# Most efficient LED available??



## Arch_NME (Nov 11, 2009)

I'm looking for the most power efficient LED. It's for replacing the lighting in my sailboat which I need to maximize the length my batteries last. Every milliamp counts. I came across this forum while I was browsing for the perfect LED and you seemed to have some really well informed people on the subject around here.

I found an article stating that the Cree EZ bright got 131 lumens per watt but I have had a hard time finding any place to buy the from. 

So, basically I just want to find the LED with the most lumens per watt that is available to buy somewhere right now.

Any good suggestions?


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## IMSabbel (Nov 11, 2009)

For what its worth, the most efficient LED is the XP-G R5 from Cree. Al low currents, its aboce 160 lumens/Watt.

But if its about batteries lasting, there is something thats much more important than lumens/w. Your eyes are amazingly sensitive devices. If you get an homogenous, low level illumination going, it might look brighter than a different one where hotspots kill night vision...


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## saabluster (Nov 11, 2009)

Arch_NME said:


> I'm looking for the most power efficient LED. It's for replacing the lighting in my sailboat which I need to maximize the length my batteries last. Every milliamp counts. I came across this forum while I was browsing for the perfect LED and you seemed to have some really well informed people on the subject around here.
> 
> I found an article stating that the Cree EZ bright got 131 lumens per watt but I have had a hard time finding any place to buy the from.
> 
> ...


First off what type of LEDs are you looking for? Are you trying to replace with the same type? Do you have pictures you can post of the fixtures? Do you care at all about color rendering? Do you know what controls the current to the existing LEDs? Once you change the LEDs out you may also need to change the driver/resistor to see any reduction in power consumption. A more efficient LED may only give you more light without this change. Welcome to CPF!


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## Arch_NME (Nov 11, 2009)

I'm not looking for them to fit into my current fixtures. I have incandescents in there now. I don't even really care about having fixtures really. I'm basically planning to build a whole new light system from the ground up.

I need to be able to read charts and books but yeah I really would like a low light level spread out around like IMSabbel is suggesting. Maybe have it be able to dim somehow also.

Light color isn't really a problem, I'm not bothered by colder bluish looking light or anything like that. Just want to be able to see with as low power consumption as possible. I was read this article earlier about light color and it's got me thinking it doesn't really matter.

http://stlplaces.com/night_vision_red_myth/


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## saabluster (Nov 11, 2009)

So I assume you are running off of some batteries. What is the voltage? Also you want to have these LEDs behind a diffuser so some kind of fixture is going to be necessary. I have no idea what the inside of your boat is like but you may also be able to aim them at the ceiling to get a soft reflective, homogeneous, glow. That would be ideal I imagine but the ceiling would need to be painted white.


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## Arch_NME (Nov 12, 2009)

My batteries are standard 12v AGM deep cycle. They go from about 13.5v fully charged to like 10 towards the end. I was under the impression that the chip type LEDs would have more of an omnidirectional light than standard 5mm type LEDs. Is that not the case? I don't think the pointing them at the ceiling thing would work for me. I found these though. http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productid=1671 Also, I found those cree XP-Gs on digikey but they aren't listed as R5s, there is a letter in the model number E, F or G. Is G the R5? Is there a good place to read more info about these LED drivers? My original plan had been just using resistors to get to voltage down to 3.5 and maybe put a small pot in the line for a dimmer? Thanks for all the great info you guys are providing by the way.


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## saabluster (Nov 12, 2009)

Check out this site for driver info.


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## JohnR66 (Nov 12, 2009)

Using a resistor is a horribly inefficient way to drop the voltage to 3.5v for one LED. On a 12v (nominal) system you drop 8.5 volts through the resistor and that is wasted heat. It is much better to use 3 LEDs in series so there is a much smaller voltage to drop in the resistor. This makes the system more prone to dimming as the battery voltage drops. Better would be a 12 volt regulated driver.

Secondly, look at NSPWR70CS-K1 This 50ma flux LED by Nichia claiming 150 lumens per watt. It is claimed to last 15,000 hours at 50ma or 40,000 hours at 20ma. These can be used in areas where power LEDs aren't needed.


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## Linger (Nov 12, 2009)

JohnR66 said:


> Using a resistor is a horribly inefficient way to drop the voltage to 3.5v for one LED. ... It is much better to use 3 LEDs in series so there is a much smaller voltage to drop in the resistor.


+1
Another easy option is an mc-e wired in series (4 dies in the emitter).
Drivers are can be very in-expensive. I'd definately suggest it for the efficiency and flexibility they offer.


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## HarryN (Nov 13, 2009)

If efficiency is paramount, and you can deal with the color, red / orange has exceptional efficiency. The reasons have to do with how your eye deals with this color, as well as the very low forward voltage (due to the lower energy photons) Nominally is is 615-620nm, and used in traffic stop lights.


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## waddup (Nov 15, 2009)

Arch_NME said:


> I'm looking for the most power efficient LED. It's for replacing the lighting in my sailboat which I need to maximize the length my batteries last. Any good suggestions?



lots of good and cheapish solar panels available on teh www.

get 1 and recharge your batteries every day...for free

then you can use any led you want:candle:


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