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BQ25892: Charger always in CV mode

YU-SHUN LIU
Prodigy 20 points
Part Number: BQ25892
Other Parts Discussed in Thread: EV2400

Hi there,

My name is Fenrir, I'm doing a charge test with BQ25892. 

The problem that I face is, when the battery is 3V charging current will go down from 2A, the charger can not get in CC mode. Should I disable the ICD then try again?

Input Power = 12V/3A from power supply


Battery information:
Nominal Voltage = 3.8V
Max continuous charge current = 2A
End Voltage = 2.92V
Full Voltage = 4.2V

Thermistor = TH05-3H103FR



The inductor specification, which is L15 in schematic.



Below is register table: 
REG0 = 0x7F
REG1 = 0x06                   
REG2 = 0x1D
REG3 = 0x1A
REG4 = 0x20
REG5 = 0x13
REG6 = 0x5E
REG7 = 0x9D
REG8 = 0x03
REG9 = 0x44
REGA = 0x73
REGB = 0x47
REGC = 0x85
REGD = 0x53              
REGE = 0x00               
REGF = 0x00               
REG10 = 0x00             
REG11 = 0xDF             
REG12 = 0x00             
REG13 = 0x3F
REG14 = 0x05

I don't have a EV2400, so I read I2C value from "Total Phase" then fill in the register. 

  • 0
    TI__Guru 57871 points

    Hi,

    According to the register readings, there's NTC fault. Please make correction and try again. Please refer to 9.2.7.5 Thermistor Qualification on the d/s for the details.

    Thanks,

    Ning.

  • 0 in reply to Ning T
    Prodigy 20 points

    Hi Ning, 

    Thanks for help.

    I have soldered a 7.5Kohm to replace R283, which is lower resistor in TS voltage divider, in order to keep TS pin in "normal".
    But it didn't help.

    So I check my power cable and replace cable to a good one ( resistance only 0.04ohm ) then the charging current rise up from 700mA to 960mA but still slightly goes down. The charging current still can not maintain on 2A. 

    My charger is still stuck in CV mode when battery voltage below "Charge Voltage Limit" (4.208V).


    One more question, can I change REG0B from "USB CDP" to "Adapter" by doing something?

  • 0 in reply to YU-SHUN LIU
    TI__Guru 57871 points

    Hi,

    Since Monday (9/5/22) is a federal holiday, we will get back to you on Tuesday.

    Thank you very much for your understanding,

    Ning.

  • 0 in reply to Ning T
    TI__Guru 57871 points

    Hi,

    After you change TS resistor, did you read the GUI again and confirm NTC status was normal?

    Thanks,

    Ning.

  • 0 in reply to Ning T
    Prodigy 20 points

    Hi Ning,

    Thanks for help.
    Finally, I found the root cause of issue, it was caused by digital multimeter.
    I selected the 3Amp gear for 2Amp charging current sense, unfortunately, seems the ESR of this gear is too high to let charger stock in CV mode.
    Once I change gear to 10Amp range, the issue will be gone.

    BTW, the multimeter I use is Keysight 34465A. So I didn't suspect it at beginning.

    Thank you again and if you have concern please let me know.