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Playing with a Vapcell YR1030 AC Resistance Tester

Discussion in 'Batteries and Chargers' started by Rossum, Mar 3, 2018.

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  1. Rossum

    Rossum Surly Curmudgeon Verified Member ECF Veteran

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    Dec 14, 2013
    NE FL
    @Mooch did a quick review here, which got me intrigued enough to buy one. I'm primarily interested in seeing whether it's useful to evaluate the condition of cells as they age, both with use and over time. So:

    =-=-=-=-=-=-=-=

    First up, four brand new Samsung 30Qs that I got in the same order as the meter. These are totally virgin; I've never even charged them. I'm going to put two of these in rotation in my most-used mod while I'll leave the other two on a shelf to age at ~3.7V.
    #1: 12.65 mΩ; 3.45V
    #2: 12.91 mΩ; 3.46V
    #3: 12.84 mΩ; 3.45V
    #4: 12.63 mΩ; 3.45V
    Those are some nice, consistent readings.

    =-=-=-=-=-=-=-=

    Next, four LG HG2s. I've had these for the better part of two years. Two of them have been in daily rotation in my most-used mod. That's a mechanical squonker, with a ~0.75Ω coil in it. It gets a freshly charged cell in it every day, while the other cell gets charged and then rests until the next day. So the two "used" cells each have about ~350 cycles on them, but these cycles are not at all hard. I use VP1/VP2 chargers exclusively so I always know the voltage of a cell when take it out of mod and put it in the charger, and they're basically never below 3.7V when they come out, and usually higher. The other two cells have fewer than 10 such cycles on them. Let's see if we can tell which cells are which:
    #1: 15.05 mΩ; 3.70V <- I think this one has zero cycles
    #2: 15.34 mΩ; 3.84V <- This one has fewer than 10, probably fewer than 5.
    #3: 20.8 mΩ; 4.16V
    #4: 21.5 mΩ; 4.15V
    It's quite obvious which pair has and been used and which one hasn't. I sure wish I had baseline readings on these from when they were new, but I don't; that's what the above 30Qs are for.

    =-=-=-=-=-=-=-=
    For laughs, some pretty old stuff:

    Four 3-1/2 - 4 year old VTC5s. Some have been cycled more than others. FWIW the #1 cells are about 6 months older than the #3 cells.
    #1A 15.32 mΩ; 4.19V
    #1C 15.15 mΩ; 4.15V
    #3C 13.25 mΩ; 4.01V
    #3D 13.62 mΩ; 4.16V
    All I can say here is: Wow! Still lower (or at least on par with) the substantially newer HG2s! One of the things that amazes me about these cells is that unlike other well-used or older cells, they don't drop in voltage after being charged; they show a solid 4.20V no matter how long I leave 'em in the charger.

    Two 3-4 year old LG HE2s. I don't know how many cycles these have. Not a lot.
    #1: 27.3 mΩ; 3.87V
    #2: 30.5 mΩ; 4.11V
    I find those readings a bit disappointing.

    A 3-4 year old Panasonic NCR18650PF (10A cell) with zero cycles on it:
    21.1 mΩ 3.71V
    I'm amazed how low that resistance is -- as good as my well-used pair of HG2s.

    A Nitecore NL183 2300 mAh (unknown CDR):
    68.1 mΩ 3.84V <- This thing came out of someone else's flashlight; I gave him a better cell.

    =-=-=-=-=-=-=-=

    That's it for now; I don't think I have any other cells here. I do have more cells in some of the other locations I hang out in, and will post more data when I get to those locations again. Of course I'll also update what happens to these cells as more time passes.

    PS: If anyone else bought one of these meters, jump in here, post data!
     
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  2. Rossum

    Rossum Surly Curmudgeon Verified Member ECF Veteran

    Supporting member
    Dec 14, 2013
    NE FL
    Oh silly me. I found another pair of cells that I'd forgotten about. These are virgin (zero cycles) VTC6s that are about one year old.

    #1: 12.90 mΩ; 3.58V
    #2: 12.87 mΩ; 3.57V

    So after one year in storage, the readings are very comparable to the brand new 30Qs. Of course there's no way to tell how fresh the 30Qs are, right? I kinda wish cell manufacturers would date-code their cells.

    I'm going to bring the voltage on these up just a tad before they go back on the shelf.
     
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  3. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

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    May 13, 2015
    Samsung, Sony, LG, Panasonic, and Sanyo cells are date coded. :)

    18650 Date Code Lookup Tool
     
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  4. Rossum

    Rossum Surly Curmudgeon Verified Member ECF Veteran

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    Dec 14, 2013
    NE FL
    I'm now at one of the other locations where I keep a few spare batteries. Let's call this "Location V"

    Two more HG2. P055 / February 2016 Production Date Code. I've had them since May of 2016. These should be from the same batch as the four in post #1, but I haven't verified it. These have zero cycles, but have receive two short storage boosts to bring them back up to 3.7V.
    Cell A: 14.72 mΩ, 3.70V
    Cell B: 14.78 mΩ, 3.69V

    Two VTC6. YI26 /September 2016 Production Date Code. I got these early in 2017. They also have zero cycles and been brought back to 3.70V once.
    Cell A: 12.87mΩ 3.69V
    Cell B: 12.92mΩ 3.69V

    I've got more in a 3rd location, and will post numbers for those by the weekend.

    Since I'm interested in what happens over time with cells in storage (as well as with use) this thread is going to be a bit like watching grass grow, or watching nic base oxidize. Right now I'm just getting "baseline" data. I intend to obtain and post updated readings every once in a while during my travels.
     
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  5. Rossum

    Rossum Surly Curmudgeon Verified Member ECF Veteran

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    Dec 14, 2013
    NE FL
    Wait! Looking in some mods I keep here, I found a couple of baby-blue Samsung 25Rs. I got these from a ECF Coop late in 2014. I'm mildly surprised to find that they have different production date codes, E82 (Aug 2014) and E95 (Sept. 2014) respectively. These cells have both been cycled, but I have no idea how much. The E82 cell was placed in service at the end of Sept 2014 (so immdiately upon receipt) While the E95 cell was in storage until July of 2016.

    Cell E82: 17.55 mΩ, 4.01V
    Cell E95: 14.76 mΩ 4.10V

    Those are surprisingly good readings, because I was never all that enamored with these cells.
     
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  6. Mactavish

    Mactavish Ultra Member Verified Member ECF Veteran

    Jan 19, 2010
    New York
    Mooch can correct me if I’m wrong. I bought the same tool, but I don’t believe comparing different cells as well as different brands in their IR readings would mean anything. Just looking at the Sony spec sheets for a VTC4 and VTC5, show many huge differences. I suspect every cell may have its own IR rating when new. The IR specs for both batteries I mentioned above are different from each other.

    The biggest problem with this tool/meter, is trying to find out what the IR readings really mean. In Mooch’s review thread on this meter, I asked about this, as well as another battery expert (HKJ) and neither could point me to a graph or chart or database.

    Also what is the KNOWN percentage of IR loss that is acceptable in determining when to remove a battery from service. That would make a tool like this invaluable, but so far I have not been able to find this pertinent information. You take a IR measurement when the battery is new, compare to manufacturers spec sheet if available, and then chart readings over time, but the KEY here is at what reading or percentage loss, is the battery no longer considered “good”?

    So far this tool seems good for measuring the IR of a new battery and the charting it over time under the same conditions. Then the readings have true context.
     
  7. Rossum

    Rossum Surly Curmudgeon Verified Member ECF Veteran

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    Dec 14, 2013
    NE FL
    That's what I'm primarily intending to do -- to see what happens over time and with use. See the last paragraph of post #4. :)
     
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  8. Mactavish

    Mactavish Ultra Member Verified Member ECF Veteran

    Jan 19, 2010
    New York
    Yes, but I was editing my post above to add:

    Also what is the KNOWN percentage of IR loss that is acceptable in determining when to remove a battery from service. That would make a tool like this invaluable, but so far I have not been able to find this pertinent information. You take a IR measurement when the battery is new, compare to manufacturers spec sheet if available, and then chart readings over time, but the KEY here is at what reading or percentage loss, is the battery no longer considered “good”?

    I have yet to find anything regarding this.
    HOW MUCH IR LOSS IS ACCEPTABLE!!!
     
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  9. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

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    May 13, 2015
    Whatever threshold you set is the correct one.

    You can’t find this number because it is application and user dependent. For some applications an increase of 10% might be the limit. For another application the limit could be over a 100% increase in internal resistance.

    I’ve seen some cells mention an increase of 30%-40% as an end-of-life indicator (I don’t remember which) but that number would mean nothing in a low current application where IR increase is a lot less important than capacity loss. In a high current application, where you have significant voltage sag causing loss of useful capacity, the IR of a cell is much more important.

    You can track the IR increase of your cells over time and when their performance drop becomes unacceptable you can note the average IR increase. That will become your IR increase threshold for retiring a cell.
     
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  10. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

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    May 13, 2015
    The difference between cells of the same model number tested under identical conditions is typically a lot smaller than the spec. The spec has to cover worst case conditions.

    IR comparisons are very useful to determine the hardest hitting cell as well as which cell, assuming equal capacity ratings, would run the longest in a regulated mod. The higher a cell holds its voltage, i.e., the lower the IR, the longer it will run before hitting the mod’s cutoff voltage.
     
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  11. Rossum

    Rossum Surly Curmudgeon Verified Member ECF Veteran

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    Dec 14, 2013
    NE FL
    I ended up delaying putting these into rotation because the previous pair of HG2s that I was using in the mod in question were put in service in May of 2016, so I thought I'd see if I could make a full 2 years (365 "cycles", but my cycles aren't very hard). More on that pair of HG2s in another post. In the meanwhile, I thought I'd take another reading on the 30Qs before I give 'em their first charge, to see if anything changed after almost 3 months in storage:

    #1: 12.52 mΩ; 3.45V
    #2: 12.71 mΩ; 3.45V

    The answer is clearly, no, that's not a significant change. In fact, the AC resistance on both cells is slightly lower, which I find surprising. I'm going to guess it's due to the somewhat higher ambient temperature here in FL in late May than in PA back in early March?

    Another thing that's somewhat puzzling about these cells is that the Battery Bro Date Lookup doesn't know what to make of the "136" on them.

    [​IMG]
     
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  12. Rossum

    Rossum Surly Curmudgeon Verified Member ECF Veteran

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    Dec 14, 2013
    NE FL
    So the HG2s mentioned in the above post are now officially retired.

    These are the current readings on them after they've rested for a couple of days:
    22.4 mΩ 3.88V
    21.2 mΩ 3.84V
    That's not much change since I first measured them about 3 months ago in post #1.
    I'm going to keep them around. I plan to check them again in, say one year, to see if they change much.

    For laughs, I'm going to compare them to a different set of HG2s that have zero cycles on them. This is not the same set of "virgins" as in post #1, but I bought them at the same time (spring of 2016, and they are February 2016 production):
    15.00 mΩ 3.69V
    14.09 mΩ 3.68V
    These readings are very comparable to the virgin HG2s I have up in "Location P".

    I've been vaping the new 30Qs for a couple of days now. My perception is that they do hit a bit harder than the well-used HG2s. But I wonder if this is all in my head. With the tootle-puffing 0.75 ohm coil I have in that mod, the difference between 12 mΩ and 20 mΩ of internal resistance in the battery should only produce about 40 mV of difference at the coil....
     
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  13. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

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    May 13, 2015
    The AC IR isn’t what's used to calculate battery voltage sag though as it measures more of how the ions distribute and other short time related aspects of the battery’s operation. While a lower AC IR typically means a lower DC IR (which can be used to determine voltage sag) it’s not always true.

    The IR also takes a back seat to other aspects of a battery’s performance as the discharge proceeds. The chemistry, Wh spec, etc., have a huge effect on the voltage under load. This effects the power delivered as the discharge proceeds.

    In my testing though the 30Q did have a slightly higher Wh spec than the HG2, hitting a touch harder and running a touch longer for most, if not all (I don’t remember), of the discharge.
     
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  14. Rossum

    Rossum Surly Curmudgeon Verified Member ECF Veteran

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    Dec 14, 2013
    NE FL
    What's a good way to measure DC resistance? I was thinking I'd just get some 1% 100W resistors, but they're hard to find and bloody expensive!
     
  15. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

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    May 13, 2015
    Measure the voltage quickly under a light load and then quickly switch to a heavy load and reread the voltage after a couple dozen milliseconds. Then stop the current.

    Run ohm’s law for the current draw and difference in the two voltages. That’s the resistance that would cause the sag you measured from the light load to the heavy load.

    You’re only pulsing at high current levels so 10W resistors are plenty.
     
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