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Thread: Building Balanced Battery Pack

  1. #1

    Default Building Balanced Battery Pack


    I'm wondering if anyone can point me in the right direction to find instructions on how to build a balanced battery pack for a can light (in this instance a Light Monkey Salvo HID). I plan to use 18650's. Thank you!


  2. #2

    Default Re: Building Balanced Battery Pack


  3. #3
    archimedes's Avatar
    Join Date
    Nov 2010
    CONUS, top left

    Default Re: Building Balanced Battery Pack

    Quote Originally Posted by Paperdesk View Post
    The Special Applications Lighting subforums do not see nearly as much traffic as the main flashlight forums here.

    It may well take more than 24 hours for a response to such a specialized question.

    If you can be patient, however, the experts here in the Dive Lighting forum are typically quite helpful ....
    ... is the archimedes peak

  4. #4

    Default Re: Building Balanced Battery Pack

    Thank you, I appreciate the post.

  5. #5
    Flashaholic* lucca brassi's Avatar
    Join Date
    Feb 2008
    Kocevje , Slovenia, Europe

    Default Re: Building Balanced Battery Pack

  6. #6

    Default Re: Building Balanced Battery Pack

    Ah, so nice to bump into you here Lucca! That spot welder looks really interesting, I wish he were still selling it!

    Question, is there any reason not to build a balanced charging battery pack? I just haven't seen any and got to wondering if there might be a good reason.


  7. #7
    Flashaholic* DIWdiver's Avatar
    Join Date
    Jan 2010
    Connecticut, USA

    Default Re: Building Balanced Battery Pack

    Balancing a battery pack that suffers any significant imbalance involves dissipating a significant amount of heat. Most balancing is done by the charger, not the battery, because the charger is better suited to dissipating the heat. If you look at most commercially made packs, they have two large wires for the main current, and several smaller wires, usually in a different bundle, for balancing.

    I thought my drill/driver batteries had only two connections, so I just went and looked. Sure enough, two large and three smaller terminals.

    So-called 'hobby' chargers are designed specifically for the purpose of charging multi-cell LiIon packs with balancing connections. Most of them will handle packs with 2 to 6 cells in series. I'm sure a search would reveal a number of threads on CPF discussing them. Google would find much more.

  8. #8
    Join Date
    Dec 2006
    New Jersey, USA

    Default Re: Building Balanced Battery Pack

    Go here and read their articles.
    They sell kits for building battery packs, most likely not suitable for diving canister but they explain process of building pack pretty well.
    Especialy lern about BMS (battery management system) used for protection and balancing cells

    You can find stuff for building packs on
    They also sell whole battery pack and can make custom one.

    Idealy you want matched cells for battery pack and if some company makes packs they have larger pool of batteries to pick ones for particular pack.
    I mean batteries obviously should be identical (part number) but ideally they should have similar capacity and internal resistance.

  9. #9

    Default Re: Building Balanced Battery Pack

    balance\hobby chargers equalize without making much heat, they just continue charging weak cells, they monitor each one, balance pcb otoh do balancing by draining cells that have most voltage, that does produce heat. but also it depends on pcb, some make little heat other a lot more.
    i used to build packs with pcb that had balance function, but i figured using hobby charger would be simpler, and involves less circuits, but if that is not an option, (can only use 2 wires for charging) balance pcb is the only way.

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