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BQ24170: Intermittent charging

Hexor
Prodigy 70 points
Part Number: BQ24170

Hi,

I made a PCB with the BQ24170, but I have an issue : 

Charge start, but after a few second charge are stopped (approx 4sec), few seconds later (approx 1/1.5s) charge start again, and so, and so....

Schematic: 

Vin = 15V

Lipo are 3cells - actually 11.7Volts

Viset = 508mV 

Vovp = 1.23V

TS = 2V (fixed, I haven't NTC here)

Vacset = 660mV

Do you know where can be the issue ?

Thanks

  • 0
    Prodigy 70 points

    When Charging :

    SW signal : 

    STAT was tied to GND

    When not charging :

    SW signal is DC, voltage of the pack.

    STAT was Vref (pull up resistor)

    ----- EDIT ----------

    initially I was charging to approx 2.6A, now the charge current is approx 700mA (due to the pack being more charged) and I haven't intermittent charging....

  • 0 in reply to Hexor
    TI__Mastermind 40305 points

    Hello,

    Please explain your current question. Are you still having intermittent charging?

    Thanks,

    Mike Emanuel

  • 0 in reply to Michael Emanuel35
    Prodigy 70 points

    Yes, when charge current is between, approx 1amp and 2.6amp, charging is intermittent. Below the charging is constent.

    I hayen't yet the right value at which the charge is constent, I will make some anothers tests.

    (I do not manually change the current setting, the current decreasing because bttery is charging.)

  • 0 in reply to Hexor
    TI__Mastermind 40305 points

    Hello,

    Please describe, preferably with a waveform of the charge current, what is meant by intermittent charging? I do not understand your problem and need to see some waveforms to help diagnose. Please supply PVCC voltage, SW voltage, SRN voltage, and charge current.

    Thanks,

    Mike Emanuel 

  • 0 in reply to Michael Emanuel35
    Prodigy 70 points

    Hi,

    intermittent charging : BQxx is charging well during a few seconds, stop charging few seconds (as if it's Off), charge again etc etc.

    Current is mesured with an ampmeter during this test it was 720mA when charging and 0 amp when not charging.

    I take the two pictures when charging at 720mA, when I want to mesure the SRN voltage I see on the ampmeter was charging (without intermittent) at 880mA... I haven't change anaything...

    PVCC on the left / SW on the righ

    4 seconds charging / 2 seconds "OFF" etc etc.

    I discharge a bit the battery, and charge again.

    Charge is at 2.16A approx and intermittent.

    Voltage between SRN and PGND :

  • +1 in reply to Hexor
    Prodigy 70 points

    My bad !!  The issue is due to the BMS , not the charger ! 

    I made several measurement and think it was the charger but.... not...

  • 0 in reply to Hexor
    TI__Mastermind 40305 points

    Glad you figured out your issue!

    Thanks,

    Mike Emanuel

    Please click "Resolved" if this answered your question.