BQ40Z50-R2: BQ40Z50-R2 wrong capacity measured with calibrated gauge

Part Number: BQ40Z50-R2
Other Parts Discussed in Thread: BQ40Z50

Tool/software:

Dear TI Team,

im using a 4s2p battery pack with the BQ40Z50 R2 with the R5 FW.
The Chemistry was provided by the Pack manufacturer:  2851  cell is Panasonic NCA653864SA 2400mAh

I've applied the ChemID, it was programmed successfully.
I properly calibrated the gauge (current, voltages, temperatures), there is no leak current.
I can connect and disconnect the gauge from the system to ensure there is no current flowing to take an OCV.

However, my capacity measured by the gauge is still around 4000mAh insted of 4800mAh that should be the nominal capicity.
Therfore no QMAX update is taken.... 
My discharge current is usually around 700-900mA at the cycleing.
Did i missed someting?
TIProgData.gg.csv

Many thanks for your support!

  • Hello,

    This question has been assigned within the team and will be followed up when possible. In the meantime please attach associated .gg/.log file.

    Thank you,
    Alan

  • Hello M,

    Yes. there is various steps that need to be taken to get correct perfomrance of the gauge. 

    Please check the following:

    By importance, we want to check the following parameters one by one:

    1. 1.Calibration of IVT
      1. 1.Calibration of the current readings
      2. 2.Calibration of the voltage readings (BAT, VC1, PACK)
      3. 3.Calibration of the temperature sensor
    2. 2.CHEMID (Catalogue/ Custom)
      1. 1.Used Tool?
      2. 2.Check initial Ra table values
    3. 3.Learning Cycle
    4. 4.Load Mode
    5. 5.Qmax Updates
      1. 1.Good OCV
      2. 2.Where is the jump?
      3. 3.What term voltage?
    6. 6.Ra Tables Updates
      1. 1.Are updates within a few 10 of mΩ?

    -Miguel

  • Hello Miguel
    Calibration was done for all values in the same value range where the charge, discharge current is: 900mA
    ChemID: 2851 ToolEV2400 Version 0.18 + BQ Studio 1.3.127
    Learning cycle was done based on the slua777.pdf doc ftom TI
    First ive updated the Gauge FW From R2 to R5, then applyed the ChemID, did the calibration and started the learning by starting the discharge.
    The issue is, that the QMax Passed and the DOD0-s are to low relative to the nominal capacity (4800mAh) and never reaches the 90% for the initial update.
    It reaches about 3980mAh and i would need 4400mAh measured at lest for the first update. Updates status stays at 04.
    At the end of discharge i disconnect my load to let the Battery get its OCV and REST. This part is okay. The need flags are set or clear.
    Then im starting the charge state. The the charging voltage is ste to 16,8V current around 900-1000mA. The FD and TC flasg are set at the end of charge.
    Charge Term Taper current is 240mA
    Charge Term Charging Voltage is 4000mV
    COV 4300mV



    Discharge: Temr voltage 12000mV
    Term Min Cell voltage 3000mV
    CUV 2700mV

    pleas find the program data in the initial post. Im just uploaded one cycle log. Unfortunatly there i've hit the CUV threshold, but you can see the curves anyway.

    BR,

    Martin


    ChemCycle_2025_09_24_2.log

  • Addon: i have uploaded the log to the GPC Tool
    The report shows just one ChemID that is really off (9%) but hte Batterie is confirmed from the manufacturer tobe the 2851.
    Any ideas on this?

    Chemistry ID selection tool, rev=2.57		
    		
    Configuration used in present fit:		
    ProcessingType = 2		
    NumCellSeries = 4		
    ElapsedTimeColumn=2		
    VoltageColumn = 12		
    CurrentColumn = 13		
    TemperatureColumn = 11		
    		
    Best chemical ID : 2615	Best chemical ID max. deviation, % : 9.18	
    		
    		
    		
    Summary of all IDs with max. DOD deviation below 3%		
    		
    Chem ID	max DOD error, %	Max R deviation, ratio
    0	0	0
    		
    Warning: Deviation is above recommended level. New chem ID needs to be released for this cell. Please contact your TI representative to send the cell to Dallas for characterization		
    		
    		
    Selection of best generic ID for ROM based devices like bq274xx		
    		
    		
    Device / Family #1		
    Generic Chem ID	Device/ Voltage/ Chemistry	max DOD error, %
    3142	bq27421-G1D: 4.4V LiCoO2	26.32
    354	bq27411-G1C: 4.35V LiCoO2	28.65
    128	bq27421-G1A: 4.2V LiCoO2	42.44
    312	bq27421-G1B: 4.3V LiCoO2	49.67
    Best generic ID 3142		
    Warning: Generic ID Deviation is so high that it is most likely due to anomaly in the data. Please check that data files have recomended format, units and test schedule		
    		
    		
    Device / Family #2		
    Generic Chem ID	Device/ Voltage/ Chemistry	max DOD error, %
    354	bq27621:  (ALT_CHEM2) 4.35V LiCoO2	28.65
    1202	bq27621: (default) 4.2V LiCoO2	29.67
    1210	bq27621:  (ALT_CHEM1) 4.3V LiCoO2	31.51
    Best generic ID 354		
    Warning: Generic ID Deviation is so high that it is most likely due to anomaly in the data. Please check that data files have recomended format, units and test schedule		
    		
    		
    Device / Family #3		
    Generic Chem ID	Device/ Voltage/ Chemistry	max DOD error, %
    3142	bq27426: (ALT-CHEM2) 4.4V LiCoO2	26.32
    1202	bq27426: (ALT_CHEM1) 4.2V LiCoO2	29.67
    3230	bq27426: (default) 4.35V LiCoO2	31.57
    Best generic ID 3142		
    Warning: Generic ID Deviation is so high that it is most likely due to anomaly in the data. Please check that data files have recomended format, units and test schedule		
    		
    		
    Warning: Discharge rate is too high. High rate reduces ID detection accuracy	 10 hr rate is recomeended. Total discharge time is less than 5 hrs	 t_hrs=  4.00140222222222
    
     

  • I see in your .gg file that your design voltage is ~14V. but the battery you descripted is typically 3.6V or 7.2 since you have a 2S configuration. Shouldn't this design voltage be lower?

    Can you double check the Ra table initial values when you pogrammed it? I see ~350mohms for the first which seems like too high, but it could be correct.