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BQ34Z100 / state-of-charge varies without load

Ulrich Schmidt49
Intellectual 340 points
Other Parts Discussed in Thread: BQ34Z100, BQ34Z100-G1

Dear BQ Experts,

on behalf of my customer I'd appreciate if you could take a look on below:

==============================================

we are using a TI BQ34Z100 Fuel Gauge Sensor in our Application.

In our tests we noticed some strange behavior.

Often the state-of-charge changed its value over night from circa 15% to circa 7% (and backwards) without any load.

Also the state-of-charge wasn’t stable. So it varied highly in the range between 5% and 25%.

Is this a normal behavior of this sensor? Maybe our flash settings are not correct. I send you the configuration settings as well.

A possible option is to use the BQ34Z100-G1 instead. Is there anything else changed in this new sensor than the bugfix for the ALERT-pin?

==============================================

There are already e2e posts about a migration to the -G1, but the answer is only posted offline. Appreciate if you could add this as well.

Best regards,

Uli

  • 0
    TI__Guru 73830 points
    Ulrich,
    There was another e2e posting about this recently and it was probably for the same case. They were gauging LiFePO4 cells in that case and i noted that the voltage profile for this chemistry is very flat. The gauge will take an OCV reading and run an FCC simulation every 5 hours and it can update the capacities. This can result in SOC changes, if the pack is resting in a very flat portion of the curve, because the gauge has trouble determining where the capacity is on the curve. They should set the DoDWT bit to help reduce these changes with LiFePO4 cells. The bq34z100-G1 also has features that prevent SOC jumps when in relax mode.

    Tom
  • 0 in reply to ThomasCosby
    Prodigy 20 points

    Tom,

    thank you for your reply.

    The "DoDWT" bit was set already when this changes occured.

    Can you say, that  the bq34z100-G1 with this new features you mention can prevent this SOC jumps definitely?

    Jan

  • 0 in reply to Jan Vollaard
    TI__Guru 73830 points
    The -G1 device has a smoothing algorithm and this feature will have the biggest impact on preventing SOC jumps.