Safe to test voltage and IR of L91 in Opus BT C-3100 v2.2?

pdirt

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I've been dumpster-diving my local recycle center, pulling out L91 lithium primary AA's and various NiMH cells. What I've been doing is using my multi-meter to measure voltage of the L91's. Some read as fresh at 1.8v, most are 1.6-1.7v. For the NiMH, I first see if I can get a reading for internal resistance using the Quick Test mode on the Opus. If the cell is completely dead, I'll pop it in the Xtar VC2 Plus Master for a few minutes to "revive a 0v cell", then I can usually get a IR reading. If it's 1500 or less on the IR test, I'll charge it at 200mA and re-test, then run a Test cycle to measure capacity. If it has decent capacity then I will run the Refresh cycle to see if I can regain some mAh. After Refresh, often the IR goes down dramatically as well (is this really possible, or is it due to flaky test nature of testing IR on the Opus?)

Anyways, is there any harm or value testing voltage and internal resistance of lithium primaries on the Opus BT C-3100 v2.2 charger? My understanding is it won't start charging for 6 seconds, which is plenty of time to catch a voltage reading. Also, I don't fully understand how the internal resistance testing works or if it even applies to a different chemistry like an L91, as the Opus is designed for li-ion and NiMH.

A less important question regarding internal resistance. I've read that a good IR reading is less than 100. I've tested brand new Eneloops and AmazonBasics NiMH right out of the box and get IR readings of 200-400. Rarely do I ever see a reading under 100. Is that normal for the Opus? Being such a budget analyzing charger I thought perhaps that the IR feature is not all that accurate. I couldn't quite justify the cost of the SkyRC MC3000! I have a few cells that consistently read out 1500-1700 on the IR test, is that high enough to warrant recycling them back to the recycle center? I had one Energizer AA NiMH cell I found today that read 7000 multiple times, which is definitely going back to recycle.
 

klrman

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Most chargers have flaky IR readings that change often when you rotate the battery a little in the slots. To get very good and consistent IR readings, with the help of someone I recently purchased the SM8124A impedance tester and it is really impressive. It uses 4 wires for accurate readings and + - probes each have two retractable pins for a solid connection. Readings are very close to specs printed on battery data sheets. I'm not sure if you can use it for all the batteries you listed though and maybe someone can jump in here to confirm that or not.

I also learned this week what IR readings will go down in lithiums after charging/discharging as when the cell warms up there will be less resistance.

If you really need a good tester, the older model named SM8124 instead of SM8124A does not have the two pinned probes and works with the AA batteries. The newer two pinned probes are too wide for smaller batteries like AA which I just found out myself today.
 
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HKJ

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SM8124 do not test IR the same was as chargers, it uses AC.

I wrote a bit about it here: https://lygte-info.dk/info/Internal impedance UK.html

With chargers the problem is connection resistance. It can be between the battery and the charger and on some chargers also between the sliding connection and the rail. The lowest reading you can get will usual be the most correct one.
 

klrman

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Even though the SM8124 does not test the same way, isn't it still very accurate overall when compared to battery data sheets?
 

HKJ

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Even though the SM8124 does not test the same way, isn't it still very accurate overall when compared to battery data sheets?

I have not tested it, but I would expect it matches battery data sheets fairly well because it test the same way (1 kHz AC), chargers test another way that gives different results.
 

klrman

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Thanks for that clear up as I was never sure. How can we twist your arm to test the newer SM8124A?
 

Gauss163

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Even though the SM8124 does not test the same way, isn't it still very accurate overall when compared to battery data sheets?

Accuracy is not really relevant because these AC (1kHz) impedance tests aren't very useful for inferring behavior under DC loads. I explained this at length in prior posts, e.g. see my posts here (and their links).
 
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klrman

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It's not a question of accuracy but rather utility. AC (1kHz) impedance tests aren't very useful for inferring behavior under DC loads. I explained this at length in prior posts, e.g. see my posts here (and their links).

Thanks Gauss, I will be reading it all with great interest as it is one of those topics where I really want more knowledge. Just clicking your link and learning right away that the AC(1kHz) is used by manufacturers as a cheap test to weed out massive failures is a real bonus to know right off the bat.

BTW, is there any other reasonably priced tester that would do a better job than the SM8124A for testing under DC loads since my one tests under AC?
 
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pdirt

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Most chargers have flaky IR readings that change often when you rotate the battery a little in the slots. To get very good and consistent IR readings, with the help of someone I recently purchased the SM8124A impedance tester and it is really impressive. It uses 4 wires for accurate readings and + - probes each have two retractable pins for a solid connection. Readings are very close to specs printed on battery data sheets. I'm not sure if you can use it for all the batteries you listed though and maybe someone can jump in here to confirm that or not.

I also learned this week what IR readings will go down in lithiums after charging/discharging as when the cell warms up there will be less resistance.

If you really need a good tester, the older model named SM8124 instead of SM8124A does not have the two pinned probes and works with the AA batteries. The newer two pinned probes are too wide for smaller batteries like AA which I just found out myself today.

Yeah, i've heard about the flakiness of IR testing in chargers. I see the SkyRC M3000 has two external probes for testing IR, which I assume is far superior to the method the Opus uses.

That tester you showed looks handy, but I don't think I can justify such an expense yet!

The tip about IR going down with li-ion due to warmth (or perhaps any battery for the matter) makes sense. I will try testing them both at the end of a cycle on the charger and when they're cold and see if I notice a difference.
 

pdirt

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SM8124 do not test IR the same was as chargers, it uses AC.

I wrote a bit about it here: https://lygte-info.dk/info/Internal impedance UK.html

With chargers the problem is connection resistance. It can be between the battery and the charger and on some chargers also between the sliding connection and the rail. The lowest reading you can get will usual be the most correct one.

Thanks for the link. Much of it is over my head, but I do get the idea that there is quite a lot involved in testing IR. All the photos are quite helpful, even though I doubt I will ever learn enough to understand how to use the setup you've made. I think I'll stick with the less-accurate method built-in to the Opus charger.

Your post also leads me to believe that the answer to my original question is "yes" (Is it safe to test IR on a lithium primary AA/L91 using the Opus charger). It's simply a test that could be applied to any battery that could fit in the charger. Also the IR test ("Quick Test" on the Opus) is totally separate from the other modes, so no charge or discharge would be applied.
 

HKJ

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Your post also leads me to believe that the answer to my original question is "yes" (Is it safe to test IR on a lithium primary AA/L91 using the Opus charger). It's simply a test that could be applied to any battery that could fit in the charger. Also the IR test ("Quick Test" on the Opus) is totally separate from the other modes, so no charge or discharge would be applied.

The Opus will do a short discharge pulse to test IR, this is safe enough on a Lithium primary, but the IR value is not correct. This has to do with the Lithium chemistry used in AA cells.
 

klrman

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Yeah, i've heard about the flakiness of IR testing in chargers. I see the SkyRC M3000 has two external probes for testing IR, which I assume is far superior to the method the Opus uses.

That tester you showed looks handy, but I don't think I can justify such an expense yet!

The tip about IR going down with li-ion due to warmth (or perhaps any battery for the matter) makes sense. I will try testing them both at the end of a cycle on the charger and when they're cold and see if I notice a difference.

I think you mean the XTAR Dragon. My MC3000 doesn't have any external probes.
 

Gauss163

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The Opus will do a short discharge pulse to test IR, this is safe enough on a Lithium primary, but the IR value is not correct. This has to do with the Lithium chemistry used in AA cells.

What precisely do you mean when you claim that "the IR value is not correct", and what does this have to due with the "Lithium chemistry used in AA cells"?
 

HKJ

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What precisely do you mean when you claim that "the IR value is not correct", and what does this have to due with the "Lithium chemistry used in AA cells"?

Because IR for lithium chemistry in AA (Li Fe type) cannot be measured that way
 

Gauss163

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Because IR for lithium chemistry in AA (Li Fe type) cannot be measured that way

Still quite imprecise. What precisely is "that way"? Perhaps what you mean is that for Lithium Iron Disulfide (LiFeS2) chemistry one obtains more accurate pulse-based IR readings by using double pulses (to eliminate OCV effects). and Opus does not do such? Doesn't the MC3000 use a double pulsed test? Have you actually tested those chargers on LiFeS2 batteries or are you simply quoting datasheets (e.g. Energizer mentions this briefly).
 
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HKJ

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Still quite imprecise. What precisely is "that way"? Perhaps what you mean is that for Lithium Iron Disulfide (LiFeS2) chemistry one obtains more accurate pulse-based IR readings by using double pulses (to eliminate OCV effects). and Opus does not do such? Doesn't the MC3000 use a double pulsed test? Have you actually tested those chargers on LiFeS2 batteries or are you simply quoting datasheets (e.g. Energizer mentions this briefly).

I have tested the batteries and you can see in my review how specific chargers test IR.
 

Gauss163

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I have tested the batteries and you can see in my review how specific chargers test IR.

Which doesn't answer any of the questions I posed to you (nor are the answers in any of your reviews or web pages). So I will answer my questions so that readers can learn more about this topic. Just as in our earlier discussion of primary Li-SOCl2 (Lithium Thionyl Chloride) batteries, there are delay effects caused by passivation in LiFeS2 batteries. To avoid these effects from causing false IR readings one needs to delay doing a pulsed IR test till the passivation layer has reached steady state. One way to do this is to use a double pulsed load - the first pulse overcomes the passivation effect so that the following pulse yields more accurate results. Below is what Linden and Reddy write about impedence of LiFeS2 batteries in their popular battery handbook

Linden and Reddy said:
Impedance. AC impedance is an electrical characteristic that is frequently used as an indicator of performance for aqueous batteries. The correlation is only poor at best with Li/FeS2 batteries. There is a protective film that forms on the surface of the lithium anode. This film is an important factor in the excellent shelf life of the Li/FeS2 cell. As the cell ages, this protective film increases with age. As the film increases, the impedance does as well. However, this film is easily disrupted when the battery is put on load, making impedance inappropriate as an indicator of expected Li/FeS2 battery performance, especially after storage.
This is also mentioned briefly in the IR section of the Energizer datasheet that I linked above (but in a way that does not promote better understanding of the heart of the matter).
 
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Gauss163

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Now you have the answer to why I wrote that.

It's rather sad that you play these puerile games. If in fact you knew the answers to these questions then you should have had the decency to answer them. But I don't see any clue above (or on your web pages) that you knew the answer. Again, you can't expect to learn battery electrochemistry from datasheets alone (but here the matter is simple enough that you could have run your own tests but I see no such data on your site). Oh well, some things never change...
 
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