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BQ20Z80: RSOC jump after charging

Part Number: BQ20Z80
Other Parts Discussed in Thread: GPCCHEM

Hi E2E Members

We have a battery on which we perform maintenance before shipping to manually initialize the impedance track (charging and discharging with appropriate relaxation and waiting times, see graphic). To comply with international transportation regulations, we only charge the Li-ion battery up to 30% RSOC.
We have now found that jumps in the RSOC occur during the relaxation phase at the end of the cycle (yellow marked in graphic). We would like to know why these jumps occur. The charging current is switched off and the temperature dropped by approx. 5°C some time ago. Why does it happen after some time? And it doesn't happen with all batteries. Is it due to the adjustment of the FCC algorithm? 
I hope you can help us determine the root cause.

  • Hello Van,

    Please review our Impedance Track FAQ which has some guides with the information we need in order to help with debug.

    https://e2e.ti.com/support/power-management-group/power-management/f/power-management-forum/1100653/faq-impedance-track-faqs

    FCC is constantly recalculated depending on the load condition and temperature.

    What chem ID is being used now and how was it selected?

    Sincerely,

    Wyatt Keller

  • Hello Wyatt,

    Our chem ID is ID203. It's a Panasonic cell CGR18650CG. Selection was done over the chemistry selection of bqEasy.

    attached you will also find the gg file.

    I wonder why the jump happens in the middle of the rest period which lasts 2-3 hours. There is no load change and the temperature should be in a stable state.

  • goldenFile.txt
    [Header]
    bq EVSW Version = 0.9.79	
    DeviceName = bq20z80 v1.10
    
    
    
    [Voltage(1st Level Safety)]
    COV Threshold = 4300
    COV Time = 2
    COV Recovery = 3900
    COV Delta = 20
    COV Temp. Hys = 100
    POV Threshold = 17200
    POV Time = 2
    POV Recovery = 16000
    CUV Threshold = 2400
    CUV Time = 2
    CUV Recovery = 3000
    PUV Threshold = 11000
    PUV Time = 2
    PUV Recovery = 12400
    [Current(1st Level Safety)]
    OC (1st Tier) Chg = 4000
    OC (1st Tier) Chg Time = 5
    OC Chg Recovery = 200
    OC (1st Tier) Dsg = 9000
    OC (1st Tier) Dsg Time = 10
    OC Dsg Recovery = 200
    OC (2nd Tier) Chg = 4500
    OC (2nd Tier) Chg Time = 2
    OC (2nd Tier) Dsg = 9500
    OC (2nd Tier) Dsg Time = 2
    Current Recovery Time = 8
    AFE OC Dsg = 0A
    AFE OC Dsg Time = 0F
    AFE OC Dsg Recovery = 100
    AFE SC Chg Cfg = 56
    AFE SC Dsg Cfg = 56
    AFE SC Recovery = 1
    [Temperature(1st Level Safety)]
    Over Temp Chg = 500
    OT Chg Time = 2
    OT Chg Recovery = 450
    Over Temp Dsg = 600
    OT Dsg Time = 2
    OT Dsg Recovery = 550
    [Host Comm(1st Level Safety)]
    Host Watchdog Timeout = 0
    
    [Voltage(2nd Level Safety)]
    SOV Threshold = 18000
    SOV Time = 5
    Cell Imbalance Current = 5
    Cell Imbalance Fail Voltage = 500
    Cell Imbalance Time = 30
    Battery Rest Time = 1800
    PFIN Detect Time = 5
    [Current(2nd Level Safety)]
    SOC Chg = 11000
    SOC Chg Time = 5
    SOC Dsg = 11000
    SOC Dsg Time = 5
    [Temperature(2nd Level Safety)]
    SOT Chg = 600
    SOT Chg Time = 5
    SOT Dsg = 750
    SOT Dsg Time = 5
    Open Thermistor = -333
    Open Time = 5
    [FET Verification(2nd Level Safety)]
    FET Fail Limit = 20
    FET Fail Time = 5
    [AFE Verification(2nd Level Safety)]
    AFE Check Time = 0
    AFE Fail Limit = 10
    AFE Fail Recovery Time = 20
    AFE Init Retry Limit = 6
    AFE Init Limit = 20
    [Fuse Verification(2nd Level Safety)]
    Fuse Fail Limit = 2
    Fuse Fail Time = 0
    
    [Charge Inhibit Cfg(Charge Control)]
    Chg Inhibit Temp Low = 0
    Chg Inhibit Temp High = 500
    Temp Hys = 10
    [Pre-Charge Cfg(Charge Control)]
    Pre-chg Current = 550
    Pre-chg Temp = 120
    Pre-chg Voltage = 3000
    Recovery Voltage = 3100
    [Fast Charge Cfg(Charge Control)]
    Fast Charge Current = 3000
    Charging Voltage = 16800
    Delta Temp = 25
    Suspend Low Temp = -50
    Suspend High Temp = 500
    [Pulse Charge Cfg(Charge Control)]
    Turn ON Voltage = 4150
    Turn OFF Voltage = 4250
    Max ON Pulse Time = 240
    Min OFF Pulse Time = 40
    Max OFF Voltage = 4270
    [Termination Cfg.(Charge Control)]
    Maintenance Current = 0
    Taper Current = 550
    Termination Voltage = 300
    Current Taper Window = 40
    TCA Set % = -1
    TCA Clear % = 95
    FC Set % = -1
    FC Clear % = 98
    [Cell Balancing Cfg(Charge Control)]
    Min Cell Deviation = 1750
    [Charging Faults(Charge Control)]
    Over Charging Voltage = 500
    Over Charging Volt Time = 2
    Over Charging Current = 500
    Over Charging Curr Time = 2
    Over Charging Curr Recov = 100
    Depleted Voltage = 10000
    Depleted Voltage Time = 2
    Depleted Recovery = 10500
    Over Charge Capacity = 1000
    Over Charge Recovery = 2
    FC-MTO = 21600
    PC-MTO = 3600
    Charge Fault Cfg = 3F
    
    [Data(SBS Configuration)]
    Rem Cap Alarm = 700
    Rem Energy Alarm = 10000
    Rem Time Alarm = 10
    Init Battery Mode = 8081
    Design Voltage = 14400
    Spec Info = 0031
    Manuf Date = 03-Jul-2013
    Ser. Num. = 1
    Cycle Count = 0
    CC Threshold = 2812
    CC % = 25
    CF MaxError Limit = 4
    Design Capacity = 11250
    Design Energy = 16200
    Manuf Name = Thoratec
    Device Name = bq20z80
    Device Chemistry = LION
    [Configuration(SBS Configuration)]
    TDA Set % = 6
    TDA Clear % = 8
    FD Set % = -1
    FD Clear % = 5
    TDA Set Volt Threshold = 13200
    TDA Set Volt Time = 5
    TDA Clear Volt = 13400
    FD Set Volt Threshold = 12000
    FD Volt Time = 1
    FD Clear Volt = 12400
    
    [Manufacturer Data(System Data)]
    Pack Lot Code = 0000
    PCB Lot Code = 0000
    Firmware Version = 000B
    Hardware Revision = 0000
    Cell Revision = 0000
    [Manufacturer Info(System Data)]
    Manuf. Info = 12345678
    [Lifetime Data(System Data)]
    Lifetime Max Temp = 250
    Lifetime Min Temp = 250
    Lifetime Max Cell Voltage = 4000
    Lifetime Min Cell Voltage = 4000
    Lifetime Max Pack Voltage = 16000
    Lifetime Min Pack Voltage = 15000
    Lifetime Max Chg Current = 2000
    Lifetime Max Dsg Current = -2000
    Lifetime Max Chg Power = 4966
    Lifetime Max Dsg Power = -3595
    Life Max AvgDsg Cur = -1000
    Life Max AvgDsg Pow = -3569
    Lifetime Avg Temp = 250
    [Lifetime Temp Samples(System Data)]
    LT Temp Samples = 5404
    
    [Registers(Configuration)]
    Operation Cfg A = 0F39
    Operation Cfg B = 6540
    Operation Cfg C = 0000
    Permanent Fail Cfg = 5DFF
    Non-Removable Cfg = 0000
    
    [LED Cfg(LED Support)]
    LED Flash Rate = 512
    LED Blink Rate = 1024
    LED Delay = 100
    LED Hold Time = 4
    CHG Flash Alarm = 10
    CHG Thresh 1 = 0
    CHG Thresh 2 = 20
    CHG Thresh 3 = 40
    CHG Thresh 4 = 60
    CHG Thresh 5 = 80
    DSG Flash Alarm = 10
    DSG Thresh 1 = 0
    DSG Thresh 2 = 20
    DSG Thresh 3 = 40
    DSG Thresh 4 = 60
    DSG Thresh 5 = 80
    
    [Power(Power)]
    Flash Update OK Voltage = 9500
    Shutdown Voltage = 9000
    Shutdown Time = 10
    Charger Present = 16000
    Sleep Current = 10
    Bus Low Time = 5
    Cal Inhibit Temp Low = 50
    Cal Inhibit Temp High = 450
    Sleep Voltage Time = 5
    Sleep Current Time = 20
    
    [IT Cfg(Gas Gauging)]
    Load Select = 3
    Load Mode = 1
    Term Voltage = 12000
    User Rate-mA = 0
    User Rate-mW = 0
    Reserve Cap-mAh = 0
    Reserve Cap-mWh = 0
    [Current Thresholds(Gas Gauging)]
    Dsg Current Threshold = 100
    Chg Current Threshold = 50
    Quit Current = 10
    Dsg Relax Time = 1
    Chg Relax Time = 60
    [State(Gas Gauging)]
    Qmax Cell 0 = 11450
    Qmax Cell 1 = 11468
    Qmax Cell 2 = 11446
    Qmax Cell 3 = 11416
    Qmax Pack = 11416
    Update Status = 02
    Avg I Last Run = -2039
    Avg P Last Run = -2991
    Delta Voltage = 12
    
    [R_a0(Ra Table)]
    Cell0 R_a flag = 0055
    Cell0 R_a 0 = 40
    Cell0 R_a 1 = 46
    Cell0 R_a 2 = 55
    Cell0 R_a 3 = 67
    Cell0 R_a 4 = 60
    Cell0 R_a 5 = 42
    Cell0 R_a 6 = 51
    Cell0 R_a 7 = 70
    Cell0 R_a 8 = 62
    Cell0 R_a 9 = 72
    Cell0 R_a 10 = 91
    Cell0 R_a 11 = 201
    Cell0 R_a 12 = 676
    Cell0 R_a 13 = 1207
    Cell0 R_a 14 = 2499
    [R_a1(Ra Table)]
    Cell1 R_a flag = 0055
    Cell1 R_a 0 = 33
    Cell1 R_a 1 = 37
    Cell1 R_a 2 = 46
    Cell1 R_a 3 = 55
    Cell1 R_a 4 = 51
    Cell1 R_a 5 = 34
    Cell1 R_a 6 = 42
    Cell1 R_a 7 = 59
    Cell1 R_a 8 = 49
    Cell1 R_a 9 = 58
    Cell1 R_a 10 = 76
    Cell1 R_a 11 = 159
    Cell1 R_a 12 = 566
    Cell1 R_a 13 = 1052
    Cell1 R_a 14 = 2176
    [R_a2(Ra Table)]
    Cell2 R_a flag = 0055
    Cell2 R_a 0 = 34
    Cell2 R_a 1 = 38
    Cell2 R_a 2 = 46
    Cell2 R_a 3 = 55
    Cell2 R_a 4 = 53
    Cell2 R_a 5 = 32
    Cell2 R_a 6 = 40
    Cell2 R_a 7 = 59
    Cell2 R_a 8 = 51
    Cell2 R_a 9 = 60
    Cell2 R_a 10 = 76
    Cell2 R_a 11 = 159
    Cell2 R_a 12 = 566
    Cell2 R_a 13 = 1069
    Cell2 R_a 14 = 2204
    [R_a3(Ra Table)]
    Cell3 R_a flag = 0055
    Cell3 R_a 0 = 40
    Cell3 R_a 1 = 45
    Cell3 R_a 2 = 53
    Cell3 R_a 3 = 63
    Cell3 R_a 4 = 57
    Cell3 R_a 5 = 41
    Cell3 R_a 6 = 49
    Cell3 R_a 7 = 68
    Cell3 R_a 8 = 60
    Cell3 R_a 9 = 72
    Cell3 R_a 10 = 88
    Cell3 R_a 11 = 194
    Cell3 R_a 12 = 640
    Cell3 R_a 13 = 1138
    Cell3 R_a 14 = 2352
    [R_a0x(Ra Table)]
    xCell0 R_a flag = 0000
    xCell0 R_a 0 = 40
    xCell0 R_a 1 = 46
    xCell0 R_a 2 = 55
    xCell0 R_a 3 = 67
    xCell0 R_a 4 = 60
    xCell0 R_a 5 = 42
    xCell0 R_a 6 = 51
    xCell0 R_a 7 = 70
    xCell0 R_a 8 = 62
    xCell0 R_a 9 = 72
    xCell0 R_a 10 = 91
    xCell0 R_a 11 = 201
    xCell0 R_a 12 = 676
    xCell0 R_a 13 = 1176
    xCell0 R_a 14 = 2435
    [R_a1x(Ra Table)]
    xCell1 R_a flag = 0000
    xCell1 R_a 0 = 33
    xCell1 R_a 1 = 37
    xCell1 R_a 2 = 46
    xCell1 R_a 3 = 55
    xCell1 R_a 4 = 51
    xCell1 R_a 5 = 34
    xCell1 R_a 6 = 42
    xCell1 R_a 7 = 59
    xCell1 R_a 8 = 49
    xCell1 R_a 9 = 58
    xCell1 R_a 10 = 76
    xCell1 R_a 11 = 159
    xCell1 R_a 12 = 566
    xCell1 R_a 13 = 1040
    xCell1 R_a 14 = 2151
    [R_a2x(Ra Table)]
    xCell2 R_a flag = 0000
    xCell2 R_a 0 = 34
    xCell2 R_a 1 = 38
    xCell2 R_a 2 = 46
    xCell2 R_a 3 = 55
    xCell2 R_a 4 = 53
    xCell2 R_a 5 = 32
    xCell2 R_a 6 = 40
    xCell2 R_a 7 = 59
    xCell2 R_a 8 = 51
    xCell2 R_a 9 = 60
    xCell2 R_a 10 = 76
    xCell2 R_a 11 = 159
    xCell2 R_a 12 = 566
    xCell2 R_a 13 = 989
    xCell2 R_a 14 = 2039
    [R_a3x(Ra Table)]
    xCell3 R_a flag = 0000
    xCell3 R_a 0 = 40
    xCell3 R_a 1 = 45
    xCell3 R_a 2 = 53
    xCell3 R_a 3 = 63
    xCell3 R_a 4 = 57
    xCell3 R_a 5 = 41
    xCell3 R_a 6 = 49
    xCell3 R_a 7 = 68
    xCell3 R_a 8 = 60
    xCell3 R_a 9 = 72
    xCell3 R_a 10 = 88
    xCell3 R_a 11 = 194
    xCell3 R_a 12 = 640
    xCell3 R_a 13 = 1073
    xCell3 R_a 14 = 2218
    
    [Device Status Data(PF Status)]
    PF Flags 1 = 0000
    Fuse Flag = 0000
    PF Voltage = 0
    PF C4 Voltage = 0
    PF C3 Voltage = 0
    PF C2 Voltage = 0
    PF C1 Voltage = 0
    PF Current = 0
    PF Temperature = 0
    PF Batt Stat = 0000
    PF RC-mAh = 0
    PF RC-10mWh = 0
    PF Chg Status = 0000
    PF Safety Status = 0000
    PF Flags 2 = 0000
    [AFE Regs(PF Status)]
    AFE Status = 00
    AFE Output = 00
    AFE State = 00
    AFE Function = 00
    AFE Cell Select = 00
    AFE OLV = 00
    AFE OLT = 00
    AFE SCC = 00
    AFE SCD = 00
    
    [Data(Calibration)]
    CC Gain = 0.9048
    CC Delta = 269878.125
    Ref Voltage = 2452.2
    AFE Corr = 1288
    AFE Pack Gain = 30625
    CC Offset = -11831
    Board Offset = 0
    Int Temp Offset = 0
    Ext1 Temp Offset = -7
    Ext2 Temp Offset = -15
    [Config(Calibration)]
    CC Current = 3000
    Voltage Signal = 16800
    Temp Signal = 298.0
    CC Offset Time = 250
    ADC Offset Time = 32
    CC Gain Time = 1000
    Voltage Time = 1984
    Temperature Time = 32
    Cal Mode Timeout = 38400
    [Temp Model(Calibration)]
    Ext Coef 1 = -28285
    Ext Coef 2 = 20848
    Ext Coef 3 = -7537
    Ext Coef 4 = 4012
    Ext Min AD = 0
    Ext Max Temp = 4012
    Int Coef 1 = 0
    Int Coef 2 = 0
    Int Coef 3 = -11136
    Int Coef 4 = 5754
    Int Min AD = 0
    Int Max Temp = 5754
    [Current(Calibration)]
    Filter = 239
    Deadband = 3
    CC Deadband = 102
    CC Max Deadband = 5
    CC Deadband Sample = 256
    CC Max Offset Sample = 64
    

  • Hello Van,

    The gauge will take an OCV reading while in relax and cause the FCC to be recalculated. That's why a proper matched chem ID is very important, either selected through GPCCHEM or an exact match of the battery model.

    Sincerely,

    Wyatt Keller

  • Hi Wyatt
    The ChemID is definitely chosen correctly because it matches our cell exactly (see screenshot). This error is therefore excluded.
    Do you have any idea why these two RSOC jumps were triggered (at 75% to about 78% and at 30% to about 35%, both during relaxation)?

  • Hello Van,

    It can be related to calibration or Qmax as well, if the gauge is expecting less total charge the coulomb count while in active mode will be skewed in one direction. After a relaxation the voltage will correct any errors in the coulomb count itself.

    Sometimes with older cells the manufacturing process changes at some point which can also impact the OCV curve from when the cell was characterized.

    Sincerely,

    Wyatt Keller