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BQ40Z50-R2: Full Charge Capacity & OCD Recovery

SeungMin Choi
Prodigy 40 points
Part Number: BQ40Z50-R2
Other Parts Discussed in Thread: BQSTUDIO, BQ40Z50

Hello

I'd like to inquire about BQ40Z50-R2.
I am using 4S3P battery pack and the cell is LGC INR18650MJ1. (Chemistry ID 0x2059)

The total capacity(Full Charge Capacity) of the battery pack is 10500mAh, three times the total capacity of 3500mAh, but changing the value of the Design Capacity does not change the capacity to 10500mAh.

I'd like to ask you how to change the total capacity of 10500mAh.

Also, I would like to ask you if there is any way to prevent the capacity change by charging discharge cycle.

Finally, I have an OCD Recovery question.

The 4S3P has an Over Voltage Protection of 17.0V, but if the battery pack voltage is 16.4V and the OCD (DSG OFF, CHG ON) is cut off, charging 16.8V/1A does not charge.
Other conditions 17.2V/1A current will charge, but for some reason it will not charge if the battery pack voltage and the charging voltage are small.

Cf. OCD Recovery releases the OCD if the charging current is greater than 200 mA.

I need some advice on this.

Thank you.

5126.MS-418_V103_210219.gg.csv

  • 0
    TI__Genius 11535 points

    Hi SeungMin Choi,

    You will need to change the Design Capacity as well as the Qmax. When changing a value in BQStudio make sure you press Write All and then confirm it is changed by doing a Read All.

    There's no way to prevent the capacity change because that is essential to battery gauging.

    I'm not sure I understand your last question, can you please clarify?

    Best,

    Jessica

  • 0 in reply to Jessica H.
    Prodigy 40 points

    Thank you for your kind advice.

    Additional explanations and photos are attached.
    First of all, I would like to change the full charge capacity to 10500mAh.
    As shown in the picture, we have also changed the Design Capacity and Qmax to 10500 and confirmed the change by pressing Write_All and performing Read All. However, as you can see in the picture, the capacity of Full Charge Capacity is changed to 8394mAh instead of 10500mAh.



    Also, our Battery Pack 4S3P COV is 17.0V.
    If the OCD is operated at Pack Voltage 16.4V, CHG ON or DSG OFF. (Normal operation) If the charging current is applied (Approval condition 16.8V/1A) to release the OCD, it will not be released (Release condition is 200mA or more charging current).

    However, if the charging current application condition is changed to 17.2V/1A, the charging current is applied to OCD Release, but I wonder why the charging current is not applied at 16.8V.

    Please advise if there is any setting I need to check.

    Best, Regards

  • 0 in reply to SeungMin Choi
    TI__Genius 11535 points

    Hi SeungMin Choi,

    You cannot change the full charge capacity, this is something that is calculated by the Impedance Track algorithm. Full charge capacity is usually less than the design capacity, especially as the battery ages.

    Can you send me your gg.csv? 

  • 0 in reply to Jessica H.
    Prodigy 40 points

    Thank you for your kind reply.

    We will send you the file as requested. (gg.csv)
    Please check if I need to change the setting of Data Memory and if there is any problem that the capacity is decreasing.

    Lastly, if there is no significant potential difference between battery pack voltage and charger voltage (about 400mV charger is high) in OCD status, please advise if it is correct that it cannot be charged.

    Best, Regards

    TEST_210329.gg.csv

  • 0 in reply to Jessica H.
    Prodigy 40 points

    Hello

    In response, you advised that it is difficult to change the overall charge capacity, which is calculated by the impedance track algorithm, and I have a question here.

    1. How many times does it fit to the capacity (10500mA) I set after the charging discharge cycle?

    2. When setting Qmax and Design Capacity (10500mAh), please advise if there is only approximate value compared to the set value.

    lastly
    Is it possible to change the release condition to DSG ON when removing load from the OCD status?

    Best, Regards

  • 0 in reply to SeungMin Choi
    TI__Genius 10370 points

    SeungMin,

    1) FCC is a function of QMax + IR loss. Not DesignCapacity. Design capacity plays no role in the mAh your battery can produce. IR loss is determines based on the Ra table (resistance) and current (load select) within the gauge simulation. Please update the QMax value then follow the "learn cycle" application note on the bq40z50 ti page.

    QMax is a parameter that is constantly updated by the gauge and should go down overtime at the gauge ages. 

    2) OCD stands for Over current discharge. You can modify the recovery threshold lower to recover based on less current applied. you can set the value to 0 to it recovers when the dsg current is removed.

    Thanks,

    Eric Vos