Surefire L2 dual stage question

I've been reading up on the L2, and it seems like a lot of you really like it. But at a glance from the Flashlightreviews.com runtime graph of it, the high output lasts for a very short amount of time. A few have said that the L2 should be thought of as a low-output light with the added capabilities of being able to bump it up to high mode when you need it, as opposed to the A2 which is a high-output light that can switch to low output.

So, the question is, if you've been running the L2 on low for a while, say, 4-5 hours, will high mode still bump up the brightness to around 80-100 lumens?

Yes It will still run on Hi after using the low mode for a number of hours I use low almost all the time as my L2 is my EDC I can get about 50 min on just HI I havent keep trac of Low runtime

Bogie said:

Yes It will still run on Hi after using the low mode for a number of hours I use low almost all the time as my L2 is my EDC I can get about 50 min on just HI I havent keep trac of Low runtime

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Is the high mode roughly as bright as when the batteries were new?

I would say it is pretty close

Get these 14670 Protected rechargeable batteries from AW. http://candlepowerforums.com/vb/showthread.php?t=103009
Runs about 35 minutes on high.

I am thinking of getting a couple of these for my L2.

I think there is something wrong with the L2 runtime plot on flashlightreviews.com. It differs dramatically from the plot on ledmuseum.com and as I have an L2 I can personally testify that high lasts way longer than the 10 or so minutes I think are quoted on flashlightreviews. On low it is significantly underdriven and doesn't use up a great deal of power so after a few hours of use on low there is usually a fair amount of power left for high albeit not at its very maximum brightness.

My SF L2 usually runs for around 30-50 minutes on high before becoming obviously dimmer. There is no immediate, rapid fall from regulation in the first 5 minutes as shown in the current flashlightreviews runtime plot. Given both the runtime tests have given strange results, I think it's possible there's something wrong with his L2 -- Occam's Razor and all.

Incidentally, aren't runtime tests on flashlightreviews generally done with the type of batteries originally suppied with the flashlight? The second runtime test was done with Titaniums...

(And don't get me wrong, flashlightreviews is an amazing site and is incredibly useful. But something strange does seem to be doing on with this particular light.)

Am I correct in assuming he used the same exact light for both tests? If so, that particular light may have some issues. I know several others who swear their L2s run about 40+ minutes before it really becomes noticeable on high. It would be great if we can get some members to do their own runtime tests. I am interested in the L2, but would like to see some additional data.

Either there's something wrong with the testing, or there's something wrong with his L2. I'm more inclined to think the latter, since he tried it twice with poor results.

Here's a runtime plot done by kj. It compares a Surefire L2 on high and a Surefire L4.

http://www.obaq.tv/cpf/images/SureFire_L2_L4_Runtime.png

I'll run some tests Wednesday and give a detailed post then. (Thats when I'll have access to a fellow CPF member's Meterman-LM631.)

EDIT: I have thought of a plan. I will put in a new set of batteries and take the highest lux reading on high and low. I will let it run on low for an hour, turn it off, turn it on for another hour, turn it off, then turn it on for its final hour run (should be 3 hours on all together; trying to replicate real world use, for on/off's.) I will then go over to the lux meter and take a lux reading on high and low. I will use Surefire 03-2015 dated CR123's. I will also take some lux readings from some depeleted but not dead batteries from my SF M6 running the HOLA.

Thanks Hoghead! That seems to be in line with what I heard from some others who have L2s. I know that Flashlightreviews just called it as he saw it with that particular light. I think he does a great job. I wonder if SF would replace that light for another FR comparitive test? Just thinking aloud..
I do think the runtimes observed in the tests scared a few potential L2 buyers. I know I was on the fence afterward.
I have no criticism whatsoever of FR here, as he just goes with the honest data he gets from his tests!

Quickbeam and his Flashlight Reviews are not in question. He performs a great service for us all. His L2 runtime plot is just not what I would expect.

I agree completely on FR. Thanks for looking at the runtimes, Jason. Will look forward to it!

Hoghead said:

Quickbeam and his Flashlight Reviews are not in question. He performs a great service for us all. His L2 runtime plot is just not what I would expect.

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Take note that KJ is using a fan. These lights get hot (newer version have more mass on the head to help) and either the L2 has a temp protection circuit (or a smart circuit to detect the light being left on in pocket via heat-- you never know the PK easter eggs ) or the cells have hit thermal.

Runtime with the air moving around and do it in a closed space ...

I was at fellow CPF member luxlover's lab today utilizing his Meterman LM-631 to conduct this on the fly test (uhm, letting the light run through its paces without watching it carefully.)

So here are my results.

New batteries, low lux reading is 102 and lux reading on high is 622 lux. Sure you may be saying, what? the lux is so low. The L2 is a wall of light and lux measures light in one spot, so tighter beams have higher lux readings. So basically I was using this as an aid to measure light output in the fairly large hotspot of the L2.

I took out the new batteries and put in the batteries I had in there to begin with (said why not? The batteries are fairly new with only about 2 minutes total use.) The batteries (new and used) are Surefire SF123A's with a date of 03-2015.

So I continued the test with the partially used batteries.

Lux reading on low 95 and on high 616 lux.

I left the L2 on at high and let the timer begin. At 12 minutes and 30 seconds the lux reading was 555, then at 25 minutes the lux reading was 518. At 29 minutes the lux reading was 265. The L2 was REALLY HOT at this point, almost burning to the touch.

There was also a slight smell of like when you turn on the oven for the first time, theres that hot metal smell or something. Can't really put my finger or nose on it exactely but the smell as there.

I let it run until 32 minutes when the lux was 280. I turned off the light and let it cool off with the batteries out and tailcap off.

10 minutes later I re-assembled the light.

The starting lux on high is 599. I let it run for 4 minutes at 543 lux and at 5 minutes the lux was down to 531. The light was HOT.

I took it apart and let it cool for 5 minutes.

Now it was time for low/high testing.

1450: I turn on the light on low and leave it on until 1558. Lux reading on low was 84 and on high it started at 570 and after 45 seconds settled down to 550.

I turned off the light and let it sit (assembled.)

At 1606 I turn on the light on the low setting and leave it on until 1753. The lux reading on low was 71 and on high the lux was 480 and after 45 seconds it was at 400 and dropping at a steady rate.

THis is where I stopped the test. The Surefire L2 performed as I think it would. The batteries weren't brand new but close enough to new. Hope you guys and gals understand my results.

Jason

Thanks Jason! Nice Job!

So are we concluding that the goofy runtime plot at FR is because the light is shutting itself down because it's thermally protected?

Planterz said:

So are we concluding that the goofy runtime plot at FR is because the light is shutting itself down because it's thermally protected?

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or the cells, I'd vote the former without tearing the light apart. i guess when it gets hot and the output decreased, you could see if new cells would take it back to the higher lux. If it doesn't, it is obviously thermal protection,

I think if the light was thermally protected at FR, when it cools off the light output will rise again. I am not going to question Quickbeam's testing methods (which is by far one of the top ones) but question his L2 and/or Titanium cells.

I will post a picture of two L2's showing the difference of the heatsinks when I get home later.