Cree led deterioration
 

I was going to ask last week if Cree LED's deteriorated with age, but I
have just installed a new set of batteries (3x AAA) and it is back to
its full amazing power. I bought the little Cree torch around 8 years
ago in Aldi or Lidl and I was astounded by its intensity of its beam. I
guess I rather expected it to just rapidly dim as the batteries failed,
rather than the slow deterioration I got. A battery tester suggested
the batteries were still good.

I also had in mind to keep my eyes open for another Cree torch as a
replacement.

Cree led deterioration
 

Harry Bloomfield wrote:
I also had in mind to keep my eyes open for another Cree torch as a
replacement.

It should be borne in mind there is 'Cree' and 'ebay Cree', the latter being
whatever LEDs the Chinese vendor managed to find and label as Cree. I
wouldn't be surprised if the latter isn't as high quality. I'd expect
Aldidl quality to be somewhat better.

Theo

Cree led deterioration
 

In article ,
Harry Bloomfield wrote:
I was going to ask last week if Cree LED's deteriorated with age, but I
have just installed a new set of batteries (3x AAA) and it is back to
its full amazing power. I bought the little Cree torch around 8 years
ago in Aldi or Lidl and I was astounded by its intensity of its beam. I
guess I rather expected it to just rapidly dim as the batteries failed,
rather than the slow deterioration I got. A battery tester suggested
the batteries were still good.

I would have expected it to produce the same light output then deteriorate
rapidly as the batteries reach the end of their life.

Only LEDs I've had which deteriorated - rather than fail - were some cheap
warm white low current types. They got dimmer and dimmer - despite being
conservatively driven.

--
*You're never too old to learn something stupid.
Dave Plowman London SW
To e-mail, change noise into sound.

Cree led deterioration
 

I think it very much depends on the circuit running the leds. Some of them
actually use a stabilisation system so the battery really needs to be pretty
knackered for it to dim, while others perform more like a real old fashioned
torch and the light dims as the battery volts drop.

Brian

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"Harry Bloomfield" wrote in message
...
I was going to ask last week if Cree LED's deteriorated with age, but I
have just installed a new set of batteries (3x AAA) and it is back to its
full amazing power. I bought the little Cree torch around 8 years ago in
Aldi or Lidl and I was astounded by its intensity of its beam. I guess I
rather expected it to just rapidly dim as the batteries failed, rather than
the slow deterioration I got. A battery tester suggested the batteries were
still good.

I also had in mind to keep my eyes open for another Cree torch as a
replacement.

Cree led deterioration
 

On 06/06/2018 07:25, Brian Gaff wrote:
I think it very much depends on the circuit running the leds. Some of them
actually use a stabilisation system so the battery really needs to be pretty
knackered for it to dim, while others perform more like a real old fashioned
torch and the light dims as the battery volts drop.

If the torch has three cells I suspect it's connected directly to the
LEDs with resistors to drop the voltage to 4V and limit the current. A
torch with two cells must have some kind of voltage multiplier which may
regulate the current in a clever way as the battery drains.

--
Max Demian

Cree led deterioration
 

In article ,
Max Demian wrote:
On 06/06/2018 07:25, Brian Gaff wrote:
I think it very much depends on the circuit running the leds. Some of them
actually use a stabilisation system so the battery really needs to be pretty
knackered for it to dim, while others perform more like a real old fashioned
torch and the light dims as the battery volts drop.

If the torch has three cells I suspect it's connected directly to the
LEDs with resistors to drop the voltage to 4V and limit the current. A
torch with two cells must have some kind of voltage multiplier which may
regulate the current in a clever way as the battery drains.

Yes - have a two D cell Lidl one which is brilliant. That seems to stop
working suddenly. But has a very good battery life.

--
*I'm planning to be spontaneous tomorrow *

Dave Plowman London SW
To e-mail, change noise into sound.

Cree led deterioration
 

Dave Plowman (News) wrote :
Yes - have a two D cell Lidl one which is brilliant. That seems to stop
working suddenly. But has a very good battery life.

All are a long way from the glow worm filament lamps of a few years
ago.

Cree led deterioration
 

In article ,
Harry Bloomfield wrote:
Dave Plowman (News) wrote :
Yes - have a two D cell Lidl one which is brilliant. That seems to stop
working suddenly. But has a very good battery life.

All are a long way from the glow worm filament lamps of a few years
ago.

Absolutely. If only domestic LEDs gave the same improvment over tungsten
(I'm not talking efficiency)

--
*Indian Driver - Smoke signals only*

Dave Plowman London SW
To e-mail, change noise into sound.

Cree led deterioration
 

On Wed, 06 Jun 2018 07:25:00 +0100, Brian Gaff wrote:

I think it very much depends on the circuit running the leds. Some of
them actually use a stabilisation system so the battery really needs to
be pretty knackered for it to dim, while others perform more like a real
old fashioned torch and the light dims as the battery volts drop.

Avoid the ones that utilise 3 or 4 AA cells since that *usually*
indicates the use of a simple dropper resistor to limit the LED current
to a safe maximum limit on a fresh battery of cells. Not only is this
wasteful of expensive battery energy, it also leads to a rapid reduction
in light output and a shortening of battery life during the all too brief
useful light output phase.

A much safer bet that a proper electronic ballast circuit has been used
to stabilise the light output efficiently and improve battery life, is to
pick a torch that uses only one or two cells since the lower voltage
mandates the use of an electronic ballast to drive the LED.

That's not to say a 3 or 4 cell torch can't use a proper electronic
ballast module as in the case of the LED bulb upgrade modules for the
three D cell "Maglight" torches and clones, it just seems so unlikely
that anyone would encumber a 'designed from scratch' electronically
ballasted LED torch with more cells than are strictly required.

In the days before LED Torch bulbs existed, there was a very good reason
to use 3 or 4 D cells in a torch; the higher wattage tungsten filament
torch bulbs needed that extra voltage (and battery life) to provide the
brighter light output for which they'd been designed.

The only downside of an electronically ballasted LED torch is the
ballast circuit's negative load impedance which makes battery contact
resistance effects even more of a nuisance than they were with good old
fashioned torch bulbs (and the tungsten filament torch bulbs had their
own built in negative impedance effect due to their extremely positive
temperature coefficient of resistance over their normal working voltage
range). Good quality high pressure spring battery contacts are a vital
part of a modern day torch using an electronically ballasted LED lamp.

--
Johnny B Good

Cree led deterioration
 

On 05/06/2018 15:44, Dave Plowman (News) wrote:
In article ,
Harry Bloomfield wrote:
I was going to ask last week if Cree LED's deteriorated with age, but I
have just installed a new set of batteries (3x AAA) and it is back to
its full amazing power. I bought the little Cree torch around 8 years
ago in Aldi or Lidl and I was astounded by its intensity of its beam. I
guess I rather expected it to just rapidly dim as the batteries failed,
rather than the slow deterioration I got. A battery tester suggested
the batteries were still good.

I would have expected it to produce the same light output then deteriorate
rapidly as the batteries reach the end of their life.

For short bursts quite badly deteriorated batteries can drive an LED
torch OK - especially one which has a voltage to current converter drive
for the LED. It will run the batteries down until they leak if you let
it (especially one with three batteries where the weakest one dies).

Only LEDs I've had which deteriorated - rather than fail - were some cheap
warm white low current types. They got dimmer and dimmer - despite being
conservatively driven.

That is quite unusual. The only power LEDs I have ever seen dim with age
have been on inadequate heatsinking and run *very* hard. After a while
you can see blackening of the previously yellow phosphor and yellowing
of the nominally water clear plastic lens.

--
Regards,
Martin Brown

Cree led deterioration
 

Johnny B Good presented the following explanation :
The only downside of an electronically ballasted LED torch is the
ballast circuit's negative load impedance which makes battery contact
resistance effects even more of a nuisance than they were with good old
fashioned torch bulbs (and the tungsten filament torch bulbs had their
own built in negative impedance effect due to their extremely positive
temperature coefficient of resistance over their normal working voltage
range). Good quality high pressure spring battery contacts are a vital
part of a modern day torch using an electronically ballasted LED lamp.

Thanks, I was thinking to buy a newer one anyway.

Cree led deterioration
 

In article ,
Martin Brown wrote:
Only LEDs I've had which deteriorated - rather than fail - were some
cheap warm white low current types. They got dimmer and dimmer -
despite being conservatively driven.

That is quite unusual. The only power LEDs I have ever seen dim with age
have been on inadequate heatsinking and run *very* hard. After a while
you can see blackening of the previously yellow phosphor and yellowing
of the nominally water clear plastic lens.

These looked perfectly normal. They were used to illuminate a meter -
replacing the original pea bulbs.

I just assume I got a bad batch somehow. They were pretty cheap ones from
China via Ebay. Not silly cheap though. Replaced them using exactly the
same drive electronics, and those have been fine.

--
*IF ONE SYNCHRONIZED SWIMMER DROWNS, DO THE REST DROWN TOO?

Dave Plowman London SW
To e-mail, change noise into sound.

Cree led deterioration
 

On 06/06/2018 17:26, Martin Brown wrote:
On 05/06/2018 15:44, Dave Plowman (News) wrote:
In article ,
Â*Â*Â* Harry Bloomfield wrote:
I was going to ask last week if Cree LED's deteriorated with age, but I
have just installed a new set of batteries (3x AAA) and it is back to
its full amazing power. I bought the little Cree torch around 8 years
ago in Aldi or Lidl and I was astounded by its intensity of its beam. I
guess I rather expected it to just rapidly dim as the batteries failed,
rather than the slow deterioration I got. A battery tester suggested
the batteries were still good.

I would have expected it to produce the same light output then
deteriorate
rapidly as the batteries reach the end of their life.

For short bursts quite badly deteriorated batteries can drive an LED
torch OK - especially one which has a voltage to current converter drive
for the LED. It will run the batteries down until they leak if you let
it (especially one with three batteries where the weakest one dies).

Only LEDs I've had which deteriorated - rather than fail - were some
cheap
warm white low current types. They got dimmer and dimmer - despite being
conservatively driven.

That is quite unusual. The only power LEDs I have ever seen dim with age
have been on inadequate heatsinking and run *very* hard. After a while
you can see blackening of the previously yellow phosphor and yellowing
of the nominally water clear plastic lens.

+1, IME even cheap eBay "Crees" last very well. I have them all over the
place.

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