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BQ24125: 3 Cell battery charging issue

vinod sharma
Intellectual 450 points
Part Number: BQ24125

Hi,

We are using BQ24125 to charge 3 cell Li-ion battery & facing issue in battery charging. Required charging current is 1 Amp, Pre-charge current 0.1Amp.

Input voltage is 15V. Battery current state voltage is 10.8V.

We are following below schematic.

Please clarify below points:

1. ISET2 resistor value (10k) in schematic PMMP5309 & calculation given in datasheet is doubtful. It should be 1k to set a pre-charge current of 100mA. 

2. We have clearly observed battery detection voltage waveform as per Figure 12 in datasheet but current does not rises. Battery current remains ~2mA. What could be the issue?

Please note that TS pin voltage is 1.58. TTC pin is grounded.

regards

Vinod Sharma

  • 0
    TI__Guru 57341 points

    Vinod,

    1.Referring to the equation below, VISET2=100mV, KISET2=1000V/A, RSNS=0.1OHM, RISET2=10KOHM, so IOPRECHG=0.1A.

    2. The output signal switches between VOREG and GND until a battery is inserted. Only when the battery is detected, the output current increases.

    Thanks,

    Ning

    Please click "This Resolved my issue" button if this post answer your question.

  • 0 in reply to Ning T
    Intellectual 450 points

    Hi Ning,

    1.RSET2 is for fastcharge  OR pre-charge. Please see below figure. Also please note that with 10k resistor we observe 1V & with 1k resistor we observe 0.1V at ISET2 pin.

    2. Our battery is detected but still current is not rising. What could be the issue? It seems that it is in some fault state.

    regards

    Vinod Sharma

  • 0 in reply to vinod sharma
    TI__Guru 57341 points

    Vinod,

    1.RSET2 is to set pre-charge current only. The device can’t be controlled by both fast charge loop and pre-charge loop at the same time. The fast charge loop will be disabled when pre-charge loop is in control. Please refer to the functional block diagram for the details.

    2.Do you have gauge or protection IC in between the charger and the battery pack?

    Thanks,

    Ning.

    Please click "This Resolved my issue" button if this post answer your question.