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Thread: Battery Pack Configuration 28S 17P

              
   
   
  1. #1
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    Battery Pack Configuration 28S 17P

    Greetings to all.

    I am new to the EV world and I am starting on my electric motorcycle conversion. I acquired some a123 26650 batteries, used, but in good condition still. They were built in packs of 40V for electric buses.

    Anyways, I am planning my pack design as I have almost all of the components to start building the pack.

    I have attached the layout of what my thoughts were. With my tight dimensions I have with my bike, I am doing a 28S 17P pack. I am more concerned about the individual connections to make sure I have the right concept.

    Please let me know your guys thoughts of what I can do. I am doing 17 "layers" of the 28 cell blocks. a 4 x 7 block is the 28 cell block layer so to say. The top view is what each block looks like and have those stacked 17 times to achieve my desired dimensions.
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  2. #2
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    Your connection plan looks fine, no problem there.
    Serious lump of a pack that!

  3. #3
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    Yeah I traded some batteries and other items for these units. The guy had double of what I picked up, but I am needing a 108V System for what I'm working with and would like a good bit of range with it as well. Now how would I attach the the BMS I have? I am using the ZEVA 12 unit modules. I have 3 of the 12 unit modules only using up 28 out of the 36 available slots. The attached document may help with coloration. The green is the series connection, the teal is the parallel connections and the red and black are obviously your positive and negative leads.
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  4. #4
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    Right so first - you know that you've only got ~90Vnom there right? About 103.5V hot off the charger?
    Those are LiFePO4 cells, so they're nominal at 3.2V not 3.7V.

    As for the Zeva modules - the usual approach is to split the pack evenly among the modules, so in your case you'd run 9 cells to 2 modules and 10 cells to one of them.
    You then tie all of the unused taps together to the high potential connection.

    So for example in your case

    1- -> M1-0
    1+ -> M1-1
    2+ -> M1-2
    3+ -> M1-3
    4+ -> M1-4
    5+ -> M1-5
    6+ -> M1-6
    7+ -> M1-7
    8+ -> M1-8
    9+ -> M1-9
    10+ -> M1-10,11 & 12
    11- (10+) -> M2-0
    11+ -> M2-1
    12+ -> M2-2
    .
    .
    .
    19+ -> M2-9,10,11,12
    20- (19+) -> M3-0
    20+ -> M3-1
    .
    .
    .
    28+ -> M3-9,10,11,12

    That clear enough?

  5. #5
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    Quote Originally Posted by Spoonman View Post
    Right so first - you know that you've only got ~90Vnom there right? About 103.5V hot off the charger?
    Those are LiFePO4 cells, so they're nominal at 3.2V not 3.7V.

    As for the Zeva modules - the usual approach is to split the pack evenly among the modules, so in your case you'd run 9 cells to 2 modules and 10 cells to one of them.
    You then tie all of the unused taps together to the high potential connection.

    So for example in your case

    1- -> M1-0
    1+ -> M1-1
    2+ -> M1-2
    3+ -> M1-3
    4+ -> M1-4
    5+ -> M1-5
    6+ -> M1-6
    7+ -> M1-7
    8+ -> M1-8
    9+ -> M1-9
    10+ -> M1-10,11 & 12
    11- (10+) -> M2-0
    11+ -> M2-1
    12+ -> M2-2
    .
    .
    .
    19+ -> M2-9,10,11,12
    20- (19+) -> M3-0
    20+ -> M3-1
    .
    .
    .
    28+ -> M3-9,10,11,12

    That clear enough?
    Thanks for making me realize the chemistry of the cells I have. I may to do some reconfiguration, but I was just over viewing the ZEVA manual/installation https://www.zeva.com.au/Products/dat...MS3_Manual.pdf and I just came across your scenario where you mentioned to split it up amongst the ports for the modules.

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