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BQ40Z80: Questions about Bq40z80

z4ci4n
Prodigy 80 points
Part Number: BQ40Z80
Other Parts Discussed in Thread: BQ78350

Hi,

I am planning to design 4S battery pack which is more than 70Ah. Also the user should be able to turn on/off the dsg fet with an external switch and check the SOC with LED’s and button.

According to my research, BQ40z80 looks suitable for this project. I read some topics about scaleability and dsg fet control so I would like to be sure about there is any problem with that features.

 

My questions;

  1. Is there any problem about scaling the capacity from 29Ah to 70Ah? In a topic, a TI expert said that there is a fw bug on 6th of October 2020 . Did you fixed that bug with the last software?

That topic: https://e2e.ti.com/support/power-management/f/196/t/946102

  1. Is it possible to turn on/off the fets manually with an external switch like BQ78350 Key-in function? I have read a topic about this subject then I would like to be sure.

According t this topic (https://e2e.ti.com/support/power-management/f/196/t/849965), Emergency shutdown fet feature will let me control fet manually with a switch. When I turn off and turn on the fets with this feature, Do I have to reset the IC? Does this situation affect my fuel gauge accuracy?

  1. Is there any other method for controlling fets like a configurable gpio pin?

Thanks,

  • 0
    TI__Guru** 105940 points

    Hello,

    The scale factor has a bug, but you can manually do calibration as mentioned in the thread linked, just input the current scale you want during calibration.

    The emergency shutdown feature only applies to the FETs, I think it would work for your needs of only turning the FETs on/off.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 80 points

    Hi Keller,

    I had some experiments about scale factor and EMShutdown feature. I see the cell currents and pack currents are not mach when I use scale factor. I would like to be sure that I am using it correctly. 

     

    Which way is correct ? If both of this ways are incorrect, could you explain me the data memory and calibration settings(such as scale factor, design cap, calibration current, cell currents eg...)  for a 100Ah battery?

    1)I have 100Ah battery. Set design capacity 25Ah, scale factor 0. Apply load with 1A. Calibrate it to 250mA.   

    RESULTS:Pack current shows 250mA, cell current shows 250mA. 

    2) I have 100Ah battery. Set design capacity 100Ah, scale factor 4. Apply load with 1A. Calibrate it to 1A.

    RESULTS: Pack current shows 250mA, cell current shows 1A. 

     

    Also If I turn on and off the fets with EMSHUTDWN feature again and again, is the fuel gauge will be affected from this situation?

    Thanks,

  • 0 in reply to z4ci4n
    TI__Guru** 105940 points

    Hello,

    You should use the method you are using to calibrate the gauge in method 1, the second method shows the issue with the scale factor I mentioned previously.

    The EMSHUT doesn't have a limit to the number of times it can be used.

    Sincerely,

    Wyatt Keller