Opus BT-C3100 Wire Mod Results


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Testing18650

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Came across this thread: https://secondlifestorage.com/showthread.php?tid=4767

I just made this mod to my Opus BT-C3100. I didn't see any major changesin the Quick Test values after doing it -it gave me almost the same numbers as before.
I tested few Samsung 30Q cells and got results ranginganywhere from 37 to 62. I'm not sure if these are good readings or not (?). Another question is, does this mod
will make the Opus device to show more accurate readings of the internal resistance values, or is it just to make sure the results are more consistent?

By the way, I did this mod with a 22AWG silicone wire,not sure if that matters.
 

Wolf

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The Wire mod on an OPUS does absolutely nothing as far as IR readings are concerned.
The Opus does a simple V drop /R check and calculation. The contact resistance is not calculated in as per OPUS instruction manual.

image_vllyky.jpg

If you want a proper IR get a IR meter meant forsuch as the RC3563,YR1030, YR1035 or a derivative there of.

Samsung INR18650-30Q spec ?18m? brand new
As it is INR chemisty and a high drain battery IR should be in the 20m? to 25m? range for a usedbattery with reasonable results.

image_cvffcj.jpg



Wolf
 

507PowerWall

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Wolf said:
If you want a proper IR get a IR meter meant for i such as the RC3563,YR1030, YR1035 or a derivative there of.

In ur Experience which is the most accurate among these three... or testing with two of them will give us the best avg. IR Rating
 

Wolf

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507PowerWall said:
In ur Experience which is the most accurate among these three... or testing with two of them will give us the best avg. IR Rating

They are all within .05m? of each other. So all of them are good.
I prefer the RC3563 with the cell holder for ease of use.
Wolf
 

Testing18650

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Wolf said:
The Wire mod on an OPUS does absolutely nothing as far as IR readings are concerned.
The Opus does a simple V drop /R check and calculation. The contact resistance is not calculated in as per OPUS instruction manual.

image_vllyky.jpg

If you want a proper IR get a IR meter meant forsuch as the RC3563,YR1030, YR1035 or a derivative there of.

Samsung INR18650-30Q spec ?18m? brand new
As it is INR chemisty and a high drain battery IR should be in the 20m? to 25m? range for a usedbattery with reasonable results.

image_cvffcj.jpg



Wolf

Thanks for your reply!
So I should subtract30m? from my results, right?Hence the internal resistance of my Samsung 30Q is somewhere between 15-30m?, I guess they are good enough?These are brand new cells.
 

507PowerWall

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Wolf said:
507PowerWall said:
In ur Experience which is the most accurate among these three... or testing with two of them will give us the best avg. IR Rating

They are all within .05m? of each other. So all of them are good.
I prefer the RC3563 with the cell holder for ease of use.
Wolf

Im trying to get together best tools for the goal.... what about Liitokala and XTAR charges IR readings.... are a good reference to start ?
 

Wolf

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507PowerWall said:
Im trying to get together best tools for the goal.... what about Liitokala and XTAR charges IR readings.... are a good reference to start ?

LiitoKala no not even close.
XTAR marginal.
OPUS bad
Zanflare bad

You see they all depend on a V drop and measure that against a resistor to get m?.
A 1kHz 4 wire meter designed for the job will give you accurate results.
It is what the manufacture checks with.


Wolf
 

Wolf

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Testing18650 said:
Thanks for your reply!
So I should subtract30m? from my results, right?Hence the internal resistance of my Samsung 30Q is somewhere between 15-30m?, I guess they are good enough?These are brand new cells.
Yea if they are brand new cells then you know their IR should be 13.13 2 and ?18 m?.
So if your OPUS reads 45m? -30m? =15m? it's a good cell.
The problem with the OPUSis that it is not consistent. Also when Harvesting used cells there is going to be nickel strip residu, some oxidation on the contacts of the cell, and as the OPUS ages it will have more resistance on the contacts also.
So again to get proper IR get an IR Tester. :)
This way you wont even have to make a calculation and have consistent results every time.

Wolf
 

Overmind

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Note that specs of the cells (seen that on LGs) state that IR should be measured at full charge.
 

Wolf

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Overmind said:
Note that specs of the cells (seen that on LGs) state that IR should be measured at full charge.
That is true but if you are harvesting cells and you have some at a lower SOC you can still measure IR.
It may be a little higher than when fully charged but will still give you an indication whetherthe cell is any good.
My experience is that most good cells will have ?5% increase in IR at a low SOC so its not that much.
As you know an out of spec high IR no matter what V or SOC the cell is will indicate a poor SOH battery.

Wolf
 

gauss163

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[size=small][size=small]A few points worthy of emphasis:[/size][/size]

[size=small][size=small]First, the wire mod actually should (slightly) lower its calculated DC IR (Internal Resistance) values since it should reduce the resistance along the rail and its contact with the slider. This is probably a nontrivial chunk of the Opus-claimed 30m? overhead due to contact resistance (and wiring along the voltage sense path) - which is not cancelled out by the current-step test methodmethod employed.[/size][/size]

[size=small][size=small]However, anyimprovementmay well be drowned out by other factors introducing largervariations, e.g. large contact resistance due to dirty terminals. Try cleaning the terminals with alcoholor similar (this can make ahugedifference - e.g. cleaning tailcap threads of a flashlight can change it from very dim to very bright). Before running the test, squeeze theterminal tight against the celland rotate the cell to abrade away contact grime, then continue the pressure during the test (also press so that the slider contacts the rail well if you don't have the mod). Doing so should yieldvalues consistent to a fewm[size=small][size=small]?[/size]in repeated tests in the same slot, e.g. see HKJ's tests.[/size][/size][/size]

[size=small][size=small][size=small]Second, be aware that DC IR depends on SOC (State Of Charge) and temperature - at extreme SOC and temp it can increase by 10x or more, e.g. see the graphs below. So don't measure it in these extreme ranges (unless testingthoseextremes).[/size][/size][/size]
image_pfdfgb.jpg

[size=small][size=small]Above graph is excerpted from p. 1-4 of[/size][size=small]Challenges and Solutions in Battery Fuel Gauging[/size][size=small], by Yevgen Barsukov (a battery guru at Texas Instruments)[/size][/size]

image_kzpnox.jpg

image_bpvjfl.jpg

Above graphs areexcerpted fromthis Endless Spherethread.

Third, be aware that DC IR values may differ greatly from theAC impedance valuestypically listed in datasheets, as we can see in the above graph and the table below fromhere(see also Elithion's graph)
image_dqtbfn.jpg
[size=small][size=small][size=small]The common AC high-frequency (1 kHz) impedance test listed in datasheets is used during manufacture because it can be performed hundreds of times faster than more thorough tests (including DC IR), and it suffices to test for catastrophic failures such as shorts, detached current collectors, etc. It can be little correlated to the typical DC (low frequency) loads of concern to most readers here - where DC IR tests are far more pertinent. For further discussion seehereandhere.[/size][/size][/size]
 

507PowerWall

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Wolf said:
This way you wont even have to make a calculation and have consistent results every time.

Wolf

YR1030 is on his way ...
 

gauss163

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507PowerWall said:
Wolf said:
This way you wont even have to make a calculation and have consistent results every time.

Wolf

YR1030 is on his way ...

Such AC 1kHz tests arethe wrong tool for DC loads like powerwalls - see my prior postabove and its links for why. It would be much better to get a charger with a well-implemented DC IR test, e.g. a SkyRC MC3000. Unfortunately this point is widely misunderstood - but the links in my post will lead you to literature explaining it further (including remarks by experts in the field).
 

Wolf

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gauss163 said:
Such AC 1kHz tests arethe wrong tool for DC loads like powerwalls - see my prior postabove and its links for why. It would be much better to get a charger with a well-implemented DC IR test, e.g. a SkyRC MC3000. Unfortunately this point is widely misunderstood - but the links in my post will lead you to literature explaining it further (including remarks by experts in the field).
gauss163,

In principle I agree with you that a DC IR test is more indicative of the SOH of a Li-Ion cell. However even the SKYRC MC3000 falls short on a proper test. Also most of us that test high volumes of cells don't have the time to squeeze the contacts and wait 10 seconds or so to see if the cell is good. Additionally repeatable readings are definitely a misnomer as you can never duplicate the exact pressure and contact position every time.
Additionally the only proper way to really measure m? resistance is with a 4 wire kelvin measurement device. I do not see any OPUS, SKYRC, or any other reasonably priced off the shelf tester offer that. The XTAR Dragon comes close but still is lacking.

So we move on to an easy "reasonably priced" and simple way of measuring the "SOH" of a Li-Ion cell. The 1 kHz 4 wire Kelvin methode. It is a preliminary test to determine if the cell is even worthy of testing.
I have developed a cheat sheet of IR values for 18650 cells of various manufactures and modelsthat if the cell falls within those values it will perform well in a test.
Additionally as the graph from Endless Sphere so eloquently demonstrates that the AC IR does not change much with the SOC, so we are able to determine if the cell is good by this measurement alone and not necessarily have to charge the cell to 100% SOC.Also most all of these "scientific" tests are done on new batteries not ones that have been used.

image_ezxwpd.jpg

(Additional note: the cell in the chart at 14m? is more than likely a INR, IMR or NCA chemistry hence the low m? value.)

Once the cell passes that test then the cells get C/D/C at 1A (Note: Only OPUS and SKYRC offer a 1A discharge) after ?25 to 30 days the V gets checked for any signs of SD and either accepted for the build or not. As far as I am concerned if a cell performs well at a 1A C/D/C cycle it will work in my powerwall just fine especially when most "properly" built walls will draw maybe 250mA from each individual cell. In my case the worst case scenario is a 625mA draw if my inverters where to run 100% which rarely happens. 90% of the time I am drawing <200mA per cell.
Also if the cell performs within 80% of its rated capacity at that C/D/C level then I fell very confident the cell will work just fine.

Expert or not who am I to dispute the "Experts". I am in no way disputing anyone other than reporting my own findings.
After testing and recording over 6000 18650 cells of varying manufactures I have a pretty good idea of what cells will and won't produce satisfactory results based on 1kHz AC IR.
Additionally I performed and recorded the "Testers" IRresults OPUS, Zanflare, and LiitoKala where recorded.
SKYRC MC3000 was not because it was to cumbersome. Also Foxnovo does not offer this feature.
Snippet of the sheet.

image_fjqkwe.jpg

You can view the wholesheet anytimehttps://drive.google.com/file/d/1NujY1eO6MKwGrpyEm185m6vpkMdb_Gp9/view?usp=sharing

If you have any personal experience to share with us that would be great.
It would helpin expanding our knowledge base on testing LI-Ion batteries.
Pictures and spreadsheets gladly accepted of your own personal results.

Wolf
 
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