Surefire M3 on Li-ions

[monkeyboy]

I've just got my first decent incan, the SF M3. I compared the brightness of 3x CR123a primary vs 2x 17500 Li-ion. The 2x17500 option is noticibly brighter with both of the lamp assemblies but requires a double click with the high output lamp. I can only conclude that cr123a's have quite a big voltage drop under these loads.

Am I in any danger of smoking the lamp using 2 x 17500?

 

[pete7226]

You should be ok, I've used 2x18650, 2x18500, and 2x17500 with no burned bulbs so far, thats right off the charger. Been using this setup for about 6 months now and have probably gone thru 15 hours of use with no negative effects. Try stepping up to 18500 or 2x17670 or 18650 for longer run-time, even brighter output, and no double clicking. Boring out your body will be necessary and/or using an a19 extender for the increased length. Enjoy!

 

[monkeyboy]

Thanks pete.

I actually had a 2 x 18650 Leef tube but accidentally destroyed it in one of my modding disasters; taking two perfectly good pieces of equipment and attemping to combine them with a hammer (yes it actually was as retarded as it sounds)

I'm now tempted to get a 2 x C cell Leef body which should be out soon. I wonder if that would be too much overdrive?

 

[pete7226]

If you are referring to using AW's C-cell batts, you still would be ok. The cells are still 3.7 volts, just like your 17500's, just much more capacity. 3300mah vs Im guessing around 1100-1200 on the 17500.

 

[monkeyboy]

The C cells will have less voltage drop than 17500. I guess it should be OK though.

 

[mdocod]

the 17500s shouldn't be used with the SF HOLA lamp. I mean, you *can,* but it will wear out the cells very quickly. monitor the cells regularly, test voltage going on and off charger to check for any irregularities. Test cells after they come off the charger, and then about 20 minutes later to insure they are holding above 4.00V and you should be ok. cells that won't *hold* above 4.00 V anymore should be disposed of, and using 17500s with a 2.7A load, will lead to them behaving poorly pretty fast. When they behave poorly is when they are most dangerous, please be careful....

The 2xC-li-ion will reduce the life of the lamp pretty dramatically in comparison.... a good 17500 will start off at about 3.7V at the load of an MN11, a very large cell, like a C size cell, could probably deliver upwards of around 3.9V into that same lamp.... this may not seem like much difference... but it's quite amazing really...

see... The MN11 was originally designed to operate at around 6.7V @ 2.5A on 3xCR123s. At that configuration, it is conservatively rated around 30 hours life. I tend to believe that on a bench supply at 6.7V, it would last closer to 50-100 hours, but they de-rate to accommodate for irregularities in cell performance, which can sometimes include "spikes" of power during initial turn-on.

Now having said that, you can see why your 17500s are driving it brighter, they are starting off hitting that lamp with about 7.4V, that's almost a 40% difference in light output. At 7.4V, the lamp should still have "10-15 hours" life in it or so... factor in the fact that voltage diminishes as you run it, and you haven't actually lost much life over running CR123s at all.....

But then step up to a huge cell, like the Cs.... You could probably hit that thing with 7.8V if you weren't careful.... By my calculations, the bulb should technically survive, but will have a noteworthy risk of instaflash on fresh heated cells. 18650s are a nice stopping point, most won't deliver any better than 3.8V into a SF HOLA load, which keeps you just on the other side of the instaflash fence IMO.

 

[monkeyboy]

mdocod, thanks, that's exactly what I wanted to know.

pete7226, 18500s sound like a good option since it won't affect the appearence. How did you go about boring the tube?

 

[pete7226]

I sent mine out to CPF member Highorder. I don't have the time, patience or the necessary tools to do it myself.