Surefire E2E: want long runtime, which module?

I want about 10 hours of runtime and corresponding lumens.

What are my options, which KL* head do I use?

I want to use Li-Co 17670 but also 2x123 sometimes.

The Surefire KX2 "A" head is a single level 45 lumen head that will run at least 9 hours in regulation on 2XCR123 cells. It's a very nice head. It strikes a very good balace between brightness and run-time.

Thanks for the info.

I am thinking I want at least that much in runtime, maybe even more. 9 hours is pretty good I think. You are right, it does sound like a nice compromise. Can you still get that much off 1x17670?

I don't want it bright, as I have a Malkoff for pure lumens, but this one I want for runtime.

etc said:

Thanks for the info.

I am thinking I want at least that much in runtime, maybe even more. 9 hours is pretty good I think. You are right, it does sound like a nice compromise. Can you still get that much off 1x17670?

I don't want it bright, as I have a Malkoff for pure lumens, but this one I want for runtime.

Click to expand...

yep, 17670s will power it for halfway then goes blip. Its caused by the regulator selection of surefire as they used a buck [or step down] driver that requires the input voltage [Vin] to be higher than the operating voltage [Vout], 2xCR123A = 6V, 1x17670 = 4.2V (3.6 nominal)

I've never actually tried the runtime on a 17670...just with regular CR123As it takes me about half a year to accumulate ~6 hours to runtime to tell the difference. Now my KX2s are the 1st generation where there is only one mode. Now KX2s come in dual modes and the low mode lasts practically forever.

User Bigwaffles did runtime curves on the E2L [essentially an E2e + KX2]
high: [Advertised: 9 Hours] [Tested: 6.5 hours]
[Runtime graph here]
low: [Advertised: 100 hours] [Tested: 63 hours]
[Runtime graph here]

for more runtime plots, visit the link on my sig

Hm, doesn't look like 1x17670 is such a good choice for E2E?

Is there another module that will use the cell in its full capacity, not half way?

well, generally 17670s are for applications where you will need to use lots of power and have it recharged at night and cycled again the next time.

The KX2 sips power rather than stuffing it down its throat in gulps...so naturally an 17670 is not a very good alternative to use aside from CR123As, which it was designed to conserve power from. Rechargeables are designed to save money in high powered lights that have short runtimes in design when used with disposable cells. So using a rechargeable cell in a naturally long runtime light is sort of contradictory, if not ironic.

hmm...the KX2 is about the longest runtime you can achieve, and there are other alternatives to LED: they are mostly in the incandescent department but few succeed in running for more than an hour with the 17670:candle:

So what is the best rechargeable chemistry for E2E with KX2 head?

none that I know of...
For the "A" unit [single stage] which is what I own [Bigwaffles runtimes are for the B versions, which is what surefire sells as of now]
regular runtime curve using CR123As, 9 hours [source here]


Runtime curve using 17670, ~5 hours [source here]


If you need ~5 hours of light every night then it'll be best for you.
While li-ion chemistry is stable, it isn't healthy for it to be left on the table uncharged after use, but due to the KX2 heads nature of sipping power you'll have to run it at least several hours or the charger will just give you the green light "indicating" the battery is charged when it really isn't.

I use Pila charger, do you think it would do the same thing?

So let me get this straight - with E2E with KX2 head and 1x17670, I would get 5 hours of runtime, at 60 lumens?

etc said:

I use Pila charger, do you think it would do the same thing?

Click to expand...

Pila's cells are known to be of higher quality than these Li-COs many here [me included] are using such as the 17670. But its the capacity that determines the runtime. IIRC 17670 dimension equivalent is the Pila 600S cell, but not sure regarding capacity. For reference AW protected 17670s are rated for 1600mah.

etc said:

So let me get this straight - with E2E with KX2 head and 1x17670, I would get 5 hours of runtime, at 60 lumens?

Click to expand...

Yep, 6 hours if your quoting to 50% Almost half of what you'd get with CR123As...
17670:[3.7V x 1.6AH = 5.92WH] versus. 2xCR123a: [6V x 1.4AH = 8.4 WH]...surprising now much additional runtime 2.5watt hours can do eh?

But that is if you are able to obtain the earlier version, the KX2[A] to match the runtime graph you are seeing on my previous post. Post a "WTB" in CPFM -> BST~Light Related -> Flashlights & Parts -> WTB: Flashlights & Parts subforum
For the Single stage KX2.

While it is possible that the new version [two modes, KX2B] will also attain the same, if not better, performance...I don't have anything to back that claim up in terms of runtime charts

If you're up for a bit of modding you could select a P4 with a low vf in a KL1 head for good runtimes, with either 2 x 123a's or 1 x AW 17670 cell.

The KL1 head is flexible and you can run this in an E1E body using a single CR123a or 16340 cell. As you like long runtimes simply carry 2 x 17670 cells with your E2E.

The KX2b dual output head is rated at 60 lumens on high, and runs 6 hours regulated from what I can find. I have an E1L rated at 45 lumens and it seems nearly as bright as my new E2L lights in actual use, so if the KX2a is as bright as the E1L it should be an awesome head! 3 more hours runtime for only a few lumens less light. Why don't they still make this head, at least as an option? 3 hours additional runtime seems pretty significant to me for something so close in brightness.

Just for those wondering, I got a KX2a today and yes, its just as bright as my E1L dual mode on high. 45 Surefire lumens for each head. I can't tell any difference between them at any distance, absolutely the same. That KX2a is very nice and bright with SUPER runtime!

Yes that 1st Gen Cree KX2 head is the best LED Surefire product to date.

It does 1 thing and it does it well. I did not care for the newer 2 stage version. They should of set the new one's high at the same output of the first one so the runtime didn't get cut down. I did like the low mode.

How does the 2 stage work?

click on low, click off, click on high