H7 LED bulbs?

RatLabGuy

RatLabGuy

You look like a monkey and smell like one too
Joined
May 18, 2005
Location
Churchville, MD
Getting tired of replacing the halogen bulbs in my Mazda. The stock ones suck, I've used the XTraVisions (or whatever they're clalled), Osram NightBreakers, all kinds of things over the years. Nothing lasts long.
My night vision isn't great so I like more light

I'm sure part of the problem is the 13 y/o wiring, in combo w/ the heat buildup but I really don't feel like screwing with it.
Whats the real story on the new drop-in replacement LEDs? I'd need a standard H7. Reviews seem pretty mixed, but w/ the lower load and heat it seems like a good replacement for older cars. Is there something that really works well? Or give it another 6 months...
 
Subbed just because I'm curious. I've heard the mixed reviews as well, mainly just scatter and the light doesn't project as far.
 
I had to buy a new bulb the other day for the Dodge (first time ever). I was a little overwhelmed by all the choices on the shelf, so I started reading the backs of the boxes. The cheapest ones had MTBF in the neighborhood of 5-600 hours. The fancy expensive ones had MTBF of 200 hours. One was 175 hours. There was nothing else substantial on the packages to justify the cost difference except for ambiguous claims of "whiter" (cooler color temperature?) light.

So that might be your problem.
 
Yeah, the "better" (e.g. expensive, but brighter) ones really don't last long. My feeble understanding is it's the added heat.
No question there is a tradeoff. Hence considering the new LEDs.

I keep 'em well-aimed, and in this car they are only like 2' off the ground anyway.
 
RatLabGuy said:
My feeble understanding is it's the added heat.
Click to expand...

There's no added heat. Maximum wattage is limited by DOT. That's also why there aren't any substantial claims as to what's "better" about those bulbs. They put coatings on them to shift the color temperature, but the coatings reduce the total lumens emitted by the bulb.

So if you want the brightest, longest-lasting bulb, buy the cheap one.
 
shawn said:
There's no added heat. Maximum wattage is limited by DOT. That's also why there aren't any substantial claims as to what's "better" about those bulbs. They put coatings on them to shift the color temperature, but the coatings reduce the total lumens emitted by the bulb.

So if you want the brightest, longest-lasting bulb, buy the cheap one.
Click to expand...

The brighter aftermarket stuff uses slightly different filament alloys and changes the filament size and length to change the filament temperature, which can change the brightness and the color. The term "color temperature" just that, the light color emitted Those tricks also shorten the life, because higher filament temperature stresses the filament more.

The wattage classification still has to remain the same, but that only means that the overall bulb resistance has to stay within the same classification range. How you turn that wattage into visible light is how the brighter/whiter aftermarket stuff differs from OEM bulbs, but is also the reason that they don't last as long.
 
Last edited:
If they're hotter, brighter, and have the same resistance, it sounds to me like we're violating the First Law.
 
shawn said:
If they're hotter, brighter, and have the same resistance, it sounds to me like we're violating the First Law.
Click to expand...
I'm no ta thermodynamics guy... but if you are changing the material and other properties then it seems perfectly reasonable for that to happen.

This weekend after one of the Osrams went out, I needed a bulb and happened to have one of the old "cheap" ones, popped it in so I could still be legal (cops around here are notorious to popeye tickets).
The difference in both brightness and color temp is obvious.
Hell maybe if I get bored tonight (unlikely) I'll put an ammeter on each line and see what the actual difference in draw is.
 
I understand your thermodynamics argument, but that assumes a lot about what is being changed or not changed in the bulb, and how those changes translate to light output. Sure if, you keep the same filament material, diameter, etc., and then start promising changes, that would violate the first law. By that logic, converting the same wattage to light using an LED would violate the first law, because the light output would be greater for the same wattage.

Having the filament glow at a higher temperature doesn't mean the overall bulb heat output is greater, because the filament temperature is a function of material, applied voltage, resistance per length at that temperature for that material, and obviously then filament length.

Color temperature is a main factor in perceived brightness, so if you go closer to white then you get better perceived brightness, and then as you go toward blue and purple you get lower perceived brightness. So just changing the color temperature by messing with the filament characteristics can change brightness.
Normal bulb color temperature is a tradeoff of filament characteristics based a lot on bulb life, so you can change the color temp and brightness (but shorten the life) by changing filament characteristics, etc.
 
Last edited:
yep, "brightness" is a characteristic determined by physiology of the human eye, shifting the color so that the light spectrum is it is more centered into that which our eyes are most sensitive in fact makes it "brighter"... e.g. more useful.

As an aside, this is where light measurements like lumens can be misleading. Lumens is power output at a particular frequency, usually the center frequency of the output. A 5,000 lumen lens at only say 500 nm wavelength will still look very dim b/c your eye can't see it.

OK so anyway - anybody else know about LED headlight bulbs?
 
Back
Top