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BQ27441-G1: External resistance

Zahir Khan
Prodigy 100 points
Part Number: BQ27441-G1
Other Parts Discussed in Thread: GPCCHEM, BQSTUDIO, BQ27421EVM-G1A

Hi All,

We are use bq27441-g1. 

In our case distance between the battery & sensor pin is bit long.

May constitute 100mOhm as external resistance between battery & sensor pin.

Will this impact gauging or learning cycle? or having big external resistance a cause of concern? 

Appreciate your feedback.

Regards,

Zahir

  • 0
    TI__Guru* 76230 points
    Hi Zahir,
    it potentially could. The first thing you need to do is determine if this gauge is a good fit for your battery chemistry given the gauge has predefined chem ids. To do this you need to run the test specified in our online tool, gpcchem. If the results say the device can be used, then you need to perform a learning cycle so the gauge learns the impedance of the battery in addition to the trace. Personally, I would recommend a flash based gauge like the bq27520 as that would allow you use a chem id that is a good enough match for your cells.

    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Prodigy 100 points

    Hi Onyx,

    Thanks for your quick response.

    We are having BQ27421EVM-G1A & bqstudio. And BQ27441. Will that help to generate logging required for chem id.

    I failed to find option with these. Or I missed something.

    Regards,

    Zahir

  • 0 in reply to Zahir Khan
    TI__Guru* 76230 points
    Hi
    Yes you can log voltage current and temp with the device and bqstudio. You cannot however automate the charge discharge cycles. Our tool GDK helps automate the charge and discharge cycles. It is not an absolute requirement though. You can just manually control the power supply for charger and electronic load.
    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Prodigy 100 points

    Hi Onyx,

    Uploaded the logs to the link as suggested & got the quick report.

    PFA the report & the logs uploaded. I am not that clear with the report. 

    Appreciate your feedback.

    Regards,

    Zahir

    BQ27441_20190319-report.zipBQ27441_20190319.zip

  • 0 in reply to Zahir Khan
    TI__Guru* 76230 points
    Hi Zahir,
    The report says that you do not have a close chem id match. Does your cell by any chance have a a protector inbuilt. If so remove it and rerun your test connected directly to the battery terminals. if you still do not have a match then the cell will have to be characterized by TI
    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Prodigy 100 points

    Hi Onyx,

    Thanks for your response.

    We do have the protector inbuilt, over current & short circuit protection. Will be highly risky to run full load without protection in our case.  

    Does with these external resistance(100mOhm) + protector circuit is it difficult to get/match chem-id or their is some wayout?

    Attached another report with protection. 

    Related to doing characterization, appreciate some more insight (Whats the process, what is needed, how long will it take, etc)

    Highly appreciate your feedback.BQ27441_20190320-report.zip

    Regards,

    Zahir   

  • 0 in reply to Zahir Khan
    TI__Guru* 76230 points
    Zahir,
    I am not saying to run your application without the protector. I am saying run the test without the protector just to identify the chem id. Subsequent evaluations would be with the protector
    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Prodigy 100 points

    Hi Onyx,

    As our device draw huge current when full load, highly risky to run even for test, without protection chances of accident are quite high. 

    Regards,

    Zahir

  • 0 in reply to Zahir Khan
    TI__Guru* 76230 points
    hi Zahir,
    You are not listening to me.I am saying run your chemid identification test independent without the protector circuit. use a constant electronic load current to do this not your actual load.
    thanks
    Onyx