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Thread: Series Parallel

              
   
   
  1. #21
    Senior Member Nicman's Avatar
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    Quote Originally Posted by Spoonman View Post
    Nope dude, you're still arranging cells back-2-back here. Sum voltage will be zero.

    You need, in the parallels, to tie BOTH poles together - in effect creating ONE battery.
    THEN you wire that battery into series.

    See attached.

    Attachment 7688
    12s2p Series Parallel.jpg

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  3. #22
    Senior Member Nicman's Avatar
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    Empulse R #24 frodus's Avatar
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    Now you're getting it!

    Just remember, there are 2s2p in those leaf cells. So the 3 terminals, are the cell taps. One is the most positive, one is the most negative, and the center is the middle tap. I'd suggest connecting that as well, to get things balanced right.

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  7. #24
    Senior Member Stevo's Avatar
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    Hey Travis, in your experience, what's the fastest way to bottom balance a single cell? What product would you recommend?
    Right now, all of my cells are perfectly bottom balanced. I'm asking for future balancing. The cells I am using are 75 aHr so it could take quite a while using the 6 cell balancer that I currently have. I'd rather balance just one cell at a time as needed, but at the fastest pace possible.
    Last edited by Stevo; 19 June 2018 at 0928.
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
    Current builds: WORX.VOR.v3.2

  8. #25
    Empulse R #24 frodus's Avatar
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    Quote Originally Posted by Stevo View Post
    Hey Travis, in your experience, what's the fastest way to bottom balance a single cell? What product would you recommend?
    Right now, all of my cells are perfectly bottom balanced. I'm asking for future balancing. The cells I am using are 75 aHr so it could take quite a while using the 6 cell balancer that I currently have. I'd rather balance just one cell at a time as needed, but at a faster pace.
    I don't really recommend bottom balancing. I have always done a top balance.

    My reasoning: There's more energy in a cell when it's fully charged, than at the bottom. So if you bottom balance, how can you guarantee they're all at the same voltage while charging?

    Also, I don't know of any products that bottom balance.

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  10. #26
    Senior Member Stevo's Avatar
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    With my Leaf pack, I would notice some millivoltage differences after riding to and from work (22 miles) after a few months. However, whenever I charged them (everyday), the cells were balanced at the top after charging. So I would "bottom" balance (actually middle to lower) to help avoid over discharge, since I am running without a BMS. Using cellogs the charger is shut off if any cell gets to 4.15v to prevent overcharging, but I have nothing on the bike to prevent overdischarging unless the Sevcon can be set to default to a reduced power output if a specified pack voltage is detected. I don't leave cellogs attached because they will unbalance one of the cells that they monitor, but I would occasionally run cellogs just as a test monitor like a Holter monitor.
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
    Current builds: WORX.VOR.v3.2

  11. #27
    Empulse R #24 frodus's Avatar
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    Stevo,
    The Sevcon can be set to a pack voltage threshold, so it reduces power below a certain voltage, and reduces to zero below another voltage. I can help set that if you have the programming cable + software.

    I'm looking at Zeva BMS currently, and they seem to do what I want them to do. They balance and monitor the cells. TheBMS (Orion, Elithion) that I've worked with are both top balancing BMS. But they monitor cells as well. So if one goes above a certain level, you can disable the charger. If one goes below a certain level, then you can disable the controller.

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  13. #28
    Senior Member Stevo's Avatar
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    Depending on cost of Zeva, my cellog set up paired with the Sevcon should suffice ( the most cost effective way)... good enough for me.
    Thanks for the input. I will top balance my new pack instead of middle balance.
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
    Current builds: WORX.VOR.v3.2

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  15. #29
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    As Frodus says, top balance is best even if for no other reason than you're at the top of the pack far more regularly than you're at the bottom which makes the whole lot far easier to monitor.
    Set your bulk lower limit conservatively and you'll be grand at the low end.

    @Nicman - now you've got it!
    Last edited by Spoonman; 20 June 2018 at 0457.

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