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Molicell P26a 18650’s

Discussion in 'Batteries and Chargers' started by Heidi S, Mar 5, 2019.

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  1. Heidi S

    Heidi S Full Member

    Jan 24, 2019
    UK
    So this is the 3rd charge cycle on a Xtar vc2. Batteries were bought as a pair from fogstar but had them re wrapped before being sent to me. Have been charged together and used together etc in a dual mod so are married. I have noticed a difference in mah when both are fully charged since I got them.

    Bay 1 shows 1853 mah
    Bay 2 shows 1802 mah

    Is this normal? Should I be concerned if there is a huge difference?
    I.e putting a strain on one battery vs the other
    Or how much of a difference is acceptable?
    Or will this level out the more charging cycles it goes through?

    Thanks for any input
     
  2. Robin Becker

    Robin Becker Senior Member ECF Veteran

    Feb 3, 2018
    Berlin
    Most probably the deviation is caused by the Charger and does not mean difference in your 2 batteries. Those Chargers are not really accurate. They are however doing a good job on Charging
     
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  3. mimöschen

    mimöschen Ultra Member ECF Veteran

    Jul 15, 2016
    Capacities of new cells will never be 100% the same. On top of that the first bay in the mod always gets strained a tiny bit more. Just cycle the cells inside the mod with every use and you should be fine.
     
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  4. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

    Supporting member
    May 13, 2015
    Which bay is the “first” one?
    Why does the battery in this bay get strained more?
     
  5. mimöschen

    mimöschen Ultra Member ECF Veteran

    Jul 15, 2016
    In series devices one bay is the first. Depending on the mod that might change of course. But in practice it doesn't make any difference whether you know which one is actually first or not.

    I don't know or even care for the electrochemical or physical reactions behind this, but through long-time observation of multiple battery mods, one cell always gets strained a bit more than the other(s), resulting in slightly lower voltage and mah.

    But if you'd like to enlighten the unworthy crowd: go on.:thumb:
     
  6. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

    Supporting member
    May 13, 2015
    I would hope that that everyone would want to learn what is really going on.:)

    Yes, one cell always drops in voltage before the other but that is because every cell is different. No electrochemical or physical reaction talk to bore you with.

    Both cells are, by definition, strained the exact same amount when connected in series as they are both providing the exact same amount of current.

    You’re just seeing the differences in capacity between any two cells. Or even the internal resistance differences as that can make their voltages different for a few minutes after use.

    Which bay is the “first” though? The 0-4.2V one or the 4.2V-8.4V one? I’m genuinely curious about this.
     
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  7. mimöschen

    mimöschen Ultra Member ECF Veteran

    Jul 15, 2016
    So why is it always the cell in the same bay that comes out lower, despite the fact they're cycled?

    I didn't disassemble my mods. Nor do I want to. But I guess it's the bay marked as "1".
     
  8. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

    Supporting member
    May 13, 2015
    You’re saying that different cells placed in Bay 1 are always the one that test out at a lower voltage and/or capacity when recharged?

    The running myth about series-connected batteries is that the “top” battery, the one “closest” to the atomizer is the one stressed the most. Bay 1 would seem to be the “bottom” battery. Batteries aren’t even connected to the cells in a regulated mod but that’s a different issue. :)

    No need to disassemble your mods and I would never ask you to do that.

    The mod could be malfunctioning and drawing current from the voltage sensing pin between Bay 1 and Bay 2 or the issue could be with the charger. Do you always place the cell from Bay 1 into the same charger bay?

    There’s no battery-related reason why any battery in Bay 1 would always be the lower voltage one when charged.
     
  9. mimöschen

    mimöschen Ultra Member ECF Veteran

    Jul 15, 2016
    I get the same results with different mods/chargebays.
     
  10. Mooch

    Mooch Electron Wrangler Verified Member ECF Veteran

    Supporting member
    May 13, 2015
    Then it’s quite the mystery!
     
  11. mimöschen

    mimöschen Ultra Member ECF Veteran

    Jul 15, 2016
    It doesn't matter in the end.
     
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