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BQ78350-R1: CEDV Gauge Chemistry ID setup and CEDV configuration setup

JPAlleyne
Expert 1565 points
Part Number: BQ78350-R1
Other Parts Discussed in Thread: BQ78350, BQSTUDIO, EV2400,

Hi T.I.,

I've been trying to find solid information on equipment setup and steps in order to compile a GPC package to upload chemistry and CEDV gauge constants, but I can't seem to find any concrete methodology to do it. I've been taking info from here and there, but a comprehensive list of necessary or suggested equipment and a list of steps would be helpful. We are currently using the bq78350, with the EV2400, and bqstudio 1.3.80 for an 11000maH, 6S, 22.2V lipo pack [LiCoO2 cell chemistry (unknown manufacturer)].

1) I've seen that you will need 6 data log files + a config file, zipped and uploaded in order to configure the CEDV coeffs.
        i) What should be the equipment setup to ensure we get accurate data?
       ii) What's the step by step procedure for acquiring the data. Can I use the steps in "Simple Guide to CEDV Data Collection for Gauging Parameter Calculator (GPC)"?

2) I read that you need to do a relax-discharge-relax log to get a new Chem ID.
        i) Should I use the same equipment setup as with the CEDV coeffs to do this log?
       ii) Is the 2-hour relax- C/10 discharge to Vterm - 5-hour relax the valid procedure?
       iii) Is this going to help accuracy seeing that I have the above info about the battery/ cell?... should I do this to increase accuracy?

Thanks, 
JP

  • 0
    TI__Guru 54715 points
    Hi JP,
    It is supposed to be simple in theory. The tools work for many parts which have some differences, so it may not be as simple as the authors think.
    The entry point is www.ti.com/.../gaugeparcal, which shows both the CEDV information.
    Steps for CEDV collection are www.ti.com/.../sluub45b.pdf but they are high level. There will be variation for your equipment.
    You will need a way to charge your pack to full
    You need something to discharge the pack to empty or just below but not to damage the cells.
    You need the temperature sensor to measure the cell temperature, not the environment.
    You need a temperature chamber or method to control the environmental temperature.
    It does not matter which load current or temperature you do first.
    Set your environment.
    Charge the battery.
    Start your log.
    Discharge at the selected rate until empty.
    Stop the log.
    Charge the battery to full.
    Repeat at the other rate saving the log.
    Change the temperature and wait to stabilize.
    Repeat the 2 loads for that temp.
    Change to the third temp, repeat the load cycles
    Use the GPC packager tool (tab) in bqStudio to enter the file names and build the zip file.
    Submit the zip file to the web tool at www.ti.com/.../gpccedv.

    For identifying a chemistry, you can use the chemistry tab in bqStudio to sort and select your cell type. It is odd you would not have some cell information. If you wish to match the chemistry, use the chemistry matching process from http://www.ti.com/tool/gpcchem. It is the same basic collection method but 1 cycle with the requirements in the procedure. Chemistry is not as important for the bq78350-R1 since it is used only to estimate capacity at reset.
  • 0 in reply to WM5295
    Expert 1565 points

    Thank you for the detailed explanation for the CEDV logging. That description of methodology is clear, concise and super helpful.

    With respect to the chemistry identification: for the cell info, I don't have the manufacturer name (we are using packs that are created from
    "proprietary" cells), so all I have is the pack info: 11Ah, 22.2V Nominal, the discharge rate etc. It is 6S1P, so I know the cells are 11Ah, with a nominal of 3.7V and the chemistry used is LiCoO2.
    Is there (or can you recommend) something in that chem list that I can use that is similar? Like Chem ID 1529?
    Should I instead just do the chemistry matching process for better accuracy?
    Also this guide says "The battery pack must use one of TI’s Impedance Track algorithm-based fuel gauges.", is it also okay for CEDV gauges?

    Should I have a temperature-controlled environment for the chem identification as well?

  • 0 in reply to JPAlleyne
    TI__Guru 54715 points
    Hi JP,
    In bqStudio you can open the chemistry tab and click on the "Description" header to sort. You might pick a LiCoO2, but there are several variants. You could try some to see if they match your expectation and that may be close enough. Running a cycle and submitting to the tool should give you a mathematical match to available chemistries rather than visual match one at a time. The idea here is to match the voltage vs capacity profile which will be stored in the gauge (bq78350-R1) for capacity estimation after reset. It is the same data base as used for the IT gauges, just used differently. It is OK to use.
    Maintaining a uniform environment during that log would be good, and again you want the temperature sensor on the cells rather than just the environment.
  • 0 in reply to WM5295
    Expert 1565 points
    Thanks again for you help, WM5395. Always helpful.