• State TI Thinks Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 3 answers
  • Subscribers 63 subscribers
  • Views 352 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

BQ40Z50-R1: Chem ID accuracy

Clement MAGNIEN
Intellectual 390 points
Part Number: BQ40Z50-R1

Hi,

I performed the cycle to obtain the chem ID of my battery.I have a deviation of 8.44%.the app note SLVA 725 recommends less than 3%.

I would like to know if a deviation of 8.44% will create a large measurement errors during the life of the battery?

Does the learning cycle also helps to improve the accuracy of the gas gauge too?

Regards,

Clement

Fullscreen GPC_report_clement-29-08-2019.txt Download 
Chemistry ID selection tool, rev=2.48		
		
Configuration used in present fit:		
ProcessingType=2		
NumCellSeries=4		
ElapsedTimeColumn=0		
VoltageColumn=1		
CurrentColumn=2		
TemperatureColumn=3		
		
Best chemical ID : 457	Best chemical ID max. deviation, % : 8.44	
		
		
		
Summary of all IDs with max. DOD deviation below 15%		
		
Chem ID	max DOD error, %	Max R deviation, ratio
457	8.44	0.18
446	11.03	0.03
478	11.47	0.01
435	11.49	0.96
6106	11.53	0.58
462	12.05	0.79
436	12.38	0.92
425	12.45	0.54
464	12.47	0.75
450	12.97	0.73
445	13.65	0.84
		
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, %
354	bq27411-G1C: 4.35V LiCoO2	33.81
3142	bq27421-G1D: 4.4V LiCoO2	34.76
128	bq27421-G1A: 4.2V LiCoO2	3072.65
312	bq27421-G1B: 4.3V LiCoO2	4791.99
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 #2		
Generic Chem ID	Device/ Voltage/ Chemistry	max DOD error, %
354	bq27621:  (ALT_CHEM2) 4.35V LiCoO2	33.81
1210	bq27621:  (ALT_CHEM1) 4.3V LiCoO2	42.06
1202	bq27621: (default) 4.2V LiCoO2	2776.45
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, %
3230	bq27426: (default) 4.35V LiCoO2	28.34
3142	bq27426: (ALT-CHEM2) 4.4V LiCoO2	34.76
1202	bq27426: (ALT_CHEM1) 4.2V LiCoO2	2776.45
Best generic ID 3230		
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: First OCVpoint has non-zero current I=  -0.003 Please make sure you have a 2 hr relaxation period before the beginning of discharge.		
Warning: Last OCVpoint has non-zero current I=  -0.003 Please make sure you have a 5 hr relaxation period after the end of discharge.

  • 0
    TI__Mastermind 42535 points

    Hi Clement,

    A high DOD error may affect performance. However this can be offset by running a learning cycle. The chem ID 457 is an LFP cell. If yours is also an LFP cell, you can use it. LFP cells typically have a higher error because of a larger flat region. However, if you want to verify the result, you can run the test again to check the ID you obtain.

  • 0 in reply to Batt
    Intellectual 390 points

    Hi Batt,

    I tried again to perform the chem ID cycle , I un-soldered all the other chips on my board( the consumption of my board is  2 mA when the battery is in relax mode and I read that this current should be under 1 mA to perform the chem ID cycle correctly).

    Unfortunately I still have an error of 8%.

    When I performed the learning cycle, it failed: after the step "Relax for at least 2 Hours" , the  "LStatus() sould now be 0x05" but it is still 0x04 (CF0 not set).

    I read that a not accurate chem ID could be the reason of a failed learning cycle, is it true?

    Do you have any other solution that to send the battery to TI to let your team to evaluate the chem ID?

    Best regards,

    Clement

  • 0 in reply to Clement MAGNIEN
    TI__Mastermind 42535 points

    Hi Clement,

    It is possible that a bad chem ID can give you bad accuracy. However with OCV taken at relaxation in dsg and chg you should be able to learn capacity. It is possible that the current might affect the gauge. Please check if you were in relax before you started the chg or dsg cycle.

  • 0 in reply to Batt
    Intellectual 390 points

    Hi Batt,

    It is  in relax mode(REST=1) and QMAX=1 , I think it works, it is just the LStatus which is not updated(still 04)

    But Update status(data memory--> Gas gauging) is 0e --> I don't understand this setting, it is something I have to set or a reading only or both , 0e should mean that the learning cycle is fully completed(QMax updated in the field)?

    I am following the app note slua848 for the learning cycle, the doc says  LStatus, value  should be 0e at the end of the learning cycle, I have 0e but only for Update status? 

    Could you help?

    Regards,

    Clement

  • 0 in reply to Clement MAGNIEN
    TI__Mastermind 42535 points

    Hi Clement,

    Update status should be 0e. That is in the df and indicates a successful completion of the learning cycle.

    You can ignore LSTATUS.