18650 vs. CR123

Probably a stupid and over-simplistic question, but is the difference in performance of adjustable output lights running an 18650 vs. two CR 123 primaries interchangeably in the same unit going to be similar across different makes? I'm mainly referring to lumen limitations as opposed other variables that may be impacted.

Maybe I should dig my "ignorance hole" deeper. I have one light that runs a 16650 or two cr123's and another that runs and 18650 or two cr123's. Max lumens are slightly different but comparable. I've run the rechargeables for quite a while now, but I've had a stash of primaries ever since my first LED, a Surefire 6P I was gifted. I realized I probably need to start using those primaries before I exceed their shelf life (if I haven't already). One light the drop isn't irritating while the other is obvious. By the way, these happen to be the same make, but not the same model. I won't name names because it's irrelevant and may all be due to "user error" and me missing something glaring( pardon the pun)!

There's really no clear answer here as this primarily depends on the driver used by each specific light having the most effect. In terms of the "limit" a single modern 18650 has more energy capacity or Watt-hours than 2XCR123A and at the very same time the ability to discharge far more energy than 2XCR123A. A circuit designed to push lithium-ion to its limit likely isnt designed for CR123A as it is quite expensive. There is one that I can think of that pushes both to their limit being Lux-RC.

I have old CR123's for the same reason, but I'd advise against using two or more old CR123s in series. If they have self-discharged to a different level they could be a fire/explosion hazard.
The Chinese made CR123s seem particularly bad about self discharge, they do not seem to live up to the 10 yr shelf life claim. The US made batteries seem to still work well after 10 yrs, but use them individually just in case.

Generally speaking...
123A strengths: nominal 10 year shelf life, less mass
16650 strengths: greater energy density (3.6V x 2.5A = 10.08Wh vs 6V x 1.3Ah = 7.8Wh), generally better power delivery, lower cost of operation over the long haul

18650s are more common that 16650s and generally peak out at 3.5Ah or 12.6Wh.

I don't know what the current limits are on some of the specialty 18650's, however...

I have a couple of newer Nitecore flashlights that take higher amp rated 21700's and have a 2xCR123 adapter. IIRC... The P20i states 1800 lumen hi with the 8a 21700 and 1100 lumen hi with 2xCR123's. The i4000R states 4000 turbo is not available with the 2xCR123's and maxes out on the hi (1000 lumen) vs the 15a 21700.

Additionally, I tested a Craftsman 4xAA worklight with Alkalines, NiMH rechargeables, and an LG 18650. The mesaured amps, calculated power output, and visual brightness and heat went up with each respectively.

Check 18650batterystore dot com for a large selection and great prices on legit cells.

olddogrib said:

two CR 123 primaries

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stacking two cells can be risky. If they dont match in voltage and capacity, the strong cell will try to equalize (recharge) the weak one, and they can overheat.

cave dave said:

I have old CR123's for the same reason, but I'd advise against using two or more old CR123s in series. If they have self-discharged to a different level they could be a fire/explosion hazard.

Click to expand...

I agree, and so does Prometheus Lights:

'BATTERY WARNING: The QUARK QK16L MKIII will accept 2xCR123 or 2xRCR123 batteries. However, we STRONGLY ADVISE AGAINST THEIR USE. Catastrophic failure can occur when one of the two cells is not functioning correctly, causing thermal runaway in the other cell. There is a significant risk of fire and/or explosion when using two cells."

Two different types of chemistry. Li-ions are becoming more and more popular. CR123A are kind of expensive to rely on a daily basis, unless you use a very low powered device.

Li-ions, such as 18650 and flat cells is what powers laptops for example.

There are 20mm and 21mm Li-ion cells available these days but torch makers have not really caught on yet en masse.

I only run 123 in a low powered 1x123 light. 100+ hours on low.