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Automotive HID vs LED

35W 4300K "OEM White" D2C HID Bulbs
Soon to Replace the 6K Bulbs in Astro
Brighter, longer life, less energy, HID is better than halogen in every way that matters! For now HID is even superior to LED for reasons discussed in this posting. 

HID is still the premiere choice for high brightness mobile lighting solutions. 3000hr lamp life of an Automotive HID bulb is 3x better then that of a halogen headlamp. A 35w automotive HID bulb can throw out up to 3600 lumens, roughly 5 times more light than a 55w halogen automotive headlamp bulb. Good forward illumination makes driving in the dark safer, and thus high output automotive HID is still the best choice for exceptional optical performance and safety.

Pay special attention the HID bulbs if you handle them during a retrofit or replacement. Your fingers contain perspiration, oils and acids that can destroy the bulb if your skin contacts the bulb during installation. If you accidentally touch the glass portion of a HID bulb make sure to wipe it down with alcohol and a soft cloth to remove the skin residue that could otherwise cause the bulb to explode or fail prematurely. 

The technical dynamics of HID bulbs are interesting. At their full operating temperature the inner bulb package can reach 1500 deg F and the can achieve gas pressures in excess of 400 psi. HID bulbs are also specially designed to operate in the horizontal position, and as such operating a HID bulb outside of the headlamp assembly can cause it to malfunction, fail early or explode. The high temperatures, high pressures, and high voltages in an HID system make it hazardous to handle, so make sure everything is powered off during a retrofit or installation of HID systems. If you do not have the technical skill, time and tools needed to safely replace your HID bulbs, take your vehicle to a professional mechanic for the work.

Look and the difference between HID and Halogen

Image Credited to "Click for Source URL"
LED headlight?

High brightness LED chips require very sophisticated heat-sink solutions  and complicated driver circuits. This has so far prevented LEDs from being integrated into an automotive headlight bulb package as a replacement bulb for Halogen or HID bulbs assemblies. The small bulbs in automotive headlights cannot provide enough room for anything other than a very costly liquid cooling solution for an LED. This means that LED headlight assemblies have to be custom designed to take advantage of the current LED chip thermal and optical limitations. Special headlights in high end Mercedes, Audi, Lexus, Porsche, and other luxury vehicles now have LED based DRL lights arranged in special line arrays of interesting profiles and shapes that give each vehicle a distinctive appearance. In most of these high end applications the LED DRL lights are combined with a HID projector setup to give the best of HID with state of the art LED technology in a combined headlight package. 

Note the LED Headlights
Note the LED DRL Lighting
A Legacy of LED in Automotive Applications

Automotive LED bulbs have primarily been used as runner, signal, brake, indicator and marker light applications. Some recent high brightness automotive LED's have been used as daytime running lights in niche luxury vehicle segments, while prototype Audi vehicles have shown full LED headlight assemblies in use. The automakers have been slow to adopt LED headlights because of technical and cost problems that are only now being solved. We should start seeing high brightness LED headlights out on the roadways in the next several years.

LED brakes lights are already displacing traditional solutions in mainstream vehicle segments. LED can be illuminated faster than any other lighting technology, giving rise to brake lights that illuminate quicker, for a slightly more responsive warning light to the following vehicle. LED brake lights are safer because they can light up faster! If you look carefully you can see all sorts of cool LED brake light assemblies in modern vehicles. Toyota for Example has been using LED in the brake light assemblies of the Prius since 2004. In the second generation Prius 9 high brightness red LED's project against engineered reflectors to form the rear brake light, and it lights up fast (about 1/4 of a second faster than any other lighting technology) which gives following drivers a little bit of extra time to react to the brake lights. 

2004-2009 Prius Brake Lights Utilize red LED's
As low output indicator lights LED's are hard to beat and they have been used in this capacity since they first became commercially available. In these "low light" applications LED's can last more than 50,000 hours of operation. With minimal heat production, low energy consumption, and extremely long life, LED's provide the best lighting solutions for indicator lighting applications.

The LED Future

There are currently single chip LED's that can throw out 2500 lumens, like the SST-90 from Luminus Devices.  Unfortunately these exotic LED chips require elaborate cooling solutions and are cost prohibitively expensive as a result to use in mainstream real world application. Luxury vehicle segments manufacturers are making use of LED headlamps that cost thousands of dollars, and some day that technology will trickle down to cars, bicycles and flashlights. In some ways high performance LED lighting technology is already proliferating into lower cost vehicles, flashlights and even interior BR30 and A19 bulb replacements. 

I currently use a $9 LED headlight solution on my bicycle, and while it is bright (~45 lumens), the output is not enough to light up the road well, but does increase my visibility while giving somewhat functional short distance illumination of the roadway for low speed functionality. In my home LED lighting has completely replaced CFL lights from a few years ago. 

Today the high output Halogen and HID automotive bulb market is strong but in the future LED's will overtake these older technologies. Given the technical problems associated with cooling high output LED's I imagine it will be several more years before a feasible LED replaces the 35w HID solutions currently used in high brightness headlight applications.

It took decades of technological innovations for HID lighting technology to migrate into mainstream commercial automotive applications. Large format (250-1000W) HID bulbs with magnetic ballast have been around since the 1960's. It was the development of compact digital instant re-strike ballasts and ultra-compact HID bulbs that enabled automotive applications of HID. Since their introduction in the late 1990's, 35w HID headlamps have proven to be highly reliable, highly efficient, and functionally superior to the legacy halogen technology.

Astro's Lights Reconsidered

Long enthused with HID I ordered the tech package on Astro the Prius way back in 2005. It shipped with a very expensive setup. After a few years I swapped out the 4300K OEM DR2 Hid lamps with 6000K aftermarket bulbs (a fairly involved mechanical procedure unfortunately). The OEM ballasts continue to function and I located some fairly priced ($120) replacements on Amazon should one of my factory units ($600) burn out.

I recently ordered some Korean D2C 4300K bulbs from Amazon ($33 for the pair O.o with free shipping- See picture and link at the top of this posting) and installed them. While the 6000K blueish light of the aftermarket bulbs I installed a few years ago was fun (cool), the blue hue of the light actually reduced net usable illumination a fair amount. 

For practical safety reasons I went back to the warmer 4300K color, and the D2C bulbs from Amazon work great. They are at least 2x brighter than the old bluish bulbs and produce a crisp cool white color that is really vivid and clear. After performing the bulb replacement late this evening Meg and I took Astro the Prius out for a spin down a dark road and were both very impressed with the dramatically improved forward illumination provided by the new relatively inexpensive 4300K HID bulbs. 

Special thanks to Maxlux & Amazon for the fairly priced quality HID replacement bulbs.

Back to Incandescent in Certain Cases 
When I first got Astro the Prius I was so excited about high efficiency LED's that I went to and ordered a complete retrofit set to change out all the OEM incandescent bulbs in Astro to LED.

After about a year some of the festoon shaped LED bulbs in the cabin went out and I never replaced them. The little 168 marker light LED's also died early and I reverted to the OEM bulbs that shipped with my car.

In 2007 I was issued a citation to change my front turn signal bulbs 7440red LED's back to amber, and simply replaced them with the OEM 7440A that I had saved way back when. The rear turn signals are still red LED's as this is permissible by the law, and those old red LED blinkers are still working great.

My backup lights 7440 were also retrofitted to 6500K blue white 9 LED units way back when and they still work but last night I swapped them out for some $8 Made in Japan Sylvania LL bulbs that are much brighter. My decisions to revert from LED to incandescent was one of lumens and safety in this instance. The LED backup lights were just not bright, barely 35 lumens at most, where the incandescent 7440 is more than 400 lumens. The LED was bright enough to "indicate" that Astro was in reverse to other drivers, but the low output of the LEDs was insufficient to provide any meaningful rear illumination. Now with more than 800 lumens of long life tungsten action I can not only indicate when Astro is in reverse to others, in dim lighting the reverse lights will actually illuminate the area behind Astro enough to give decent vision assistance during a reversing maneuver. 

The from Map lights suffered a death of the natural white LED, one among two other blue LED's in the sub-assembly. A trip back to netted 3 new low output 194/168 natural white LED bulbs to replace the dead one and the blue ones that Meg dislikes. I also nabbed some low output LED festoon bulbs for the rear Dome light and Trunk/Cargo area light. These LED lamps are somewhat cheap and like the ones they are replacing I wonder how they will hold up over time. My primary reason for using LED's in these applications is to prevent a dead battery if a map or dome light is left on overnight. The reviews of the natural white color were what steered me away from warm white this time around :) After installation of  the new LED's I agree with the reviewers of the natural white bulbs, its a nice bright white LED color with only a tiny hint of blue and enough warmth to feel bright without feeling cold :)

The rear 168 tail marker lights and 168 plate lights were just changed out with new Sylvania LL type; $11 for all four. The swap was relatively quick, but now I have to repair a plastic bracket that I cracked when removing the hatch door cover to access the plate bulbs. In these two applications LED was not ideal either. In the case of the tail markers, the bulbs are housed inside a red filter box, which means that only red LED can be effectively used, and after reviewing what is available I have not found one that I would like to use for that application, the OEM style 168LL bulb makes more sense than anything else. For the plate light the bulb space is confined and there is no value for me to illuminate my plate more. Furthermore the geometry of the plate light is not ideal for a 168 LED. In both of these applications the OEM style 168LL incandescent makes more sense than an LED retrofit.

While I have long waxed and waned about the benefits of LED, there are clearly many things you have to consider when choosing artificial light source technologies in specific applications. Sometimes the heat from the incandescent can be a benefit (to defrost) the fixture in freezing conditions for example. Sometimes the size of the lamp, the color, the operating parameters and other factors make one technology more appropriate than another.

HID is great, but it is expensive, hot, and complicated. LED is great, but they are also expensive, they have to be well cooled to last, and in certain application retrofitting with LED requires a very specialized LED bulb in order to achieve good optical function. The 7440A turn signal bulbs in astro or backup lamps are a good example: only the most sophisticated and costly LED perform on par with inexpensive long life tungsten style OEM bulbs. Fluorescent never went mainstream in automobiles for a lot of good reasons; long warm up time, dimminished light output in cold conditions, early failure with frequent on off cycling, hazardous metal content, complicated recycling, large format bulb designs.

When it comes to forward illumination on a vehicle HID is the best solution because it provides the most light. When it comes to marker lights the choice between long life incandescent and led comes down to specific factors for each application. Think about what you need the bulb to do, look at your options and then think about it more.


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