replace 3 AAA holder with 18650

Does anyone know of a small LED light that uses a 3AAA holder that can be replaced with a 18650? This would give a smaller form factor and larger capacity.

I replaced a 3aaaa coast light with a 14500,much brighter,longer running,and no ordering special batts.I did it over 1 year ago,no problems.

18500 will always work in the space of 3xAAA, and provides about 60% more energy than good NiMH cells.

2xTrinity said:

18500 will always work in the space of 3xAAA, and provides about 60% more energy than good NiMH cells.

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Not always, it really depends on the light.
Take this one, for example.
A 3AAA carrier is slightly longer than a 18500; it doesn't matter in some lights, but this one needs its contacts stretched to reliably contact a 18500.
Also, it is completely unresistored. I did some testing in my review of it, and current draw from a fresh 18500 is way too high for those poor LEDs.

In other words: if a light is resistored, then it's probably ok to run it from a 18500 or 18650 if it fits. If it's not resistored, doing that is asking for trouble.
It would be easy to build a spacer containing an appropriate resistor, though, which would also solve the problem of the shorter length of the 18500 cell.

Thanks for the great info! The 18650 is too long for most of my AAA lights but the 18500 fits great! Much easier to stretch the spring if needed than to try and jam a cap on that's too tight.