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BQ25710: Where is battery depletion threshold for 4s battery

Koyo Asaishi
Intellectual 1960 points
Part Number: BQ25710
Other Parts Discussed in Thread: BQ25720,

Hi team,

EN_LEARN can't work when the Vbat is below battery depletion threshold but there is no clear specification in the datasheet.
Is the threshold 2.8V/cell (typ)? If 4cell application, the threshold is 11.2V as below image indicate?

How about BQ25720?
Is battery depletion threshold 2.4V/cell (typ)?

Best regards,
Koyo

  • 0
    TI__Mastermind 33035 points

    Hi Koyo,

    When the host determines the battery voltage is below battery depletion threshold, the host switch the system back to adapter input by writing this bit back to 0b. Our charger does not exit the learn mode automatically. The customer determines the battery depletion threshold based on the battery spec. The battery depletion threshold is not related to the battery low volt comparator nor battery under voltage lockout spec. 

    Regards,

    Tiger

  • 0 in reply to Tiger Zhou
    TI__Intellectual 1960 points

    Hi Tiger,

    Thanks for the answer.
    Let me ask some questions.

    1. What voltage is the depletion threshold after all? 2.8V/cell?
    2. Can you share min/max of depletion threshold?
    3. Can you share the transition time between Vbat reach to be below the threshold and the host switch the system back to adaptor input?
    4. When Vbat is below the threshold, is charge current 384mA based on 0x3E?

    Best regards
    Koyo

  • 0 in reply to Koyo Asaishi
    TI__Mastermind 33035 points

    1) The customer determines the battery depletion threshold based on the battery spec. 2) Typically the battery depletion threshold should be greater than the VSYS_MIN so that the battery capacity can be fully utilized for maximum battery run time. 3) When EC disables the LEARN mode, the charger switches to adapter input immediately. 4) When VBAT is below min_sys_voltage 0x3E, the charge current is clamped at 384mA. 

  • 0 in reply to Tiger Zhou
    TI__Intellectual 1960 points

    Hi Tiger,

    How to determin the depletion threshold?
    I think BQ25710 can't determin the depletion threshold and EC or gas gauge don't always have this threshold.

    Best regards,
    Koyo

  • +1 in reply to Koyo Asaishi
    TI__Mastermind 33035 points

    I would suggest you starting with VSYS_MIN as your battery depletion threshold.