How should I test CR123's?

[rockz4532]

If any of you remember the free 123's that were given out a while ago, I have some of them. They had differentiating levels of charge. The problem is that most of my lights are 2 cells, and I don't want mismatched cells causing any problems. I've read a 10 ohm resistor and a multimeter works well for testing AA's, but what method should I use to match my CR123's for use in my lights?

Thanks in advance.

 

[Wilmette]

I bought a ZTS Pulse Load Tester after reading about its use here on CPF. Someone else with more time and credibility should probably chime in here to let you know if it's worthwhile across a broad spectrum of use. I know I like it.

There are several models, depending on how many different types of cells and different voltage levels you want to measure. The readout is a series of LEDs labeled 100%, 80%, etc.

If I understand correctly, the basic problem with just measuring open circuit voltage of a cell with a VOM is that it's a somewhat inaccurate indicator of remaining cell capacity. I don't fully understand the reasons but many cells will "bounce back" and give you a higher static open circuit read after some use than if they were measured under some load. Hence the pulse load tester. This is someone else's territory to explain for sure, not mine.

I know I still tend to use my VOM to check my rechargeables, i.e. >3.6 volts prior to charging and 4.1 ~ 4.2 volts hot off the charger. I have several Flukes and a Simpson 360 and all read within 0.01 of a volt DC using the same leads to eliminate that as a variable. My $0.02.

 

[Kestrel]

From the thread where those cells came from, there was this post by Illum which dealt with that question.

 

[rockz4532]

From the thread where those cells came from, there was this post by Illum which dealt with that question.

I completely forgot to check that thread. Thanks a ton, I'm gonna go build the rig now.

 

[rockz4532]

Ok, I've tested a couple batts using a green LED and a 10 ohm resistor, and the results are confusing me.
Heres the time/voltage chart for cell #1 and #2
#1-
2 sec= 2.84v
10 sec= 2.84v
20 sec = 2.84v
30 sec = 2.86v
40 sec = 2.88v
50 sec = 2.89v
60 sec = 2.90v
#2-
2 sec= 2.87v
10 sec= 2.87v
20 sec = 2.87v
30 sec = 2.88v
40 sec = 2.89v
50 sec = 2.90v
60 sec = 2.91v
Why is this happening??? I thought the load was supposed to make the voltage sag over time. Can someone tell me how to match the cells when this is happening?

 

[march.brown]

For CR123 primary cells , I would suggest that the load (10 ohms) is applied at the same time as the meter and for no more than about twenty seconds whilst a reading is made ... You can then sort the primary cells in voltage order ... If you need two batteries for your torch , pick two that are as near identical as possible ... If they are well spaced out voltage-wise , I would use them in a single cell torch ... I wouldn't bother with an LED in circuit , just a resistive load of 10 ohms and at least one watt , preferably two watt.

If I was using a CR123 multi-cell torch , I would check even the brand new primary batteries.
.

 

[rockz4532]

For CR123 primary cells , I would suggest that the load (10 ohms) is applied at the same time as the meter and for no more than about twenty seconds whilst a reading is made ... You can then sort the primary cells in voltage order ... If you need two batteries for your torch , pick two that are as near identical as possible ... If they are well spaced out voltage-wise , I would use them in a single cell torch ... I wouldn't bother with an LED in circuit , just a resistive load of 10 ohms and at least one watt , preferably two watt.

If I was using a CR123 multi-cell torch , I would check even the brand new primary batteries.
.

Do you think that maybe the resistor is heating up which is causing the weird readings? I think my resistors are 1/2 watt.

If heat affects resistors that much, I will go buy some 10 watt ones.

 

[Kestrel]

um, you mean 1/2 ohm / 10 ohm, not 'watt', right? ;-)
Edit: and yes, my guess would be that their resistance is changing as they heat up.

 

[rockz4532]

The resistors are marked 1/2 watt, 10 ohm. My question is, is the heat the reason I'm getting funky readings, or is it just the batteries waking up from a year of no use causing voltage rising?

 

[rockz4532]

Ok, I'm going to ditch the LED and go with a straight 10 ohm resistor. The LED in series is making the load only 23.5 mAh which is not near the 833mAh of the ZTS thats proven. Hopefully the resistor itself will give me a better reading.

 

[Kestrel]

The resistors are marked 1/2 watt, 10 ohm. My question is, is the heat the reason I'm getting funky readings, or is it just the batteries waking up from a year of no use causing voltage rising?

OK, so the 10 ohm resistor is rated for 1/2 watt of energy dissipation - so since Power = V x I = I2 x R, you should be guaranteed to get the rated 10 ohms up until a current of 0.22 amps. Sounds like you might need a resistor rated for a higher wattage?

FWIW, of all my engineering classes in college, my only 'C' was in electrical engineering BTW...

 

[rockz4532]

Dang, only .22 Amps. Maybe thats the reason why it melted the hotglue I potted my contraption in....
Anyways, thanks for your help, but I figured out I could use my charger in discharge mode at anywhere between 0.1-1.0 amps and see the voltage.
That charger has been proving the best $40 I've ever spent on something hobby-related.

 

[march.brown]

Do you think that maybe the resistor is heating up which is causing the weird readings? I think my resistors are 1/2 watt.

If heat affects resistors that much, I will go buy some 10 watt ones.

Does the resistor feel hot ?

If you are testing a 3 volt battery with a 10 ohm resistor , the current will be 0.3 Amps ... Watts equals Volts times current , so in this case it would work out at 0.9 watts dissipation ... Ideally , I would choose a two watt ten ohm resistor.

When you measure the cell voltage , the resistor needs to be across the battery at the same time , so you are measuring the cell voltage under load conditions ... You could make up a simple set of leads with the resistor soldered across ... It would be quicker to measure the batteries then.

Personally , I would check the 123 primaries fairly regularly just to see if the pairs of cells are staying closely matched.

I don't have any torches that use two or more 123 primaries ... I only have single 123 torches ... My prefered bigish torch is the Solarforce L2 using a single 18650 battery , but these bring their own little problems if you are not careful.
.

 

[ampdude]

I just use a multimeter, works pretty good.

 

[rockz4532]

I just use a multimeter, works pretty good.

That's not good. Today, I took 10 cells that all read 3.09v from my box of cells. They all were exactly the same on the multimeter. When put under a .5A load, some were in the 2.1's and some were staying steady at 2.7v. Mix both of those cells together accidentally and you have a dangerous situation.

 

[march.brown]

The armed forces and some public utility companies use torches that use two primary lithium cells ... There is no way that they are all going to do an on-load test on all their cells just to get a matched pair.

Even with brand new primary 123s there can be differences in capacity or voltage ... So , are we all worrying too much about finding matching cells ?

Are any of our boys injured by mismatched Lithium primary cells ?
.

 

[rockz4532]

The armed forces use brand new cells which though they might not be matched, they are much more matched than my random cells. I wouldn't bother measuring brand new cells because they come from the same lot, and are manufactured at the same time, which drastically reduces risk of something bad happening.
With cells like mine that are so unmatched, something like this can happen.
http://www.candlepowerforums.com/vb/showthread.php?t=120888

Its better to be safe than sorry.

 

[march.brown]

The armed forces use brand new cells which though they might not be matched, they are much more matched than my random cells. I wouldn't bother measuring brand new cells because they come from the same lot, and are manufactured at the same time, which drastically reduces risk of something bad happening.
With cells like mine that are so unmatched, something like this can happen.
http://www.candlepowerforums.com/vb/showthread.php?t=120888

Its better to be safe than sorry.

I had a brief look at the above report on the exploding CR123 primary cells ... One recommendation is to check the voltage of the cells ... I didn't see anything about doing the test under load conditions ... I didn't read all 25 pages though , so I might have missed it.

I realise that the armed forces use brand new cells , but how do they carry the spares ? ... It is still possible that brand new and part used cells can be used together in the heat of the moment ... I doubt whether they are all aware that there can be serious problems with using mismatched cells ... They practice tactical reloading of weapons till it is second nature , but I doubt whether they have been told that the 123 primary cells need to be from the same batch and that they should be new.

Perhaps they simply throw away the used cells so that only brand new ones are in their possession ... Are the new ones kept in wrappers till they are needed ? ... I doubt it ... It would take too long to replace the batteries ... It might be that the odd problem that they get with Lithium primaries is nothing in comparison to what they experience when on patrol and therefore not worth reporting.

Perhaps manufacturers should be producing high energy lithium primaries that are similar in size to the 18650 cells ... That way , the armed services could use single cell torches and therefore avoid these problems.
.

 

[ampdude]

That's not good. Today, I took 10 cells that all read 3.09v from my box of cells. They all were exactly the same on the multimeter. When put under a .5A load, some were in the 2.1's and some were staying steady at 2.7v. Mix both of those cells together accidentally and you have a dangerous situation.

I only use quality cells with a known history and in incan lights. If one cell suddenly goes to crap (which could happen with any cells) it's fairly evident, unlike it would be with some LED lights. I'll drain my used cells of unknown history in a single cell light. I mostly use safer chemistry rechargeables in my lights with LED dropins. It's true that the voltage of dead lithium primaries can bounce back, I've seen it myself, that's why I take care in matching cells, looking at dates, and not mixing old cells.

 

[march.brown]

I had a play today initially with three rechargeable lithium camera batteries to see the affect of a load resistor on their open circuit voltages ... These batteries are "3.7 volt 1300 mAh" and are used in a Panasonic camera ... The chargers are 4.2 volt 500mA.

The load that I used was a 20 Watt , 12 Volt Halogen capsule lamp ... The G4 type with two metal pins on the end ... I checked the current through the lamp from one of the batteries and it was 0.91 Amps ... I then checked the voltage across the load resister and it was 3.8 Volts ... The resistance worked out as 4.18 Ohms ... That battery was put on charge.

I measured the open circuit voltage of three other batteries and these were 4.14V , 4.13V and 4.11V ... All pretty similar , off load.
I then measured the battery voltages under load and these were 3.76V , 3.91V and 3.78V ... I assume that the differences are due to differences in internal resistances of the three cells , since the same load was being used on each.

The highest open circuit voltage was also the lowest voltage under load.

During the test , the Halogen lamp glows and gets very warm.

I have now made up a 9" test lead with the lamp at one end and prods at the other end ... There are test points on the lead to clip on a voltmeter for ease of use.

I have tried the test on two new / unused 123 Energiser lithium primary cells ... Open circuit voltages were 3.25V and 3.26V ... On-load voltages were 2.82V and 2.85V , so pretty close.

I realise that this load on a 123 primary is probably a bit higher than it should be at 0.9 amps , but I was only experimenting ... I thought that a higher current drain would show up any cell differences better.

My two chargers terminate the charge at 4.17 Volts.

I'm not certain if this information is of any use , but I do enjoy playing with torchy things.
.