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  • TI Thinks Resolved

BQ24157: charge current decreases prematurely during current regulation phase

Part Number: BQ24157

Dear all,

register 0x04(B4~B6) 0x06 or 0x07, charge current decreases prematurely, please refer to the attached.

register 0x04(B4~B6) 0x05 or lower, charge current decreases normally until entering CV .

what's the reason for the difference? thanks

  • In reply to user4733531:

    Hi there,

    The impedance between the battery voltage sensing CSOUT and the PACK influences the entrance of the CV mode. The CSOUT pin is what the battery remote sensing for the battery voltage. The parasitic impedance between the CSOUT and the batter terminal has impedance including the long cable resistance in the setup. Although battery terminal seems not reaching the CV voltage, but the CSOUT feedback the charger with a higher voltage, causing the charger CV mode earlier. Higher charging current causes the CV mode entrance earlier. From this point of view, the layout and setup need to be optimized for the CSOUT pin to reflect the real battery pack voltage with minimal impact of the current.

    Regards,

    Eric

    Texas Instruments

    Battery Charger Solutions

  • In reply to ezhao:

    Dear Eric,

    thanks for your reply.

    Does diffrent charging current cause diffrent impedance? the lower current is normal.

    thanks

  • In reply to user4733531:

    Hi there,

    The lower charging current will have less impact to the early entry of the CV mode.

    Regards,

    Eric

    Texas Instruments

    Battery Charger Solutions

  • In reply to ezhao:

    Dear Eric,

    When and how can i confirm the impedance between the CSOUT and the batter terminal ?

    thanks

  • In reply to ezhao:

    Dear Eric,

    Could you please provide a testing method for us to confirm impedance problem?

    thanks
  • In reply to user4733531:

    Hi there,

    PCB impedance, cable connection, and connectors all contribute to the impedance. You might compare two cases charging with two different sets of cables with different impedance (the impedance can be calculated using current injection and Kelvin sensing) to compare the effects.

    Regards,

    Eric

    Texas Instruments

    Battery Charger Solutions

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