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BQ27421 : Battery level changes improperly

Dhaval V
Genius 4470 points
Other Parts Discussed in Thread: BQ27421-G1, BQ27621-G1

Hi,

I am using BQ 27421 for measuring the Battery level. I am reading battery level at every 1 second and send it over BLE. The battery fuelgauge returns correct value normally. But when I observed it continuously, the battery percentage jumps directly from 48 to 45 and from 45 to 43. It was not changing in sequence.

Do I need to configure it somewhere? Has anyone face this issue?

Thanks,

Dhaval

  • 0
    TI__Genius 14985 points

    Hi Dhaval,

    When you say you "observed it continuously" do you mean you were logging it periodically or do you mean you were polling it frequently?

    How frequently are you reading from the gauge?  If you poll it tens-of-thousands of times per second you could cause a watchdog timeout and the gauge would reset.  On each reset you could get a different SOC since the battery voltage and current would not be stable during the initialization.  Also, you would need to reconfigure the gauge each time it is reset.  You can check the ITPOR bit to see if it was reset since the previous configuration and is in need of configuration again.  This is a gauge in which the configuration is held in RAM, as opposed to gauges with flash memory like bq275xx.

    Also, please tell us what kind of configuration you have done to the gauge.  There is some minimum configuration required, like the capacity of your battery and other system characteristics.  The bq27421-G1 Quick Start Guide outlines the minimum procedure.  This would not cause the behavior you mentioned of SOC changing, but it is something I want to make sure you have done.

    The bq27621-G1 is the closest gauge we have to something where you might be okay with skipping configuration entirely.