outer bulb approx. 10 mm (.4 inch) in diameter which contains the arc tube (inner bulb). The outer bulb is made of special quartz such as cerium-doped quartz which blocks most ultraviolet, especially the more dangerous short and medium wavelengths as well as much of the 365-366 nM longwave mercury line cluster.
The arc tube or inner bulb is made of plain fused quartz and has tungsten electrodes with the distance between the tips approx. 4.2, maybe 5 millimeters (approx. or slightly under .2 inch). Its construction resembles that of a miniaturized short arc lamp, but true short arc lamps have a much more concentrated arc.

The arc tube has xenon gas in it at a couple of atmospheres to maybe a few atmospheres when cold and a few to maybe several atmospheres when hot. There is also mercury in the bulb, and when it is vaporized the mercury adds at least 20 atmospheres of pressure for a total pressure of around or maybe even over 30 atmospheres.

Metal halides - salts - are also in the arc tube. The formulation in automotive HID lamps includes sodium and scandium halides (probably iodides) and maybe traces of others such as lithium and thallium halides.

More ordinary metal halide lamps do not have high pressure xenon but have low pressure argon instead. The high pressure xenon is used to obtain some usable light output during warmup before the other ingredients have vaporized.

Theres a lot going on in those lamps

How do they work?

The electrical requirements of D2 type lamps are nasty. They require ballasts which are more difficult to homebrew than other ballasts. I strongly encourage hobbyists, do-it-yourselfers, and hackers to *NOT* try this. Try homebrewing a D2 ballast only if you have the patience of two saints, lots of electrical and electronic project skills including high voltage skills and skill in homebrewing high voltage transformers with the combined difficulties of flyback transformers and xenon trigger transformers, and a budget for replacing lots of blown parts before you get it working. You are better off buying ballasts from Osram, Bosch, or Aromat (a division of Matsushita) or others. For one thing, these lamps require special sockets made by few manufacturers and mostly sold only to ballast manufacturers.
The D2 types require a starting pulse. 7 kilovolts may on an average spark through these bulbs, but for reliability you need more, maybe 10 or possibly 12 kilovolts. Automotive use requires ability to restart a hot bulb with the mercury vapor pressure high, and this requires even more voltage - 12 to 15 kilovolts and maybe even more for good reliability. The usual ballasts supposedly produce starting pulse voltages like 18 kilovolts minimum, 20 kilovolts typical.

D1 types have an integral ignitor which the ballast has to work with.

Starting pulses must be repeated frequently until the arc is established.

The ballast must supply an open circuit output voltage - other than the starting pulses - of over 300 volts, preferably 400 or maybe preferably 450 volts - to force the arc to establish.

D1 and D2 type lamps are 35 watt lamps. Once the arc is established, the ballast must supply limited current or else the arc will draw extreme current and this will be bad for the bulb and/or other parts. The voltage across the lamp is normally around 80-90 volts when it is warmed up, but will be less during warmup. The ballast must handle a lamp voltage possibly as low as 16 volts early in warmup, although this voltage usually bottoms out higher - probably at least in the 20's of volts.

The ballast must deliver 35 watts to the lamp when the voltage across the lamp is between 70 and 110 volts. When this voltage is lower, the ballast must deliver at least .5 amp but generally no more than 2 amps and preferably as close to 35 watts as possible. Higher currents are preferred - a partially warmed up metal halide lamp sometimes has an unstable arc at lower current.

An automotive grade ballast often delivers boosted power (above 35 watts) at some times during warmup to give near-full light output. Note that a xenon arc or a mercury vapor arc does not produce visible light as efficiently as a metal halide arc does. Automotive grade ballasts with boosted power at some points of warmup have circuitry that models the thermal characteristics of the bulb. The maximum safe current for the bulb's electrodes must not be exceeded during a power boost during warmup.

A voltage across the bulb higher than 110 volts only occurs in the early stage of establishing the arc or if the bulb is failing. The ballast should deliver enough power to heat up the electrode tips enough for the arc to establish - more is better and over 35 watts is OK as long as the current is not excessive. But excessive power delivered to an aging bulb can cause the bulb to explode.

D1 and D2 lamps and most other metal halide lamps require AC. DC is tolerable briefly, and then preferably only if the bulb is cold. A DC electric field, hot quartz or hot glass, and salts or alkalis is not a good combination - electrolysis effects can occur which can create weak spots or cracks in the arc tube.

The AC delivered to a D1 or D2 type bulb usually has a frequency of a couple hundred to a few hundred Hz. Higher frequencies are probably OK with D2 types but the ignitors in D1 types may only work correctly or even be adequately conductive in a certain range of frequencies.

The AC current waveform in a D1 or D2 type lamp is traditionally a squarewave or close to a squarewave. Other waveforms have higher peak current for a given average current or RMS current, and the higher peak current is harder on the electrodes and may shorten the life or cause problems with the use of higher currents during warmup.

Metal halide lamps should not be overpowered, except where permissible for accelerated warmup and near-full light output during warmup. Overpowering one will shorten its life and increase the risk of the lamp exploding.
Underpowering a metal halide lamp is also bad. If the electrodes are not hot enough, they do not do a good job of conducting electrons into the arc and voltage drop in this process (known as the "cathode fall") is excessive. Excessive cathode fall causes positive ions in the arc to hit the electrode at excessive speed which "sputters" electrode material onto the inner surface of the arc tube. For more info on discharge lamp mechanics, look in my Discharge Lamp Mechanics File.
It is not recommended to experimentally operate metal halide lamps at reduced power. Besides the bad effects of high cathode fall on hot electrodes, an unusual temperature pattern can have the chemicals in the arc tube condense in locations that can block some of the light. And if the electrode cathode falls are excessive and unequally so, a DC electric field can result, which can cause destructive electrolysis effects on hot salts on hot quartz. This can cause the arc tube to crack.

Metal halide lamps should have power input within 10 percent of their rated wattage

Are they reliable?

Please note that D1 and D2 type bulbs operate at high temperature with great pressure probably near or over 30 atmospheres. The internal quartz arc tube temperature is probably typically around 800 degrees C (1400-1500 degrees F or so). The outer bulb is not this hot, but it is definitely burning hot. The arc tube always has at least some miniscule risk of exploding and should only be operated in a headlight housing or other suitable container. Improper operation increases the risk of bulb explosion.
The bulb must be clean and free of dirt, grease, organic matter, ash, salt, or alkali. Salts, ash, and alkalis have a tendency to slowly leach into red-hot and nearly red hot quartz which will result in strains, weak spots, and maybe cracks.

A metal halide lamp does not like frequent starting. D1 and D2 types can be blinked, but this should only be done for a limited amount of time. Starting causes wear on the electrodes. Excessive evaporation of electrode material will deposit it onto the inner surface of the arc tube which results in darkening and overheating of the arc tube. In D1 and D2 and some other metal halide lamps, there is a halogen cycle which cleans deposited tungsten electrode material from the inner surface of the arc tube. Prolonged continuous operation at proper internal temperatures is required for the halogen cycle to work.


So now you know