L4 regulation???

If I understand correct the SF L4 is regulated on 2 cells and will operate on one cell but not in regulation.If this is correct how did this light perform so well in the 123 shootout test recently done?It showed this light still running brightly at over two hours.It even was brighter than other regulated lights and I was curious how this was if it was not regulated.Any one have any info. on this?

Depending on the cell, I believe it will run in regulation for a while at least. But regardless, the boost circuit will do what it can with the available power, and since Li batteries enjoy a relatively flat output over their life, the L4 on one cell does a reasonably good job of staying bright.

Can't comment on the "shootout" you refer to since I didn't see it. And I'm sure there are others out there who will be able to offer a better (hey, maybe even accurate) explanation than I did.

According to the shootout thread, the TW4 (1 cell L4) stayed cool, so that is a good indication that everything is running efficiently (less energy converted into heat).

Erik.

If it ain't drawing any appreciable current, it will run long and cool. It's running out of regulation but I don't know if that means it's more efficient.

CM

CM, you are certainly the electro guy (I know very little). However, I am curious, if there is less heat being generated while equal light is generated, what else are the electrons doing? (assuming the same color spectrum spread)

I would think that a measure of total light produced (over time) + total heat produced (over time) should tell the whole story. Or is efficiency not related to heat???

Thanks for any insight,

Erik.

i think the long runtime has to do with both the KL4 running out of regulation and its LED being underdriven. from what i've read, LEDs generally become more efficient the softer they're driven. running the KL4 out of regulation also probably means no current is wasted on the regulation circuitry. i'm no techno whiz though, so don't take my word for it. i'm sure someone more well-informed will chime in soon enough /ubbthreads/images/graemlins/smile.gif

Having had just one sample each of every light the whole setup was probably more indicative of the Luxeon Vf and brightness binning lottery than anything else. For a real comparison of driver circuit setup efficiency one would need to equal the playing field in using the "exactly same" Luxeons if such beasts exist - at least out of the same shipment, same binning and tested for a somewhat equal brightness and Vf to catch the not unusual Lumiled binning errors.

As it stands now the whole shootout is only valid for Bernhards lights - other light shootouts might probably result in totally different results - a 5W LS with a Vf difference of 1V up or down or an 1W LS with probably 0.5V up/down Vf would bring some 30% error margin into the game.

Remember that early reports of the L4 showed differences in regards to 1 cell setups between that it wouldn´t run at all and nice and bright for well over an hour. This I **think** would primarily be dependant of the Vf in the actual flashlight and I just mention it here to show that the good performance of Bernhards L4 might not show for sure that all L4s in general would perform well like that.

Just my 2 €cents

Klaus

Klaus I see your point now and understand a little more however I am still confused.I am currently seeking a light for duty and have limited space available on my belt.I want an LED that is fairly bright and can be used on one or two cells(123s)thus my interest in the L4.I thought the purpose of a regulated LED was to maintain peak brightness over the entire life of the battery.This test I speak of showed the L4 last just as long as other regulated lights and was more bright at the end of testing even outlasting all others.It is confusing to me as I do not see the advantage of regulation if the test was accurate.I am leaning towards the L4 as there is a dealer nearby who gives all law enforcement officers a great deal.I read above that chamenos believes a softer driven LED is more efficient.Well if the L4 is underdriven on one cell it was still brighter than the other single cell lights.I do not understand why any light would then be ran overdriven if it is not necessary to make a bright light.I am basically trying to determine what to purchase here.I will buy both the ARC and L4 as I like both lights but can only carry one on duty as a back up.If the L4 is brighter for longer on one cell well then that is my choice but still confuses me.Thanks for all the replies on this as I am learning much here.

My TW4 ran in regulation for quite some time before it dropped out. It would then gradually dim until one time it wouldn't really turn on any more once the battery got too low ( it was kind of cool - you could see the individual chips on the luxeon just barely glowing once the battery got low ). Put in a fresh surefire and it was back up to blinding intensity.

The TW4's regulate surprising long for running on just one cell. While I didn't do any quantitative tests, I estimate that I would get between 45 and 55 minutes regulation time before it would drop into a lower output. I may have gotten so much time out of the battery because I didn't run it all at once, but used the flashlight for only a few minutes at a time, each time. I was thoroughly surprised by how much runtime I could get out of 1 CR123.

It also never got too hot to handle - it would get pretty darn toasty, but never so that it would actually be hard to hold from the heat.

I also compared it to my friend's full size L4 and there was really no significant difference in brightness when the batteries were fresh. My buddy simply got longer run times due to the extra cell. It truly was quite an impressive light - I HIGHLY recommend the little TW4 torches !

Wow, your TW4 ran for 45+ minutes in regulation? My setup shows a difference in brightness between 1 and 2 cell configs. I was assuming that my one cell configuration was never in regulation. What batteries where you using? (I have only used Surefire)

Erik.

[ QUOTE ]
Mednanu said:
My TW4 ran in regulation for quite some time before it dropped out. It would then gradually dim until one time it wouldn't really turn on any more once the battery got too low ( it was kind of cool - you could see the individual chips on the luxeon just barely glowing once the battery got low ). Put in a fresh surefire and it was back up to blinding intensity.

The TW4's regulate surprising long for running on just one cell. While I didn't do any quantitative tests, I estimate that I would get between 45 and 55 minutes regulation time before it would drop into a lower output. I may have gotten so much time out of the battery because I didn't run it all at once, but used the flashlight for only a few minutes at a time, each time. I was thoroughly surprised by how much runtime I could get out of 1 CR123.

It also never got too hot to handle - it would get pretty darn toasty, but never so that it would actually be hard to hold from the heat.

I also compared it to my friend's full size L4 and there was really no significant difference in brightness when the batteries were fresh. My buddy simply got longer run times due to the extra cell. It truly was quite an impressive light - I HIGHLY recommend the little TW4 torches !

[/ QUOTE ]

It may have appeared to be in regulation to your eyes, but there's no way the KL4 was in regulation on 1-cell for 45-minutes. It's physically impossible, unless you got some sort of deformed KL4.

Gotta agree with nascar. The circuit itself in conjunction with the limited power of the 123 is not capable of keeping the light in regulation. I took data on three L4's a while back and the most efficient one dropped out of regulation around 3.0V at a current draw of 1.8A from a bench supply. Trying to draw that much current from a 123 will probably sag the voltage to about 2.5V and at that voltage level, the regulator is definitely running on fumes.

This is still a mystery to me as I have yet to see how this L4 ran so long and so bright without regulation.If I can get an un-regulated light to run as long and as bright as a regulated light why would I ever need any regulated light?I was a big fan of regulation however I am still learning the pros and cons of it but the regulated lights all fell short of the 5 watt L4 with it running no regulation.I found the thread and it was a very good contest written up by Kiessling who is a member here.This review gave my friend the info needed and he purchased a L4 the following day.I am trying to grasp this and from what I have read so far the L4 was underdriven and never got hot thus it was brighter and lasted longer than the other single 123 lights in regulation.If this is correct why not just underdrive every LED if this works better and is brighter?And why not use direct drive with 123 cells if they work so well with their discharge rate?I am sorry to drag this thread out but I have a thought in my mind and can not explain it in writing.Basically I want a regulated light but not if they do not out perform an unregulated light.I do not know how to link a thread but the search I did was 123 shootout.If someone could read the thread began by Kiessling and make sure I am reading this correctly I would be very thankful.Once again thanks for your patience as I know that I have repeated myself here but I just want to understand the best light for my needs.Thanks.....

Has anyone run a runtime plot? If not, I'll volentear my services and will run a runtime plot for you. Someone just needs to send me a L4 to test! /ubbthreads/images/graemlins/santa.gif ....I'd probably even send it back! /ubbthreads/images/graemlins/thumbsup.gif

My friend Owen should be here sometime tonight and he has the light I speak of.I know he uses it with two cells mostly and lately with the Pila re-chargeables.I will ask him to try a run time with a fresh single 123 cell.If it is possible I will post the results shortly.He has offered to let me use it on duty for a trial in the field however I hate to do this with such an expensive piece that is not mine.We all know how these flashaholics are with their lights.I would hate to suffer the rage of a man who had one of his prize lights destroyed or lost...hehe

Robocop,
Is this the link you wanted?
http://www.candlepowerforums.com/ubbthreads/showflat.php?Cat=&Board=UBB16&Number=374761&Forum=All_Forums&Words=&Match=Entire%20Phrase&Searchpage=0&Limit=25&Old=allposts&Main=374761&Search=true#Post374761

[ QUOTE ]
Robocop said:
I would hate to suffer the rage of a man who had one of his prize lights destroyed or lost...hehe

[/ QUOTE ]Yeah and an armed man at that.

If you run an L4 off of one cell, it will be noticeably dimmer than with two cells. It will not be the same brightness as with 2 cells except for maybe a few seconds. However, it will be a bit brighter than the Arc LS but with a more diffused beam. Why? 5W LED -vs- 1W LED. 5W is going to put out more light. It will also dim continuously throughout it's runtime on one cell, were on 2 cells it will not. This dimming is gradual enough that the naked eye has a hard time percieving it.

Overall, you can get good, diminishing brightness from one cell in the L4, but you will get full brightness from a Pila or 2 cells. Pila's are the way to go. 65 lumens for 50 minutes and no batteries to throw away. Just carry an extra pila and/or extra 123's.

That was the correct link...thanks HogHead.If a 5 watt pulls out more light would this not be quickly evident in a test with several other 1 watt lights?It seems to me that the 5 watt would quickly eat up the battery however this was not the case in this test.How is this possible to run ahead of several other 1 watt regulated lights?I realize it dims gradually however it was still brighter,after dimming, than the other lights.Even if it was not enough for the eye to see why is regulation better in this case?If I take two lights and turn them both on with fresh cells and allow them to run until depleted.One is 1 watt regulated and the other 5 watt but not regulated.If at the end of this test the 5 watt ran just as long and brighter at all stages how is this better?I am desperately trying to figure out how to say what I mean but I just dont get it.Would it not be better to run the 1 watt lights without regulation if a 5 watt can hang in there without it?

I knew that I had posted THIS however it took me some time to locate it. It clearly shows the KL4 on 1-cell may run in regulation mode the first 10 or 15 minutes.