# SureFire Z48 tailcap clicky + LF IMR-M3T = is it safe?



## Outdoors Fanatic (Jun 30, 2009)

I do not understand the reason behind Lumens Factory warnings condemning all clicky tailcaps and IMR lamp assemblies combos, especially considering the fact that SureFire sell clicklies for all HOLA options-- except for the M6. The P91/MN16/MN61 seem to pull even more amps than most IMR lamps, so why does SureFire takes the risk by selling clickies for these lamps, while Lumens Factory says it's unsafe? :shrug:


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## mdocod (Jun 30, 2009)

Howdy!

It has to do with a combination of factors that all come in to play. At the end of the day, LF is better off recommending against the use of "clicky" switches to reduce the liability... Here's some components of the equation that went into that decision:

When LF did IMR bulb tests with clicky switches, they did extended continuous runs, allowing everything to get hot in the process. They managed to destroy numerous SF clicky switches in their continuous run tests. They used the IMR-M6 and IMR-M3T in these tests primarily as I understand, which both do draw more than an SF HOLA (not considering M6 bulbs)..

Many li-ion powered configurations will run longer than a CR123 powered configuration under a similar load because the larger li-ion cells have better capacity, so those continuous runs are much longer than what a stock SF configuration would deliver, which adds up to more heat buildup in the switch from resistance. Consider- A pair of IMR18650s will drive an IMR-9 or IMR-M3 for upwards of 30-35 minutes, a set of 3 CR123s would only run that same bulb for ~15-20 minutes. Technically speaking, the IMR series of lamps *can* be run on many LiCo cells as well, provided they are large enough to safely deliver the current, this was probably taken into consideration- A pair of modern high capacity LiCo 18650s will drive that IMR-9 for roughly an hour. Obviously, for overall safety, it would be best not to run a high powered compact incan for that long, as the heat would likely make the flashlight body impossible to hold, and put the cells at risk of explosion in worst case scenario, reduced useful life at best case scenario..(which is why there are "heat" warnings and continuous run limits recommended on many higher power LF bulbs as well)

One of the primary factors that went into the decision to recommend against clicky switches is likely the low internal resistance of LiMn chemistry cells and the effect that has on peak current flow when starting from a cold filament. With CR123s, a cold filament will never be able to get more to flow from those cells than slightly less than they would deliver into a dead short, which isn't all that much since CR123s have an impedance of ~0.25 ohm per cell, (~0.75ohm for a stack of 3 in series). An 18650 size LiMn chemistry cell has as little as ~0.05 ohm resistance (0.1ohm for a stack of 2 in series), which translates to potential current spikes on a cold filament many times greater than can be delivered by CR123s. There is noteworthy resistance in those clicky switches, anywhere from ~0.1-0.3 ohm depending on the condition of the switch is pretty common. Sudden failure from high current spikes seems possible to me especially when working with the larger LiMn cells (like 18650s). 

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All that said, many people will probably use clicky switches and not have any problems. I have been using the clicky on a modern E2E for a little while now with a pair of IMR16340s and the IMR-E2 lamp and have not had it fail yet. I am accepting that I am taking a risk of damaging the clicky. I try not to use it for more than a few minutes at a time. 

Some configurations, like, say, a pair of IMR16340s driving an IMR-9, actually have less running current and runtime than 3 CR123s driving a P91, I don't see any reason why one shouldn't feel comfortable running that configuration with a Z59. I guarantee that [email protected] would agree that this configuration would technically be "fine" in a private "off the record" conversation with a known educated individual, but maintain the broad sweeping general recommendation against all clicky switches speaking on behalf of LF. From the perspective of LF, much like any company, it's much better to simplify recommendations, making simple broad sweeping recommendations rather than try to have a complicated reference to determine how the products can be used. It's the job of someone like you or myself to come along and read between the lines and fill in the blanks for folks who would like to have a broader understanding but without increasing the liability for LF in any way since we are operating completely independently. 

To illustrate an example of this self-preserving behavior that must be used in business... email SF and ask them if you can run 17500s in the 9PLED. More than likely, the person you talk to won't even know what a 17500 is, but regardless of whether they do or not, they will recommend only using SF brand cells in their flashlights, which insures their survivability by reducing liability for warranty work, or injury, or property damage caused by alternative configurations. If SF gives the "go-ahead" to the use of various 3rd party add-ons or modifications, then SF is opening themselves up to unwanted and un-deserved liability. LF is essentially doing the same thing here. Many of us here on CPF are well aware that a quality set of protected LiCo 17500s in that 9PLED would be both safer and more economical than CR123s. 

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I think an educated CPF member can probably make an informed decision about which configurations are suitable for use with the clicky switches and get by pretty well. Obviously, lamps with a running current that are lower than SF HOLAs, that you intend to use with cells that won't deliver radically high potential current spikes (protected LiCo instead of LiMn) and only used in short "bursts" of say, 5 minutes or less, will very likely never be the culprit in a destroyed clicky switch. Higher current lamps, like the IMR-M3T, used on IMR18650 size cells, do have a pretty good chance of damaging a clicky switch in my opinion.... Keep in mind that they are ~3.4A compared to the ~2.4A of a SF HOLA that is intended to be used with CR123s. 

SF used to sell a bulb for the M4 called the N62 IIRC. It was basically an IMR-M3T/WA1111/64250 category bulb, drawing enough current to sag those poor CR123 cells down into that ~1.75V per cell range. Runtime was horrible and the safety wasn't too great with the cells. I am pretty sure the reason it was eliminated was probably the safety issue at the cells, but I also wonder how many clicky switches they blew out on those bulbs. 

---

I did find a definite guaranteed way to destroy a solarforce reverse clicky...
2xIMR18650s>64275 (well over 6 amps). 2 clicks was all it took. 

-Eric


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## Outdoors Fanatic (Jun 30, 2009)

Great post!!!

Thanks a lot Eric.

Cheers.

P.S - Bear with me now... What if I use 2x18500 liCo (instead of 2xIMR 18650) + IMR-M3T? Will this setup generate enough current to kill a Z48? Can you post of a list of known LF and SF lamp assemblies + battery options which are safe to use with clicky tailcaps? That'd be extremely helpful....

Thanks again.


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## Kestrel (Jun 30, 2009)

mdocod said:


> With CR123s, a cold filament will never be able to get more to flow from those cells than slightly less than they would deliver into a dead short, which isn't all that much since CR123s have an impedance of ~0.25 ohm per cell, (~0.75ohm for a stack of 3 in series). An 18650 size LiMn chemistry cell has as little as ~0.05 ohm resistance (0.1ohm for a stack of 2 in series), which translates to potential current spikes on a cold filament many times greater than can be delivered by CR123s.


That is very interesting data, thanks for the info. 


mdocod said:


> I did find a definite guaranteed way to destroy a solarforce reverse clicky...
> 2xIMR18650s>64275 (well over 6 amps). 2 clicks was all it took.


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## mdocod (Jun 30, 2009)

Outdoors Fanatic said:


> Great post!!!
> 
> Thanks a lot Eric.
> 
> ...



The argument against "clicky" switches for ALL IMR configurations has it's roots in different reasons for different configurations. In the case of the lower current lamps, like the IMR-9, it's the cold-start current pulse and longer possible runtimes that are the concern. On higher current lamps like the IMR-M3T, the high operating current stacks in on top of the cold-current spike problem. Technically speaking, the IMR-M3T should not be run on any LiCo cell smaller than an 18650. The 18500 might fire it up on one click but the discharge rate would be approaching 3C which would not be advisable IMO. 

The concepts here can be translated to non-LF lamps as well. Say for instance, a pair of IMR18650s running an MN20 (~2.5A)- this configuration would also be harder on switches than the usual 3xCR123>MN16 configuration. 

On the flip side of all of this, I seem to recall reports that the Z48 is of a different construction internally than a Z59 and may theoretically be more tolerant to high current configurations. 

Running an IMR-M3T on a pair of protected LiCo 18650s would have less of a chance of destroying a clicky than the same lamp on IMR18650s. Both configurations are probably capable of wearing out that style of switch prematurely, however, it would also likely depend on how the flashlight is used as to whether or not problems would surface in the time-frame in which said configuration was implemented. 

A chart would involve a lot of "maybe's" as it's impossible to answer definitively without very expensive and time consuming testing. We can make educated guesses about what may or may not work but in the end, the real world test is the only way to answer the question...

Something to consider:
I am pretty confident that people have been putting WA1111s and 64250s into FM bi-pin>MN sockets and running them on a pair of protected 18650s, many of them running Z48/49/58/59s. This has been going on for at least a few years now and I can't recall any specific mention of a clicky failure that was thought to be attributed to the configuration. Those bulbs are almost identical in power consumption to a IMR-M3T. Most people are probably using the configurations in relatively short bursts that don't give enough time for the resistance in the clicky to over-heat the switch. I have run the IMR-M3T in a few short bursts on a Z59 without any negative side effect as well...

Here's an idea:
If running a clicky is high on your list of priorities, along with a high power lamp like an IMR-M3T- I wonder if there is a way to take apart that SF clicky and do some resistance-fix type mods, same way we do mag-switches. like maybe de-ox and pro-golding the contact surface in there and beefing up any weak current carrying points. I'm sure someone on here has had some of those things apart and could give some guidance about how to do this. 

-Eric


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## vic303 (Jul 2, 2009)

Question folks: I've been out of circ on lights for a bit. I have an old 6P that I want to Malkoff and to put a z48/z59 type tailcap on. I only run primaries in this light, so other than a KB from mismatched cells, will a Solarforce tailcap work long and as well as a real Surefire?


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## DM51 (Jul 2, 2009)

Very good and informative posts from mdocod. 

I can comment specifically on the Z48 and med-high current. The Z48 is essentially the same as the SW02, except without the crenellations. 

I've been using them (Z48 and SW02) with WA 1185 (~3.3A) and WA 1111 (~3.5A) using LiMn (IMR) and LiCo (ordinary Li-Ion) cells. No problems to report!


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## Outdoors Fanatic (Jul 28, 2009)

DM51 said:


> Very good and informative posts from mdocod.
> 
> I can comment specifically on the Z48 and med-high current. The Z48 is essentially the same as the SW02, except without the crenellations.
> 
> I've been using them (Z48 and SW02) with WA 1185 (~3.3A) and WA 1111 (~3.5A) using LiMn (IMR) and LiCo (ordinary Li-Ion) cells. No problems to report!


I hope mine will survive as well... I gonna try it tonite... If it gets hot I'm switching back to the boring Z41.


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## cernobila (Jul 29, 2009)

mdocod said:


> Something to consider:
> I am pretty confident that people have been putting WA1111s and 64250s into FM bi-pin>MN sockets and running them on a pair of protected 18650s, many of them running Z48/49/58/59s. This has been going on for at least a few years now and I can't recall any specific mention of a clicky failure that was thought to be attributed to the configuration. Those bulbs are almost identical in power consumption to a IMR-M3T. Most people are probably using the configurations in relatively short bursts that don't give enough time for the resistance in the clicky to over-heat the switch. I have run the IMR-M3T in a few short bursts on a Z59 without any negative side effect as well...
> -Eric



I think you have accurately described what is actually going on with most people here, doing exactly the above, myself included.


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## Outdoors Fanatic (Jul 29, 2009)

cernobila said:


> I think you have accurately described what is actually going on with most people here, doing exactly the above, myself included.


How "short" are these bursts you're all talking about? Are we talking less than a full second (like a brief "tactical" momentary press) or 10 or more seconds at a time? 

I really don't need 30 full minutes of blinding incan light on constant-on, two minutes or less would be plenty.


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## mdocod (Jul 29, 2009)

Like I said in my post above, LF was able to destroy SF clicky switches by doing continuous runs. Like, complete start to finish runs on a set of cells. This causes a heat buildup from the resistance in the switch. As conductive materials heat up, their resistance rises, and so the heat production gets worse and worse, this eventually leads to something melting or breaking in the tailcap. 

I would guesstimate that a minute or 2 at a time is probably not an issue for most of these configurations.


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## cernobila (Jul 29, 2009)

mdocod said:


> I would guesstimate that a minute or 2 at a time is probably not an issue for most of these configurations.



Well I did not time my usage with these combinations but I had mine going till the light felt obviously warm around the head or tail. I use lights with these combinations all the time now and still have the original clickie switches.


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## Outdoors Fanatic (Jan 26, 2010)

Well, one thing I have to report: I've had no clicky failure so far, but an IMR-M3T in a KT2 + Leef Body gets scorching hot after a continuos 2 to 3 minute run. So if anything, it's your hands that are going to "fail" before your clicky or cells...


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