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BQ27531-G1: during the learning cycle, [VOK] is not cleared after relax for 2 hrs

Eric Kwok
Prodigy 115 points
Part Number: BQ27531-G1
Other Parts Discussed in Thread: BQ24192

Hi, Ti 

I'm using the BQ27531-G1 + BQ24192.

And I do the cycle learning forllowing the instruction of http://www.ti.com.cn/cn/lit/an/slua597/slua597.pdf .

After charging the battery, the [FC] bit is set , so I stop charging, and let it relax for over 2 hrs, but the [VOK] is not cleared.

How is that?

  • 0
    TI__Guru* 76230 points
    Hi Eric,
    What kind of cell are you using? I would suggest ignoring the fact that the vok flag is not getting cleared and continue to the learning cycle process. Just make sure to log your data incase learning Isn't successful so we figure out what is going on.
    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Prodigy 115 points

    Hi，Onyx，I'm using the single cell Li--ion battery.

  • 0 in reply to Eric Kwok
    TI__Guru* 76230 points
    I mean is is it a regular lithium ion cell or Lithium ion phosphate . If lithium ion phosphate, the relaxation period after charge should be atleast 5 hours
    thanks
    Onyx
  • 0 in reply to Onyx Ahiakwo
    Prodigy 115 points

    Hey，Onyx

    I charge the battery to full, and let it relax overnight, the [VOK] is not cleared,  I follow your suggestion and continue the cycle, discharge the battery at about C/5, near the end of discharging process,  the [RUP_DIS] flag is set,  does that mean the learning cycle failed? 

    log attached. ( I see the [VOK] get cleared for only one second in the charge relax time（at 22:09:48）, and get set again )6320.learning.log

    here is mt report about Chem_ID, I programed the Chem-ID as recommended, anything that could go wrong?

    Fullscreen 2625.GPC_report.txt Download 
    Chemistry ID selection tool, rev=2.42		
		
Configuration used in present fit:		
ProcessingType=2		
NumCellSeries=1		
ElapsedTimeColumn=0		
VoltageColumn=1		
CurrentColumn=2		
TemperatureColumn=3		
		
Best chemical ID : 254	Best chemical ID max. deviation, % : 2.95	
		
		
		
Summary of all IDs with max. DOD deviation below 3%		
		
Chem ID	max DOD error, %	Max R deviation, ratio
254	2.95	-89.41
		
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	13.86
354	bq27411-G1C: 4.35V LiCoO2	14.97
312	bq27421-G1B: 4.3V LiCoO2	16.93
128	bq27421-G1A: 4.2V LiCoO2	18.1
Best generic ID 3142		
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, %
1210	bq27621:  (ALT_CHEM1) 4.3V LiCoO2	14.13
1202	bq27621: (default) 4.2V LiCoO2	14.84
354	bq27621:  (ALT_CHEM2) 4.35V LiCoO2	14.97
Best generic ID 1210		
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, %
3142	bq27426: (ALT-CHEM2) 4.4V LiCoO2	13.86
1202	bq27426: (ALT_CHEM1) 4.2V LiCoO2	14.84
3230	bq27426: (default) 4.35V LiCoO2	16.3
Best generic ID 3142		
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.		
		
		
Warning: First OCVpoint has non-zero current I=  -0.04 Please make sure you have a 2 hr relaxation period before the beginning of discharge.		
Warning: Last OCVpoint has non-zero current I=  -0.039 Please make sure you have a 5 hr relaxation period after the end of discharge.		
Warning: Max R deviation ratio can not be checked because discharge hr-rate is above 12.  Hr rate = 12.4153016260642		
Warning: Max R deviation ratio can not be checked because discharge hr-rate is above 12.  Hr rate = 12.4153016260642		
Warning: Max R deviation ratio can not be checked because discharge hr-rate is above 12.  Hr rate = 12.4153016260642

  • 0 in reply to Eric Kwok
    TI__Guru* 76230 points

    Hi Eric,

    You chem id report is showing that the files you submitted had issues. It is saying that your test did not start with a charge then relax before discharge. It seems you started the test with a discharge right away. I would recommend redoing the chem id identification process as the chem id which you identified is right on the border of the the disqualification criteria of 3% max DOD error. Your identified chem id has 2.95% max dod error.

    Now when you have identified your chem id, i would recommend using a c/7 discharge rate for learning. C/5 is right on the threshold and that could cause negative resistances to be learnt.and that is likely why the rupdis flag is getting set.

    thanks

    Onyx

  • 0 in reply to Onyx Ahiakwo
    Prodigy 115 points
    I removed the load, and the gauge still detected -35mA current flowing out of battery, and about -160 mW power consumption. Is that normal?
  • 0 in reply to Eric Kwok
    TI__Guru* 76230 points

    No That is not normal. The gauge ought to report 0mA when there is no load. Check your connections and try to trace the source of that current as that could prevent learning from occurring.

    thanks

    Onyx