SureFire 9P/M60 with 2x18500 body

Okay, question about SureFire 9P. I am trying to mod it beyond Malkoff M60, which is a great module. Having a hard time deciding if I should keep the stock body and use 2x17500, or get the Leef 2x18500 body, retaining the same over-all-length.

If I use a 2x18500 body, can I still use 123 cells, with an insert perhaps? They seem to be a bit loose as it is.

Using Li-Ion cells in it is a step forward. But I think retaining compatibility with 123 cells is a good thing.

I would ideally like to get 2x18650 for best runtime but I think it would lose the EDC status and become too big.

Can I get the runtimes for SF 9P with Malkoff M60 mod and:

1. Primaries
2. 2x17500
3. 2x18500
4. 2x18650

Finally, if I got the 2x18650 body, could I use any other cellls in it, or am I stuck with 18650 cell?

You should be able to use 3xCR123 in the 2x18500 body. With a 2x18650 body, you could use 4xCR123 with it. Just not with the Malkoff M60.

h = mAh / mA

Runtime (hours) is equal to the capacity (mAh) of the cell divided by the current draw (mA) of the drop-in.

You can find cell info HERE and the current draw of the M60 is listed HERE

And remember that two cells in series gives you twice the voltage. Not twice the capacity (1x18650 = 3.7V and 2200mAh but 2x18650 = 7.2V and 2200mAh)

Convert the modules power consumption to watts

convert the cells capacity to watt-hours

then you can figure it out.

The unknown variable I don't know, is whether gene tested his module at 750mA at 6V from a bench power supply, or from a pair of CR123s, this makes a slight difference in the results but I'm not going to get into that now...


Lets assume a constant 4.5W of consumption when the module is in regulation for comparison purposes.

this link:
https://www.candlepowerforums.com/threads/67078
shows some common discharge characteristics of CR123s, and we can make some estimates from this.

We know that a M60 draws ~750mA when you have 6V power supply, so if you had 3 CR123s in series, you would have more voltage, and less current draw (same 4.5W in the end). So the Performance of 3xCR123s driving an M60 should correlate to the 0.5A discharge chart semi-accurately. For comparisons sake, I'm going to go on the bet that you choose some good quality cells, and give the average CR123 a capacity value of 3.75 watt-hours per cell for this comparison.

This link:
https://www.candlepowerforums.com/threads/117117
shows some discharge characteristics of various size li-ion cells.

So lets assign some values to various size li-ion cells... now, keep in mind, most of these tests were performed at 1 amp or greater, this is a problem because we know that the malkoff M60, when powered by a ~7.4V source, will probably be drawing much less than 1 amp, probably closer to 600mA (guessing!). So we need to try to extrapolate some values that make sense. I'll do the pleasure:

1. 17500: 4.3 watt-hours
2. 18500: 5.1 watt-hours
3. 18650: 8.2 watt-hours

So now we need to add up the total available power in each configuration:

1. 3xCR123: 11.25 w/h
2. 2x17500: 8.6 w/h
3. 2x18500: 10.2 w/h
4. 18650 16.4w w/h

These are all educated guesses that will vary depending no many factors and what cells are chosen. but:
Based on these very rough numbers, I would say the comparison is as follows:

1. 3xCR123s: 2:30
2. 2x17500: 1:55
3. 2x18500: 2:16
4. 2x18650: 3:39

Eric

Thanks, this is awesome info.


What are the pros/cons of boring out the stock 9P body vs. getting a Leaf one?
Is it easy to find a machine shop that can do this?

etc said:

Thanks, this is awesome info.


What are the pros/cons of boring out the stock 9P body vs. getting a Leaf one?
Is it easy to find a machine shop that can do this?

Click to expand...

FYI, Fivemega is also an option for a 2x18500 or 2x18650 body.

I would keep the 9P body as stock and get a 2x18650 body
That way if you need to revert back to CR123s you can still use the 9P
body, kinda like a backup.

I noticed there is a huge jump in capacity and runtime between 2x18500 and 2x18650.

Both are pretty tempting as with 2x18500 I can still use the original primaries, with an insert, while 2x18650 would give better runtime but be a bit bigger and non-compatible with primaries (even if possible to put 3x123 in it, doesn't make sense due to size)

Oh the easiest would be to grab the avalible 5mega body. I like the 2X18650 capacity myself. To see it for yourself lie down 4 cr123 primaries end to end. It isn't that much longer really!

Is 2x18650 wider in diameter?

here's a thought, if you decide you want the capacity of the 2x18650 body, and also want to be able to use primaries as backup in it while taking advantage of the extra space, use a DereeLight 1SM-2(1-stage multi power) Cree XR-E Q5 module (16V max) instead of the M60 module. With up to 16V supported, you could load the body up with 4xCR123s when needed.

Runtime on 4xCR123s with that module would probably be close to 4 hours with the very low drain rate on the cells. And right around 4 hours or more on 18650s.

Any cell that starts with 18XXX will be the same 18mm.
18500 and 18650 is the same width, just like 17500 and 17650 is the same 17mm.

So no, not wider at all. Just a little longer to give you alot more runtime.

Sgt. LED said:

Any cell that starts with 18XXX will be the same 18mm.
18500 and 18650 is the same width, just like 17500 and 17650 is the same 17mm.

Click to expand...

What I am saying is -- is either Leef or FM 2x18500 or 2x18650 body wider on the outside than the stock body?

If not, then that means the body thickness is lesser (which is probably of no real consequence?)

If they maintain the same body thickness, then the outside diameter has to increase vs stock 3x123 body.

like half a mm difference.

Thanks for clarifying that.

I finally got everything I wanted - in addition to M60/Leef, I also got AW's 18500 cells and also the Pila charger. (Also got a couple of 18650 bodies but didn't get to test them yet)

I really wanted to validate the runtime and thus I ran a test, turned the lite on and got precisely 2:16 hours runtime. I used a fan to make sure that the module didn't overheat, even though I am aware of its heatsinking capabilities. That was reassuring news.

However, one question: Given you don't usually constantly run the lite until the batteries get depleted but rather use it in relatively short bursts, it seemed to me you get lesser runtime if you use it in such a manner of a few mins here and there. Just doesn't seem to add up to 2:15 hours. This is considering that I got the AW protected 18500 cells charged only 4.1V initially, while my test was run on them fully charged at 4.2V.

So yo do get less runtime if you use it in short bursts? Or is it an illusion?

This is just me thinking but I guess for an incan that is true and in the case of the LED an illusion.

Just keep in mind that right now I have no idea what I am talking about. :tinfoil:

Any logical explanation? I am convinced I am not getting the full 2:17 hour runtime using it a few mins (or even 30 secs) at a time.