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BQ78350-R1A: The fuel gauge shows wrong sometimes

Josel Go
Expert 6335 points
Part Number: BQ78350-R1A
Other Parts Discussed in Thread: BQ78350, BQ76930, GPCCEDV

Hi Experts,

Good day.

I use BQ78350 and BQ76930 together, but sometimes the fuel gauge shows completely wrong. The full charge shows 60% fuel. After resetting it will show correctly, do you know why this happens?



Please advise

Regards,

Josel

  • 0
    TI__Guru 57697 points

    Hello Josel,

    Check if current is reading correctly. If not then calibrate current.

    When there is an offset current, the gauge sees a current and this is added/subtracted over time resulting in wrong values. A reset forces the gauge to take an initial reading based on voltage.

  • 0 in reply to Shirish
    TI__Expert 6335 points

    Hi Shirish,

    Thanks for the information, the current reading is 3mA with no load as I send you the pictures last time. It may be the other problems or reasons which make the fuel gauges read wrong about a 40% difference.

    Please advise

    Regards,

    Josel

  • 0 in reply to Josel Go
    TI__Guru 57697 points

    Hello Josel,

    Calibrating the current will help.

    Did you configure the CEDV parameters by using the GPCCEDV tool?

  • 0 in reply to Shirish
    TI__Expert 6335 points

    Hi Shirish,

    I have calibrated the current.
    I did not configure it with the GPCCEDV tool but ChemID is set to the right one, if you could have a look the CEDV is set correctly.
    But the battery did not get discharged and the fuel gauge shows wrong, looks not the compensated discharge voltage.
    I have attached the CEDV setting.


    Regards,

    Josel

  • 0 in reply to Josel Go
    TI__Guru 57697 points

    Hello Josel,

    The CEDV parameters are probably not matched to the battery. The chemID is only used to estimate SOC on startup, so that is working correctly. The GPCCEDV tool provides the matching CEDV settings for the battery.

  • 0 in reply to Shirish
    TI__Expert 6335 points

    Hi Shirish,

    Thanks for your information, I found the GPCP pack will apply by the discharge rate with the different temperatures. But is the SOC shows wrong, because it is fully charged? It should be 100% fuel but show 60%. And it is the room temperature all the time.

    This there any SOC settings problems or sensing problems that will apply this fault? If any experts could solve this.

    Regards,

    Josel

  • 0 in reply to Josel Go
    TI__Guru 57697 points

    Hello Josel,

    The battery must be at rest(no charge discharge for 2 hours) when the gauge is reset to read a good estimate of SOC. After that the current is tracked to update SOC.

    Make sure that calibration is correct before the gauge is reset (or cells attached)