# Which SMD or Non SMD LED out there gives the highest lumen per watt today?



## nobleimd (Jul 17, 2015)

Have a bit of a challenge going on. Trying to develop a light that has total of 7W power consumption max. But must give at least 900 lumens of light , trying to run this off a 3600 mAH battery and need at least 6-8 hours of good effective lighting, so maybe a lumen /watt of 180-200? Is it possible with any available SMDs today?


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## lightfooted (Jul 17, 2015)

While there may be something in developement, if you do the math on your expectations you will realize that you are expecting a draw of around 3 amps to last 6-8 hours. 900 Lumens is still a lot of light to expect from a single cell LED especially if that's OTF and not emitter lumens. Until a new LED is developed that operates at less than 2 volts, you're going to need something closer to 300 lumens per watt to obtain the 900 lumens output you want.


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## RetroTechie (Jul 17, 2015)

@ 120 lm/W, 900 lumens = 7.5W. @ 150 lm/W, 900 lumens = 6W. Say you need 7W, at ~3.5V (single Li-ion) that's about 2A. Which would give you <2 hrs runtime with a 3.6 Ah battery. Want more runtime? Add more/bigger batteries, or lower that lumens requirement.

That is assuming a high-efficiency driver, and LEDs that actually hit those lm/W figures under operating conditions. You'll have the best chance of hitting those figures when the LED(s) are driven at a modest level. Read: grab a LED than _could_ output much more lumens than what you're aiming for (like a Cree XHP50 / XHP70). Or use multiple LEDs. Oh and: the highest-output LEDs will normally be cool white ones...


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## SemiMan (Jul 17, 2015)

And the assumption of course being made, right or wrong by the last two posters, that the battery is a LiIon and / or a single cell.

Can you give us a better idea of what your battery is?

200 lumens/watt at the LED is not that out of reach. High bin XPG2, high bin 5630's, etc. run at approximately 5-20% rated current can hit those performance figures.

Count on electrical efficiency of 90% done right, and if you use a clear cover with no dead spots, then 90% optical too. That gives you 160 lpw, but call it 150lpw to be safe. 900 lumens = 6W ... noted above. If you want 6 hours, you need 36Watt-hours .... amp hours are pretty meaningless. Need to know the watts and volts.


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## m.pille.led (Jul 17, 2015)

Hi,
if you are looking for a smd, the 5630`s have the best lumens/watt of the smd`s.
But na alternative I see apart from the XPG2 is the XP-L.

Ohh wow!! The new Xhp35 takes 13w and makes 1800lumen.
I think this will bring you more than 900lumen at 7w

Regards


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## nobleimd (Jul 18, 2015)

Ok, I'll elaborate.


This is for a DC powered LED Bulb. Need 900 lumens of output from the bulb and the total power consumption must not exceed 7-8 watts. 
Right now the prototype has 18 x 5730 SMD LEDs of 0.5 watt giving about 50 lumens each.
So a total of 9 Watts is giving 900 lumens of light.
It is powered by 2x 18650 lithium ion batteries - connected in serial giving 7.4 V with 2000 mah capacity. Can get about 3-4 hours of runtime with this setup. 


Requirement is good amount of lighting for 18-25 hours. I think about 500-600 lumens would do so an automatic brightness gradient would reduce the brightness to 60-50% of original brightness over a time period to get max runtime. But even this gradient mechanism only gets to about 6-8 hours in total. 
Solutions I could think of was 
1) Increasing the battery capacity - max I could find was 3400 mah in the 18650 size
2) Finding better SMD or other LED's which would give more lumen for less watts
3) Incorporating optics or lens to increase light output or dispersion

https://www.dropbox.com/s/0c3yqu7t9ewbo5q/IMG_5716.jpg?dl=0

https://www.dropbox.com/s/yq1r28n4htvv8dj/IMG_5719.jpg?dl=0


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## m.pille.led (Jul 18, 2015)

Hi, looking good so far
Some questions
1- Is that the led driver (already conected to the leds)? If yes, what are the input voltage range?
2- Does all have to fit in to that "bulb" case?
3- What kind of light angle/distorcion do you need/prefer? 
4- Can we ask what is the lights purpose? (outside/ inside/dry/wet enviroment....)

In case of the battery capacity expansion using the same space, you can get good Panasonic 3400mah 18650`s for a reasonable price, or other 3000/3100mah from Soshine for instance. There are better alternatives, It all depends on the space available.

If you want to focus the light a little , these smds aren`t the best option

Regards


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## RetroTechie (Jul 19, 2015)

nobleimd said:


> Right now the prototype has 18 x 5730 SMD LEDs of 0.5 watt giving about 50 lumens each.
> So a total of 9 Watts is giving 900 lumens of light.
> It is powered by 2x 18650 lithium ion batteries - connected in serial giving 7.4 V with 2000 mah capacity. Can get about 3-4 hours of runtime with this setup.


*NO YOU CAN'T!* :huh: Either some of above figure(s) aren't correct, your math is off, or those LEDs have made a magical jump in efficiency.

7.4V * 2 Ah = 14.8 Wh. Over 3 hours, that's 4.9W, or 3.7W over 4 hours - not 9W. 900 lumens / 4.9W = ~184 lm/W, or ~243 lm/W if you take that 3.7W figure (ignoring driver losses). That's not realistic for these SMD leds, especially not running at specified (read: maximum) power. So either you're putting in less power & not getting those 900 lumens, or you're putting in 9W but less runtime, or your batteries are way above that 2 Ah.

That said: seems you have the bases covered. Perhaps you could find a bit higher lm/W LEDs. Change those 18650's to ~3.5 Ah cells. But other than that, it's a matter of [not get 18-25 hrs, _by far_], or [add more cells], or [dial down the lumens output].

You can't get around physics... (but if you do, please let us know!  ).


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## m.pille.led (Jul 19, 2015)

Can you test the current going from the batteries to the driver/leds? and the voltage.
Like this you know what the leds are really using, and you can better calculate the runtime.

So let`s say your leds are using 9w, and you want to run them for 20hours, then you will need a battery with 180Wh 
( In the case of a 7,4v battery that would be a capacity of 24.32Ah )

As soon as you measure the led exact consumption you can rectify this battery values.
Regards


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## nobleimd (Jul 23, 2015)

@ m.pille.led , Thanks for replying...

The bulb has an emergency function. It works on AC power when there is power. When the power goes off the internal battery kicks in and the bulb stays on till you switch it off. 

1) The driver is connected to the LED board in the picture. I think the driving voltage is 6.3 V, this based on what the chinese manufacturer has told me. 
2) Yes it has to fit inside the bulb case.
3) As much as possible. Right now being flat its 180 degrees, but more would be better, its a general purpose bulb so directional would not help.
4) Indoor use but can be used for emergency, camping events etc.

Although everything has to fit into the bulb case , the case itself can be resized to a bigger one so that probably a bigger battery can be fit in. Say a 26650 .



@ RetroTechie , Thanks for replying.

The figures are given by the chinese manufacturer, I am trying to find a way to achieve the specs:

400-500 lumens on DC mode with 20 hours runtime.
Are there more efficient LED'S now better than a 50-60 lumen 5730 SMD? If there are more efficient LED's could use them instead. I read that a 0.2 watt 2835 has better efficiency than a 0.5 watt 5730 in terms on lm/watt , so would it be better to use a 2835 here? The number of LEDs would def be an issue i guess.


Also is there a way to charge larger capacity batteries faster without damaging them?


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## SemiMan (Jul 24, 2015)

Is this for commercial purposes you are developing this .. to sell? ... or a hobby undertaking?

You are not going to get around what Retro-techie is pointing out. Based on the size constraints you have shown, without going with custom cells, you are limited to 3500mAH * 2 * 3.7 or about 25.9 watt hours. Assume say 93% boost efficiency and that gives you 24 watt hours at the batteries.

Let's assume you get 200 lumens/watt at the LEDs, and 87.5% optical efficiency. That gives you 175 lumens/watt at the LEDs ..... again best case.

So you have 24 * 175 = 4200 lumen hours .... best case. That assumes not inexpensive batteries AND it assumes high binned LEDs and more of them than typical. Practically you may be more in the 3500-4000 range, but let's take 4000.

You said you would be willing to have it dim from full to 50% over the discharge. That means 75% average brightness, so let's say 5300 total lumen hours based on initial brightness (roughly). So you could start at around 500 lumens, dim down to 250ish, and stay on for 10 hours .... best case.

Of course, here are two things you need to take into account:

- If you are doing this commercially, you better take a look at the patents out there. There are products like this on the market and some have been patented.
- Given the construction you are showing, and depending on bulb orientation (or if in a recessed can), you are going to be cooking your batteries ... and cobalt electrode lithium ions and related types ... don't like to be cooked. Given the way you describe it, the bulb is going to be on most of the time, that means you could be cooking your batteries 24/7. That 4000 lumen hours we calculated above could be 3000 and then 2000 in not that long of a time.


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