Flashlights with less common battery types...

Been looking at buying some new Li-ion batteries and I notice many places list options such as 17500, 17650, 18500's. I don't think I've seen any flashlights claiming to support these batteries.

Are there many, or some good examples of ones that do?

Two 17500s will usually fit into a light made to take three CR123a batteries.
A 17670 will usually fit into lights made to fit two CR123a batteries, though the voltage is a bit lower than two CR123a's.
Two 18500s will fit into a three CR123a battery light that has been bored for larger diameter cells.

Peak has the Logan that's been made to use 17500s. I'm sure there are others.

PCC said:

Two 17500s will usually fit into a light made to take three CR123a batteries.
A 17670 will usually fit into lights made to fit two CR123a batteries, though the voltage is a bit lower than two CR123a's.
Two 18500s will fit into a three CR123a battery light that has been bored for larger diameter cells.

Peak has the Logan that's been made to use 17500s. I'm sure there are others.

Click to expand...

Thanks, I didn't think of it like that. Guess it makes a bit more sense.

Personally I'd have thought 18500's would be quite interesting, as you could have a light hardly any bigger than an 1xAA, offer up huge punch and longer run times than a 14500.

The first two digits in the battery number refer to the nominal diameter in millimeters (17500, 17650, 18500, 18650). The second pair of digits refer to the nominal length of the battery (17500, 17650, 18500, 18650). The 17650 and 18650 are roughly equivalent in length to two CR123 primaries. Two 17500's or 18500's are roughly equivalent to three CR123 primaries.

The 17500 and 17650 are often used in flashlight hosts that were designed for standard CR123's but that aren't large enough to accept 18mm batteries with the most common examples being stock Surefire lights. For example, using a 17650 in a stock 6P, C2, or Z2 body or using two 17500's in a stock 9P, C3, or Z3.

The 18500 and 18650 have the same application in hosts that are large enough to accept them. Examples include bored Surefire hosts, Malkoff light bodies, and several other brands.

All of the above refers to the physical size of the batteries. When switching from primaries to Li-Ions, voltage must also be considered. (CR123's = 3 volts each, Li-Ion's = 4.2 volts each). Unlike incandescent bulbs, LED's usually operate efficiently across a range of voltages but care must still be taken to ensure the battery combination falls within range for a given light.

Edit: I type too slow. Good answer PCC

And I think the last "0" means that the battery has a " Round" shape.

... and protected cells may often exceed the "nominal" length and/or diameter ...

For example, HDS called the battery tube designed to fit a protected 18650 cell, a "19670" tube.