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BQ40Z50EVM-561: BQ40Z50-R2

Bruce Morris
Prodigy 80 points
Part Number: BQ40Z50EVM-561
Other Parts Discussed in Thread: BQ40Z50, GPCCHEM

I have just run a test to see the accuracy of the BQ40Z50 with the load we are planning to be using a battery to supply. The test was as follows.

1) Start with a full battery. 2) discharge the battery for 1 hour at 2A. 3)Recharge the battery at 1A until it is full. 4) Run our load on the battery for 48 hours. 5) Recharge the battery to see how many mAh we need to bring it back to a full charge. Let the battery rest until it indicates it is ina rest state.

On revuing the ata in the log file it seems that the chip did not do any gauging even though the gauge flag was set all the time though the test.

I also not that even though the balancing flag was set during all the charging periods no balancing seems to have taken place.

Attached are the log file, the last gg.csv file and a word doc with some graphs in it.

I hope you can help.

8081.23-08-2022 Full Cycle Energizer GassGauge.log7026.200-1-GassGaugeSettings2022-08-23.gg.csv6557.Results of test 48hour test.docx

  • 0
    TI__Guru** 105760 points

    Hello Bruce,

    I took a look through your data, there's definitely a couple weird things I will point out.

    • The gauge is reporting 0 for DOD at EOC, this indicates that the chem ID may not be the best match, since you are charging over the maximum we characterized the battery for, so we have no more data so the gauge sets it to the max of 0.
    • The TrueRemCap is decrementing correctly, it is the filtered values that are not decrementing. this indicates it may be an issue with your Chg/Dsg Current Thresholds or the SOC smoothing options.

    When the gauge is in relax we use voltage as the primary  adjustment factor since the voltage should be stable and very little current is flowing, if the thresholds are not set correctly it will lead to errors since we only correct based on voltage every 10 hours. Check section Impedance Track Configuration Options of the TRM to make sure you allow RSOC to jump in relax mode.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 80 points

    Hi Wyatt,

    In respect to my question about the shape of the load current being so very lumpy in the form of very short pulses, what sort of A/D converter is used for measuring the current. and will there be a requirement for us to put in some sort of filtering to average the voltage used for reading the current. Reading the documentation readings seem to only be taken every 250ms, or have I missed something.

    I will look into the issue with DOD to try and better understand the problem. it looks like I may need to run the cycle to trey and get a better chemistry ID for the battery. The chemistry ID we are using is for a single sell as supplied by the battery manufacturer. If we are running a 2S2P system would this be causing the problem.

    Regards

    Bruce

  • 0 in reply to Bruce Morris
    TI__Guru** 105760 points

    Hello Bruce,

    You can find this information in the datasheet:

    Also the sampling frequency used by the ADC is in the datasheet as the LFO:

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 80 points

    Hi Wyatt,

    The ChemID was done on a single cell. As we are using 2 cells in parallel and then 2 sets of parallel cells connected in series (2P 2S config) do we need to rerun the ChemID test and send the files to confirm the ChemID. In short with our configuration what is the best setup for determining the ChemID.

    Bruce

  • +1 in reply to Bruce Morris
    TI__Guru** 105760 points

    Hello Bruce,

    If you have already found the chem ID using GPCCHEM or there is already the exact same cell characterized you do not need to recapture data and try to find it again with GPCCHEM.

    You can collect the data on the whole system following the GPCCHEM guide. we usually recommend doing it with one cell so the best voltage measurements can be used to find the chem ID without any system level influences.

    Sincerely,

    Wyatt Keller