Yet another LED storry: Cree 7x XM-L LED 9000LM T6 Bicycle Head - Page 1
Forum section: electronics / general

author: Unknown
author_rank: Unknown
timestamp: May 14, 2014, 11:51:32 pm
content: *REMOVED BY MOD AT USERS REQUEST*

author: David_AVD
author_rank: Super Contributor
timestamp: May 15, 2014, 02:12:42 am
content: Do you honestly believe any rating or brand claim when it comes to eBay stuff like that?

author: staxquad
author_rank: Frequent Contributor
timestamp: May 15, 2014, 05:21:25 am
content: That driver probably can't handle high current, they surely are not driving the leds in series from the 8.4v batteries (differing current to each led in parallel, more prone to damage), and the leds can't be driven at high current for lack of proper heat sinking. XML T6 max lumens are around 900lm at 3A with optic losses of more than 10%, so at .7A for 7 leds, you're getting max 1960lm which is a decent amount of lumens/$.With leds more efficient at lower current, you're getting more lumens per watt and less heat. Trying to drive the 7 leds at full current is inefficient, producing lots of heat that can't be gotten rid of easily, increasing the weight of the light if you try and cost of the driver (can't use a cheap driver).The reason why you increase the number of leds in a light is to make the light more efficient, not to blast away. Their performance claims on those EBAY lights always make no sense, but it helps to sell their product.from the Cree Product Characterization Tool

author: ConKbot
author_rank: Super Contributor
timestamp: May 15, 2014, 01:20:14 pm
content: Take and post the best macro photo of the LED from the front that you can. A lot of times you dont need to pull it apart to identify the LED as you can see the important stuff from the front, and there isnt that much important stuff on the sides.

author: Corporate666
author_rank: Unknown
timestamp: May 15, 2014, 04:02:04 pm
content: Almost certainly not a real Cree LED.I'm with the other guy - I don't get why people buy this junk thinking they are getting anything like what the ads say. Assume that anything coming from China with LED's is knock-off junk, and presume it's a 100% fact for anything bought on eBay or Alibaba or DX.Cree XM-L's are just over $3/ea in reels. eBay fees are about 15%. So for this auction at $31, that's $4.65 to eBay leaving $26.35. If they were real Cree XM-L's, there would be about $21.50 worth of LED's, leaving $4.85 for the housing, lenses, switch, packaging, anodizing, driver, strap and all the manufacturing costs. There's at least a couple bucks worth of aluminum in there, and I'm guessing a few bucks worth of parts in the driver at least, plus a couple bucks of labor and packaging. So if this device had real Cree XM-L's, it would be a money loser.There isn't a single LED from Cree, IMO, that isn't knocked off in China, especially the more popular ones.Simple answer - it's not Cree XM-L's. As should be expected.

author: staxquad
author_rank: Frequent Contributor
timestamp: May 15, 2014, 04:50:41 pm
content: QuoteI don't see what pereczes' problem is. He was satisfied, until he delved into the fictional specs, and at that price, he's getting lots of lumens in an efficient manner.There aren't any lights at any price out there that output 9000 lumens from 7 XML T6 leds. It doesn't exist, not even for $12,000,000. Get realistic.When you buy a fake Rollex for $40, you can't expect it to look, perform, contain gold and other precious metals and jewels, have a Swiss movement, a sapphire crystal, waterproof to 200M, have a 2 year warranty and last a lifetime like a real Rollex. Some people are even satisfied with their fake Rollexes, knowing what they are and what they paid.The Lupine Betty R7 costs $1,100, has 7 XML-2 leds, their maximum output is 4500 lumens because they only drive their light to 1.7A. It's not the max current that's paramount, it's the efficiency. And if you run that $1,100 light at max, you get only 1 hr run time. It's not designed to run at max, unless you are prepared to load up in batteries (and blind everybody you encounter).At $40, Lupine wouldn't even let you sniff their light, and pereczes expects double the performance at $40 against a $1,100 light.Even a taskled H6Flex or b3Flex costing $40 each can't drive 7 leds in series (max is 5), you'd need 2 of them, so just the drivers would cost double pereczes' light. (georges80 would know the solution for 7 series XML-2,Taskled makes the hyperboost which can drive 7 XML in series, costs $40, the same cost as pereczes' light; Lupine spare no expense to make their custom driver and custom optics and most likely get choice leds from Cree that are exacting in color temperature (6000K) and intensity. Those cheap lights probably use less desirable color temperatured leds: reject bins.(running the leds is series forces each led to get the same current)

author: staxquad
author_rank: Frequent Contributor
timestamp: May 15, 2014, 06:22:47 pm
content: Quote from: pereczes on May 15, 2014, 05:58:41 pmI'm sure you can find a Lupine clone from China for less than $100 with twice the specs. Just don't go comparing them side by side."is far from being what is advertised", when it's impossible, and you expect them to deliver, you are deluding yourself.bottom of the barrel bins are cheap, but don't expect them to deliver like the choice ones you can't get because you're not a respected manufacturer of quality EXPENSIVE lightsMy advice, put lipstick on your light, instant transformation, or send the light back and continue to buy and return the cheap lights from China until one delivers 9000 lumens from 7 XML T6 leds.

author: dannyf
author_rank: Super Contributor
timestamp: May 15, 2014, 06:57:12 pm
content: QuoteYou are too kind.

author: staxquad
author_rank: Frequent Contributor
timestamp: May 15, 2014, 06:59:46 pm
content: Quote from: pereczes on May 15, 2014, 06:43:44 pmthere's no defect, except your ethicsall ebay sellers here will/should avoid you like the plague

author: staxquad
author_rank: Frequent Contributor
timestamp: May 15, 2014, 07:35:38 pm
content: Quote from: pereczes on May 15, 2014, 07:15:59 pmThere's nothing wrong with your light, yet you want your money back and keep the light or get another for free. That's a red flag to sellers that they will go in the hole dealing with you.

author: ConKbot
author_rank: Super Contributor
timestamp: May 15, 2014, 07:56:32 pm
content: Quote from: pereczes on May 15, 2014, 02:09:07 pmThats definitely an XM-L, or at least a more than minimal effort copy. Not like they were sticking 3W LEDs in and calling it XM-L's So they arent being totally facetious. Though there is a conformal coating over the whole board which is kind of naughty to do over the dome of the LED.

author: dannyf
author_rank: Super Contributor
timestamp: May 15, 2014, 07:58:31 pm
content: QuoteLet me be the first one to say that it is you who are writing those offending messages. Other people were trying to help you see the light and have a more realistic understanding of the situation.If it were me, I wouldn't have responded to you at all. Those other people were obviously much nicer and kinder than I am.BTW, please stop sending me private messages to threaten me, as I have no interest in hearing from a bully like you.If any part of this is not clear to you, please ask again in public.

author: ConKbot
author_rank: Super Contributor
timestamp: May 15, 2014, 08:08:03 pm
content: Quote from: pereczes on May 15, 2014, 08:00:41 pmhttp://www.ledsmagazine.com/content/dam/leds/migrated/objects/news/7/11/12/Cree11110v2.jpgUsing that as a reference, the orientation of the bond wires and the current distribution grid on top of the die match up. The orientation of the big and small bare metal in the corners. The orientation of the ESD diodes in on the side opposite of the bond wires. I'd expect at least something to get messed up or omitted for a cheap and dirty knock off. Since its all there, it means either(in decreasing order of probability) A) its a knock off that took more than a little effort B) its a cree reject which found its way into the grey market. C) somehow, its a real cree, and someone got a good deal.

author: ConKbot
author_rank: Super Contributor
timestamp: May 15, 2014, 08:32:54 pm
content: Quote from: pereczes on May 15, 2014, 08:21:42 pmThe offical way to do that is an integrating sphere. It is coated with a diffuse, reflecting surface inside of it, this scatters the light all around evenly so that every surface in it is homogenous. Then a lux-meter measures out the brightness on one section of that surface. Backwards with a little math and out comes lumens.You could also buy a known legit XM-L and a lux meter. Put the questionable source 'XM-L' and the legitimate one on the same type of MCPCB (Yes, it makes a difference) mount them next to each other on a heat sink, set up your lux meter, a fixed distance away. Turn on one, see how many lux you get, turn on the other, see how many lux you get.

author: dannyf
author_rank: Super Contributor
timestamp: May 15, 2014, 08:35:31 pm
content: QuoteKnocking off LEDs isn't that difficult - China has a gazillion LED fabs / repackaging shops so I wouldn't be surprised if they managed, long time ago, to make copies of real leds, with high degree of similarities to the real thing - there is actually a terminology in China for that: "high fidelity knock-off".