Testing 123s

Hi!

I carry an Arc LSL every day, and have other 123 lights. I decided that with the regulation on the LSL, I will not know if the battery is almost dead until it dies in the light! So I decided that I needed a battery tester. I found one here at Radio Shack. It even tests 3V lithitum batteries!

HOWEVER, there is a problem. It tests AAA batteries at 50mA, and AA and larger at 150mA. But it tests 3V lithiums at only 1mA! It assumes that all 3V lithiums are button cells!

I am planning on opening the unit up and adding a resistor (switched, so I can disable it) to increase the load at 3V. However, what should I increase the current to? It measures 6V photo batteries (2 lithiums in one package) at 10mA, but measures a 1.5V AA at 150mA. Any ideas what the best current to measure is?

Search through the forum for "flash amps". Some discussions about a way to test 123 lithium cells.

Because the lithium 123 (and other lithiums) typically have a flat voltage output especially under low/minimal loads, using voltage to check them for their condition is usually fruitless. Short-circuit amperage is a better (only) way to check them out. New (good) 123 cells seem to put out 7+ amps in a short-circuit (take a decent ammeter in the 10A setting and touch the probes to the terminals of the cell -just- long enough to get an amp reading, a second or so). Used cells will put out less. Even pretty dead cells can put out 2.8+ V under no/minimal load.

See Duracell 123 data or Energizer 123 data for some manfacturers' data. Also see Battery University for more battery info.

If you are heart-set on modifying your R-S battery meter, try a 1-ohm 5W resistor.

Harrkev, with 123 cells you need to test for "flash amps," as Mike (MoonRise) mentioned. I happen to be the author of one of the posts about flash amps... take a look at my writeup from last summer over here. Please note that what I called "MUC" at first is in fact the same thing as flash amps.

The bottom line is that you'll need a DMM capable of measuring current up to at least 10A. Fortunately, there are LOTS of DMMs capable of this, priced as low as $3. Others have posted on CPF about various units that would work. Test several fresh 123 cells to get a sense of the flash amps readings for that particular brand, as various brands will have slightly different readings when full. The rest is easy: any time you want, test the cell you're using in your light for flash amps. If your fresh cells have been reading 9.5A or so, but the one in your light reads 5.2A, the cell is pretty substantially used. In my experience, by the time a 123 cell's flash amps drop to 3A or so, it's going to stop working sometime soon. In fact, you might decide to replace the cell whenever it drops below 6A to give you some confidence that it'll keep running a little while. As you gain experience, you'll come up with your own preferences for these sorts of things.

Hope it helps, and best of luck with this! /ubbthreads/images/graemlins/thumbsup.gif

Milky & Moon's method is what I rely on too. That also works for alkaline cells.

As a reference point, I grabbed a new and a used 123 cell and a DMM.

used 123 - voltage 2.821v no load, 0.46 A short-circuit
new 123 - voltage 3.226 no load, 9.8 A short-circuit

The used cell looks pretty used. It still will run my Arc4+ at the lower light levels though.

I didn't have time this morning to do a simultaneous voltage/current check under the short-circuit load conditions.

I'll bet the used cell won't work for an incan lamp. For all practical purposes it's dead.