Led headlight swap

Hello,

I have a old headlight that has terrible runtime of 2 hours for not many lumens,it also has a red and green led. Thing is that I like the size and focus capability of the beam and wish t install a far more efficiant led in walm colour. It doesn't have any reflectors only a lens. Do you think that adding adding a new led will help and is it even possible? [/url]

Hey petro. What is the power source for the light? Also what kind of output are you looking for? Just based off size I would tell you to look into something like a Cree XP-G led, but I'm not sure if you could power it well with the current driver and battery. Also keep in mind you don't have much room for a heatsink in there so that's going to limit you output potential.

Hello black mag

Its got 2 aa and a nicha led ( im guessing around the standard 3v mark, but ill measure it) developing 0.5w oficially, but id actually say it pulls more like 1w with an output of 26 lmn.

The output i'mlooking for is more for longevity rather than power, the brightness does me at the moment so round 30 to 40lmn mark, hopefully rummung for 8 hours ish.

I have seen the leds of that chip size but bearing in mind that the pillar only allows for a circular 7mm diameter heat sink, and it has to be a sealed unit for waterproofness, so no air ventilation. Would an led of the undomned type burn up?

I think the driver will surfice and the voltage, being as the current is almost certainly going to have to be reduced, I think a resistor should curtail that. But as I obvious with head torches theres not much room for modification in aspecifically designed unit. Is it possible or do you think it Is a road to nowhere ?

Well as far as size goes you could easily fit a bare XP-G or XP-G2 in there and since you only want to drive it around 40 lumens you wouldn't need much of a heatsink. And assuming it puts out around 3 volts that would work fine with an xp-g too. But as you said you would have to seriously limit the current somehow. Here is the spec sheet for XP-G2 http://www.cree.com/~/media/Files/C... Modules/XLamp/Data and Binning/XLampXPG2.pdf. Note the lumen output on page 3 at 350mah.

1W and 26 lm doesn't sound right. That would be absolutely terrible efficacy for a modern LED. Nichia is normally a pretty good LED, so I wonder if maybe your numbers are a bit off? You should be able to get 100 lm/W today without even trying.

2 AA cells give around 6 W-H, so running at 1W should give you around 6 hours at 100% efficiency. The drivers you need to run a white LED on 2 AA cells will probably be in the 70-75% efficiency range, so you should probably expect 3.5-4.5 hours at 1W or 7-9 hours at 0.5W. Running at 0.5W should easily give you 50 lm at the emitter, 30-40 lm OTF. So you are not asking for anything that's unreasonable.

Thanks for the help, wasnt sure whether such a tiny heatsink would cut it.

I made a mistake actually, its a 2 AAA battery headlamp, withzoom 1 to 4, which is why I like it so much over others, its small and light, with good optics, and even a red and green led if needs be. Its one of these. Nice button controls too. The problem is the fancy optics constrain heatsinking almost entirely In all directions.

http://www.climbers-shop.com/10893101/products/cybalite-trio-headtorch.aspx

Generic out of china job to be rebadged by whomever. Theyve come down in price over the years!

So 2 AAA s are about 2watt hours minimum or 3 with better batteries. At 70% efficiency thats coming in at 1.5watt hours minimum, or 200 lumens to be divided up as you see fit, so 4 times the led thats in there at the moment. I think about 40lumens is about all i'll allow on high (I never use anything on low, as high is just so appealing).

I thanks for the info.

Edit:

Something else has just rung a bell as well, the batteries being AAA would be draining at around 350ma which would absolutley kill them, so that may be why swapping the led for something drawing 150ma will greatly improve the run time, and I think thats why the nichia led is soo poor, or is it the driver/regulator is abysmal? Apologies for the AA AAA mistake when typing it up, it may have had quite an effect on the anwers.

I have the xpg installed now, after having reducing the aluminium heatsink down by 3\4 and I am thinking that to reduce a 1w led current will be one of the following:

A) simple enough 1/4 watt

Or

B) a lot more as the base is so small now the heat is some how greater closer to the led.

Any help appreciated

DIWdiver said:

1W and 26 lm doesn't sound right. That would be absolutely terrible efficacy for a modern LED. Nichia is normally a pretty good LED, so I wonder if maybe your numbers are a bit off? You should be able to get 100 lm/W today without even trying.

2 AA cells give around 6 W-H, so running at 1W should give you around 6 hours at 100% efficiency. The drivers you need to run a white LED on 2 AA cells will probably be in the 70-75% efficiency range, so you should probably expect 3.5-4.5 hours at 1W or 7-9 hours at 0.5W. Running at 0.5W should easily give you 50 lm at the emitter, 30-40 lm OTF. So you are not asking for anything that's unreasonable.

Click to expand...

Your suspitions where correct, the circuitry is absolutley useless. The nicha led, even though it had heatsinking of just 2 thickish wires, no alu base, it was primarily faulted by the onboard circuitry, pulling a whopping 450mah 1.35w roundabout, for the output of 26lumen. The thing is that I do not know how they have achieved this, attaching 3AAA direct to the xpg2 led with no resistance gives almost as much light at 75mah, or 0.33w. Oh well it always was a project for the sake of it, I like the the optics so it will have to be done in the future, i'll just have to scrape the circuit board as the optics are mounted to it, 2 toggle push to make switches also that I could not replace are also attached, so ill have to put a citcuit on that.