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BQ34Z100: BQ34Z100 FCC abnormal reading issue

Sherman Xin
Prodigy 350 points
Part Number: BQ34Z100
Other Parts Discussed in Thread: BQSTUDIO, EV2400

Hi Team,

Have a good day! My customer meets technical issues on BQ34Z100. They mainly reported two problems: 1) After the battery is fully charged, the SOC is zero; 2) The SOC accuracy is seriously inaccurate;

After analyzing the existing information we obtained: 1) The SOC is 0 when fully charged, and the FCC has become zero;
2) The SOC accuracy is seriously inaccurate, the FCC has deviated far from the rated value we set (rated capacity 33Ah);
3) There is no abnormality in the initial use, and it appears after dozens of cycles (the cycle is not fixed);


After this abnormality occurs, we have asked the customer to re-do the battery aging study. After the aging study, the FCC has increased, but it has not returned to the rated power range; (after the study, the FCC has become about 25Ah). Some abnormal phenomena appear as shown in the figure: (SoC=0, FCC=0) And also schematic is put here.

So we need your help on below two actions: 
1) What is the reason for this exception?
2) After this abnormality occurs, is there any way to restore the battery to normal besides doing aging learning?

Many thanks!

BRs, Sherman

  • 0
    TI__Guru 61006 points

    Please attach the gg file (configuration) extracted from a gauge that reports 0% SOC after a full charge. You can extract this from the gauge by connecting SCL and SDA to the EV2400 connected to a PC running bqStudio. Go to Data Memory and click on Export.

    I need to check how the gauge estimates load for a discharge and how the gauge learned cell resistance.

  • 0 in reply to Dominik Hartl11
    TI__Prodigy 350 points

    Hi Dominik,

    Thanks for your support! 

    I have described the current difficulty to you via email. And the urgency action now we need to do is to recover the FCC data to a right number. So if the FCC is wrong, how we can recover it? can we re-write the register? and which register to write? Or any other effective ways we can try? 

    Many thanks!

    BRs, Sherman

  • 0 in reply to Sherman Xin
    TI__Guru 61006 points

    FCC is a gauging result and cannot be directly written to. I'll check the configuration and get back to you.

  • 0 in reply to Dominik Hartl11
    TI__Prodigy 350 points

    Hi Dominik,

    Any update this week? If FCC can not be written, which register we can write to fix or reset the wrong FCC result? Thank you.

  • 0 in reply to Sherman Xin
    TI__Guru 61006 points

    The configuration shows a Design Capacity of 6000mAh and Qmax of 6432mAh. Hence FCC will be in this range. Do you have any background how they developed the configuration? The gauge reports FCC = 6244mAh when I program it with the .dffs file that you sent to me. So this looks like it's a different configuration. Do you have a configuration that was extracted from the gauge when it reports FCC = 0mAh?

  • 0 in reply to Dominik Hartl11
    TI__Prodigy 350 points

    Hi Dominik,

    It's the same configuration. In fact, the FCC is normal at the beginning 30-40 times charge/discharge. But when run after 30-40 times, FCC will become smaller, even to zero. So could we explain it from software level? If any unreasonable code design?

    And if it goes wrong, do we have some ways to recover FCC value? Thank you!

  • 0 in reply to Sherman Xin
    TI__Guru 61006 points

    There are several reasons why this may diminish. The gauge predicts capacity so if it somehow learns properties like cell resistance, chemical capacity or load prediction incorrectly, it can cause a reduction in FCC.

    That's why I need the configuration pulled from a gauge that shows the low FCC, not the configuration that is used to initially program the gauge.