+ Post New Thread
Results 1 to 6 of 6
  1. #1
    Full Member level 6
    Points: 4,419, Level: 15
    Externet's Avatar
    Join Date
    Jan 2004
    Location
    Mideast US
    Posts
    377
    Helped
    26 / 26
    Points
    4,419
    Level
    15

    Behavior of lithium cells...

    Hi.
    Noticed for multiple occasions, after recharging 18650 lithium cells individually on the same charger, after days/weeks removed from the charger, some stay at about 4.2V. Others show 3.7V.
    Has anyone read any report about it ? Is it because of their chemistry, age or health ?
    Abolish the deciBel !

    •   AltAdvertisment

        
       

  2. #2
    Advanced Member level 5
    Points: 31,272, Level: 43
    Achievements:
    7 years registered

    Join Date
    Sep 2008
    Location
    cambridge
    Posts
    6,527
    Helped
    475 / 475
    Points
    31,272
    Level
    43

    Re: Behavior of lithium cells...

    could just be the tolerance on the different leakage current.



    •   AltAdvertisment

        
       

  3. #3
    Super Moderator
    Points: 70,834, Level: 64
    Achievements:
    7 years registered
    Awards:
    Most Frequent Poster 3rd Helpful Member

    Join Date
    Apr 2014
    Posts
    14,492
    Helped
    3299 / 3299
    Points
    70,834
    Level
    64

    Re: Behavior of lithium cells...

    Hi,

    I assume you did a forum search for similar topics or an internet search...

    Then you most probably already heard about http://batteryuniversity.com/


    Klaus
    Please don´t contact me via PM, because there is no time to respond to them. No friend requests. Thank you.



    •   AltAdvertisment

        
       

  4. #4
    Advanced Member level 5
    Points: 15,537, Level: 30

    Join Date
    Nov 2012
    Posts
    2,861
    Helped
    676 / 676
    Points
    15,537
    Level
    30

    Re: Behavior of lithium cells...

    after recharging 18650 lithium cells individually on the same charger, after days/weeks removed from the charger, some stay at about 4.2V. Others show 3.7V
    I too had similar experiences but I did not probe further. They were all purchased together I presumed they came from the same batch. Out of 10 (bought together from aliexpress) three are unable to retain their charges.

    I guess the cause is basically poor quality control. But I too am not so sure...



  5. #5
    Member level 2
    Points: 1,920, Level: 10
    Achievements:
    7 years registered

    Join Date
    Oct 2009
    Location
    Italy
    Posts
    43
    Helped
    3 / 3
    Points
    1,920
    Level
    10

    Re: Behavior of lithium cells...

    some stay at about 4.2V. Others show 3.7V.
    This is why lithium cells needs of battery management systems with charge balancing.
    Note the State of charge (SOC)/V characteristic of lithium cells: at high or low SOC the cell voltage vary a lot.
    ----------------------------
    Lucast85



    •   AltAdvertisment

        
       

  6. #6
    Full Member level 6
    Points: 4,419, Level: 15
    Externet's Avatar
    Join Date
    Jan 2004
    Location
    Mideast US
    Posts
    377
    Helped
    26 / 26
    Points
    4,419
    Level
    15

    Re: Behavior of lithium cells...

    Battery management circuitry is for batteries; not for individual cells. The charger manages the charging recipe for a single cell.
    When removed from charger as the process is finished, weeks after set aside unused, some show 3.7V, some 4.2V. Never seen an in-between value.

    Lithium cells have a 'nominal' voltage of 3.7V. Where does that figure come from ? Some show 4.2V. Data sheets show mostly 4.2V charts at full charge.

    Like a lead-acid automotive battery. Charging voltage is 14V. But the battery shows 12.6 at rest or 'nominal' 12. Lithiums have a charging voltage of 4.2V. But not all come down to 3.7V at rest.
    Abolish the deciBel !



--[[ ]]--