How to match batteries for 2-cell lights?

[BigBluefish]

Funny that I'm rated a "flashaholic" and I have to ask this:

I'm wanting to get a couple of 2-cell CR123a lights - I only have single cell CR123a lights now - but how do I "match" the batteries so my light doesn't go ? I'll only be using primaries.

Is there some sort of voltage tester I need to get? Or do I just grab two cells from the same original packaging and cross my fingers?

 

[buickid]

Get a multimeter, set it to DC Volts, check the batteries, and use the two with the closest voltage. Multimeters are infinitely useful, especially when working with electronics. :twothumbs You can pick up a decent meter for less then $20, but we have several long threads covering this.

 

[Marduke]

You're generally okay if you use new cells, and keep a pair of cells paired up until they are depleted.

Mix-and-match is where you run into the big problems.

 

[buickid]

Although every once in a while some people receive defective cells that come partially depleted... Are ya' feelin' lucky?

 

[s.c.]

I got a multimeter the other day to check the voltages of my rechargeables. For the hell of it, I went through my stock of never used cr123s and found a dud (it was a Duracell, expiry 3/2018). Knowing that I've significantly reduced the chance of something blowing up was well worth the cost of the mulitmeter, especially considering my latest purchase is a 2xcr123 headlamp.

 

[StarHalo]

First, make sure you're using quality cells; cheap batteries individually are about as dangerous as mixing cells. Recommended brands are Sanyo, Panasonic/Surefire, RayOVac, Streamlight, and Duracell.

Next, get a digital multimeter (which you'll need for certain if you ever use Li-Ions anyway); this is neither complex or expensive, Harbor Freight carries a perfectly good model for $3 (http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=90899). As noted above, you set it to Volts DC and perform an "open voltage" check on each cell, showing you how much voltage the cell can provide without a load.

If you really want to be thorough, you can do a more precise test by measuring how much voltage the battery can provide under a load, a "load test", which better simulates the working conditions a battery would be under in actual use. You can buy a $70 ZTS pulse load tester for this, but building your own is far simpler and cheaper - all that's required is $2 for a resistor from Radio Shack; see more detailed instructions here: http://www.candlepowerforums.com/vb/showthread.php?t=214963&page=2 (Read most of the page as there's a lot of data and diagrams there. Also, the circuit I built/illustrate in post #35 tests 123 primary cells at exactly 1 amp.)

 

[buickid]

especially considering my latest purchase is a 2xcr123 headlamp.

Ouch. Dodged a bullet on that one!

 

[Carpenter]

<snip>
If you really want to be thorough, you can do a more precise test by measuring how much voltage the battery can provide under a load, a "load test", which better simulates the working conditions a battery would be under in actual use. You can buy a $70 ZTS pulse load tester for this,<snip>

+1 on the ZTS tester, but you can buy the least expensive model and still get the same results for CR123's. The $70 one will test just about every type of battery in existance.

 

[Oddjob]

A load tester is a more reliable way to determine a cells state of discharge. IIRC Silverfox did some test on CR123's and even some cells that were nearly fully discharged still showed greater than 3 volts on a multimetre. Using both a multimetre and a load tester would greatly increase the matching of cells.

 

[BRO]

I purchased the ZTS for around $28.00 at Thomas Distributing and this thing works great. I also use the DMM but the ZTS is the way to go.
There are two ZTS tester that look and cost the same but only one of them with do the CR123's. Now the $70 dollar ZTS tester is very nice but i really did not need to spend that much since my battery plateforms were covered with the smaller ZTS units.
For matching it would seem testing on the ZTS and with a DMM would be a good practice.

 

[BigBluefish]

Thanks for all the input, guys. I think I"ll check out one of those $28 ZTS testers over at Thomas and get a multi-meter, too.

I usually carry my light in my front jeans pocket - hate to have a meltdown in that location.

And my wife will kill me if one of my batteries goes and burns the house down. That would be embarrassing, to say the least.

And for a slightly off-topic thought, would a single 18650, even though rechargeable, be a 'safer' alternative to 2 x CR123a? (With a light set up to take 18650s, and I realize most 2 x CR123a lights aren't.) I understand, somwwhat, that rechargeables have their own issues - don't overcharge, or over-discharge, and don't short them, just like primariy cells. But at least, there wouldn't be the cell matching issue.

 

[BRO]

Thanks for all the input, guys. I think I"ll check out one of those $28 ZTS testers over at Thomas and get a multi-meter, too.

BigBluefish; I also purchased my DMM for Thomas Distributors, I think for $8.00 (it ws on sale) and it works well.

Another option is to carry single cell lights. I'm carrying a RA Clicky, plenty of beam and only one cell. And there are many nice 1 cell lights out that will fit the front pocket well.

As far as the single 18650 goes, I don't have an answer other then I think it is safer with nothing to match up. I am thinking about buying a TK11 and find out for myself. But well see, good luck.

 

[SUREFIRED]

On a multimeter, if the two batteries' voltage are 3.25 and 3.21, is that a good match? Most of my 123s have 3.24v though.

 

[BigBluefish]

Thanks for all the input, guys. I think I"ll check out one of those $28 ZTS testers over at Thomas and get a multi-meter, too.

BigBluefish; I also purchased my DMM for Thomas Distributors, I think for $8.00 (it ws on sale) and it works well.

Another option is to carry single cell lights. I'm carrying a RA Clicky, plenty of beam and only one cell. And there are many nice 1 cell lights out that will fit the front pocket well.

As far as the single 18650 goes, I don't have an answer other then I think it is safer with nothing to match up. I am thinking about buying a TK11 and find out for myself. But well see, good luck.

Thanks for the tip on the DMM.

As for single-cell lights, that's what I carry now. Currently, I'm carrying an Olight T10, or a Fenix L1T v2. I like the idea of a little more brightness and throw, and the much longer runtimes on some 2-cell lights, though. But the T10 seems to have a pretty good throw for a 1 x CR123a. I've also got a D-Mini Digital, and I don't think that little light gives up much in the throw department to even many 2-cell CR123a lights, even with the OP reflector, and runtimes on the lower levels are pretty good, too. It's actually a very impressive little light, IMHO.

But there are some really nice 2 x CR123a lights, and 18650 lights...all the Surefires, the Solarforce L2s, the Eagletac P100C2, the Inova T1, the Olight T20 T, the Dereelights, the Lumapower Encore... I feel I'm missing out due to my uncertainty about branching out into 2 cell, or rechargeable lithium cell lights.

I would actually hazard a guess that the 18650 cells aren't really any more risky than my laptop battery...maybe even safer. But that's just a guess.

 

[BRO]

BigBluefish; Your reasons for going to 2 cr123's flashlights are why I am considering the TK11. Fenix is good and inexpensive quality light just to play around with. Plus, the TK11 uses both the rcr123's and the 18650 cells, not at the same time of course. Good Luck.