The SF M6 X-LOLA: 200 lumens for 2.5 hours

js

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So, one day, I get a package from bwaites, and inside is a SF M3T. Cool! I thought. I'd been wanting to check this light out for a long time. Bill sent it to me with Pilas installed, actually, but I was more interested in the performance of the light when powered as intended--with 123 primaries.

So I install the MN15 and drop in three brand new SF 123A batteries. And . . . was rather disappointed. The beam was a bit cold. Not as white as I had hoped for. A definite disappointment. I guess that's why some have suggested that using the N2 LA instead of the MN15 is a cool thing to do. But I've never seen an N2 so I wouldn't know one way or another.

Anyway, I was thinking about M6 lamp choices a couple weeks ago and all of a sudden it hit me! Why not make the M3T's loss the M6's gain? Both flashlights use the exact same turbo-head, so the only difference between them is the battery configuration driving the lamp. And, if you don't already know, both the M3T and the M6 are nominally 9 volt lights, driving lamps with three series CR123A batteries. The difference is that in the M3T, there is only a single stack of three series CR123A's, but in the M6, there are two parallel stacks of three CR123A's. Or electrically there are! Physically it looks like three stacks of two CR123A's, but the MB20 battery holder electrically connects this 3p2s physical arrangement into a 2p3s electrical arrangement. And a voltmeter will confirm that the MB20 battery holder loaded with 6 CR123A's has an open circuit voltage of approximately 9 volts.

(And by the way, I will mentioned that if you remove the correct 3 CR123A's from the holder, you can still have 9 volts from a single stack of 3 CR123A's but in the form-factor of the SF M6, but with the same battery configuration as the M3T. But I digress . . .)

The point is that if the MN15 was a bit less white than it should be on a single stack of three 123's, wouldn't it be perfect on TWO STACKS of three 123's? In case you're wondering what the reasoning here, I will quickly say that the voltage under load of a battery (and especially CR123A batteries) very much depends on both the state of charge and the draw rate. Draw more current and you have less voltage at the lamp. Draw less current, and you have more voltage. And since the two stacks of 3 CR123A's in the SF M6 share the load equally, they will have half the current draw of what they would have in the M3T driving the MN15, so there will be an increase of voltage applied at the lamp. And since it is, in my estimation, a little underdriven in the M3T, I figured it would be a litter overdriven in the M6. A little, but not too much, I hoped. My hotwire intuition told me that the MN15 in the M6 should be just about perfect!

Well, sure enough, it is PERFECT IN THE SF M6. I estimate it to be the same CCT as the A2: 3300 K, which is nice and white. About the same as the MN20. Plus, the slight overdrive pushes the output up a little as well as the whiteness.

So, I would guess the MN15 in the SF M6 is about a 175 to 200 lumen LA. And I'm guessing it will run for about 2.5 hours. I'm calling it an "X-LOLA" for Extra-Low Output LA. Or Extra-long running LA.

I went out tonight and field tested the beam, and I really, really like it. It easily throws 600 feet, and puts out a decent amount of light, with a lovely, white, pleasing beam. The MN20 is definitely brighter and longer throwing, but the MN20 won't run for 2 and 1/2 hours.

The thing about 123's is that at the lower draw rates, you really start to take advantage of their superior energy density, and they have better discharge curves--i.e. they hold better voltage under load over their run time.

Chamenos actually got me into the whole extra-long running lamp thing by recommending the MN02 for the E2e. He has since un-recommended it due to the fact that he has had two of the lamps exhibit very premature blackening and has gone back to the MN03. But still, the point is that 2.5 hours of runtime is a great thing, especially when the beam is nice and white and pleasing.

The SF M6 running the MN15 is like the SF A2's bigger brother. It might as well be regulated! I have used this combo for 30 minutes so far and haven't noticed the least bit of dimming or drop-off of whiteness.

I will be testing this combination extensively over the next several weeks and will do definitive runtime tests and make some bench measurements, and so on. But for now, I feel confident enough about it to post.

And, as it turns out, SureFire will warrantee this combination, as batman posted about in post #298 of this thread! He says that:

Sorry to double post it up, but this is news. Surefire IS warranty covering the MN-15 in the M6 as of last week. I got an RMA and am getting a free replacement MN-15 for the M6.. In fact, the rep said that they know most people are having pretty good luck with the MN-15 in the M6. A new lamp assembly for me, only cost is sending the old, burned out MN-15 back to them.
This is a case where honesty paid off and Surefire customer service is great.

So, that's awesome news!

However, do not run the MN16 in the M6. The MN16 is NOT underdriven on a single stack of three 123's, so two parallel stacks will push it too hard, and it might possibly flash at start-up, or have a much foreshortened life.

Thus, it is my distinct honor to introduce the "X-LOLA" SF M6 lamp configuration! Thank you SureFire for making such awesome lights!

MN15-package.jpg
MN15-lamp.jpg


So, to recap, I believe the stock SF M6 now has three viable LA's to use:

HOLA: MN21. 630 lumens, 20 minutes.
LOLA: MN20. 400 lumens, 1 hour.
X-LOLA: MN15. 200 lumens, 2.5 hours.
 
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nickz

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Re: The SF M6 U-LOLA

Nice find.... Now if I could only convince the wife that I "needed" A surefire M6... What do you estimate runtime at in this format?
 

js

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Re: The SF M6 U-LOLA

nickz,

2.5 hours of runtime is my guess right now. I don't believe it will be more than that, and it could very well be less than that. However, it will be at least 2 hours I think. I'll be doing a runtime test in the next few days and will post about it when I do. For now it's pretty safe to say it will be somewhere between 2 and 2 1/2 hours.
 

nickz

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Re: The SF M6 U-LOLA

js said:
nickz,

2.5 hours of runtime is my guess right now. I don't believe it will be more than that, and it could very well be less than that. However, it will be at least 2 hours I think. I'll be doing a runtime test in the next few days and will post about it when I do. For now it's pretty safe to say it will be somewhere between 2 and 2 1/2 hours.

Very nice...!
 

cue003

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Re: The SF M6 U-LOLA

looking forward to your runtime results. I wonder if there are any other bulbs we can run in the mighty M6.
 

Flea Bag

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Re: The SF M6 U-LOLA

Thanks for posting that Jim!

I was always wonderring about whether the MN15 could work in the M6 but never had the guts to give it a try. I still don't dare to do it! Hope your long-term results come out fine.

Of my experiences with MN10,11,15,16,60,61,20&21 LAs in stock form, the MN20 in M6 has impressed the most for its consistancy specifically because of its 3s2p config. I got about 1h10 minutes of useful output. The M4-MN60 is nowhere near as consistant and at the later stages of its run it even loses out to the the MN15 running on 2x17670. I believe SureFire's ratings of 225 lumens for 1h in the M4-MN60 is less conservatively rated relative to the ratings of the M3 and M6.

If the filament can take it, I think you'll get more than 2.5 hours of better-than-stock output with the M6-MN15. If you can, try to compare the MN15 on 2x17670 with the M6-MN15. I've been using the former for quite some time and if both are similarly overdriven then there's good reason to think they'll both have excellent bulb lifespan purely in terms of theoretical runtime -assuming perfect reliability at every cold startup -which I don't think we can assume. Or heck, I might just compare them myself a little bit in the future.
 

js

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Re: The SF M6 U-LOLA

LED61,

Well, the MN61 would "work" for sure, but it would definitely be underdriven. It's drive voltage on 4 123's is probably somewhere around 9.0 volts, and so even 2 parallel stacks of three 123's would be well under that. Like 7.0 volts or something. So the MN61 and the MN60 in the stock M6 are non-starters.

cue003,

Well, in stock configuration, the only other possiblities are the N2 and the MN16. I feel confident about the MN15, less than confident about the N2, and decidedly NOT confident about the MN16. But, either one or both could be workable in the M6.

Then of course, there is the LED head meant for the M3T body (the L6, IIRC. Right?). It will fit on the M6 body just as well as on the M3T body, and should also give around 2.5 hours of runtime.

Flea Bag,

You're welcome! I feel very confident that the long term tests will come out fine, but I will still definitely be doing them to make certain! The MN15 on 2p3s 123's is not into any kind of serious overdrive at all. It's about the same drive level as the MN20. So I would be very surprised to run into any problems. I am guessing it will have a very solid 35 hours of bulb life.

As for runtime, the MN15 will run for 1 hour on a single stack of 123's. So when you take into account the lower draw rate, and ignore losses due to internal resistance, for two stacks, you would get 2 hours even. But the lower draw rate for each stack (since they are sharing the load) means less I^2 * R losses, which means MORE than twice the runtime. (Same reason you get only 20 minutes of runtime from the SF HOLA's vs. 60 minutes of runtime from the LOLA's, even though the HOLA's are only double the power--approximately). So it's definitely going to be more than 2 hours even, but I would be surprised if it were more than 2.5 hours. We shall see, though.

OK. Moving on to 2x17670 Li-ion cells. Hmmm. I am guessing that the MN15 is being driven at about 7.8 volts on 2p3s 123's (i.e. about 2.6 volts per cell). This would be 3.9 volts per cell on two Li-ion's, which is decidedly too high. i.e., two Li-ion cells would be more likely to drive the MN15 at 7.4 volts or so. Thus, the MN15 driven by the MB20 M6 battery holder loaded with primary 123's will almost certainly be driven a bit harder than on 2 17670 Li-ion cells. But not by much. And, in fact, I suspect that the MN15 on a single stack of three 123's would be driven at about 7.5 volts.

As for lumens ratings, I think I have settled in on 185 lumens for the MN15 in the stock M6. The reason why is that it is noticeably LESS bright than the TL Gen 4 LA, which is 275 lumens, and it is about the same proportion (brightness wise) as the Gen 4 is to the MN20--which is about 50 percent brighter, MN20 vs. Gen 4. So if the Gen 4 is 50 percent brighter than the MN15/M6 combo, you get 185. i.e. 185 * 1.5 = 275 lumens (approximately). But, to be clear, I am just guessing, although it IS an educated guess.

Anyway, runtime test soon to come.
 

Flea Bag

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Re: The SF M6 U-LOLA

Thanks Jim,

I came up with the more-than-2.5 hour figure partly out of estimation and calculation.

For the calculation part, I noticed that the MN20 could get out 1h10mins of useful output from its cells. Even past this mark, the beam would have been brown but still very useful even outdoors. So for the MN15 I took that figure and multiplied it by two.

For the estimation part, I found the batteries at the 40 minute mark and at the end of the run to be very very hot -too hot to hold and much hotter than the external and internal surfaces of the M6's body. They also took quite a while to cool down. Quite some energy wasted there. I assumed a lot less resistance and heat would come from using the MN15 so I thought it would be good to add a few more minutes on top of the 1h10mins x 2.

It also depends on what kind of beam performance one would deem to be unacceptable from the MN15 in order to call an end to the runtime test. If SureFire can claim the MN15 to be 1h (given how yellow the beam was at the 1h mark using 3xCR123), then the MN15 in the M6 will probably produce a very acceptable beam for quite a while after the 2h20min mark. Again, there's quite a lot of estimation in my predicitons! :ohgeez:

But the really good news of it all is that the MN15 would make an excellent back-up bulb in the case of a failed MN20. The extra runtime would be very desirable in such situations and the beam, though suffering from a smaller, more concentrated hotspot size, would still have adequate throw.
 
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js

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Re: The SF M6 U-LOLA

Flea Bag,

Yes, it all will depend on just how dim you decide to go before cutting things off and declaring the run over. Personally, I find there is a period where the dimming becomes more rapid and pronounced, and that is where I call it. I focus in on the RATE of dimming, more so than the amount of dimming, although obviously if the beam dims down to less than 50 percent of starting, that's too much and I would call it there at that point regardless of the rate of dimming. In any case, yes, it is a judgement call.

And, yes, absolutely, there is a significant amount of power used up as heat inside the 123's the higher the draw rate, so yes, tacking on some extra is par for the course. These are the I^2*R losses I was talking about.

AilSnail,

Hmmm. Two votes for X-LOLA. OK. I kinda like that. Anyone else have a preference? So far we have U-LOLA, X-LOLA, and S-LOLA.
 

Flea Bag

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Re: The SF M6 U-LOLA

How about VLOLA for very low output? Sounds close to voila! :) We could use SLOLA for an even lower output lamp like the N2.
 

js

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Re: The SF M6 U-LOLA

OK. I actually finished the runtime test several days ago now, but since CPF was down, I couldn't post about it. So here it is:

2.5 hours

A very solid 2.5 hours. There was probably another 10 minutes of decent light left, but as far as I could judge, at somewhere around 2 1/2 hours, give or take 5 minutes, it reached about half of the starting output.

At 1 hour into the run, however, it seemed every bit as bright as in the first 5 minutes. And I compared the CCT against the A2 at this point, and still could not see any difference.

At 2 hours, the beam was just noticeably less white than the A2, but still quite respectable.

At 2.5 hours, the beam was definitely down in CCT, but in no way displeasing or sickly. It was still a very useable beam, just not as bright and white.

Also, I have again revised my lumens estimate with some more ceiling bounce tests and other comparisons and thoughts. I now estimate that the MN15 in the M6 is putting out 200 lumens. Mostly, I am revising it back upwards again because even at 2.5 hours, the beam was still easily brighter than the A2, which would mean it was at least 50 percent brighter than 75 lumens. But if it was 50 percent down from start, that would mean start was 225 lumens (!). That and the X-LOLA is only just barely noticeably dimmer than the TL Gen4 LA, which is about 275 lumens, which means about 30 percent less than that, which would mean about 200 lumens.

I'm still just guessing, but I feel better about the 200 lumens guess. I will edit my original post and post title to reflect the new information!
 

LED61

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Re: The SF M6 U-LOLA

Wow!!! Jim, thank you very much for this.....why bother with the rechargeable deal when you can have this brightness for 2.5 hours ? I think your original advice to never underestimate the convenience of running the M6 on primaries takes on even more validity now. I imagine heat is negligible Jim?
 

js

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Re: The SF M6 U-LOLA

LED61,

You're welcome! No problem. And, yes, heat was minimal from this setup. I imagine it is about a 10 watt lamp when driven by the stock M6 MB20 battery holder. And with the cooling fins on the head and top of the body, the light never gets anywhere close to "uncomfortably" warm. Quite manageable. I did not use a fan during the runtime test or anything. It was just sitting on a table. So this was probably a worst-case scenario in regards to heat buildup. So, nope, no heat problems at all.

On a more general note, I have been using this as my walk light for the past couple weeks, and I really love it. I think it has become my new favorite. The beam strikes the perfect balance point between too much light, and too little throw. If you let your eyes dark adapt, and then turn on this combo, it will not ruin your dark adaption. Even if you accidentally bring the hotspot right near your feet and look down, your eyes will recover in about 30 to 60 seconds. But, of course, you would avoid doing something like this (!) but the point is that it will sometimes happen, and with this beam, you're still OK.

Before this, I would most often use my SF A2 or my TL with Gen4 LA as my walk light, and the A2 incan was not potent enough to throw out far across a field, even with more sensitive dark adpation to help. The Gen4 LA, on the other hand, would hurt my dark adaption too much if I accidentally got the hotspot too close to me.

So the MN15 strikes the middle ground between these two, and works especially well when flashed now and again for far viewing, or for the spill light, with most of the walking done with the light turned off. Most of the time dark adapted eyes win out over massive lighting scenarios. At least they do for me. Turn on a massively powerful light and you only have the relatively small area of the beam (even if it throws), all else is nearly impenetrable darkness. But with dark adapted eyes, you have a lot larger area, and the stars and the sky, and it saves on runtime too! LOL!

I will, however, definitely say that the Gen4 TL, or the MN20 or MN21 or MagCharger (and so on) will THROW farther than the M6 X-LOLA. If you need to really see out to far distance, this is not the LA for you. It throws quite well in my opinion, just not extremely well.
 

LED61

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JS, I never got around to tell you that I bought another M6. It will be for my landkeeper at the lake house. It is the light he NEEDS to take care of things there. it was going to be run exclusively with the MN20 lamp on primaries (yep, batteries are on me), but now you´ve got a better solution with the MN15 and primaries!! he flashes the light at random spots where things are at about 100 feet maximum distance and the outfit will be `perfect for the job.
 

Flea Bag

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Thanks for taking the time and trouble Jim! I'll stick with the MN20 in the M6 but it's nice to know that when extended runtime is needed, the MN15 can step in and provide quality output for a very very generous runtime. :) Sigh... Another reason to buy another M6!
 
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