LED headlamps

[vfx]

So do they have to have multiple bulbs to make enough output?

[Norbert]

So do they have to have multiple bulbs to make enough output?

For most LED's, multiple ones would be needed, including the Cree XP-G mentioned above. I'm not sure how efficient this LED is, but it seems to have more than needed with a single large LED:

SST-90 White Series PhlatLight LEDs (up to 2200 Lumens)

I've been reading a few high-power-LED flashlight reviews, and those reviewing flashlights with 700 Lumens (which are usually about $150-$300) often claim that they are as bright as a car headlight. However, it might be that these cover a smaller area than a car headlight, and I wouldn't know (yet) how many Lumens a car light would really need.

[Norbert]

I've been reading a few high-power-LED flashlight reviews, and those reviewing flashlights with 700 Lumens (which are usually about $150-$300) often claim that they are as bright as a car headlight. However, it might be that these cover a smaller area than a car headlight, and I wouldn't know (yet) how many Lumens a car light would really need.

I've been reading some more, and should improve these numbers (for those who are interested, though probably some of you already know much more than this):

A halogen bulb commonly used in cars is the H7 bulb. It has about 1500 Lumens at 55 Watt. That's about 27 Lumens/Watt, much less than HID(Xenon) or LED lamps.

HID(Xenon) Lamps used in cars seem to be typically 3200 Lumens at 35 Watt, but I've also stumbled across some advertised to be 5300 Lumens at 50 Watt and even 8300 Lumens at 75 Watt.

Again, the typical value seems to be 3200 Lumens at 35 Watt, which is about 91 Lumens/Watt

So the latest generation of LED's (those which are currently becoming available commercially) appears to be better than that (or at least comparable). Considering that LEDs seem to be improving continuously, the next generation will probably clearly surpass HID lamps. Plus, LEDs appear to be much more reliable, as far as I can tell.

Back to VFX's question of how many LED bulbs are needed:

The SST-90 mentioned above has a max of 2200 Lumens (according to the manufacturer), so at least two would be required to be equal to an HID lamp in output.

However, there is also the CSM-360 (although I'm not sure whether it is already available, and whether it would be a good fit for automotive applications):

http://www.luminus.com/stuff/content...lumination.pdf

According to the manufacturer's data, it has (for the highest rated version) a range of 3600 Lumens to over 6000 Lumens, and at 3600 Lumens, an efficiency of over 100 Lumens/Watt.

If these numbers actually mean what they seem to, the CSM-360 LED is preferable to a typical HID bulb in probably every regard.

Now, the other choice might be to take advantage of the Cree XP-G LED's high efficiency of almost 150 Lumens/Watt at 200mA (according to the test referred to above). (It is available now.)

At 200mA, it delivers about 100 Lumens, so one would need about 35 of them. Printed circuit boards like the following (with matching optics) can be used to assemble 7 of them into one unit of 40mm diameter:

Cutter Electronics

So 5 of these, each with a diameter of about 2 inch, would be needed on each side of the car. I don't know if it would be worth the effort, compared to an easier-to-manufacture solution using the CSM-360 LED, but it doesn't seem impossible.

[Norbert]

Or, since the availability and price for the CSM-360 LED is unknown to me at this point, using the already shipping Cree XP-G LEDs, but just 2 bulbs, since 5 seems a lot:

So with 2 bulbs (2 PCBs, 40 mm diameter, with 7 LEDs each), running each LED at 625mA, it would be:

At this current, they have 120 Lumens/Watt, and 2 bulbs would generate about 3500 Lumens (more than the HID lamp's typical 3200 Lumens), and use 29 Watt (less than the HID lamp's typical 35 Watt). Cost: about $42 per bulb in single quantities.

[TEG]

http://www.ecogeek.org/automobiles/3...e-by-six-miles
"LED Headlights Can Extend EV Range by Six Miles"

[Jaff]

They look cool too TEG!

Does anyone know if TM has ever looked at LED's to replace their "underpowered" current stock headlamps?

[vfx]

http://www.ecogeek.org/automobiles/3...e-by-six-miles
"LED Headlights Can Extend EV Range by Six Miles"]

Model S!!

[mpt]

Does anyone know if TM has ever looked at LED's to replace their "underpowered" current stock headlamps?

Much discussed on TMC; but we think EM has xenon on his car and that new headlights cost about $1/2M to design, test, approve.

[dpeilow]

There's a story on LED headlights saving 6 miles doing the rounds today:

http://venturebeat.com/2011/01/24/le...tra-six-miles/


This was my response:

Umm, does Osram have an LED headlight to sell?

Let's do the math:

A typical Halogen headlight bulb is 55W. Autoblog Green said in their original story that the LED system is 28W. So LED will save 82W for the pair.

An EV uses about 300Wh/mile in real world highway driving. Therefore, you'd have to be driving for 3.6 hours to save 1 mile's worth of energy with the LEDs over the halogens. Thus, to save 6 miles' worth of energy you'd have to drive for 22 hours between charges. Not even a Tesla can do that.

The case is even more extreme with Xenon HIDs. They are typically 35W per bulb or a saving of 42W for the pair between that and LED. So now you'd have to drive for over 7 hours to save 1 mile of energy or 43 hours for the claimed 6 miles' saving.

I allow for a mile hit on range when driving the Tesla at night. That's being generous.

[TEG]

http://green.autoblog.com/2011/01/20...ric-car-range/

...Over only that last 2-3 years, the efficiency of LEDs has increased to the point where LEDs use less than 25% the energy of halogen bulbs...

... a 28 watt LED ... compared to .... conventional 110 watt H7 halogen bulbs.

The "6 miles range" quote is squishy and dubious, but the technology does offer a noticeable improvement.
(And LED vs bulb longevity is way better.)

http://www.electronicsweekly.com/Art...emium-cars.htm