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BQ40Z50-R2: Learning Cycle step 4.2.4: No valid OCV reading after hours of relaxing in FC state

Contantin Baumann
Prodigy 60 points
Part Number: BQ40Z50-R2

Tool/software:

Hello,

i am attempting to perform a learning cycle as in slua848. However, i am stuck at the relaxing step after charging the battery to full. The REST bit is not being set, even after (so far) 12 hour of relaxing.
I am glad about any help possible, as i am at this point for a few weeks now. Each attempt of the learning cycle takes a >20 h.

i will attach the .gg file, the log of the current learning cycle and a few pictures.

I am using two LiFePO cells in series with 15000 mAh each.

kind regards

Constantin

goldenimage.gg.csv 1588.registers_log.log

  • 0
    TI__Intellectual 2020 points

    Hello,

    Could you send us the datasheet of the battery?

    Regards,

    Siddharth

  • 0 in reply to Siddharth Venkatesan
    Prodigy 60 points

    Oh and if it helps, here is the GPC report for the chemID:

    Fullscreen 4578.GPC_report.txt Download 
    Chemistry ID selection tool, rev=2.54		
		
Configuration used in present fit:		
ProcessingType = 2		
NumCellSeries = 1		
ElapsedTimeColumn=0		
VoltageColumn = 1		
CurrentColumn = 2		
TemperatureColumn = 3		
		
Best chemical ID : 4124	Best chemical ID max. deviation, % : 4.79	
		
		
		
Summary of all IDs with max. DOD deviation below 15%		
		
Chem ID	max DOD error, %	Max R deviation, ratio
4124	4.79	0.94
4119	5.14	0.88
4134	5.45	0.94
447	5.67	4.03
4130	5.8	2.13
438	5.97	6.15
4103	6.07	2.1
474	6.29	2.95
4175	6.33	5.51
442	6.73	3.35
496	7.19	0.72
4173	7.25	5.78
4113	7.31	1.28
4109	7.4	0.88
4181	7.48	3.76
424	7.62	4.77
4150	7.7	1.66
411	7.73	3.79
4172	7.83	1.26
457	8.01	7.37
4122	8.05	0.45
6104	8.05	15.21
400	8.06	3.22
4180	8.07	3.08
4178	8.22	3.83
4174	8.31	1.2
445	8.46	9.95
4156	8.52	0.7
416	8.53	-3.58
4171	8.65	2.72
448	8.65	-98.42
6110	8.66	0.72
402	8.71	0.07
4153	8.75	0.49
4167	8.81	3.51
403	8.97	0.99
413	8.97	1.16
464	9.04	-3.52
487	9.1	0.07
485	9.1	0.07
4144	9.18	3.82
4139	9.22	0.05
4159	9.25	0.95
428	9.27	0.09
4136	9.33	0.95
4158	9.4	0.99
4140	9.42	0.87
4142	9.45	0.54
425	9.62	5.67
4148	9.63	1.34
426	9.68	2.37
6105	9.69	3.92
450	9.75	1.59
4107	9.83	0.61
405	9.84	0.86
433	9.9	-17.71
462	9.95	-3.86
481	9.96	0.07
4110	10.02	-5.16
427	10.1	0.92
461	10.17	5.29
459	10.2	14.15
4183	10.28	5.03
482	10.32	0.11
446	10.38	0.02
4117	10.4	1.29
4166	10.41	1.93
437	10.42	-13.27
6106	10.43	19.46
4133	10.51	1.4
453	10.52	0.07
4157	10.56	1.88
423	10.58	2.75
4114	10.61	1.33
422	10.72	2.27
4164	10.81	1.88
436	10.81	-2.81
420	10.92	3.4
429	10.94	1.57
435	10.99	-2.7
421	11.04	0
4149	11.04	-2.07
4118	11.07	1.23
4168	11.07	1.54
4170	11.11	2.84
4111	11.13	0.74
434	11.2	-2.81
4141	11.27	0.43
4123	11.28	1.88
444	11.35	5.37
4106	11.45	0.86
432	11.46	-48.2
4165	11.5	1.04
4100	11.58	3.48
465	11.65	-0.29
412	11.67	-0.48
4146	11.68	0.7
414	11.74	-37.07
401	11.88	0.84
4160	12.04	0.88
483	12.07	0.88
4128	12.31	2.18
410	12.36	-88.11
495	12.36	1.02
4101	12.45	0.5
4135	12.65	-1.68
451	12.65	2.24
449	12.79	-896.78
417	12.84	-3.71
491	12.96	-8.22
478	13.18	0.15
4161	13.21	1.6
4126	13.23	0.83
477	13.43	-78.63
2160	13.69	1.74
4182	13.88	3.78
443	13.91	3.38
440	14.01	2.79
4179	14.53	24.59
4145	14.78	0.66
415	14.91	2.95
439	14.97	3.12
		
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	40.04
354	bq27411-G1C: 4.35V LiCoO2	41.04
128	bq27421-G1A: 4.2V LiCoO2	52.05
312	bq27421-G1B: 4.3V LiCoO2	69.67
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	41.04
1202	bq27621: (default) 4.2V LiCoO2	55.16
1210	bq27621:  (ALT_CHEM1) 4.3V LiCoO2	58.65
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	30.84
3142	bq27426: (ALT-CHEM2) 4.4V LiCoO2	40.04
1202	bq27426: (ALT_CHEM1) 4.2V LiCoO2	55.16
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		
		
       0	0	0		
Warning: voltage in V detected	 divider changed to 1	0		
Warning: current in A detected	 divider changed to 1	0		
Warning: First OCVpoint has non-zero current I=  6.839325e-13 Please make sure you have a 2 hr relaxation period before the beginning of discharge.	0		
Warning: Last OCVpoint has non-zero current I=  7.478618e-13 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 = 15.8942267174594		
Warning: Max R deviation ratio can not be checked because discharge hr-rate is above 12.  Hr rate = 15.8942267174594		
Warning: Max R deviation ratio can not be checked because discharge hr-rate is above 12.  Hr rate = 15.8942267174594

  • 0 in reply to Contantin Baumann
    TI__Intellectual 2020 points

    Hello,

    We will look into this and get back to you on Monday.

    Regards,

    Siddharth

  • 0 in reply to Siddharth Venkatesan
    TI__Intellectual 2020 points

    Hello Contantin,

    Here is the Voltage and Current vs Time from your log file.

    I am assuming this is during rest. Notice that the current is fluctuating between -3mA and 0A. This is causing the battery to constantly discharge over the 12 hour period. There must be some load or noise with the charger/source that must be causing this issue. The gauge needs to be in a state of absolute state (no discharge or charge current) until it sets the REST bit.

    Regards,

    Siddharth

  • 0 in reply to Siddharth Venkatesan
    Prodigy 60 points

    Hello Siddarth,

    thank you very much for the reply and the analysis. I appreciate it very much.
    However, it appears that over the Weekend the relaxing has been successfull. You can see the complete learning cycle below:

    Notice that LStatus changes to 5 after around three days of relaxing. After that i could complete the rest of the learning cycle, as expected. So the issue is technically closed.

    Still, i can say that the only load on the battery during the relaxing phase in the fully charged state was the fuel gauge alone. I disconnected the charger during that phase. The 3 mA noise never disappears. Picture below:

    Therefore the 3 mA noise should not be the reason for the three days of relaxing in FC state. My guess is that i disconnected the charger at the evening of Aug 1st, when i realized that it is fully charged, and then the noise somehow changed into the positive.
    Maybe the fuel gauge is simply not correctly calibrated.

    In conclusion the reason for the long resting phase in FC state remains undisclosed and it confused me, why relaxing is correctly recognized in the FD state, but not ins the FC state.

    Anyway, i simply hope that i do not have to perform a learnign cycle again ;-)

  • +1 in reply to Contantin Baumann
    TI__Intellectual 2020 points

    Hello Contantin,

    I'm glad that worked. LFP cells require long resting times compared to other battery chemistries, but it still does not explain the 72 hour period. My guess is that the battery needed well over 12 hours to enter a state of absolute rest.

    You may be right about the 3mA discharge pulse. It is well below the discharge threshold, so the gauge wouldn't detect a discharge state. A calibration error of 3mA is not significant.

    As long as you have Ra and Qmax updates, and your update status set to 06 or 0E, you wouldn't have to perform another learning cycle.

    Regards,

    Siddharth

  • 0 in reply to Siddharth Venkatesan
    Prodigy 60 points

    Hello Siddharth,

    yes, after another charging cycle the LStatus is now at 0x0E and the Qmax and Ra values have been updated.

    This issue can be closed.
    Thanks again for the help.

    Regards,

    Constantin