Part Number: BQ20Z95
We are using the BQ20z95 in a 3s3p configuration. The cell used for this pack is the LGABB41865 using CHEM ID 0230. The design uses the internal balance fets with 100Ohm series impedance (sames are reference design) and we are using the default of 1750 s/mAHr for the Min Cell Deviation. We have been seeing packs returned due to large cell imbalances of more then 300mV. The packs cell stacks are all within 5mV of one another when the leave the factory and they are all at ~30% SOC. We are most likely to see the problem when the pack is charged to termination and then sit for several months. I have looked at the hardware for parasitic loading and in one case did see an issue but so far all the other boards have not shown a problem. I also have measured the impedance and cycled each of the individual cells and found them to be within 10mA_Hrs so it doesn't appear to be a cell issue. In two of the returned packs I charged the unbalanced cell stack to match the OCV's of the other two and then ran a charge and discharge cycle and so far the cell OCV's are within 2mV of each other.
I attached an GG file. Can you suggest some other areas to look at for root cause?
[Header] bq EVSW Version = 0.9.59 DeviceName = bq20z95 v1.50 Time = 5/17/2020 11:12:11 AM [Voltage(1st Level Safety)] COV Threshold = 4300 COV Time = 2 COV Recovery = 4000 COV Delta = 20 COV Temp. Hys = 10.0 POV Threshold = 12900 POV Time = 2 POV Recovery = 12000 CUV Threshold = 2500 CUV Time = 2 CUV Recovery = 3000 PUV Threshold = 7500 PUV Time = 2 PUV Recovery = 9000 [Current(1st Level Safety)] OC (1st Tier) Chg = 7600 OC (1st Tier) Chg Time = 5 OC Chg Recovery = 200 OC (1st Tier) Dsg = 10000 OC (1st Tier) Dsg Time = 20 OC Dsg Recovery = 200 OC (2nd Tier) Chg = 8000 OC (2nd Tier) Chg Time = 2 OC (2nd Tier) Dsg = 12000 OC (2nd Tier) Dsg Time = 2 Current Recovery Time = 8 AFE OC Dsg = 1A AFE OC Dsg Time = 0F AFE OC Dsg Recovery = 5 AFE SC Chg Cfg = 84 AFE SC Dsg Cfg = 98 AFE SC Recovery = 1 [Temperature(1st Level Safety)] Over Temp Chg = 47.0 OT Chg Time = 2 OT Chg Recovery = 45.0 Over Temp Dsg = 70.0 OT Dsg Time = 2 OT Dsg Recovery = 55.0 [Host Comm(1st Level Safety)] Host Watchdog Timeout = 0 [Voltage(2nd Level Safety)] SOV Threshold = 13500 SOV Time = 5 Cell Imbalance Current = 5 Cell Imbalance Fail Voltage = 1000 Cell Imbalance Time = 5 Battery Rest Time = 1800 Min CIM-check voltage = 3000 PFIN Detect Time = 5 [Current(2nd Level Safety)] SOC Chg = 10000 SOC Chg Time = 3 SOC Dsg = 15000 SOC Dsg Time = 3 [Temperature(2nd Level Safety)] SOT Chg = 65.0 SOT Chg Time = 5 SOT Dsg = 85.0 SOT Dsg Time = 5 Open Thermistor = -45.0 Open Time = 5 [FET Verification(2nd Level Safety)] FET Fail Limit = 40 FET Fail Time = 10 [AFE Verification(2nd Level Safety)] AFE Check Time = 0 AFE Fail Limit = 0 AFE Fail Recovery Time = 20 AFE Init Retry Limit = 10 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 = 0.0 Chg Inhibit Temp High = 45.0 Temp Hys = 1.0 [Pre-Charge Cfg(Charge Control)] Pre-chg Current = 750 Pre-chg Temp = 12.0 Pre-chg Voltage = 2750 Recovery Voltage = 3000 [Fast Charge Cfg(Charge Control)] Fast Charge Current = 5000 Charging Voltage = 12600 Delta Temp = 3.0 Suspend Low Temp = 0.0 Suspend High Temp = 45.0 [Pulse Charge Cfg(Charge Control)] Turn ON Voltage = 5000 Turn OFF Voltage = 5000 Max ON Pulse Time = 60.00 Min OFF Pulse Time = 0.00 Max OFF Voltage = 5000 [Termination Cfg.(Charge Control)] Maintenance Current = 0 Taper Current = 200 Taper Voltage = 350 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 = 6600 Depleted Voltage Time = 2 Depleted Recovery = 7500 Over Charge Capacity = 1000 Over Charge Recovery = 2 FC-MTO = 36000 PC-MTO = 3600 Charge Fault Cfg = 00 [Data(SBS Configuration)] Rem Cap Alarm = 390 Rem Energy Alarm = 4210 Rem Time Alarm = 10 Init Battery Mode = 0081 Design Voltage = 10800 Spec Info = 0031 Manuf Date = 13-Apr-2020 Ser. Num. = 9A80 Cycle Count = 3 CC Threshold = 7020 CC % = 90 CF MaxError Limit = 100 Design Capacity = 7800 Design Energy = 84240 Manuf Name = B03B03 Device Name = SM204Z Device Chemistry = LION [Configuration(SBS Configuration)] TDA Set % = 6 TDA Clear % = 8 FD Set % = 2 FD Clear % = 5 TDA Set Volt Threshold = 5000 TDA Set Volt Time = 5 TDA Clear Volt = 5500 FD Set Volt Threshold = 5000 FD Volt Time = 5 FD Clear Volt = 5500 [Manufacturer Data(System Data)] Pack Lot Code = 0000 PCB Lot Code = 0000 Firmware Version = 0041 Hardware Revision = 0000 Cell Revision = 0000 [Manufacturer Info(System Data)] Manuf. Info = SM204Z [Lifetime Data(System Data)] Lifetime Max Temp = 31.8 Lifetime Min Temp = 13.8 Lifetime Max Cell Voltage = 4305 Lifetime Min Cell Voltage = 2492 Lifetime Max Pack Voltage = 12731 Lifetime Min Pack Voltage = 9143 Lifetime Max Chg Current = 4001 Lifetime Max Dsg Current = -4011 Lifetime Max Chg Power = 49910 Lifetime Max Dsg Power = -48580 Life Max AvgDsg Cur = -4004 Life Max AvgDsg Pow = -11400 Lifetime Avg Temp = 17.4 [Lifetime Temp Samples(System Data)] LT Temp Samples = 55314 [Registers(Configuration)] Operation Cfg A = 0A29 Operation Cfg B = 6D49 Operation Cfg C = 0004 Permanent Fail Cfg = 10EE Non-Removable Cfg = 0000 [AFE(Configuration)] AFE.State_CTL = 00 [LED Cfg(LED Support)] LED Flash Rate = 2.000 LED Blink Rate = 1.000 LED Delay = 48.8 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 Sink Current = 3 [Power(Power)] Flash Update OK Voltage = 7500 Shutdown Voltage = 7300 Shutdown Time = 3 Cell Shutdown Voltage = 2400 Cell Shutdown Time = 10 Charger Present = 5000 Sleep Current = 10 Bus Low Time = 5 Cal Inhibit Temp Low = 5.0 Cal Inhibit Temp High = 45.0 Sleep Voltage Time = 5 Sleep Current Time = 20 Wake Current Reg = 00 [IT Cfg(Gas Gauging)] Load Select = 1 Load Mode = 1 Term Voltage = 9000 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 = 8067 Qmax Cell 1 = 8077 Qmax Cell 2 = 8072 Qmax Cell 3 = 7800 Qmax Pack = 8067 Update Status = 06 Avg I Last Run = -2744 Avg P Last Run = -2968 Delta Voltage = 34 [R_a0(Ra Table)] Cell0 R_a flag = 0000 Cell0 R_a 0 = 62 Cell0 R_a 1 = 74 Cell0 R_a 2 = 82 Cell0 R_a 3 = 91 Cell0 R_a 4 = 101 Cell0 R_a 5 = 83 Cell0 R_a 6 = 93 Cell0 R_a 7 = 169 Cell0 R_a 8 = 157 Cell0 R_a 9 = 214 Cell0 R_a 10 = 212 Cell0 R_a 11 = 427 Cell0 R_a 12 = 1475 Cell0 R_a 13 = 6041 Cell0 R_a 14 = 11542 [R_a1(Ra Table)] Cell1 R_a flag = 0000 Cell1 R_a 0 = 57 Cell1 R_a 1 = 67 Cell1 R_a 2 = 76 Cell1 R_a 3 = 85 Cell1 R_a 4 = 94 Cell1 R_a 5 = 76 Cell1 R_a 6 = 86 Cell1 R_a 7 = 157 Cell1 R_a 8 = 148 Cell1 R_a 9 = 201 Cell1 R_a 10 = 200 Cell1 R_a 11 = 404 Cell1 R_a 12 = 1362 Cell1 R_a 13 = 5573 Cell1 R_a 14 = 10645 [R_a2(Ra Table)] Cell2 R_a flag = 0055 Cell2 R_a 0 = 51 Cell2 R_a 1 = 62 Cell2 R_a 2 = 69 Cell2 R_a 3 = 77 Cell2 R_a 4 = 87 Cell2 R_a 5 = 72 Cell2 R_a 6 = 80 Cell2 R_a 7 = 106 Cell2 R_a 8 = 107 Cell2 R_a 9 = 215 Cell2 R_a 10 = 186 Cell2 R_a 11 = 333 Cell2 R_a 12 = 958 Cell2 R_a 13 = 2917 Cell2 R_a 14 = 9136 [R_a3(Ra Table)] Cell3 R_a flag = FF55 Cell3 R_a 0 = 94 Cell3 R_a 1 = 111 Cell3 R_a 2 = 137 Cell3 R_a 3 = 167 Cell3 R_a 4 = 242 Cell3 R_a 5 = 132 Cell3 R_a 6 = 158 Cell3 R_a 7 = 196 Cell3 R_a 8 = 173 Cell3 R_a 9 = 209 Cell3 R_a 10 = 301 Cell3 R_a 11 = 756 Cell3 R_a 12 = 2387 Cell3 R_a 13 = 4517 Cell3 R_a 14 = 8624 [R_a0x(Ra Table)] xCell0 R_a flag = 0055 xCell0 R_a 0 = 62 xCell0 R_a 1 = 74 xCell0 R_a 2 = 82 xCell0 R_a 3 = 91 xCell0 R_a 4 = 101 xCell0 R_a 5 = 83 xCell0 R_a 6 = 93 xCell0 R_a 7 = 169 xCell0 R_a 8 = 157 xCell0 R_a 9 = 214 xCell0 R_a 10 = 212 xCell0 R_a 11 = 376 xCell0 R_a 12 = 1299 xCell0 R_a 13 = 5319 xCell0 R_a 14 = 10163 [R_a1x(Ra Table)] xCell1 R_a flag = 0055 xCell1 R_a 0 = 57 xCell1 R_a 1 = 67 xCell1 R_a 2 = 76 xCell1 R_a 3 = 85 xCell1 R_a 4 = 94 xCell1 R_a 5 = 76 xCell1 R_a 6 = 86 xCell1 R_a 7 = 157 xCell1 R_a 8 = 148 xCell1 R_a 9 = 201 xCell1 R_a 10 = 200 xCell1 R_a 11 = 343 xCell1 R_a 12 = 1156 xCell1 R_a 13 = 4732 xCell1 R_a 14 = 9038 [R_a2x(Ra Table)] xCell2 R_a flag = 0000 xCell2 R_a 0 = 51 xCell2 R_a 1 = 62 xCell2 R_a 2 = 69 xCell2 R_a 3 = 77 xCell2 R_a 4 = 87 xCell2 R_a 5 = 72 xCell2 R_a 6 = 80 xCell2 R_a 7 = 106 xCell2 R_a 8 = 107 xCell2 R_a 9 = 215 xCell2 R_a 10 = 186 xCell2 R_a 11 = 333 xCell2 R_a 12 = 958 xCell2 R_a 13 = 2917 xCell2 R_a 14 = 5573 [R_a3x(Ra Table)] xCell3 R_a flag = FFFF xCell3 R_a 0 = 94 xCell3 R_a 1 = 111 xCell3 R_a 2 = 137 xCell3 R_a 3 = 167 xCell3 R_a 4 = 242 xCell3 R_a 5 = 132 xCell3 R_a 6 = 158 xCell3 R_a 7 = 196 xCell3 R_a 8 = 173 xCell3 R_a 9 = 209 xCell3 R_a 10 = 301 xCell3 R_a 11 = 756 xCell3 R_a 12 = 2387 xCell3 R_a 13 = 4517 xCell3 R_a 14 = 8624 [Device Status Data(PF Status)] PF Flags 1 = 0000 Fuse Flag = 00 PF Voltage = 0 PF C4 Voltage = 0 PF C3 Voltage = 0 PF C2 Voltage = 0 PF C1 Voltage = 0 PF Current = 0 PF Temperature = 0.0 PF Batt Stat = 00 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 = 10.424 CC Delta = 10.424 Ref Voltage = 1223.60 AFE Pack Gain = 682.50 CC Offset = -0.279 Board Offset = -31.3 Int Temp Offset = 5.4 Ext1 Temp Offset = -2.3 Ext2 Temp Offset = 0.0 [Config(Calibration)] CC Current = 3000 Voltage Signal = 11355 Temp Signal = 298.0 CC Offset Time = 250 ADC Offset Time = 32 CC Gain Time = 250 Voltage Time = 1984 Temperature Time = 32 Cal Mode Timeout = 300 [Temp Model(Calibration)] Ext Coef 1 = -28285 Ext Coef 2 = 20848 Ext Coef 3 = -7537 Ext Coef 4 = 401.2 Ext Min AD = 0 Ext Max Temp = 401.2 Int Coef 1 = 0 Int Coef 2 = 0 Int Coef 3 = -11136 Int Coef 4 = 575.4 Int Min AD = 0 Int Max Temp = 575.4 [Current(Calibration)] Filter = 239 Deadband = 3 CC Deadband = 10.0
Thanks
Brian
