MY HID experience

My night vision isn't what it used to be, so I decided to give HID lights a try. After all, you can get a conversion kit now for under $25 on Ebay, including shipping. I decided to experiment on our SLK, being its simpler to get at the bulb. I decided to go for a 55w 4300K conversion kit, which provided 3200 lumens vs 1450 lumens of the OEM 55W H7 halogens. This should be great, roughly twice the light!

I installed one bulb so I could do an HID vs halogen comparison. I marked the headlight pattern on the garage wall to make sure before/after alignment had not changed.

The HID was surely a truer white than the yellowish halogen; but to my surprise, it didn't seem much brighter. So, time for a test drive. Once again, the ability to see the lines on the side/middle of the road, especially with the glare of oncoming headlights was only slightly better. However, there was a somewhat wider pattern of illumination from the HIDs, and as noted before, the color more whiter, ie, more "natural."

So, what gives? Time to revert to a little science for a consultation. Clue #1 : human vision, like hearing, is not linear, its logarithmic. So, about twice the lumens yields about a 11% (rough calculation) in perceived brightness. Still being curious, but lacking a light meter, I decided to set my camera at a fixed shutter speed, a fixed ISO, and measure the resulting f/stop. The difference was tiny, measured either at the adjusting points on the headlight lens or at about 3 feet away zooming in on the headlight assembly. OK, there may be a better scientific way to measure the total light output, but the numbers were close enough to agree with the calculation and verified my visual experience.

Looking on Prime, I saw old posts saying a relay should be used for the 12V power when using 55 W HIDs. But, the OEM bulbs are 55W on the NSX (as well as the SLK), and the NSX high beams are 65W. Could the reason be start-up current? The HID kit I bought rates start-up current as less than 10A. This kit uses a digital "ballast" (really a controller and converter to high voltage), so perhaps the older analog HID ballasts drew a higher start-up current. But, what's the start-up current on a halogen bulb? I did a measurement on the H7 filament at room temperature and it was 0.3 Ohms (on a calibrated Fluke DMM). That means a start-up current of 40 amps for the halogen bulb. Even if my measurement was off by 33% at this low resistance, start-up current is still 30 amps. And the lower the ambient temperature (we had 0F here a few days ago), the lower the resistance of the filament, the higher the start-up current of the halogen bulb. But, of course the halogen bulb's filament resistance quickly increases to about 3 Ohms as the filament warms up so the current then is about 4.2 Amps.

My conclusions, based on the specific kit I purchased:
• 55W HIDs don't need a relay if the OEM halogens were 55W, at least for the latest HID technology
• Expect truer color, and perhaps a broader light pattern, but any gain in actual perceived brightness is minimal
• The latest HID bulbs don't affect headlight alignment
• Noise filtering on the digital ballast seems OK. I could not detect any RF interference on the radio or a change in any electronically controlled car operation.

Epilog
Installation was truly plug & play – not much more time involved than replacing the headlight bulb. But, it requires cutting a hole in the dust/moisture cap behind the bulb for the wiring to the ballast. The kit wiring includes a well-sealed grommet on the wiring so the integrity of the cap is not violated. I decided to keep the OEM halogen bulbs and the caps as back-up, and purchase a new/used set of caps for use with the HIDs. The caps will cost me a couple dollars more than the HID kit!

Two points: hid bulb and ballast aside quality of the setup depends on your headlight lenses. Also one of the reasons I really like Steve's kit is that I don't need to cut anything

I stock the cheapo kits easy install for me and doesn't cost the customer a lot of money and if it break IE ballast just swap with another one and keep driving.

There are a lot of factors going into how bright of light you'll receive. What year is your SLK? Does it have projector lights or reflector style lights?
Also, what brand HID is it? Many of the cheap HID kits are falsely labeled 55W when they are actually only 35W..
55W kits should deliver about 5000 lumens (not 3200 which is what a 35w kit typically delivers). I've had the OEM halogens, an older McCulloch 35W kit 6000K (very slightly brighter than OEM) and an older DDM 55W kit 6000k in my NSX and can tell you that the DDM 55W kit is brighter by a huge margin than all of those.

This is a good comparison I found that is similar to my own experience:


Here's a good writeup about the older HID kits and startup current draw.
http://theeshadow.com/files/volvo/hidcomp.html
Lastly, I believe your calculation for the headlight startup amperage to be off. The HID kits typically go just about 10amps (sometimes less on the newer ones). The stock fuse for the headlights is 20amps per side.

I am curious if the 55w HID is too hot for the housing. I have the DDM 35w in my other car and it is very hot.

nis350 said:

I am curious if the 55w HID is too hot for the housing. I have the DDM 35w in my other car and it is very hot.

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I've had them for about 6 years with no issues so far. I haven't opened up my housing to check, but I'm running the external wiring harness to keep the wiring safe.

Hapa88 said:

There are a lot of factors going into how bright of light you'll receive. What year is your SLK? Does it have projector lights or reflector style lights?
Also, what brand HID is it? Many of the cheap HID kits are falsely labeled 55W when they are actually only 35W..
55W kits should deliver about 5000 lumens (not 3200 which is what a 35w kit typically delivers). I've had the OEM halogens, an older McCulloch 35W kit 6000K (very slightly brighter than OEM) and an older DDM 55W kit 6000k in my NSX and can tell you that the DDM 55W kit is brighter by a huge margin than all of those.

This is a good comparison I found that is similar to my own experience:

Here's a good writeup about the older HID kits and startup current draw.
http://theeshadow.com/files/volvo/hidcomp.html
Lastly, I believe your calculation for the headlight startup amperage to be off. The HID kits typically go just about 10amps (sometimes less on the newer ones). The stock fuse for the headlights is 20amps per side.

Click to expand...

Thanks for your valuable information. The SLK is a 2001. It doesn't have the projector style lenses I've seen in some cars, it looks more like the lens in my '96 NSX. The HID kit has a digital ballast and is soo cheap, they don't even print a brand name on the unit or on its box. As I admitted up front, the idea was to conduct a cheap experiment.:tongue:

As to start-up current, I stand behind my calculation. But understand that 30amp exponentially decaying peak will be at or above 30 amp most likely for less than a millisecond and will not blow a 20 amp fuse. I'm now retired, and so can't go into a lab and borrow a good oscilloscope & inductive current sensing probe to prove my point. But that's OK. :biggrin:

The thing I still don't understand is people stating an alternate wiring harnesses is needed to protect the NSX wiring. Is the heat coming from the ballast being placed inside the headlight pod? 55W Halogens draw 55W; a 55W HID draws 55W. Watts are watts, both yielding a 4.2 amp current drain steady state.

I wish someone with bigger balls than me would try a good set of LED's in the projector housings. :redface:

Another thing to consider is that our NSX head lights (91-01) were not designed for HID light. Both the front glass and projectors will distort the HID light (causing glare, hot spots, irregular cut off). The best thing to do is retrofit your projector to HID compliant ones, as well as remove the "flutes" from the front glass.

I have a spare set of lights that I was going to retrofit (I retrofitted my Integra with Audi A6 projectors), but I got too lazy and just got an 05 instead, lol.

ftuhy said:

The thing I still don't understand is people stating an alternate wiring harnesses is needed to protect the NSX wiring. Is the heat coming from the ballast being placed inside the headlight pod? 55W Halogens draw 55W; a 55W HID draws 55W. Watts are watts, both yielding a 4.2 amp current drain steady state.

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I got the wiring harness primarily for the startup current, not the steady state.

If you're assuming a 13.1V voltage, then with a 30amp startup you're pushing almost 400W for a short period (on stock wiring).

- - - Updated - - -

ftuhy said:

Thanks for your valuable information. The SLK is a 2001. It doesn't have the projector style lenses I've seen in some cars, it looks more like the lens in my '96 NSX.

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Assuming your headlights are OEM on both cars.
The 2001 SLK has "reflector" style headlights
The 1996 NSX has "projector" style headlights.
See this picture for a side by side comparison:

davidf said:

I wish someone with bigger balls than me would try a good set of LED's in the projector housings. :redface:

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I don't think the LED's are there yet, in terms of beam pattern or reliability. At least, not for low beams.

For low-beam beam pattern, the LED replacements don't have the precise positioning of the light-generating element in the projector housings that HID's and of course the stock halogen 9005/9006 bulbs do. So the beam pattern probably won't be correct with LED's, the way it is with HID's and halogens.

For reliability, it depends on whether you're looking for brightness equivalent to HID's. You can get 40W LED bulbs with 3600 lumens of brightness, slightly brighter than 35W HID's, which are 3200-3400 LM and still brighter than stock. These come with a built-in fan in the base of the bulb, to deal with the heat generated. I recently got a set of these to replace the 9005 high-beam bulbs in my MDX; I figure the beam pattern is less of a concern with high-beams, since there's no sharp cutoff needed. Unfortunately, one of the two LED bulbs was dim and defective, and I'm awaiting a replacement. Another fellow on the MDX forums got 40W LED's for his low beams recently, and both of his failed; he's going to get some 30W LED's instead. I'm hoping the replacement bulb I get for my high beams is okay.

I think high beams may have an advantage over low beams, at least for me, because I almost never drive in rural areas so I don't leave the high beams on for long periods of time, so they shouldn't be on long enough to overheat. I use the high beams occasionally for "flashing" a car ahead of me, and for that, LED's are perfect - better than HID's or halogens - because they reach their full brightness instantly, without needing a brief warmup.

HTH

nsxtasy said:

I think high beams may have an advantage over low beams, at least for me, because I almost never drive in rural areas so I don't leave the high beams on for long periods of time, so they shouldn't be on long enough to overheat. I use the high beams occasionally for "flashing" a car ahead of me, and for that, LED's are perfect - better than HID's or halogens - because they reach their full brightness instantly, without needing a brief warmup.

HTH

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A very close friend of mine just started his own LED company after being in the business for many years. I have been to two trade shows with him in the past 6 months and now know more about LED than I really want to. If you have any LED or HID questions I would recommend you get in touch with him and if anything else you will find him an amazing resource on the subject and maybe you will purchase your future products from him.

I stop by his shop on a regular basis and he is always got a new batch of LEDs in for testing. The main issue I have seen with the LED headlights is the driver for the LED will throttle back the LED "ON" cycle if the chip starts to over heat. This means the light output drops down much below the advertised lumen output if they are on for an extended period of time and are not kept cool. Most of the replacement bulbs are using a small PAC fan to cool the larger heatsink that is part of the base. This fan is exposed to the elements and will fail. At the trade shows some of the manufacturers where starting to use larger heat sinks and fanless assemblies to prevent the inevitable fan failure. There was even a setup that was using a machined copper heatsink and a water cooled system similar to a water cooler for a PC CPU. LEDs are here now and will continue to improve over time. I do know that he has several of the replacement sets with fans in cars testing now and they were in 170 hr continuous run testing prior to that. If you need info or want help Steve is a great resource for all things LED home or auto. http://lumaleds.com/ contact info is on the site.

For the OP:
As far as the DDM HID units go, I have 3 sets in use now, one set is an early 35w set that was put in my 07 Titan (Reflector Style Housing) just after I got it and has been in use for all its life and nearly 210,000 miles with no failures what so ever. I have a 55w set in another work van that has been in place for 4 years, I have another 55w set of Hi/Lo bulbs in a 2010 Mustang with every front facing bulb converted to HID, thats the Hi and Lo beams and two sets of driving lights. With everything on the light output of that car rivals the Jeeps with the large LED light bars or multiple sets of KC style lights. The DDM 55w setup is a very noticeable difference to the DDM 35w setup. The Mustang will be converted to LED as a test vehicle for Steve and a full write up done on his website as soon as he finds a LED headlight bulb maker for the Hi/Lo bulb that passes his testing process. It is only a matter of time before the HIDs go away but since they are basically proven now compared to years back when the replacement kits were mostly crap, they are so cheap, and they are an upgrade for almost any halogen setup I would not hesitate to give them a try. The bulbs are all the same between the 35w and 55w kit so maybe just order in a set of 55w ballast and give them a try. It would not surprise me if you ordered 55w and got 35w buying from an Ebay or Amazon Vendor.

Dave