ultrafire w-878 fried LED

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karkis1
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ultrafire w-878 fried LED

Hello,

I know my problem and especially the reason for my problem will sound stupid (If not more) to you, but here goes… I am in the military(not the U.S. don’t worry :D) and i need a good flashlight for night hikes etc. I received the flashlight today that i ordered a few weeks ago. It’s called Ultrafire w-878. I liked it really much, but the genius that I am i tried connecting 2×26650 batteries to it(thought it’d shine brighter lol) even though it only supports one of them. For a few seconds it shined really bright, I even managed to get the idea that I made a smart move, but then the light stopped working. I took it all apart, tried connecting the single battery directly to the cree led, but no signs of life from it.

Sooo…. my question to you is- can I fix it? I mean i’ve seen cree leds on dealextreme today that don’t even cost that much. I know how to solder quite well. Would changing the led fix the flashlight or is it something worse?

Also I thought if it’s possible I’d like to install a more powerful led then the original one, but i know nothing about these things and i’m completely lost amongst all of the drivers, and leds and all. If it’s fixable, what’s the most powerful led I can instal without changing the driver?(as I don’t even understand how to remove it)

Thanks for the help

Oh and P.S. I checked with a volt meter, the driver doesn’t cut off the electricity coming from the battery, It comes up to the LED which doesn’t shine

Edited by: karkis1 on 11/11/2013 - 14:27
Tom E
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Welcome!

I have basically the same light I modified up with a few things. Sounds like you can simply replace the LED/star. It should be 20mm, but I'd measure it first. Best replacement would be an XM-L2 U2 on a copper star, like a Noctigon or SinkPAD. Several places to buy them, depends how fast, how much, where you are...

One good source: http://intl-outdoor.com/noctigon-xm20-mcpcb-cree-xml2-u2-1d-led-p-767.html

Here's a review with some detail info: http://budgetlightforum.com/node/20425. It's got 2 wires soldered on - you'd have to remove the connections, ans re-solder the new one. The PCMCB (ie star) is either seated with thermal greasw or thermal epoxy. If epoxied, you simply have to pry it off to break the bond. Clean up the surface well, and re-epoxy with thermal adhesive.

karkis1
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The current LED has writing saying “cree xml u2” on it. Is it possible to get a something more powerful?

Tom E
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You want to go with XM-L2 - 20% higher output or so. XM-L2 U2 is the brightest, available in 1A, 1C, or 1D tints. XML U2 is one generation back but still is commonly found in new lights.

karkis1
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Oh i see now. On dealx it says the xml u2 has 320 lumens and the xml2 u2 has 960. So it’s 3x more powerful? or do i get it wrong?

djozz
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Yes, if you are sure that the driver survived, it should not be too hard to put in a new led, if you buy one that is already mounted on a board. It should go something like this: open the head of the flashlight, get to the led board and unsolder the wires. Get a new board+led of the same size and some cheap thermal paste (the stock light may not have thermal paste under the led board, but it helps keeping the led cool if you apply a very thin layer of paste under the board anyway). Solder in the new board and assemble the light. 

EDIT: three answers during the write-up of my post, and better ones too, I am really slow!

karkis1
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Lol It’s okay. Thanks for all of the help. I just ordered a new LED. Hope everything works when it arrives.

Tom E
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Umm, don't believe DX on anything to do with lumens or amps - they lie like all the other CH/HK/eBay sources. This is a pretty good source for info: http://flashlightwiki.com/Cree. But even the lumens listed on the wiki site are theoretical - in real lights you have loss's due to reflectors, lens, optics, etc. The 878 is an aspheric lens light, so loss's are pretty high, like 20-30% or so, more when zoomed for throw. Reflector based lights have less of a loss.

Pulsar13
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Broke your first light modding? Wow – you’ll fit right in here in BLF! :bigsmile:

Did you order the XML2 on copper from IOS?

Just a heads up – single cell light might not power XML2 at full power, so it may not be much brighter as you’d like it to be. However it may still be of similar brightness, only more efficient (less heat + more battery life). Not a bad thing.