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BQ27520-G4: Calibration Process

Ryan.Bishop
Expert 3900 points
Part Number: BQ27520-G4
Other Parts Discussed in Thread: BQSTUDIO, GPCCHEM, BQ27426

Hello,

For calibrating host side fuel gauges, is there a software interface to use for the calibration or the calibration sequence should be included in the host code? I've found the below documents but I'm still a little confused on the process. The documents also mentioned needing an EVM to generate the DFI file. Does TI has dedicated modules for this?

Is the calibration process the same for all system side gauges, or is it device specific?

Thank you!
Ryan B.

  • 0
    TI__Guru* 76230 points

    Hello Ryan

    Calibrating the voltage current and temperature is different step from performing the learning cycle and creating the golden file.

    The document you are referencing is older, our tool no longer exports a dfi file but rather a dffs ,  bqfs or srec

    Calibration of V,I, T is basically the same process for all devices which you can perform using bqstudio and  a load and power supply or you write code to perform the calibration as described in the app note.  The EVM user guide describes how to perfom the V,I,T calirbation while the attached app note below describes how to perform the learning cycle to extract a golden file.

    5672.LearningCycleOverview_.pdf

    thanks

    Onyx

  • 0 in reply to Onyx Ahiakwo
    TI__Expert 3900 points

    Hi Onyx,

    Thanks for your help above. I wanted to revive this thread to ask some questions on pack-side gauges for this same opportunity.

    In this document Selecting an Impedance Track Gas Gauge for Li-Ion Single Cell Applications, it mentioned in Minimum Configuration Requirement section that the BQ274xx gauges are programmed with a default battery profile suitable for most lithium-cobalt cells and they can further refine predictions as they learn the battery profile.

    We have a few questions regarding that:

    1.       How much less accurate is the BQ274xx gauges at the beginning of and during operation comparing to the BQ275xx gauges that require advanced configuration?

    2.       How is the calibration/characterization process changed for the BQ274xx gauges?


    I want to see if the error % is tolerable for the customer's application, since it seems like the BQ274xx gauges can save them quite some development time.

    Thank you,
    Ryan B.

  • 0 in reply to Ryan.Bishop
    TI__Guru* 76230 points
    Hi Ryan,

    1. It depends on how close a match your cell is to the default chem id. You need to run our online tool, gpcchem to determine how much of a close match it is. The accuracy could be as good as 99% and could be as bad as 50%, it just depends on if the cells match the default chem id.
    2. There is a quick start guide for the bq27421 and bq27426. It is quite detailed, pls review it. Main diff between both is that you will have to make provision for non volatile memory in your host to store the golden file, qmax and Ra tables shoild power get cut off from the chip

    thanks
    Onyx