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Author 3W Cree torches in Tesco's
RJV

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3W Cree torches in Tesco's
Posted: 12/02/2020 21:45:40
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Vanoord wrote:

rikj wrote:

I think there was some spam that has now been removed.


Correct.

It lasted about 3 minutes... Guns


Unlike the Tesco torches, think I still have a couple in a box somewhere... Smile
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Speedycaver

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3W Cree torches in Tesco's
Posted: 14/02/2020 13:13:24
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I've still got one and still use it in the shed.
Mind you, I have a feeling the one I have was when they sneakily dropped it to a 1W LED as I didn't get to Tesco quick enough. Still reasonably well made though.

I am shocked by the fact it is very rare to find a torch in any high street shop that uses Li-Ion batteries, they are still either 1 or 2 AA cells or typically 3 AAA cells. So in-efficient as far as energy capacity goes. The UK is still years behind on battery technology. I have a feeling they are so cheap on Ebay, the typical shop simply can't sell them at a competitive price and make money.

USA have a better range but still not as extensive as it 'should' be nowadays.
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royfellows

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3W Cree torches in Tesco's
Posted: 14/02/2020 15:15:25
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You make a very good point.
I have often wondered why no 18650 Li Ion powered torches or cells anywhere except on the web?

Its mad.

Tony, my "Roy on torches" is possibly worth a read, if you haven't already.



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Speedycaver

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3W Cree torches in Tesco's
Posted: 15/02/2020 20:05:02
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I have already looked through your post and yes, it is interesting.

I still rely on my trusty Ultrfire WF 502B's. I use them as my back-up torch for underground as well as my main torch for site surveys for work, emergency torch in my car and general torch to hand in the house. I have them everywhere. They must be getting on for 8 or 9 years old and as good now as they were new.

I've no requirement for the search light group of torches. My view is that if 500 or possibly 1000 lumens isn't enough then check if you have remembered to open your eyes Confused Obviuously it's different if you are using them for photography or something similar.

Looking at the links you provided for the torches and LED's always makes me giggle when they state the 'Manufacturers Lumen Output'. Pretty impressive when one of the torches boasting 2200 lumens with an LED the manufacturers rated at a max of 1760 Lumens. Guns They must be refering to EU lumens which I guess must be around 30% smaller than non EU lumens Thumbs Up

I must admit, it's been years since I have looked at the latest LED on the market. I realise my lights are 'old' technology now. I'm glad to see LED's are still progressing reasonably well although the higher output ones mainly rely on being able to drive them harder and then you start expecting a single 18650 cell to provide large currents with no voltage drop, which obviously isn't going to happen. Again, with the amount of energy it takes to drive them hard, do you really need that much light from a hand torch or head torch?

I will buy a couple of the newer LED's to have a play and probably do some upgrades. Still good fun playing with LED's and batteries. Shocked
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royfellows

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3W Cree torches in Tesco's
Posted: 16/02/2020 19:12:17
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Speedycaver wrote:



Looking at the links you provided for the torches and LED's always makes me giggle when they state the 'Manufacturers Lumen Output'. Pretty impressive when one of the torches boasting 2200 lumens with an LED the manufacturers rated at a max of 1760 Lumens. Guns They must be refering to EU lumens which I guess must be around 30% smaller than non EU lumens Thumbs Up



Ah, a can of worms methinks.

The 1760 L for the XHP 35 is at the recommended max of 1050 mA. Imolent drive them at up to 1500 mA, as do others, and so do I in my new X16.

If you think about it, Cree's stated life span of 50,000 hours is Noddy land when you consider the time that a high output torch or lamp is going to be on full power. Cree have one eye on the street lighting market which makes it all add up. Plus there is the politics of their XHP 50 of which the 12V model is about 2200 L at 1500 mA. The only thing is that is poor to focus into the beam compared with the small XHP 35.

If you extrapolate the output graph you will get the output they state 1500 mA.

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ChrisJC

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3W Cree torches in Tesco's
Posted: 16/02/2020 20:52:35
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royfellows wrote:

You make a very good point.
I have often wondered why no 18650 Li Ion powered torches or cells anywhere except on the web?

Its mad.

Tony, my "Roy on torches" is possibly worth a read, if you haven't already.



I would speculate that it's the certification and compliance requirements for a product with a rechargeable battery. They are so onerous it's not worth paying the many 10s of thousands of pounds to get the pieces of paper. So sod the environment and specify Alkaline cells.

It's bad enough just doing a simple product!

Chris.
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royfellows

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3W Cree torches in Tesco's
Posted: 16/02/2020 21:07:08
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Just another comment about the overdrive on the XHP 35s

if one casts ones memory back a few years to when the XPGs were first announced, they did exactly the same thing. Max recommended drive current 1050 mA

Then later up to 1500 mA

Deja Vu?

Chris
You make a good point. Probably same unavoidable piece of paper that ended Caving Supplies bomb proof SRT sit harnesses.

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IP: 92.23.174.59 Edited: 16/02/2020 21:10:19 by royfellows
Speedycaver

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3W Cree torches in Tesco's
Posted: 17/02/2020 09:40:01
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royfellows wrote:



If you extrapolate the output graph you will get the output they state 1500 mA.


Ah yes, I see.
It would give a fv of over 12.5 volts too.
So all you need is an 18650 cell that can maintain 4.7 A @ 4.0 V, assuming no losses in the driver. No problem,... for about 1 second Roll Eyes

I guess it's always been a war of figures but pleasing to see their stated figures are actually possible. I stand corrected. Tongue

Out of interest, I have just ordered some bits and pieces from FastTech, including the S2 torch body to play with. Also, a set of 21700 cells which I didn't even realise were readily available till I read your threads Roy. I will experiment with replacing some of the older 3 x 18650 battery packs with 2 x 21700 cells. About the same weight but significantly more energy / burn time.

You have sparked my interest again my friend. Thumbs Up
IP: 86.154.231.35 Edited: 17/02/2020 10:09:10 by (moderator)
royfellows

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3W Cree torches in Tesco's
Posted: 17/02/2020 10:07:29
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Speedycaver wrote:

royfellows wrote:



If you extrapolate the output graph you will get the output they state 1500 mA.


Ah yes, I see.
It would give a fv of over 12.5 volts too.
So all you need is an 18650 cell that can maintain 4.7 A @ 4.0 V, assuming no losses in the driver. No problem,... for about 1 second Roll Eyes

I guess it's always been a war of figures but pleasing to see their stated figures are actually possible. I stand corrected. Tongue

Out of interest, I have just ordered some bits and pieces from FastTech, including the S2 torch body to play with. Also, a set of 21700 cells which I didn't even realise were readily available till I read your threads Roy. I will experiment with replacing some of the older 3 x 18650 battery packs with 2 x 21700 cells. About the same weight but significantly more energy / burn time.

You have sparked my interest again my friend. Thumbs Up


I am happy that I have rekindled your interest, and you know where I am if you need any help.

Re your second paragraph. It is technically quite possible to get that output from a single cell with a boost driver. Imolent do it. But the torch I link to fails in that it is a generic driver which typically does nothing perfectly. You will find an old thread of mine somewhere, where I lab test it.

The 21700 are quite bulky and the capacity is not much more than the 20700, but they support a higher discharge rate.
I have played around with all these and in the end found that best bang for bucks relative to weight that can comfortably be wore on the back of a helmet is still 4 X 18650.

It is fun plying around though, and it is the real way to learn about all this stuff.

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IP: 86.154.231.35 Edited: 17/02/2020 10:09:21 by (moderator)
lozz

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3W Cree torches in Tesco's
Posted: 17/02/2020 10:29:52
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From the specs. I make it approx. 12.6 to 12.7V for 1500mA.

I wouldn't recommend exceeding the manufactures spec for current by nearly 50%, at least not for continuous current.

Lozz.
IP: 86.163.245.164 Edited: 17/02/2020 10:30:46 by lozz
Speedycaver

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3W Cree torches in Tesco's
Posted: 17/02/2020 11:11:46
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lozz wrote:

From the specs. I make it approx. 12.6 to 12.7V for 1500mA.

I wouldn't recommend exceeding the manufactures spec for current by nearly 50%, at least not for continuous current.

Lozz.


12.62 was my calc but who's counting. Roll Eyes

Roy's point is that in order to maintain a certain light output after 50,000 hours or what ever, you can only drive it so hard but, in reality, we would only drive a torch at full power for 50 hours in its lifetime and so it could be driven harder and the drop in performance would be acceptable.

That said, it does depend on how over engineered the LED is and what the light is being used for. If it's a light that you will be relying on then it makes sense not to exceed the manufacturers figures but if it's just a secondary light then it's probably not such a risk.

A lot of it depends on the quality of the heat sink. A poorly heat sinked (is that a word..???) LED running at 50% duty will still burn out in minutes.
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lozz

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3W Cree torches in Tesco's
Posted: 17/02/2020 11:45:10
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Speedycaver wrote:

Roy's point is that in order to maintain a certain light output after 50,000 hours or what ever, you can only drive it so hard but, in reality, we would only drive a torch at full power for 50 hours in its lifetime and so it could be driven harder and the drop in performance would be acceptable.

That said, it does depend on how over engineered the LED is and what the light is being used for. If it's a light that you will be relying on then it makes sense not to exceed the manufacturers figures but if it's just a secondary light then it's probably not such a risk.

A lot of it depends on the quality of the heat sink. A poorly heat sinked (is that a word..???) LED running at 50% duty will still burn out in minutes.


It's the power that the device wants to dissipate that's the danger, used to get the same problem with other semiconductors, exceed the specs for any length of time and they can go splat, they generally don't like it up 'em, excess voltage, current, heat etc.

Lozz.
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royfellows

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3W Cree torches in Tesco's
Posted: 17/02/2020 11:58:14
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They don't suddenly go splat, except from overheat. They then take a blue tinge and die.

Overdrive, to go splat they need a lot more current.

As I said, Imolent are overdriving XHP 35s at 1500 mA in a lot of their torches which must sell worldwide by the thousand.

I had one running at 1500 mA for weeks up a corner, until I realised that any slight loss of performance over time would be so slight I was wasting my time doing the experiment.

I have boxes of old LEDs from upgrades etc, plenty of lab fodder!

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royfellows

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3W Cree torches in Tesco's
Posted: 17/02/2020 12:13:12
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I was just about to go and get some shipping but turned back as something occurred.

You cant compare a quad die Light Emitting Diode with other semi conductor components in this respect, the latter normally being subject to a tolerance of as little as 5%.

Anyone can do something daft at some time, well.............
I had a customers lamp returned with flood light failure. In truth the floods not the strongest point on some of my previous lamps. The lamp had 2 series wired, and upon examination, one was perfect, the other fried.

Looking closely with good magnification it became apparent that one was a XPG which was wired in series with an XPL, a completely different rated type of emitter. Both has been used at up to 3 amps, the XPG max being 1500 mA.

Obviously a mispackaging error that had carried on the the assembly. But the surprise was how long they had lasted for.

A daft mistake which I should have spotted, but it happens.

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lozz

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3W Cree torches in Tesco's
Posted: 17/02/2020 12:58:17
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royfellows wrote:

You cant compare a quad die Light Emitting Diode with other semi conductor components in this respect, the latter normally being subject to a tolerance of as little as 5%.


Exceeding any semiconductors maximum ratings can cause it to fail prematurely, whether that be excess voltage, current or junction temperature.

Just sayin'

Lozz.
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royfellows

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3W Cree torches in Tesco's
Posted: 17/02/2020 13:21:50
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lozz wrote:

royfellows wrote:

You cant compare a quad die Light Emitting Diode with other semi conductor components in this respect, the latter normally being subject to a tolerance of as little as 5%.


Exceeding any semiconductors maximum ratings can cause it to fail prematurely, whether that be excess voltage, current or junction temperature.

Just sayin'

Lozz.


and in this case "prematurely" means less than 50,000 hours, so we are not really in disagreement.
Big Grin

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royfellows

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3W Cree torches in Tesco's
Posted: 17/02/2020 13:24:09
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Just moving on a bit, anyone who messes with LEDs would be wise to grab a pair of welding goggles. Seriously.

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royfellows

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3W Cree torches in Tesco's
Posted: 17/02/2020 15:35:29
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Apologies over my last, something go wrong.

Just for the fun of it, I have taken an old, much used, Cree XPL and connected it to my lab power supply at 6 amps. This is double the maximum recommended drive current.

The supply is reading 6 amps, the light shining on it makes it look like 5. Take a look at the Vf.

Be fun to see how long it lasts, its done half an hour now. I reasonably expect it to go into diminishing output and then die. Question is "How long"?

I will advise when it dies. Not looking for an argument or anything, anyone can draw their own conclusions.

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lozz

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3W Cree torches in Tesco's
Posted: 17/02/2020 15:47:19
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Edit facility has disappeared from my last post....what's going on?

EDIT: I've now deleted the said post.

Lozz.
IP: 86.163.245.164 Edited: 17/02/2020 16:14:43 by lozz
royfellows

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3W Cree torches in Tesco's
Posted: 17/02/2020 15:54:19
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I dont know. If its my fault I really am sorry.

The LED has just failed due to overheat as the heat sink, an old computer PCB heat sink, became seriously hot. I have set up anew experiment using a sheet of 16 SWG copper and will report. I find it interesting stuff.

I can remember computers failing when the heat sink became detached from the CPU due to a clip failing. AMD processors would fail instantly if not heatsinked. Some heat sinks had a copper core protected by a strip and careless assembly would forget to remove the protection strip. Zap

Used to have an IT company. Used to do a lot of things.

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