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BQ34Z100-G1: Hit 100% CHG on charge termination

Lao Hu
Intellectual 790 points
Part Number: BQ34Z100-G1

Hello,

A system based on BQ34Z100-G1 and a 12V LifePo battery (10000mAh) get 100% in SOC during charge at the beginning of the constant voltage stage. Below a graph showing the charge stage.

The BQ34Z100-G1 can be set in order to hit 100% SOC on charge termination?

The FC Set% is equal to -1 and the device pass the learning process.

Thanks for any suggestion,

  • 0
    TI__Mastermind 42535 points

    No, such an option is not available in this device. You can reduce your taper voltage with RSOC_HOLD to see if that holds off RSOC at 99% until you reach taper. But do not use that if you use SMOOTH in pack configuration.

  • 0 in reply to Batt
    Intellectual 790 points

    Hi Batt,

    Thanks for your suggestion. 

    Currently the cell taper voltage is set to 100mV and the cell charging voltage to 3.65V. 

    I would perform the test as suggested and get you back as soon finish. 

    About to set [RSOC_HOLD], I don't understand the relation because the TRM mentions this setting prevents SOC rises during discharge. The situation reported here is during charge. If you could comment on that a bit more will be appreciated.

    Additionally, if SMOOTH = 1, there is another option in order to address this situation (SOC = 100% before taper current)? 

    Thanks

  • 0 in reply to Lao Hu
    TI__Mastermind 42535 points

    Hi Lao,

    With RSOC_HOLD you are asking the gauge to hold capacity when smoothing is active (smoothing by itself should be allowed to manage capacity in either direction), so this will interfere with it. That's why I asked you to disable it. There is no other option to address it except what I suggested. This is because this gauge is based off an old fw which is limited in flexibility.

  • 0 in reply to Batt
    Intellectual 790 points

    Hi Batt,

    Thanks for explain further details about RSOC_HOLD and the relation with this situation. Please, may you suggest a similar device with most recent firmware?

    I performed various cycles and get similar results with RSOC_HOLD active, as show the graph below.

    I will reduce the taper voltage as suggested and test again. I will change from 100mV to 50mV. If you consider a different value, please, let me know.

    Thanks

  • 0 in reply to Lao Hu
    TI__Mastermind 42535 points

    Hi Lao,

    Please disable RSOC_HOLD when you test it. Reducing taper voltage to 50mV might also work. There are no additional suggestions.

  • 0 in reply to Batt
    Intellectual 790 points

    Hi Batt,

    The RSOC_HOLD was disabled and new test was performed. The results look much better. The SOC hit 100% with lower charging current than before, which is good for this application, where the charger must be disable at 100% SOC.

    In the first post, you mention "reduce your taper voltage with RSOC_HOLD to see if that holds off RSOC at 99% until you reach taper. But do not use that if you use SMOOTH in pack configuration" and I'm still a little confuse, because in one hand you mentioned enable "with RSOC_HOLD" and in other, to disable. 

    Just to be sure, there is not misinterpretation from my end, please, may you confirm the variables used during the latest test match with your suggestion in order to hit 100% SOC in taper current:

    • Disable RSOC_HOLD
    • Taper voltage: 50mV
    • SMOOTH: enable (I don't have facts on this, but I could prefer to keep the SOC value smooth for the user, as suggested on the TRM)

    Thanks

  • 0 in reply to Lao Hu
    TI__Mastermind 42535 points

    Hi Lao,

    I'm happy this solution worked for you. You can stop chg after 30 seconds once capacity hits 100%. Yes, your settings to hit 100% at taper are correct. If you are using SMOOTH, do not use RSOC_HOLD. Otherwise it may affect gauge performance.