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Thread: 2 batteries (in parallel) discharged unevenly. Any idea why?

  1. #1
    AVF Newbie | Be nice to me
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    2 batteries (in parallel) discharged unevenly. Any idea why?

    Hi, I'm using a Tesla Invader 2 "half mech" box mod which uses 2x 18650 batteries in parallel. It's been fantastic! Yesterday I used some Samsung 25r's which have always been married/paired on the rare occasions I've used them. (maybe 6 times)

    This morning I went to chuck them on the charger, but instead of the usual two red charging lights, one was red and one was green. I was running late so I opted to not charge them until I got back home and just grabbed my regular batteries and left.

    Now that I had some time free, I tested the 25r's on a multimeter and the first battery was 3.39v. The second was 3.04v. I put them on the charger and after a short while, both lights are red/charging, and everything seems normal (no heat or exploding).

    Just wondering what would cause the uneven discharge? And is there any danger in the fact that one went as low as 3.04v?

    Incidentally, I checked the voltages of the regular batteries I used today and they discharged perfectly evenly.

    Other info: it was a 0.3 ohm coil, and a HXY charger.




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  2. #2
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    The more times you charge and discharge the battery, it starts taking a toll on the parts.
    eventually it will fail to hold a charge at all.

    Each battery is different, even if you got the brother battery from the same line in the factory.
    theres no guarantee that both will start failing at the same time.


    Battery Wisdom 101

    If in doubt, throw it out
    Vapaholic likes this.

  3. #3
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    Cheers Hoof. Yeah that's what I was thinking - only a faulty battery could really explain it (in my somewhat limited electrical understanding, lol). Bit disappointed I only got ~6 uses though! I can always use the remaining good one in my torch I guess.




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  4. #4
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    I have a dual parallel mod thats VW/TC and find that one battery consistently discharges about 5% more than the other, both take about the same time to charge.
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  5. #5
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    Since they are basically new - check/clean the connections in the mod, maybe there is some crud/less springiness on one of the terminals? Failing that, swap their positions and see if it happens the other way around.
    studiovape, Fatman and Vapaholic like this.

  6. #6
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    Cheers all. Well, they charged fine. So I left them alone for a day, then tested on multimeter, they were both 4.21v. So I gave them some light usage today and didn't notice anything amiss, then tested and they were both 3.81v.

    I guess it must've been something like you suggested mathsguy, but I can't work out why, since they're both part of the same circuit. *shrug*. Still a bit suss on them and will monitor closely if I need to use them.
    markatneerim likes this.




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    That and this, these and those
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  7. #7
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    I have a dual parallell that discharged un even last time i checked. I suppose you just need to charge them a little before you normally would, to avoid one going too low. The mod i had it occur with has a volt display, so I suppose that is the sort of average of the 2 batteries.
    Vapaholic likes this.

  8. #8
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    Either one of the above or the positive and negative contact pins aren't making proper connection. Happens to mech boxes all the time. Dunno bout the invader but it could happen.
    Vapaholic likes this.

 

 

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