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High Capacity Battery Pack Fuel Gauge

Mislav Blajic
Prodigy 120 points
Other Parts Discussed in Thread: BQ76PL455EVM, BQ34Z100-G1, BQ34110, EV2400, BQ34Z100EVM

Hi, I am using BQ76PL455EVM for monitoring cell voltages, and I want to build a battery stack of 210 LiFePO4 100Ah cells in series. I am writing my own fuel gauge algorithm, as well as capacity and impedance estimation algorithm for each cell using data from bq76pl455 ICs. Could you recommend me what evaluation boards should I buy so I can compare results and test my algorithm? I want the algorithm to be as accurate as possible for cells of different health and age. One cell to test on is enough, but maybe better to use a board that evaluates multiple cells simultaneously. It would be best if the fuel gauge evaluation board could connect directly to PC, but if not, I will use the appropriate interface board, no problem.

Thank you in advance.

Mislav Blajic

  • 0
    TI__Mastermind 19795 points
    Hi Mislav,

    For evaluation modules, I would recommend using the BQ76PL455EVM (link: www.ti.com/.../bq76pl455evm) if testing will be strictly for the PL455. This board allows for connection to a PC via an FTDI cable, with a provided GUI and monitoring/balancing up to 16 cells.

    Also, if you're interested in standalone gauge products, we do have those as well!

    Regards,
    Vince
  • 0 in reply to Vince
    Prodigy 120 points
    Hi Vince, thank you for quick response. I am using bq76pl455evm, but it only provides monitoring and balancing. I am working with that data in real time and I am writing an algorithm for fuel gauging and battery capacity and impedance estimation. I want to buy standalone gauge products for the same cells, and that I can connect it to my PC. I want to simultaneously connect bq76pl455evm and another board with as accurate as possible estimation so that I can compare the results of my algorithm and the algorithm of TI fuel gauge. If you could recommend which board to buy, I would be grateful (my application is described in the previous post).

    Mislav Blajic
  • 0 in reply to Mislav Blajic
    TI__Mastermind 19795 points
    Hi Mislav,

    I will transfer you to our gauge group for recommendations on the best gauge product for your application!

    Regards,
    Vince
  • 0 in reply to Vince
    TI__Genius 10830 points
    hi Mislav,,
    Please look at bq34410 or bq34z100-G1
    www.ti.com/.../products.html
  • 0 in reply to David Hien
    Prodigy 120 points
    Hi,
    I have looked into the ICs you suggested, and also into some other materials on the website. From what I can see, there are ICs for single cell gauge and multi cell gauge, but the multi cell gauge ones all see a series stack as one cell and do a single SOC and SOH estimation for the stack. That doesn't suit me, I would like results for each cell, so even if I buy a multi cell capable board, I would still use it on a single cell. So single cell gauges for me are just as good as multi cell. I have also read in your materials that Impedance Track algorithm is generally more precise than CEDV (I don't know how different is it for LiFePO4 chemistry because of their flat voltage curve), especially for older cells, and accuracy is important to me.

    Mislav Blajic
  • 0 in reply to Mislav Blajic
    TI__Genius 10830 points
    Hi Mislav,
    We do not have gauges measuring each cell for >7s. if you need a gauge for a battery with more than 7s, we can suggest you bq34z100-G1 (with Impedance Track) or bq34110 (CEDV) and they both measure the top of the stack.
  • 0 in reply to David Hien
    Prodigy 120 points
    Hi David,
    I'm not going to estimate for the whole stack with the gauge, I was going to use the gauge on a small number of cells just to test my algorithms. I have decided to use only on single cells, since TI boards make an estimation for the stack, not every cell. I have decided to get 2 x bq34z100evm and 2 x bq40z50evm and use them on single cells. I will also get ev2400 for PC communication.

    Mislav Blajic