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A123 Fisker Karma Battery module - 7 cells with built in BMS

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  • A123 Fisker Karma Battery module - 7 cells with built in BMS

    I have acquired a set out 15 of these A123 modules each of approx 1.3Kwh energy storage capacity, and consider using them as a replacement for my aging 12pcs 2V AGM battery each of 1100Ah.

    I have 2 elements of concern regarding these batteries.

    1) They lack one cell to simulate a proper 24V battery giving a practical voltage range from sub 20V up to 23.1V with charge Voltage at 25.2V. I believe my Tristar MPPT60 regulator can cope with that, the same goes for my Victron Multiplus 5000W inverter. Any comments from the experts on Solarpaneltalk?

    2) Is there away to utilize the built in (on-board) BMS of the modules to secure cell balance and possible feed some CAN-bus info to my inverter and MPPT without going ballistic on cost and or design issues

    Your views are highly appreciated

    PS
    For those of you who wonder why I have spent my money one these modules without sorting these issues first,,, do no be concerned - I haven't - current cost is 2 hours medium labour
    --------------------
    Norwegian off grid cabin owner
    Panels facing south

    - Kyocera panels 135W
    - Tristar 60A MPPT
    - Victron 3000w/12V / 120A

  • #2
    I would think the big issue here is the BMS. It is probable that the battery BMS will balance the batteries autonomously but I wouldn't rely on this.

    For safety and battery life I think it is critical to be able to monitor the individual cell voltages and preferably be able to shutdown the inverter or charge controller if any of the cell voltages go out of their safe operating range.

    I had a quick look to see if anybody has reversed engineered the BMS but couldn't find anything. Unless you have the technical expertise or can find the information on how the BMS works and talks to the rest of the world I would look at disassembling the batteries and reconfigure the battery to ??p8S and install a new BMS that you can use to monitor the individual blocks of paralleled cells and shutdown the charge controller and inverter.

    Simon
    Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
    BMS - Homemade Battery logger github.com/simat/BatteryMonitor/wiki
    Latronics 4kW Inverter, homemade MPPT controller

    Comment


    • #3
      Most "BMS" systems use a vampire bleeder board, usually rated at 1A or less, to attempt to bleed off excess charge of the first cell to reach FULL.

      But if you have a 9A charger, and a 1A bleeder, you still have 8 amps going into the full battery. Will that be a problem?
      Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
      || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
      || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

      solar: http://tinyurl.com/LMR-Solar
      gen: http://tinyurl.com/LMR-Lister

      Comment


      • #4
        Originally posted by karrak View Post
        Unless you have the technical expertise or can find the information on how the BMS works and talks to the rest of the world I would look at disassembling the batteries and reconfigure the battery to ??p8S and install a new BMS that you can use to monitor the individual blocks of paralleled cells and shutdown the charge controller and inverter.
        Hi Simon

        You are probably right - I have the full battery BMS harness probably including the BMS "central" if there anything like that.

        This is a bit of a long term project so I should probably spend som time investigating

        As for the 7 versus 8 cells I think it is a bit of a shame to destroy the nice and solid modules
        --------------------
        Norwegian off grid cabin owner
        Panels facing south

        - Kyocera panels 135W
        - Tristar 60A MPPT
        - Victron 3000w/12V / 120A

        Comment


        • #5
          Looks like someone has broken the CAN bus code for A123 battery with BMS

          https://github.com/MITEVT/a123-ardui...ster/README.md
          --------------------
          Norwegian off grid cabin owner
          Panels facing south

          - Kyocera panels 135W
          - Tristar 60A MPPT
          - Victron 3000w/12V / 120A

          Comment

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