Would 2x18500 be roughly length equivalent to 3x16340?

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xevious
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Would 2x18500 be roughly length equivalent to 3x16340?

I have a flashlight that will take 3×16340 cells in series. Would two 18500 cells be able to serve in replacement, presuming the width (18mm) will fit?

EDIT: Sorry, I meant “16340” not “16430”… typo. Also, sorry for not providing greater context. The Lumens Factory P60 drop-in that I’m running can handle up to 14v. I have it installed in a Pila GL3. I had forgotten what cells it originally took and learned later that they were Pila 300P cells. Two of them, driving a xenon bulb.

Edited by: xevious on 01/08/2019 - 09:29
bmengineer
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500*2=1000
340*3=1020

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polarweis
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what is the voltage going to the led?

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Streamer
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I've never had a 16430 cell. Are you sure you didn't mean 16340?

then: 2x50 = 100mm

         3x34 = 102mm

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Lenghtwise two 18500 cell’s would fit a good ol’ Surefire P9.
And as the 9 stands for 3 * 3V (CR123A) = 9V, it won’t be killed by the voltage of 2 * 4.2V either.

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Either way, it is probably not going to work because the combined voltage of two 18650 batteries is lower than either of the two types of batteries your light was designed for – see below.

CR123A is a non rechargeable 16340 lithium manganese dioxide battery with a 3V output
RCR123A is a rcchargeable lithium ion 16340 battery with a 3.7V output

I tried some 12V LED lights with three 18650 batteries in series and apparently 11.1V is close enough to light the lights for a while. Ditto for a 3 AAA bike light working off one 18560 battery. I never tried it with good Panasonic batteries but the cheap Chinese ***fire batteries would light a 100 lumen bike tail light for about 2 hours.

Barkuti
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16340 LiFePO4 cells, problem solved. They can deliver some decent current, like these generic cells (Nicjoy branded at FastTech) and these others from Soshine. Label lies, as usual.

 

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Note on terminology:

The first 2 digits are the width, the next two digits are the length. The “0” at the end means the cell is rolled up in a metal can as opposed to being a lipo cell in a foil envelope.

So a “16340” is approximately 16mm wide, 34mm long, and is in a metal can.
And an “18500” is approximately 18mm wide, 50mm long, and is in a metal can.

Note however that these numbers tend to be approximations. Cells manufactured by different manufacturers may vary slightly from the standard dimensions.

xevious
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Streamer wrote:

I’ve never had a 16430 cell. Are you sure you didn’t mean 16340?


then: 2×50 = 100mm


         3×34 = 102mm


Firelight2 wrote:
Note on terminology:

The first 2 digits are the width, the next two digits are the length. The “0” at the end means the cell is rolled up in a metal can as opposed to being a lipo cell in a foil envelope.

So a “16340” is approximately 16mm wide, 34mm long, and is in a metal can.
And an “18500” is approximately 18mm wide, 50mm long, and is in a metal can.

Note however that these numbers tend to be approximations. Cells manufactured by different manufacturers may vary slightly from the standard dimensions.

Thanks, I did mean 16340 — corrected.
I’d forgotten that the 3rd and 2nd to last digits are the cell length in millimeters. So yeah, providing the spring has adequate compression, the 2×18500 cells would work, presuming there will be some minor length variation by manufacturer. I did not know about the foil with LiPo cells. Very interesting.

xevious
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Barkuti wrote:

16340 LiFePO4 cells, problem solved. They can deliver some decent current, like these generic cells (Nicjoy branded at FastTech) and these others from Soshine. Label lies, as usual.


Cheers Party 


Thanks for the link to lygte-info.dk. Great info there! Thumbs Up
HKJ
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Firelight2 wrote:
Note on terminology: The first 2 digits are the width, the next two digits are the length. The “0” at the end means the cell is rolled up in a metal can as opposed to being a lipo cell in a foil envelope.

IEC do not agree with you on this, then say the last 3 digit is length in tents of mm. The shape and chemistry is specified with the letters before the number, like in IMR18650: LiIon, Manganese, Round, 18 mm diameter, 650 tents mm in length.

My website with reviews of many chargers and batteries (More than 1000): https://lygte-info.dk/

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If the diameter fits and the voltage is enough from 2 instead of 3, yes, you should do the upgrade. You can pack up significantly more power from 2 18650s.

I did the same except for some lasers that have 2×16340 and the diameter would fit to use 18650s but I can’t find a proper length extender.

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Overmind wrote:
If the diameter fits and the voltage is enough from 2 instead of 3, yes, you should do the upgrade. You can pack up significantly more power from 2 18650s.

I did the same except for some lasers that have 2×16340 and the diameter would fit to use 18650s but I can’t find a proper length extender.

If it has springs on both ends the 18650 should work. If not a longer spring on one, a few magnets or a solder blob could get you the 3mm you need.

Overmind
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@toddcshoe I have them with 2 16340, not 3. I need about 60 mm more body.

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bmengineer wrote:
500*2=1000
340*3=1020

Solid math Smile

Is that including the top?
Flat, raised flat or button?

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It is the other way around.
Measurements of the xx340 and the yy500 are derived from primary batteries.
These have been around for many years and are fairly detailed and strict.
The rechargeables derived from that format are newer, and hardly ever identical.
And not just because they (don’t) have a button top or built-in protection.

So, in the ballpark area 2*500 indeed is 3*340, but if YOU are going to buy batteries for your mod,
you are responsible yourself that the 2*bbb you put in are the same length as the 3*ccc you took out.

So you can gamble, order, pay, wait 3 to 6 weeks, and curse if it is not fitting.
Or ask members of this forum if they have bought these batteries, and if they are willing to measure them.
Or you can look for it yourself in the quite extensive database of member HKJ.

You are a flashaholic if you are forced to come out of the closet, to make room for more flashlights.

xevious
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From what I’m seeing, the PILA GL3 has a lot of travel in the spring… so even just 2 mm extra in length isn’t enough to cause a problem or battery crushing.

Btw, speaking of springs, I’d seen some chatter about BeCu (beryllium/copper) springs… Is it the general case that with most of these flashlights the springs are soldered in place? None clamped down with screw secured clamps?