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  1. #1
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    Question lithium cell series / paralell

    Hi guys,

    Ive been sitting reviewing info in regards to connecting cells in series and parrarlell,

    After what ive read my understanding is that

    if i want to use a voltage of 36 volts.
    I would connect 10 x 3.6 volt cells togeather in series.

    But if my aim is to create a 10ah + battery
    I would need to connect say 6 x 3.6 volt 2200mah cells in pararlell.

    Ok my question is if i want the voltage to remain at 36 volts do i reduce the series chain by one cell and connect the paralell chain in with the series given that the parallel would also = 3.6 volts

  2. #2
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    If I understand your Q, I think you need to connect 2 X 5 X 3.6v battery's in series, and then the 2 sets of 5 X 3.6 battery's in series... But I'm not an engineer, or electrician... But that is what I would look into... DrkAngel should certainly able to answer you...
    Last edited by 350htrr; 10-19-14 at 06:34 PM.
    He uses statistics as a drunken man uses lamp-posts...for support rather than illumination. I do like my beer, so sometimes I do end up leaning on the lamp-post...

  3. #3
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    battery

    Pretty sure that you need 10s X 4p, that is 10 batteries in series (positive of one to negative of next, but each cell is 4.1 or so and you would have 41V or so), then 4 "rows" in parallel (positive to positive and negative to negative) to get 10 amps. Therefore 40 say 18650 cells for most Lithium cells (at about $7.00 or more each), then you have to "assemble" it. You can save money with LiPO (look at Hobby King), but it can be dangerous (read up on them). Good luck.
    Last edited by 2old; 10-19-14 at 08:25 PM. Reason: correction

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    Quote Originally Posted by 2old View Post
    Pretty sure that you need 10s X 4p, that is 10 batteries in series (positive of one to negative of next, but each cell is 4.1 or so and you would have 41V or so), then 4 "rows" in parallel (positive to positive and negative to negative) to get 10 amps.
    Close, but if each cell is only 2200 mA-hr (i.e. 2.2 A-hr as stated by the OP) then putting 4 rows in parallel will only get you 8.8 A-hr - so still a bit shy of the OP's desired 10 A-hr rating. 5 rows in parallel where each row has 10 cells in series would give you a battery pack with an 11 A-hr rating.

  5. #5
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    Lightbulb equal packs required

    firstly cheers for all the responses guys,

    After reviewing further, Prathmann is right due to the fact each pack has to be equal to the other to what ive reviewed.

    in theory my first idea would work but in practice you couldnt mass charge in that way from what ive reviewed.

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    Lightbulb

    Quote Originally Posted by makin1 View Post
    firstly cheers for all the responses guys,

    After reviewing further, Prathmann is right due to the fact each pack has to be equal to the other to what ive reviewed.

    in theory my first idea would work but in practice you couldnt mass charge in that way from what ive reviewed.
    looks like if all cell packs need to be equal it would make more sense to create mutiple strings of parralel and then put them in to series.

    example 4 x 2200mah in pararalel would be 3.7 volts and 8800mah

    10 strings of that in series would be 37 volts and 88AH

  8. #8
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    Quote Originally Posted by makin1 View Post
    looks like if all cell packs need to be equal it would make more sense to create mutiple strings of parralel and then put them in to series.

    example 4 x 2200mah in pararalel would be 3.7 volts and 8800mah

    10 strings of that in series would be 37 volts and 88AH
    Doesn't matter if you first put cells in parallel and then in series or the other way around - you end up with exactly the same wiring arrangement either way.

    And putting 10 sets of your 8.8 A-hr (8800 mA-hr) in series will still give you only 8.8 A-hr (putting them in series increases the voltage but leaves the A-hr rating the same). To get over 10 A-hr you still need to have 5 parallel 2.2 A-hr cells.

  9. #9
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    Quote Originally Posted by prathmann View Post
    Close, but if each cell is only 2200 mA-hr (i.e. 2.2 A-hr as stated by the OP) then putting 4 rows in parallel will only get you 8.8 A-hr - so still a bit shy of the OP's desired 10 A-hr rating. 5 rows in parallel where each row has 10 cells in series would give you a battery pack with an 11 A-hr rating.
    Thanks, forgot to take my shoes off when I calculated.

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    Talking

    Quote Originally Posted by 2old View Post
    Thanks, forgot to take my shoes off when I calculated.
    after taking comments in to consideration i put this togeather. Let me know what you think. This is two strings of 10 linked in Serial / parallel
    22.2AH cell config.jpg

  11. #11
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    Quote Originally Posted by makin1 View Post
    after taking comments in to consideration i put this togeather. Let me know what you think. This is two strings of 10 linked in Serial / parallel
    22.2AH cell config.jpg
    Looks fine except for the label. A collection of cells wired together makes a battery. And the capacity rating of the one shown would be 4.4 A-hr if each of the individual cells is 2.2 A-hr.

  12. #12
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    Cool

    Quote Originally Posted by makin1 View Post
    after taking comments in to consideration i put this togeather. Let me know what you think. This is two strings of 10 linked in Serial / parallel
    22.2AH cell config.jpg
    10s would only be 37V 2200mAh not 37V 22000mAh
    Your diagram, 10s2p is 37V 4400mAh = 37V 4.4Ah

    I am hoping these are new cells?
    2200mAh cells are either very old laptop or reasonably new higher C rate cells.
    Cells should be tested, even new cells, then connected in parallel with balance leads-wires.

    10s8p
    37v_20ah_01.jpg

    See - Homemade Battery Packs

    Your cells, in diagram, as connected, without parallel balance leads, could be comparative capacity tested.
    If all new or reasonably same condition, same brand-model cells.
    Make sure all cells are at identical voltage.
    Simply discharge and measure every cell at timed intervals.
    Comparative capacity is determined by voltage loss.

    Rate by final voltage after timed discharge, (eg. 1 hour of 1A discharge?)

    Any with exceptional voltage loss should be eliminated as defective.

    2200mAh laptop cells will be hard pressed , at 10Ah, to motivate an eBike.
    Cells for power tools etc., higher C rated, might do just fine ...
    Last edited by DrkAngel; 10-23-14 at 05:03 AM.
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