CR123A into a 18650 light? Battery Sizes.

Ignoring the voltage difference for a minute, Would a light that is designed for 2 CR123A's be able to physically accommodate a single 18650?

I thought that the 18650 was slightly wider as well as longer?

On average what are the dimensions for a single 123 and the dimensions for a single protected 18650?

The battery nomenclature gives you the answer.

18650 = 18mm diameter, 65mm length, 0 means cylindrical.

CR123 are 16340, roughly, 16mm diameter, 34mm length.

There are small variances from brand to brand, but those rough dimensions are fairly standard.

So no...an 18650 won't fit a tube designed for CR123s.

CR123 is usually referred to as a 16340, some are more like a 17340, the length caries a few mm from brand to brand.

Lights designed for CR123s only are not generally going to fit 18mm cells.

Eric

PS: donn beat me to it muahah!

Hmmm looks like back to the drawing board...

I really wanted to try and do a bored out extension section for the Horus Titanium Q5 FD-1.3 so that it could have a long run from a single 18650.

I think the Horus is an AA sized cell light anyways.

Nah, just checked it's defiantly 16340 Li Ion.

There are 17670 cells that usually fit 2x123 bodies. They are slimmer, but since interest in them is low (as opposed to globally used 18650) few manufacturers bother increasing their performance, so they pay a severe capacity penalty for the size difference. They still hold more energy than two 16340s though...

I think I even saw 16650 cells somewhere, but it might be a figment of my imagination.

Lengthwise they're almost perfect, but at least in regards to surefire, the tubes are bored about 1-2mm too small for an 18650. My C2 only needs opened up about 1mm, but my G2 has no chance as a 17650 will just slide in there with some air resistance (perfect fit).

I know this is another told thread..the power of the search function..but Surefire sell lamps that are C123A and also 18650 compatible...not sure how that works though.

But in the interested of keeping the same subject in the same thread, i have not started a new thread on this subject.

the Surefire P1R Peacekeeper

So they seem to sell a lamp that can use either 1 x 18650 or 2 x 123's

Hello NeilP,

Let's take a look at voltages and then this concept may become a little clearer.

An incandescent lamp is sensitive to over voltage but when fed lower voltages it simply burns dimmer. CR123A cells run around 3.0 volts so if you put two of them in series you end up with about 6 volts. A single 18650 has a maximum voltage of around 4.2 volts. So a lamp that is designed to operate at 6 volts may also give acceptable performance at 4.2 volts.

Tom

Hi, thanks for the reply. to my rather obscure posting. In reading it now, I can't see the point I was trying to make. I think i was merely replying to the original question

Would a light that is designed for 2 CR123A's be able to physically accommodate a single 18650?

Click to expand...

I think I was pointing out that , Yes, it would be possible, and gave the name of a flashlight that did exactly that, could use either 2 x 123 cells or a single 18650.



My words

not sure how that works though.

Click to expand...

Is more a reference to wondering how physically it was achieved to keep the 18650 in contact with the spring contacts, as it would be shorter than 2 x C123 cells, and also the 123 cells being a smaller diameter.
So maybe they include a different body for each cell type, or possible spacers block and sleeve, or some sort of carrier for each battery type.



I get the voltage issue. With an LED driver I'd assume the LED to be equally bright with either voltage input as the driver chip/board should hopefully have a wide enough input voltage range to be producing constant current on the output side down to an input voltage of whatever they decide is minimum for an empty Li Ion cell..so 3 volt or so.

An 18650 is roughly the same length as 2x 123a cells. 18500's would need a spacer, but they're usually used in series to replace 3x 123a (again 2x18500's are about the same length). Most LED dropins can operate on a single lithium ion even if they say 6-12v or something, but don't use more than one cell on a 4.2v dropin.