# Common LA spring issue with Surefire M3+17500's



## ebow86 (Aug 30, 2011)

I see there are various threads here regarding a common issue when using 17500's in a Surefire M3, apparently the cells push on the LA spring in a way where it loses contact with the body of the light or something along those lines. My question is, is this an issue with both the MN10 AND the LF HO-M3, or just the LF lamp? And also, does this happen to all user's who use this setup or is this just an issue that pops up once in a while? Reason I ask is I've been considering buying a set of AW 17500's to power up my M3 with MN10, but I'm wondering if I will run into the same issue that seems to be common around here.


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## Not So Bright (Aug 30, 2011)

I have contact issues using AW 17500's & SF MN10 bulbs. I just use a magnet, it works fine.


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## oldways (Aug 30, 2011)

In my experience with the SF M3T it happens with both SF and LF lamps.


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## HotWire (Aug 31, 2011)

Frustrating, isn't it? I once had that problem and read that the spring could be bent using two needle-nose pliers. Bend just a little at a time.... and you'll find the sweet spot. On my light the battery seemed to move the larger spring away from body contact. Enlarge the aft end of the spring and maybe tweak the very end out a little. A little tweaking is often necessary when mixing/matching light modules and batteries. Good Luck! Remember it is that larger of the 2 springs that needs to be enlarged.


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## ampdude (Aug 31, 2011)

I've never experienced this issue before, though AW's P17500's are longer than they used to be years ago. I'll be on the lookout for this as well.

I know the current cells are a much tighter fit in my Vital Gear FB3 than the old white top version and compress the spring a bit more.


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## leukos (Aug 31, 2011)

As HotWire said, I've found that opening the diameter of the outer spring wide enough so the top of the battery can fit inside usually does the trick.


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## HotWire (Feb 21, 2012)

I had to bend another spring last night. The light would work with some rechargeable batteries, but not others. Some are just a whisker larger. I used two pair of long nose pliers and bent just the last coil larger. After a couple of tries I got it right.


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## RamTuff (Mar 15, 2019)

Yes, I realize I'm pulling a Lazarus here on an old thread, but I too have just come up against this issue and was hoping someone could shed a bit of light on the actions mentioned in this thread.

Thus far, I have what I call the second gen M3, the one that has the contoured z46 bezel, not the "classic?" version that is more entirely cylindrical. Like new condition.

I have a new, LM EO-M3 incand. lamp

Two new, and freshly charged KeepPower 17500 cells from a reputable retailer.

What I've found:
Lamp energizes fine and functions properly with three primary, brand cells: SureFire, Panasonic and Streamlight.

The lamp will not energize when everything is "buttoned up", that is, factory z44 tailcap rotated all the way up to constant on, also, at no point will the lamp energize at any point while rotating on the tailcap onto the body.

The lamp WILL energize when the cells are shorted to the body.

I retrieved a Malkoff Tricap and found it would not work as with the factory cap.

I did find that using the Malkoff STANDARD cap, that the lamp will energize when the cap is rotated to appx 3/16" from all the way up, and once, it "clicked on" when fully rotated on but only once or twice.

The excellent customer service at Lumens Factory was at a loss as to a remedy, and I feel that's quite reasonable, I believe they adhere to known standards that may often be circumvented elsewhere.

Please pardon my ignorance but what is a "LA spring" and which spring referred to in this thread is to be "stretched"? Moreso, is there any known diagram or YTube vid showing this procedure?

Grateful for any assistance.

-Dave


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## ampdude (Mar 15, 2019)

Maybe try some IMR cells? Depending on brand they might be shorter than the typical protected Li-ion.

I tend to go against stretching springs, it seems to just make them fail faster.


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## RamTuff (Mar 16, 2019)

ampdude said:


> Maybe try some IMR cells? Depending on brand they might be shorter than the typical protected Li-ion.



Very possible, I was too busy with something else to measure properly but the sum of the two 17500 cells comes to 106mm, the sum of three SureFire cells came out to about 102mm (analog calipers, too lazy to break out the digital and load up it's batteries



ampdude said:


> I tend to go against stretching springs, it seems to just make them fail faster.


Sound advice would agree with, not to mention, that's kinda like treating the symptoms rather than remedying the cause.

Thanks Ampdude,
-Dave


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## ampdude (Mar 16, 2019)

What the ? I just realized no one even makes 17500's anymore. That's just stupid. They're the perfect power source for 9 volt incan Surefires. I don't want to step back to 16500's.

I got one pair of AW 17500's left. When they die I guess I'm screwed.


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## RamTuff (Mar 17, 2019)

ampdude said:


> What the ? I just realized no one even makes 17500's anymore. That's just stupid. They're the perfect power source for 9 volt incan Surefires. I don't want to step back to 16500's.
> 
> I got one pair of AW 17500's left. When they die I guess I'm screwed.



I find your comments/concerns odd, 17500s are carried at least by two online retailers, one personally recommened these cells to me for any three cell body which are not bored and you don't want to have bored.

Malkoff says they carry the KeepPower brand of these, they just haven't gotten them on the website yet.

Illumn (https://www.illumn.com/17500-keeppower-protected-1200mah-button-top.html) also carries the KeepPower. The KeepPower website also still lists these.

I just presumed these were common, now you have ME concerned.

-Dave


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## ampdude (Mar 17, 2019)

Oh good, I hadn't heard of the KeepPower cells and I did look a bit yesterday. Good to know at least one manufacturer is still making them.

It says, "they are longer than other 17500 cells on the market." I wonder if they're just saying that because of the protection circuit or they are longer than other protected cells. I'll have to measure them next to my protected AW's.


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## RamTuff (Mar 17, 2019)

ampdude said:


> It says, "they are longer than other 17500 cells on the market." I wonder if they're just saying that because of the protection circuit or they are longer than other protected cells. I'll have to measure them next to my protected AW's.



The 17500 KeepFire's I have in hand; recently purchased new measure, 53mm in length, and right at 17mm dia. These measurements are with an old, analog, Swiss made General brand caliper No. 7210.

Hope you post what you find with those AWs. Evident that LM recommends/encourages the use of AWs, Malkoff recommends KeepPowers etal. So that to me is two trusted power cells.

-Dave

Edit: "Holy dimensional perception Batman!!!" Comparing the (3) cr123 (Streamlight) cells side by side with (2) 17500 cells (KeepPower), the pair of 17500s are about 3/16" (0.1875") (4.7625mm) longer than the trio of 123s!

I think the cause is evident as to why the rechargeables don't play nice!


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## ampdude (Mar 18, 2019)

I'll have to locate a metric ruler around here somewhere. I don't want to use my steel calipers and short that battery out.


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## RamTuff (Apr 19, 2019)

Well, I'd given up on running the M3 on 17500's. In the interim, I switched from the original Z41 natural tailcap to an SW02. Well, got to thinking tonight, I'd not tested the 17500's with the SW02... well, no joy their either... but the oddity continues! I screw on a KT-4 with an MN16 and viola! M3 runs on 17500's with the KT4 and an MN16. So it's bound to be something with the spring(s) of the LM lamp and/or the Z46 head or both their relationship here. :thinking:


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## ampdude (Apr 19, 2019)

I would say it is most likely related to the manufacturing tolerances of each shock resistant head and the lamp assembly itself.

I've also seen some shock resistant heads that have more play in their shock isolation system than others. Is there more play in the shock isolation off the Z46 than the KT4?


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## RamTuff (Apr 19, 2019)

ampdude said:


> I would say it is most likely related to the manufacturing tolerances of each shock resistant head and the lamp assembly itself.



This may be an UNDERSTATEMENT! I tried out a Z41 tailcap that I'd transformed with a McClicky, works perfectly find everywhere.... except this M3. So last night I gauged the depth of both the Z41 w/McC, and the SW02 that works fine. There was about* 0.5 mm difference in the depth of the two. So I cranked down on the McClicky quite hard, felt it budge "just a hair". Screwed it back on the M3 and viola! Da...rned thing worked! Talk about tolerances!



ampdude said:


> I've also seen some shock resistant heads that have more play in their shock isolation system than others. Is there more play in the shock isolation off the Z46 than the KT4?



This KT4 head might have the slightest amount more "stiffness" than the Z46 I'm using.


*about* = Using an analog caliper


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## ampdude (Apr 19, 2019)

On some of the turbohead lamps the center spring is not as long as others. Those are the ones to look at for possible tolerance issues as well.


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