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BQ27Z561: Battery percentage error in BQ27Z561

Parth Mehta
Prodigy 180 points
Part Number: BQ27Z561
Other Parts Discussed in Thread: BQSTUDIO

Hello,

Note : Continuation of Previous thread link - e2e.ti.com/.../bq27z561-battery-training-procedure-using-bq27z561-fuel-gauge-ic-and-bq-studio

After generating golden image we tested it in ti EVM as well as our development board. Everything is working fine in ti EVM board, we are getting proper voltage, current and percentage data but in our development board we are not getting readings properly. Here i am putting two scenarios and it's outcome.

Please help us to find the solution.

ti EVM = bq27z561EVM - 011, BMS011 Rev A EVM

1) We tested golden image in ti EVM board, everything works fine here.

2) We tested same golden image with our development board, here we are not getting proper readings. FCC,RC and RSOC is getting reduced continuously. When we power up the board, everything is good. But after 1-2 seconds FCC jumps to around 1000mAH from 3000mAH/Actual capacity and RC jumps to around 900mAH then it's getting reduced continuously. We tried below things to find the solution.

I - We used ti EVM fuel gauge (bypassed microcontroller of ti EVM) with our development board (bypassed fuel gauge section of our development board), everything works fine.

II - We used ti EVM microcontroller (bypassed fuel gauge section of ti EVM, only used microcontroller of ti EVM) with fuel gauge of our development board, here we are getting this problem.

III - We used only discrete circuit (Rsense section) of ti EVM instead of our development board (bypassed Rsense section of our development board). We just used gauge IC of our development board with discrete/Rsense circuit of ti EVM and here we are also getting problem.

Here i am attaching logs for your better understanding.

Battery Percentage.pdf

Thanks,

Parth

  • 0
    TI__Mastermind 25006 points

    Hello Parth,

    It sounds to me like this is a calibration issue. Did you calibrate the development board? Even though you saved a golden image in TI's EVM, you have to upload golden image in development board, then calibrate and lastly generate the golden image once again. 

    Please send the schematic and layout of development board if possible.

    Note: Also, it'd be easier to debug if you saved the log in a CSV format like the one our bqStudio tool did.

    Regards,
    Jose Couso

  • 0 in reply to Jose Couso
    Prodigy 180 points

    Hello,

    We had done calibration.

    We are sending schematics and layout section of fuel gauge section for your better understanding. 

    Thanks,

    Parth

  • 0 in reply to Parth Mehta
    Prodigy 180 points

    Hi,

    Please help us to find the solution. we have tried everything we thought of but could not find the solution.

    I have attached schematic and layout of fuel gauge section for your analysis.

    Thanks,

    Parth

  • 0 in reply to Parth Mehta
    TI__Mastermind 25006 points

    Hello Parth,

    SRN and SRP connections are swapped. 



    Regards,
    Jose Couso


  • 0 in reply to Jose Couso
    Prodigy 180 points

    Hello,

    1 - We were thinking that, due to SRP and SRN pin swapping we maybe getting reverse polarity in current readings and it should not affect the readings/system performance/RSOC calculations at all, is not that correct?

    2 - Is there any factor which can affect the results, because we observed that in TI EVM external thermistor is connected and we had performed learning cycle by selecting external thermistor in temperature configuration settings whereas in our board we have not connected any external thermistor and have kept TS Pin open. we have used this golden image generated having external thermistor settings and that is why it is not working in our case because in absence of external thermistor we have to select internal thermistor, is that correct?

    3 - If i need to change temperature setting to internal thermistor from external then do i need to perform learning cycle again by selecting internal temperature configuration in data memory settings or can i just change the temperature selection settings in data memory and can use this regenerated golden image?

    Thanks,

    Parth

  • +1 in reply to Parth Mehta
    TI__Mastermind 25006 points

    Hello Parth,

    1- Swapping SRP and SRN pins does affect gauge RSOC calculations. The gauge will operate in reverse logic and the coulomb counter used to know the accumulated charge and discharge current will not be accurate. Also, the SRP pin is designed so that its voltage does not varies much and states near GND.

    2- If you are using internal thermistor settings, you should change the settings in the golden image you are uploading. As long as the temperature reading is accurate, the gauge won't have a problem.

    3- No need to perform a learning cycle again, just change the thermistor settings to internal and it should be fine. Just make sure the temperature reading is as expected.

    Regards,
    Jose Couso

  • 0 in reply to Jose Couso
    Prodigy 180 points

    Ok, Thanks Jose Couso

    You have helped me a lot.