Is there a CR123 battery drainer available [LED]?

I have a bunch of used CR123 batteries that need a lighting device to squeeze out all the remaining power out of them. I'm looking to get something that is simple that just hooks to the battery. Probably using a lower power LED [or two. . . or three] would be best. Let me know if there is something out there, or if someone could make something like that. Preferably, something that would be used like a candle mode.

Thanks!

You could make a "Joule thief" type of device for 2 5mm LEDs or so. That would be an easy start. Plenty of schematics and guides online for that.

I will look for them. Thanks!

Curious. I had a CR123 that wouldn't light up my Fenix P1D, but I took one of those 2 AA LED candle things and it lit it up pretty well. I may see how long it last. I may have to retrofit it for CR123s if it drains them pretty much down.

LEDs will never get you all the way to zero because they have a threshold voltage below which they don't conduct. I would just short the terminals with about a meter of nichrome wire, or a 10 ohm 1W power resistor.

Orion said:

I have a bunch of used CR123 batteries that need a lighting device to squeeze out all the remaining power out of them. I'm looking to get something that is simple that just hooks to the battery. Probably using a lower power LED [or two. . . or three] would be best.

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Sounds like you need to check out THIS thread started by AOW back in 2009, essentially a 5mm LED installed in a P60 surefire compatible module :thumbsup:



This is an example of Kestrel's interpretation of a P60 based battery vampire... you get the idea

Milkyspit made some amazing battery drainers that he sold as "candles". Ran for a very long time on a mostly dead cell. His included some boost electronics to really drain out those cells.

You could make a simple version yourself as a hobby project.

At low currents, the voltage of a CR123 is still pretty flat - even when 2/3 dead. Modern LEDs have much lower Vfs than the ones we used even 5 years ago, so at 20ma, your garden variety rebel or cree part will still light up just fine.

A rotary switch and a couple of different resistances to select them and the light will come to life just fine. If you add in a method to select "white" vs "red / orange", you can drain them down even further, as the Red / orange leds have even lower Vfs- often more like 2 volts vs 3volts for white.

When the red led goes out, it really is pretty dead. Not Milkycandle dead, but pretty close.

Any driver or drop-in that will power an LED down to 0.8V or less and can handle up to 3V will work. A very good example would be a Nite Ize 3-LED drop-in, if you can find one. Mine will run fine on a single almost dead alkaline and actually outperforms my Joule Thief. Batteries that won't fire up the JT light up the NI just fine. Hook one up to a set of wire leads with magnets on the ends and you have a battery drainer that's fairly inexpensive and works great. I think they (Nite Ize) took this one off the market because too many people drain their alkaline and NiMH cells down to the point where alkalines will leak and NiMH cells are damaged. I know that I've had a single alkaline leak from being run down too far with one of these drop-ins. None of the current Nite Ize Mini-Mag drop-ins work on one cell, sadly.

PCC said:

Any driver or drop-in that will power an LED down to 0.8V or less and can handle up to 3V will work. A very good example would be a Nite Ize 3-LED drop-in, if you can find one. Mine will run fine on a single almost dead alkaline and actually outperforms my Joule Thief. Batteries that won't fire up the JT light up the NI just fine. Hook one up to a set of wire leads with magnets on the ends and you have a battery drainer that's fairly inexpensive and works great. I think they (Nite Ize) took this one off the market because too many people drain their alkaline and NiMH cells down to the point where alkalines will leak and NiMH cells are damaged. I know that I've had a single alkaline leak from being run down too far with one of these drop-ins. None of the current Nite Ize Mini-Mag drop-ins work on one cell, sadly.

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Shoot, if I had known that, I wouldn't have given mine away!!!!

One thing I have done to drain batteries is to wire enough in series to direct drive an LED. I use a variable resistor to set the output and as it dims I crank the resistance down till it gets too dim at zero then I check the batteries and toss the ones that are the lowest out replacing them as needed. 123 cells will measure voltage even dead so you need a load meter on them. You could use 2 of them in series to drive a 5mm LED at ~5-10ma or so with a resistor. You could also get a high power cree emitter and use a boost circuit from a 1 or 2 cell light along with a resistor before the boost to control output.