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BQ27542-G1: SOC not changing during first 80% of charge

Dan Bandyk
Prodigy 50 points
Part Number: BQ27542-G1
Other Parts Discussed in Thread: BQSTUDIO, GPCRB

I am doing accuracy testing of my golden image per SLUA684.  I get very weird behavior while doing the dynamic load test.  After doing the dynamic discharge and letting the unit sit idle for 45 minutes, I begin charging at C/2.  Using the Q_integrated calculation, the SOC gets over 80% before the reported SOC changes from 1% (where it was when charging started).  What would cause this?

I have attached the BQ27542-G1 logs from BQStudio for both the Registers and Data Memory, as well as logs of the power supply/constant current load used.  I am using the production board, that was used to create the golden image.  I am using ChemID 210 as provided by the battery supplier and is a valid selection according to the Chemistry ID selection tool results.

/cfs-file/__key/communityserver-discussions-components-files/196/7838.GPC_5F00_report.txt

/cfs-file/__key/communityserver-discussions-components-files/196/Fuel-Gauge-Accuracy.zip

  • 0
    TI__Guru* 76230 points
    Hi Dan
    The pulsed load caused the gauge to calculate a very high resistance scale due to the fast scaling functionality of the gauge. I would recommend disabling fast scaling by clearing the fconven flag in packconfiguration B register and repeat your test. This function doesn't go well with pulsed loads.

    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Prodigy 50 points

    I have made this change, and it was accurate for the Dynamic Loading Test.  But now at low temperature I have an issue.  I took the unit and battery to 0C, charge to cut-off current, then drop the temp to -10C. I then let it sit for an hour and the logs from BQStudio show the Capacity/SOC going to 0.  Here is the change between 2 readings at 5 second intervals.  Also the internal status register isn't defined in the Techincal Reference Manual, can you tell me the definition of it?

    Register Reading 1 Reading 2
    Sample 11085 11086
    DateTime 2/14/2019 2:48:06 AM 2/14/2019 2:48:11 AM
    ElapsedTime 55429.89 55435.531
    Control 0x0201 0x0201
    CtrlStatus 0x009B 0x009B
    SOCUnfiltered 100 0
    Temperature -11.4 -11.4
    Voltage 4061 4061
    Flags 0x0AB4 0x08B6
    NomAvailCap 4472 4472
    FullAvailCap 4472 4472
    RemCap 2921 1
    FullChgCap 2921 0
    AvgCurrent 0 0
    TimeToEmpty 65535 65535
    FCCFiltered 2921 0
    SafetyStat 0x0 0x0
    FCCUnfiltered 2921 0
    MaxLoadCurrent 674 674
    RCUnfiltered 2921 0
    RCFiltered 2921 0
    BTPSOC1Set 150 150
    BTPSOC1Clear 175 175
    IntTemp -11.1 -11.1
    CycleCnt 9 9
    StateofCharge 100 0
    StateofHealth 97 97
    ChargeVoltage 0 0
    ChargeCurrent 0 0
    Passed Charge -6 0
    DOD0 1464 1446
    SelfDischargeCurrent -74 -74
    PackConfig 0x297F 0x297F
    DoDatEOC 2672 2672
    Qstart 65133 65127
    Fast Qmax 5473 5473
    Qmax 5460 5460
    OCV Current 0 0
    OCV Voltage 4061 4061
    Int Stat 0x220 0x2240
    ResScale 0 0
    DodFinal 11407 2672
  • 0 in reply to Dan Bandyk
    TI__Guru* 76230 points
    hi Dan,

    Dropping the temperature to -11 causes the gauge to think the battery is overdischarged. Did you optimize the gauge for low temperature performance? ie did you perform an Rbtweak using our online tool gpcrb at -11 degC. If no, pls do so and that will hopefully provide improved results at low temperature.

    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Prodigy 50 points

    This tool won't accept my learned gg.csv file, does that mean I need to do a new learning cycle once I get the results back?

  • 0 in reply to Dan Bandyk
    TI__Guru* 76230 points
    you have to use the chem id default values when submitting to the tool. Once you get the results back, you program the chem.dat file, then program the gg file or at least the Trise and Ttime contant values and then you perform a learning cycle so the gauge updates the Ra tables calculated using the new Rb values which the tool returned. note that you do not have access to the Rb tables. They are contained in the chemdat file.
    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Prodigy 160 points

    hi i m using 3.7v 5200 mah battery and bq27542 fuel guage. in this taper current and taper voltage is 100 mv and 100 mah for 1000mah battery.  as we seen in the bq27411trm we used the formula for the taper voltage  we are getting for my battery is 520mah.but the default vales are 100 mah.can we use the 520mah for taper voltage for we should keep 100mah....??????please check the following attachments

  • 0 in reply to ramnagesh kattika
    TI__Guru* 76230 points
    Hi
    pls for next time start a new post and do not post a follow up to an already existing post from a differnt user. you could post a link reference the other post in your own post..

    For a 5200mAh battery, a good taper current should be bw c/10 and C/20. Quit current should be set to c/20 or less. Keep the taper voltage as the default value.

    thanks
    Onyx