Would love to have one of the 928 companies to offer a LED replacement for the for light cluster.

 

I found that lens on vs. lens off made no appreciable difference.


Since I don't have nicely integrated photos for this yet, I'll provide this (and note that your question is really about what's going on on the right sides of these photos):


First, the "test #2" photos:

Left side: , Right side:



Left side: , Right side:




and the "test #3" photos:


Left side: , Right side:



Left side: , Right side:





My conclusion (related to your question): having the lens on or off of that particular bulb makes little different for this particular application.

Secondary conclusion (not related to your question): the left side bulb is brighter than the right side bulb, but doesn't have as even a light distribution pattern.

 

The best brightness test I've found at night for brake lights, is to look in the rear view mirror and see how much light is reflected in the reflective traffic signs for the apposing lane (and how far back the signs are). I noticed this when first testing the 7watt LEDs, as they are brighter than the standard watt incandescents.

My front 1157 amber 7 watt LED measured 280mA at 12.75VDC at high brightness.

If you want to buy one for testing, VLED.com will sell them individually. They usually lists prices in pairs, but they will sell them individually if you send them a request by email to do so.

 

Very interesting Ed. One of those things that is on the long list of things to do.
Do you have any ideas for those of us with euro rear fog lights? I've got the test mule for you.

 

This sounds like an interesting project. There is a lot of hype around LED lighting (high brightness), but there is a lot of low quality garbage out there. My only caution with the higher wattage LEDs is that cooling becomes very important. The lifetime and performance of these high brightness LEDs drops dramatically if they are not cooled properly. This is one of the primary obstacles preventing the mainstream adoption of LED lighting in price sensitive applications such as residential lighting. Properly cooled residential replacement bulbs require fairly large heat sinks, which raises the price beyond what most are willing to pay today. While the LEDs do not forward radiate heat, they generate a great deal of heat in a very small area at the LED die. This heat rapidly degrades the LED lens. In the case of brake lights, low duty cycles will probably make this a non factor. However you are likely to run into problems retrofitting other external indicator lights which are on for extended periods, non-brake tail lights for example.

 

Yeah... I pay attention to that, too... but wonder whether that's really a good measure. For example, if you use the same measure for your headlights (i.e., seeing how much the signs light up), you'd probably be noticing (in some cases, depending on where the sign is relative to you) undesirable scatter, i.e., light where it doesn't belong.

I haven't taken the time to look up DOT regulations/specs related to tail lights, but I wonder if it's actually more desirable to have a large cone of light, or a more concentrated one aimed at whoever is behind you?

These different LEDs have radically different beam patterns already, and combined with different housings, overall results are all over the place.

Check this out:

Left side: Right side:



Note how the original beam pattern (yes, that's a P21/5W incandescent bulb on the right side) has its light concentrated such that it's projected at the driver behind you? Think that's significant? I'll bet it is. IMHO, that argues for LED bulbs that share this characteristic. That's one of the reasons I was doing this more comprehensive testing: I really want to understand all the significant differences.


So... my calculator says 3.57 W. And that's the same kind of discrepancy (actually not quite as bad as what) I've seen elsewhere. How do you account for that?

Maybe they're saying "14 half-watt LEDs" (true, based on the individual LED specs), but then they under-drive them for heat reasons or something, and you really wind up with a bulb that's not really 7 W at all. Interesting that in the cases where I see this discrepancy, the seller doesn't provide specs with current draw, nor do they provide luminous flux.

FWIW, the "reference LED" I'm using for the left side is a 1157-RLX5. Specs from superbrightleds were (on bright circuit) 335 mA (I measured 314 mA, but remember that it started higher and dropped as it heated up) and 132 lumens. It was sold as a "5 W" bulb, although I calculate 4 W based on the specs. That is a mighty fine LED bulb.

I'm done (for this round) acquiring bulbs. If someone wants to send me some for testing, I'll (time permitting) test it against my reference bulb and add it to the "comparison database", but I think I'm done spending money on this stuff for awhile.

And BTW... the "reference bulb" I mentioned isn't necessarily the "best bulb": I'm still undecided, especially since I've got one more (promising one) to test thoroughly. I suspect I'm going to discover that there's not a clear winner and I'll have two favorites, one with a little more brightness, but the other with better beam pattern when used in the housing.

 

Maybe they are rated at 14.7 volts at 200 degrees F. My test was lower.

Your never done. Just think.... these high power LED bulbs are cheap when compared to $300 water pumps, $170 timing belts, $100 window switches, shark tuners, etc, etc.

 

Actually... no. Maybe someday...

Agree. One thing I've noticed, though, is that some of the most recent bulbs I've gotten don't run as hot; they've apparently improved the efficiency somewhat.

That said, I've never had a single LED fail on me, and I've been running that "left-side in the photos" Luxeon-based 1157-RLX5 for brake lights for two or three years, I think. The Luxeon-based ones run pretty hot and have heat sinks to dissipate the heat.

I think they're fudging, one way or another. It's probably like the "HP" ratings on air compressors.

Yup. And messing with electrical stuff is (compared to the mechanical stuff) easy, clean, and low risk.

 

For an incandescent retrofit application, the current consumption is set by a series load resistor in most inexpensive bulbs. This means that the power consumption will be sensitive to the supplied voltage. More advanced solutions would be driven by a current controlled source.

None of the high brightness LEDs are intended to operate in 200 degree F conditions.

 

They have improved efficiencies in recent years with single LEDs reaching 160+ lumens per watt in the lab. However, all of the commercially available bulbs would require cooling for continuous duty applications. The bulbs pictured above don't seem to offer any additional cooling and the airflow in our incandescent designed bulb housings will be low. Again, I don't think it will matter for brake lights. For other lights with higher duty cycles the lifetime of the bulbs could drop from 30K hours to 5K or less. This is still better than incandescents, but not if you consider the price difference.

For brake lights there is a tangible benefit of faster turn on times which is why LED brake lights are becoming mainstream. For other automotive external lights, what other real benefit is there than lifetime.

 

Ed, great project, please keep posting your results.

 

Hi Ed,
Thanks for the explanation on the diffuser... the incandenscent comparison and your logic make good sense to me!

I can't seem to find the 1157-RLX5 anywhere. Is it still on the market?

 

really- no need.
It's sort of, how do you make your chrome shinier?

 

Just installed an LED flasher relay and the latest Super bright LED's in the taillights. Blinkers work fine when the parking/headlights are off, but go into bizzare mode when parking/headlights are on and blinkers do not flash. Also, when the parking/headlights are on, all of the pass rear lights are illuminated and do not blink. Any suggestions ? T

 

Not that I can find... in fact, that's what got me going on another round of evaluations.

I'll take a look at this phenomenon again this week (this last weekend got away from me with lots of other stuff). Are you running LEDs on the front corners, too? It would help if you tell me exactly what LED bulbs you're running front and rear and in what positions (i.e., what LED bulbs for rear brake lights, rear turn signals, front turn signals).

Other than what I recently noted on the test bench (which I can describe in more detail later), what I remember from years ago was that my front corner LEDs were staying in bright mode even when the parking lights were on. In retrospect, I believe it was due to an interaction with some other LEDs that share the same bright and/or dim circuits. I didn't think much at the time about these kinds of interactions; now that I know that it's possible, I'm pretty sure it wouldn't be all that difficult to work around it. I'd like to reproduce the problem on the test bench with the exact bulbs in question, if at all possible.