Wuben        
Results 1 to 7 of 7

Thread: 3 x 18650 in series "solved"

  1. #1
    Flashaholic* orbital's Avatar
    Join Date
    Feb 2007
    Location
    Great Lakes
    Posts
    2,493

    Default 3 x 18650 in series "solved"

    +

    3 x 18650 in series using a carrier; 2 positives up & 1 down = 12V correct?

    slight brain fade this morning
    Last edited by orbital; 03-24-2020 at 08:42 AM.

  2. #2

    Default Re: 3 x 18650 in series

    No, need 4S with LFP like A123 to get a solid 12V nominal range (12-14 actual)

    Other LI chemistries at 3.6-3.7V midpoint, can do 24V OK with 7S, but 3S is too low and 4S is too high for supporting general loads.

    Can be made to work for a specific tolerant load device, depending on their input specs or using a DC-DC converter though.

    Use 3.65V for calculation, actual range 3.2-4.1V

  3. #3
    Flashaholic* orbital's Avatar
    Join Date
    Feb 2007
    Location
    Great Lakes
    Posts
    2,493

    Default Re: 3 x 18650 in series

    +

    I was using 12V as a general voltage of 4V 'off charger' for each 18650 (I know it'll be closer to 12.6v)

    ...another way to word would be: do I get triple the voltage w/ 2 positives up & 1 positive down in a cylindrical carrier.

  4. #4
    Flashaholic* orbital's Avatar
    Join Date
    Feb 2007
    Location
    Great Lakes
    Posts
    2,493

    Default Re: 3 x 18650 in series

    +

    "solved"

    It is triple the voltage

  5. #5

    Default Re: 3 x 18650 in series "solved"

    Yes, series increases voltage, parallel keeps it the same.

    Former keeps Ah capacity the same, latter increases it.

    Just know that usually "12V" means a midpoint at least that high, many load devices will cut out before 11V.

    You should not charge LI cells past 4.1V if you want good longevity, and even at over 90% SoC, under load most will be well below 3.7V.

    3.65V is a normal midpoint but only measuring **at rest**

  6. #6
    Flashaholic* DIWdiver's Avatar
    Join Date
    Jan 2010
    Location
    Connecticut, USA
    Posts
    2,539

    Default Re: 3 x 18650 in series "solved"

    By 'cylindrical carrier' do you mean they are all in line in a tube, contacting each other directly or they are side by side and connected by a link of some sort?

  7. #7

    Default Re: 3 x 18650 in series "solved"

    Quote Originally Posted by DIWdiver View Post
    By 'cylindrical carrier' do you mean they are all in line in a tube, contacting each other directly?
    Good spot.

    Only way to get 3S that way is all "head to toe" pointing positive all in the same direction.

    Not sure what this is supposed to mean?
    Quote Originally Posted by orbital View Post
    w/ 2 positives up & 1 positive down in a cylindrical carrier.[/B]

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •