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High Internal Resistance: new(ish) batteries

Discussion in 'Batteries and Chargers' started by proax9, Dec 5, 2019.

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  1. proax9

    proax9 Super Member Verified Member ECF Veteran

    Mar 10, 2011
    Long Island, NY
    I have 4 18350 Vapecell batteries that I purchased from a reputable vendor. (Recommended by Mooch's posts and countless members on ECF.)
    Purchased at the beginning of October- each has about 10 recharge cycles. I use an Opus BT-C3100 charger. I used the charger to test the internal resistance, which came out at 82, 103, 116 and 86. Those numbers seem very high.
    (I also tested my 18650's, that are about a year old, and have countless charge cycles- on same charger) They all range 40-50 as far as internal resistance.

    Are the 18350's legit? Are they safe to use?
    • Like Like x 1
  2. madstabber

    madstabber Vaping Master Verified Member ECF Veteran

    I have a different charger but I sometimes get high IR readings. I usually just spin the batteries in the charger and clean the contacts. There isn’t anything visible but sometimes these chargers don’t make the best contact with the cell which will negatively impact the IR reading. I’ve read that our hobby chargers aren’t very accurate to begin with so that could account for a bad reading.
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  3. ShowMeTwice

    ShowMeTwice Ultra Member ECF Veteran

    Supporting member
    Jun 28, 2016
    Milwaukee, WI
    I pulled this IR chart from one of the flashlight forums a while back...
    IR chart.png
    I don't think your IR numbers are high at all.

    Mooch said our chargers can and will display different IR readings at different times. He suggested testing the IR of a battery in your charger 4-5 times in order to get a base reading. And even with that the chargers IR reading for a battery may not be 100% accurate.

    If your 18350's were bought from a reputable vendor and recommended by Mooch you should be fine. I would use them. I have a few 18650's with IR's around 200+ and they get used. They're still good. Also 18350's may have a natural higher IR than 18650's. That's just a guess on my part. I don't have 18350's so I do not know for certain.

    Perhaps someone who uses 350's will chime in.

    ETA: Did you note your 18350's IR's when you first got them and popped them in your charger?

    • Informative Informative x 1
  4. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

    Supporting member
    May 13, 2015
    A DC internal resistance (IR) of 40-50mOhms is VERY high for an 18650, even a used one. That table has values for the spectacularly inaccurate, and much too high, readings that are typical for chargers with their useless IR-reading feature.

    Clean the battery and charger contacts, charge all the batteries at a low rate, let them sit for one hour at room temperature, and then measure their IR. Press up firmly against the negative contact each time you take a reading to ensure good contact between the battery and the contacts. After each reading remove and re-insert the battery. Do not dent the battery though!

    You should be getting readings down near 50mOhms for the 18350’s, maybe lower, and they should be MUCH more consistent. Anything much more than a couple milliohms of variation between readings is too much.
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  5. madstabber

    madstabber Vaping Master Verified Member ECF Veteran

    @Mooch since you say that chart above is off with the IR numbers, can you give us numbers for an excellent cell range an average range and a poor range for an 18650? Also can you do the same for a 21700 since if I’m understanding you correctly the different size cells will have different range of IR. I’d appreciate it because I know my charger isn’t very accurate but I have no idea what’s acceptable and unacceptable IR for these cells. I retire them when the battery life starts to suffer to a point I notice it but I’d like to know about the IR for another reference point. Thank you for any info you can give me regarding this and for all you’ve done and continue to do for all us vapers. If I didn’t read your posts and blog I’d still be using the 8amp Panasonic’s that worked well in my Zmax. I knew nothing when I started vaping and I now know enough to be safe and help others also. I’m convinced you have saved some lives and at least saved some teeth and pretty faces, and that’s not hyperbole or exaggerated in any way. Anyway I’ll get off your jock now and wait patiently for any IR info you can share.
  6. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

    Supporting member
    May 13, 2015
    The best 18650’s have a DC IR around 15mOhms. Most 3000mAh 15A/20A ones are around 22mAh. The ultra-high capacity ones are around 35-40mOhms.

    The best 21700’s are down near 12mOhms and go up from there. You can check on the numbers for all the cells I have tested in the past 1-1/2 to 2 years by goi got my blog and opening up a few test reports.
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  7. Eskie

    Eskie ECF Guru Verified Member ECF Veteran

    May 6, 2016
    I always question how reliable those internal resistance readings are on "consumer" chargers. I have a Miboxer C4 (?updated with the yellow buttons, 1.5A max charge) and they seem to bounce around quite a bit. In truth for the price just charging safely and within the reported current and measured voltage without anything getting warm is all that matters to me (YMMV) but expecting these $30-40 chargers to be accurate diagnostic equipment seems like a push to me. But I'll defer to @Mooch as to the validity of that belief.
    • Agree Agree x 4
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  8. madstabber

    madstabber Vaping Master Verified Member ECF Veteran

    I have the Miboxer C4-12 which is great but every now and again I’ll get a cell will a high triple digit IR. I just spin it while it’s in the slot with contacts contacting and that usually straightens it out. Having said that there is still some variability with the readings so I don’t think I can do much with them readings. Not a big deal because I just toss them when they start dieing much sooner than my other ones. I buy 4 at a time and it seems they last about 3 years, I get 4 LG2’s then, 4 30q’s, then 4 Vtc6’s because the different color wraps help to distinguish them. The only battery I’ve had die early was a purple efest and it was just one of the two I had in a married pair. Just more confirmation that I should always stick with the big 3 brands. Thanks for the timely response Mooch, you’re the best.
    • Like Like x 4
  9. DaveP

    DaveP PV Master & Musician ECF Veteran

    Supporting member
    May 22, 2010
    Central GA
    I agree with Mooch in that the hobby chargers aren't that accurate in determining internal resistance. My Opus BT-C3100 usually starts out in a quick test with a ridiculous reading, sometimes in the 4 digit milliamp range. I re-insert it several times and it lowers to something more credible, but I don't trust the reading. That's sad because one of the reasons I bought the Opus was for its internal resistance feature.

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