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BQ34Z100-G1: Can't get Qmax to learn Correctly

Alex Klimaj
Prodigy 225 points
Part Number: BQ34Z100-G1
Other Parts Discussed in Thread: BQ40Z80,

I am trying to calibrate a 12s 12Ah LiPo battery. I am using a scale factor of 7, for a max mAh in the gauge of 1714mAh.

I have gone through about 10 charge and discharge cycles and still can't get Update Status to go to 0x05.

Looking at the register logs, it appears that the QMax Passed Q reads correctly, but that value is never applied. I end up with a max capacity around 1450mAh.

In this log, I found that FC was set very early. I found another forum post about setting FC Set to -1 and tried again.

Calibration Log 12Ah FC Set very early.log

In this log, FC Set is -1. It appears that the FC bit is set at the correct time. And Qmax passed is in the correct range of 1747mAh. But when VOK clears, update status is not updated to 0x05 and the full charge capacity is only 1460mAh.

Calibration Log 12Ah FC Set -1.log

Here are the gauge params.

bq34 params not calibrated 10-11-2022.gg.csv

  • 0
    TI__Guru 62566 points

    What ChemID are you using?

  • 0 in reply to Dominik Hartl11
    Prodigy 225 points

    I am using 2272.

    Chem ID    max DOD error, %    Max R deviation, ratio
    2272    2.06    4.83
    2526    2.59    2.72
    2246    2.61    3.76
    2370    2.84    1.72

    Fullscreen 8130.GPC_report.txt Download 
    Chemistry ID selection tool, rev=2.53		
		
Configuration used in present fit:		
ProcessingType = 2		
NumCellSeries = 12		
ElapsedTimeColumn = 0		
VoltageColumn = 1		
CurrentColumn = 2		
TemperatureColumn = 3		
		
Best chemical ID : 2272	Best chemical ID max. deviation, % : 2.06	
		
		
		
Summary of all IDs with max. DOD deviation below 3%		
		
Chem ID	max DOD error, %	Max R deviation, ratio
2272	2.06	4.83
2526	2.59	2.72
2246	2.61	3.76
2370	2.84	1.72
		
Max. deviations for best ID is within recommended range. Chosen best chemical ID is suitable for programming the gauge.		
		
		
Selection of best generic ID for ROM based devices like bq274xx		
		
		
Device / Family #1		
Generic Chem ID	Device/ Voltage/ Chemistry	max DOD error, %
312	bq27421-G1B: 4.3V LiCoO2	7.99
128	bq27421-G1A: 4.2V LiCoO2	8.04
3142	bq27421-G1D: 4.4V LiCoO2	8.06
354	bq27411-G1C: 4.35V LiCoO2	8.16
Best generic ID 312		
Warning: Deviation for best generic ID is above recommended level for this device / family. Consider using another device, flash based gauge or RAM programming of custom ID.		
		
		
Device / Family #2		
Generic Chem ID	Device/ Voltage/ Chemistry	max DOD error, %
1202	bq27621: (default) 4.2V LiCoO2	7.79
1210	bq27621:  (ALT_CHEM1) 4.3V LiCoO2	7.85
354	bq27621:  (ALT_CHEM2) 4.35V LiCoO2	8.16
Best generic ID 1202		
Warning: Deviation for best generic ID is above recommended level for this device / family. Consider using another device, flash based gauge or RAM programming of custom ID.		
		
		
Device / Family #3		
Generic Chem ID	Device/ Voltage/ Chemistry	max DOD error, %
1202	bq27426: (ALT_CHEM1) 4.2V LiCoO2	7.79
3142	bq27426: (ALT-CHEM2) 4.4V LiCoO2	8.06
3230	bq27426: (default) 4.35V LiCoO2	9.42
Best generic ID 1202		
Warning: Deviation for best generic ID is above recommended level for this device / family. Consider using another device, flash based gauge or RAM programming of custom ID.

  • 0 in reply to Alex Klimaj
    TI__Guru 62566 points

    Please attach the .srec file (this contains more information that the .gg.csv file) and I'll try to simulate the behavior based on your log files.

  • 0 in reply to Dominik Hartl11
    Prodigy 225 points

    I tried changing the chem id to 2526 and it is exhibiting the same behavior.

    0100_0_16-bq34z100G1_chem_id_2526.zip
    Calibration Log 12Ah Chem ID 2526.log

  • 0 in reply to Alex Klimaj
    TI__Guru 62566 points

    I'll try to simulate this with the files you provided and get back asap.

  • 0 in reply to Dominik Hartl11
    TI__Guru 62566 points

    The simulation shows that the passed charge only resulted in a DOD change of 0.88 (DOD0 change from 1616/16384 to 16035/16384) but the gauge requires a minimum change of 0.9 (passed charge of 90% of default Qmax) to qualify this for an initial Qmax update.

  • 0 in reply to Dominik Hartl11
    Prodigy 225 points

    Okay so discharge to a slightly lower voltage?

  • 0 in reply to Alex Klimaj
    TI__Guru 62566 points

    The total passed charge must be a bit higher. You can either charge to a higher voltage and/or discharge to a lower voltage.

  • 0 in reply to Dominik Hartl11
    Prodigy 225 points

    Thanks. I will give that a try and report back.

  • 0 in reply to Alex Klimaj
    TI__Guru 62566 points

    Please let me know if this worked.

  • 0 in reply to Dominik Hartl11
    Prodigy 225 points

    Dominik, it looks like it didn't work. See logs. I am going to try and run the chem id test again and see if it comes up with a different ID.
    Calibration Log 12Ah 10-20-2022.logCalibration Log 12Ah 10-20-2022 Charge.log

  • 0 in reply to Alex Klimaj
    Prodigy 225 points

    The results of the chem id test this time are the following.

    Chem ID    max DOD error, %    Max R deviation, ratio
    2526    1.76    0.69
    2246    2.2    1.08
    2370    2.23    0.64
    1547    2.5    1.15
    1893    2.63    0.39
    355    2.72    2.56
    1526    2.89    1.09

  • 0 in reply to Alex Klimaj
    TI__Guru 62566 points

    I'll check the charge log file with the simulator. The last time it was definitely due to insufficient DOD change (0.88 vs. 0.90 (required)). 

  • 0 in reply to Dominik Hartl11
    TI__Guru 62566 points

    Please use ChemID 2526.

    With ChemID 2526, your latest discharge log file shows that after charge, DOD is 1712/16384 = 0.10. And after discharge, the OCV settles at a DOD of 16145/16384 = 0.99. The difference is (16145-1712)/16384 = 0.88. This is still not enough. You would have to charge a bit higher (increase the charging voltage) and/or discharge a bit more so that the change in DOD exceeds 0.9.

    For a test, you can set Update Status to 5 instead of 4. This indicates to the gauge that the initial Qmax was already learned, which reduces the DOD change requirement from 0.9 to 0.37. This should give you a Qmax update (at the expense of allowing a Qmax update that may not be of high enough quality).

    Gas Gauging,State,Update Status,5,num

  • 0 in reply to Dominik Hartl11
    Prodigy 225 points

    Dominik, thanks. I am unable to discharge lower or charge higher. I can get about 12300mAh out of the pack when the voltage of two of the cells starts crashing. 12300mAh is the datasheet spec of the cells, but the other 10 cells in the pack have a higher actual capacity. I've found these high cell count packs hard to calibrate with the BQ34Z100-G1 since it uses the stack voltage. Compared to the BQ40Z80 which I think looks at the individual cell voltages?

    I will have to try and get a new pack with capacity matched cells in order to discharge lower.

  • 0 in reply to Alex Klimaj
    TI__Guru 62566 points

    Would it be possible to charge them a bit higher for the initial learning cycle? The 0.9 change in DOD only applies to the first Qmax update and is intended to measure a Qmax starting value with high precision. Your log files show that it's almost there and if you can't discharge lower, you may be able to charge the a bit higher.

    If that isn't feasible, please set Update Status to 5, set Qmax to about 5% higher than Design Capacity and run your learning cycle. This will change the DOD restriction to 0.37 (which is intended for regular use and the gauge will filter Qmax updates heavily).