3AAA LiIon Solution

[jayflash]

Hopefully others have discovered this already, but I didn't find it with a search.

Many of us avoid 3AAA LED lights due to the relatively high drain combined with low capacity cells. Beyond using three NiMH cells there's another solution for barrel bodied lights that use a 3AAA cell carrier. An appropriate length of 3/4" CPVC water pipe will hold a 17500 LiIon cell. I don't have an 18mm cell to try, but it looks like a very tight fit. A dime will force fit into the pipe, if that provided any useful info.

Cut the pipe a little longer than the cell and add a spacer contact to the negative end. I used a bent piece of 1/4" flat copper strap, but aluminum foil or other metal object will work. A stack of dimes press fit might do the trick also.

This adapter worked on the three lights I have, but may not for all. There may be better choices than the CPVC pipe that will allow an 18mm LiIon. A 17500 cell has more capacity than AAA NiMH and the juice doesn't have to flow through so many cheap contacts.

 

[Fallingwater]

This is a known solution to the 3AAA problem. However, since you have space to spare, a 18500 is a better choice than a 17500. A 18650 is even better, but they are longer and thus don't fit in many lights.

Note that LiIon cells are a poor choice for unresistored flashlights, and most 3AAA lights I've seen have no resistance whatsoever inbetween the battery carrier and LEDs. They assume they'll be used with weeny AAA cells and that their internal resistance will be enough to avoid trouble. Give them a beefy LiIon that outputs 4.2V freshly charged and the LED(s) can die really quickly.
To run unresistored lights on 18500s the best way is to use a resistored spacer.

 

[jayflash]

Thanks, Fallingwater, for the additional caution. Even using NiCds or NiMH cells may be a problem in the case of a non resistored light.

Yes, I figured someone would have discovered this adaptation way before I did.

 

[Fallingwater]

NiMH cells aren't usually a problem unless the LEDs are really bad.
A fully charged 18500 will deliver more energy to the LEDs than three fully charged AAAs.
Here's some more info.

 

[somnambulism]

NiMH cells aren't usually a problem unless the LEDs are really bad.
A fully charged 18500 will deliver more energy to the LEDs than three fully charged AAAs.
Here's some more info.

Came upon this thread while looking for information on this exact topic. Thanks a ton for that link — but the site has been changed in the years since your post, so that page is now here.

 

[daan_deurloo]

My chinese cree led came with a 3aaa adapter, but it does take a 18650, but it's lose in the body then.

But i do have 3aaa adapter with 3aaa cells in it. Yes they are rechargeable ( cheap nimh cells ). It does work, but again it's low capacity and fast drained.