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BQ25886: Charging Issue with BQ25886 at 8.2V

Tom Tsao
Expert 1960 points
Part Number: BQ25886


Tool/software:

Dear TI Support Team,

I am currently encountering an issue with the bq25886 charger IC. The charging voltage is configured to 8.2V, but as the battery voltage approaches 8.0V, the charging current starts to drop. Following this, the charging process repeatedly stops and restarts until the battery voltage reaches 8.2V.

I have attached the circuit schematic and a log file for your reference. Could you please help me review both to identify the cause of this behavior?

  • 0
    TI__Guru 59141 points

    Hi,

    Where did you measure the battery voltage?

    Thanks,

    Ning.

  • 0 in reply to Ning T
    Expert 1960 points

    Hi Ning,

    I measure the battery voltage from VBAT.

    Thanks!

  • 0 in reply to Tom Tsao
    TI__Guru 59141 points

    Hi,

    Did you measure the battery voltage at the BQ251886 BAT pin or the battery positive terminal?

    Thanks,

    Ning.

  • 0 in reply to Ning T
    Expert 1960 points

    Hi Ning,

    I measure the battery voltage at the BQ25886 BAT pin.

    Thanks.

  • 0 in reply to Tom Tsao
    TI__Guru 59141 points

    Hi,

    We are unable to observe the behavior you mentioned.

    The charger adjust the charging current based on the BAT pin to GND pin voltage of the BQ25886. The charger may not see the actual battery pack voltage if the CO FET and/or the DO FET of the battery protection circuitry in between are not properly turned on.

    In order to debug, please check the following:

    1. Connect the battery pack to the BQ25886 directly (i.e. bypass protection circuitry etc) and see if the charger works differently.

    2. For the custom board, measure the BAT pin to GND pin voltage of the BQ25886 and compare to the Pack+ to Pack - (battery pack voltage) and see if they are the same.

    Please note that this is the Thanksgiving holiday week. If further support is needed, please contact us next week.

    Thanks for your understanding,

    Ning.