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BQ27520-G4: question about battery temperature sensing

TS Yang
Genius 4800 points
Part Number: BQ27520-G4

Hi,

I'm using TI's fuel guage BQ27520-G4, and have a question about temp sensing function.

The problem is that the sensing temperature is different between when charging and not charging.

Condition A : connect to TA(charger) or PC with USB cable

Condition B : disconnect above cable

At condition B, temperature is sensed about 5~15'C higher than at condition A.  

I'd like to ask TI to confirm what caused this phenomenon.

I don't think the actual temperature is going to go up momentarily.

below is my schematic.

Thanks,

TS

  • 0
    TI__Expert 3350 points

    Hi TS,

    What kind of NTC are you using?

    Regards,

    David

  • 0 in reply to David C
    Genius 4800 points
    Hi David,
    Resistance at room temperature is 10Kohm, and resistance decrease when temperature increase.
    Actually, I don't have the datasheet, but if you need then I can request to battery maker.
  • 0 in reply to David C
    Genius 4800 points

    Hi David,

    I attached PCM DATA as below.

    Battery PCBA.DOC

    Please review and confirm that BQ27520-G4 has no problem.

    Thanks,

    TS

  • 0 in reply to David C
    Genius 4800 points
    Hi David,
    I'm still waiting your response.
    Please confirm that TI's BQ27520-G4 has no problem.
  • 0 in reply to TS Yang
    TI__Expert 3350 points

    Hi TS,

     

    Could you verify with some other means that the temperature isn’t momentarily changing?

    Due to self-heating a battery can change temperature while charging.

     

    If indeed the gauge is erroneously measuring temperature momentarily, try changing the polarity of the ground by selecting the GNDSEL if clear or clearing it if set. In your Schematic, the ground is on the other side of the sense so when current flows it will cause an IR drop across the sense resistor.

    Regardless, the temperature increasing momentarily during charging doesn’t affect gauging performance. Accuracy during charging isn’t as much of a concern as accuracy during discharge

     

    -David

     

  • 0 in reply to David C
    Genius 4800 points

    Hi David,

    thanks for your answer.

    I already tested with changing GNDSEL before write the first thread on E2E.

    And I did not find any difference between GNDSEL clear and set.

    Now I'm in trouble how to conclude..

    Can you check the history that if there's any simular issue for using TI's guage ic from now on?

    If yes, how did TI analysis and solve the problem?

    I cannot find anything at E2E anyway.

    thanks,

    TS

  • 0 in reply to TS Yang
    TI__Guru* 76230 points
    TS
    when you changed the gndsel bit, did you send the reset command so it gets updated in RAM and becomes effective? If you didn't pls try that again.


    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Genius 4800 points
    Hi Onyx,
    thanks for review my problem.
    Yes, I did reset and reboot before check.
    I also confirmed that the setting value was changed.

    Was there any simular problem for using TI's guage device even if beseides BQ27250-G4?

    Thanks,
    TS
  • 0 in reply to TS Yang
    Genius 4800 points
    Hi

    anyone can answer my above question about simular issue history?
    If TI's all guage device have no issue until now, please say no.

    thanks,
    TS