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BQ27520-G4: About cell profile selection when replacing the battery

Part Number: BQ27520-G4
Other Parts Discussed in Thread: GPCCHEM

Hello

I am developing an application that assumes battery replacement.
The bq27520-g4 is mounted on the system side.
I evaluated the Fuel Gauge with the following procedure, but it seems that the battery was not selected correctly.


1st : Write .bqfs file to Fuel Gauge
2nd : Insert the degraded battery and perform charge/discharge cycles to confirm that the FCC value decreases
3rd : Perform 10 charge/discharge cycles to ensure sufficient learning
4th : Verify correct battery pack selection by inserting a new battery and verifying that the FCC value is close to the default value.

The FCC value does not approach the default value after the 4th implementation, and the monitoring IC seems to recognize that a degraded battery has been inserted.
Could you please let me know if you have any idea why or how to fix it?

Note 
① It is assumed that the user will insert a degraded battery after shipment.
② After obtaining the Chem ID using the GPC tool, a learning cycle was performed.
③ Using the Fast Qmax feature
④ The default value of FCC value is about 3000mAh
⑤ The FCC value for a degraded battery is around 2200~2400mAh


  • Was the correct chemistry programmed. What was the max error specified for the chemistry ID in the GPCCHEM report?

  • Hello, Shirsh

    I chose Chem ID 3608.
    For the maximum error of the Chem ID 3608, please refer to the attached report.

    3542.GPC_report.txt
    Chemistry ID selection tool, rev=2.5		
    		
    Configuration used in present fit:		
    ProcessingType = 2		
    NumCellSeries = 1		
    ElapsedTimeColumn = 0		
    VoltageColumn = 2		
    CurrentColumn = 3		
    TemperatureColumn = 1		
    		
    Best chemical ID : 3608	Best chemical ID max. deviation, % : 2.03	
    		
    		
    		
    Summary of all IDs with max. DOD deviation below 3%		
    		
    Chem ID	max DOD error, %	Max R deviation, ratio
    3608	2.03	0.36
    2088	2.33	0.38
    2111	2.67	0.5
    2155	2.92	0.45
    		
    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, %
    3142	bq27421-G1D: 4.4V LiCoO2	20.77
    354	bq27411-G1C: 4.35V LiCoO2	23.89
    128	bq27421-G1A: 4.2V LiCoO2	26.84
    312	bq27421-G1B: 4.3V LiCoO2	35.32
    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, %
    1210	bq27621:  (ALT_CHEM1) 4.3V LiCoO2	22.07
    1202	bq27621: (default) 4.2V LiCoO2	22.99
    354	bq27621:  (ALT_CHEM2) 4.35V LiCoO2	23.89
    Best generic ID 1210		
    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	20.77
    1202	bq27426: (ALT_CHEM1) 4.2V LiCoO2	22.99
    3230	bq27426: (default) 4.35V LiCoO2	24.07
    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		
    		
    		
    

  • You can read ApplicationStatus( )  LU_ PROF bit to tell which profile was detected by the battery.

    Please confirm that the image contained updated values for Pack0 and Pack1 Ra/Rax tables to match the new and used batteries.

  • Hello, Shirsh.
    I will check LU_PROF bit.
    Thank you.

    If the referenced Pack is wrong, is it possible for me to change it to refer to any Pack information?
    This is because the method of sending OCV commands cannot refer to any pack from the system side.

  • I would check if both profiles are programmed properly