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Which registers do you configure to calibrate the bq27441

Gurpreet Singh92
Prodigy 60 points
Other Parts Discussed in Thread: BQSTUDIO

It seems that all the registers I need to adjust are read only. Are there any registers that I can adjust to calibrate this chip to my battery? The only one I have been able to adjust so far is the Design Capacity. Other values like the Design Energy, Terminate Voltage, and Taper Rate are mentioned as parameters that are adjusted, but it doesn't mention how to change them. 

Alternatively, if I can just upload the parameters set in one board onto many others that would also solve this. I am running a set of batteries through a discharge cycle to train the board to calibrate the right parameters. How would I move those parameters from one board to another?

  • 0
    TI__Mastermind 26215 points
    Hi Gurpreet,

    As long as the device has not been sealed, you should be able to write to the registers containing Design Energy, Terminate Voltage, etc. Additionally, you can use bqstudio to set these parameters accordingly on the data memory tab.

    In bqstudio, you can export a gm.fs file to use to configure other gauges. This is done on the "Golden Image" tab. When you bring up another board, open bqstudio, navigate to the "Programming" tab, open your gm.fs file and click the program button.

    Best Regards,
    Ben Lough
  • 0 in reply to Benjamin Lough
    Prodigy 60 points

    Awesome! I thought I couldn't change it at all. But I am still confused on the actual location of those registers. What are the addresses of those registers? And which bit do I change to adjust them properly?

  • 0 in reply to Gurpreet Singh92
    TI__Mastermind 26215 points
    Hi Gurpreet,

    The data memory tab is organized by Class then SubClass. For a full list, take a look at section 6.3 the technical reference manual:www.ti.com/.../sluuac9a.pdf.

    Design Capacity, Design Energy, Terminate Voltage and Taper Rate are all in the Gas Gauging Class and State SubClass.

    Best Regards,
    Ben Lough
  • 0 in reply to Benjamin Lough
    Prodigy 60 points
    Ahh. Ok.
    I have a board that I have ran through multiple discharge cycles, so I think this chip has calibrated to the batteries. I hope to transfer the values set in this chips registers to the rest of the boards, since thy are all using the same type of battery. Which registers are most important when it comes to calibration?
    My initial thought was to copy all the bits from subclasses Safety to Codes, however that might be overkill. Im not sure what should be transfered.
  • 0 in reply to Gurpreet Singh92
    TI__Mastermind 26215 points
    Hi Gurpreet,

    The easiest method is to export a gm.fs file from your learned device (golden image tab in bqstudio). You can use this file to program your other devices on the programming tab.

    Best Regards,
    Ben Lough
  • 0 in reply to Benjamin Lough
    Prodigy 60 points
    I tried that program out, however I unfortunatly cannot use it with my current setup. Does the gm.fs file store every single readable register, or only major ones? And what would those major ones be?
  • 0 in reply to Gurpreet Singh92
    TI__Mastermind 26215 points
    Hi Gurpreet,

    The gm.fs file would contain writes for every parameter. You want to at least make sure the correct chemID is programmed along with the Safety, Charge Termination, Registers, Current Thresholds and State subclasses. I can look into resolving your compatibility issues with bqstudio if you want to describe your current setup.

    Best Regards,
    Ben Lough
  • 0 in reply to Benjamin Lough
    Prodigy 60 points
    Hey,

    Thank you for all your help so far. I am able to write and read to/from all the registers. However, I am now running into this strange problem where the full capacity and remaining capacity read 0 mAh even though the voltage and current readings are perfectly normal.
    Do you know what could be causing this?

    Thank you,
    Gurpreet Singh
  • 0 in reply to Gurpreet Singh92
    Prodigy 60 points
    When I dont write to the registers the remaining capacity and full capacity are both in the 1200s even though the BATTERY_CAPACITY is set to 3400. I know the default is 1340 so I wonder if it is assuming that value instead 3400.