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BQ24081: Charging Current Doesn't Stay in CC Mode

PratikPanchal
Intellectual 305 points
Part Number: BQ24081

I set ISET to 1.13K resistor to achieve 750mA constant charging current. When i started 4000mAH Li-Po Battery charging than its doesn't charge the battery through 750mA current during CC mode.

Li-Po Battery & Battery Charger are capable for CC mode. 

Kindly let us know which way i can start CC mode charging using BQ24081 ?

  • 0
    TI__Guru 65846 points

    Hello

    Could you provide additional information on the circuit and behavior you are seeing:

    1.) Could you send a schematic of your circuit?

    2.) You are setting the charge current at 750mA -- does charge start and this current go to battery?

    3.) What battery current and battery voltage are you seeing? 

    4.) Note that voltage at ISET is proportional to output current

  • 0 in reply to Bill Johns
    TI__Guru 65846 points
    Hello
    Any update on this problem, do you still need assistance with the device?
  • 0 in reply to Bill Johns
    Intellectual 305 points

    Hello Bill,

    1) Kindly find my schematic design file.

    2.) You are setting the charge current at 750mA -- does charge start and this current go to battery? - No

    3.) What battery current and battery voltage are you seeing?  - Current intially takes 400mA for few minutes and than stable for 320mA around. & Once Battery Capacity Increase than charging current also exponential decrease.

    4.) Note that voltage at ISET is proportional to output current ? Kindly explain 

  • 0 in reply to PratikPanchal
    TI__Guru 65846 points
    Hello
    Thanks for the schematic. I reviewed it and did not see any problems.
    Double check, TS pin 10k resistor is not installed if 10k NTC is in battery pack that will meet requirements.

    Some things to check:
    1.) Based on #3 from above the battery appears to start charging at 400mA -- Check that input voltage is not dropping this would limit output current. Check voltage at OUT, resistance between out and battery terminal can increase voltage during charge and lead to early CV mode.
    2.) Verify connections and values match schematic.
    3.) ISET voltage is useful for trouble shooting, current at ISET and the voltage is proportional to output current. Gives an indication of what output current is.

    If you have any test data or scope captures I would be happy to review them.