BQ40Z50: Why QMax cannot update properly?

joy zhou1

Part Number: BQ40Z50

After first cycling update status 0x05 by bq.gg.csv after second cycling update status keeping 0x05.gg.csv after third cycling update status keeping 0x05.gg.csvHi Kang,

This is a continue question from my old question, I linked it below:

https://e2e.ti.com/support/power-management/f/196/t/865206

I owed you readout gg.csv before and after a learning cycling. I sent you read out the gg file.csv file before and after a learning cycle. The pack which I did cycling on has been done several cycling before. This time, in the beginning, I just set update status as 0x04, and changed cycle count and Qmax cycle count to 0 for it, then started the cycling. During learning cycling, after first cycling, update status updated to 0x05 by bq automatically, but later, I did two more cycling, but update status keeping as 0x05, I didn't see its Qmax and Ra table updated.

Please review the attached gg.csv files , and advise why QMax cannot update after the first time update, and how to solve the issue. The pack is 4s16p, CHEM ID 0x0444.

I have logged the cycling data during cycling, if you need them, please let me know.

Thanks,

JoyBefore cycling set update status to 0x04.gg.csv

over 4 years ago

0 Andy Liu (BMS) over 4 years ago

TI__Guru 52115 points

Hi Joy,

Could you please share your log file with us? Thanks.

Andy

0 joy zhou1 over 4 years ago in reply to Andy Liu (BMS)

Intellectual 470 points

Hi Andy,

I sent them separately. This is fFirst Cycling_24jan20.xlsxirst cycling log.

Thanks,

Joy

0 joy zhou1 over 4 years ago in reply to joy zhou1

Intellectual 470 points

second cycling log.

Second Cycling Part1_27jan20.xlsx Second Cycling Part2_27jan20.xlsx

0 joy zhou1 over 4 years ago in reply to joy zhou1

Intellectual 470 points

The last one(third cycling log).

Thanks,

Joy

Third Cycling_28jan20.xlsx

0 Andy Liu (BMS) over 4 years ago in reply to joy zhou1

TI__Guru 52115 points

Hi Joy,

I looked into this log "First Cycling_24jan20.xlsx".

I think you probably didn't follow our recommended learning cycle procedure.

You need to discharge your battery to empty and then let it relax for 5 hours before you start to charge the battery.

If you follow our procedure, you need to make sure the Update Status becomes 0x05 after the battery is charged to full and relaxed for 5 hours. Basically 0x05 should appear in the highlighed region.

See the following report.

7367.Achieving the Successful Learning Cycle.pdf

Andy

0 joy zhou1 over 4 years ago in reply to Andy Liu (BMS)

Intellectual 470 points

Hi Andy,

Ok, I will follow the document, and redo cycling again.

Thanks,

Joy

0 joy zhou1 over 4 years ago in reply to joy zhou1

Intellectual 470 points

Hi Andy,

Please confirm the page 8 section 5 Conclusion is correct:

-Discharge the cell to empty and let them relax for at least 5 hours. (at this time, update status is 00)

-Enable Impedance Track(0x21), issue a reset command (0x41). Update Status changes from 00 to 04

-Charge the cell to full....

Please clarify the above: in the beginning, during discharge to empty, update status should be 00 or 04?

Thanks,

Joy

0 Andy Liu (BMS) over 4 years ago in reply to joy zhou1

TI__Guru 52115 points

Hi Joy,

If you follow the step below, you Update Status should be 0x04 after IT is enabled.

Andy

0 joy zhou1 over 4 years ago in reply to Andy Liu (BMS)

Intellectual 470 points

Hi Andy,

Ok, then I follow 3.2.1, not 5. Set Update Status to 0x04, and reset bq, later start to do discharge.

Thanks,

Joy.

0 Andy Liu (BMS) over 4 years ago in reply to joy zhou1

TI__Guru 52115 points

Read the app note carefully and make sure all the important events occur in each step.

0 joy zhou1 over 4 years ago in reply to Andy Liu (BMS)

Intellectual 470 points

After second cycling update status keeping as 06_03Feb20.gg.csv After third cycling keeping as 06_ 04Feb20.gg.csvHi Andy,

I have followed 3.2.1 to 3.2.6, all important events occur in 3.2.1, 3.2.2 and 3.2.3, all important events occur in 3.2.4 except instead of Update Status would now be 0x05, it is 0x06; 3.2.5 is good, 3.2.6 is good, just Update Status is keeping as 0x06, not 0x0e. Did two more cycling again, full charging, relax over 2 hours, full discharging, relax over 5 hours, right now cycling count is 3, but Update Status is keeping as 0x06, cannot update to 0x0e.

I sent you exported gg.csv files and log files, please advise why update status cannot go to 0x0e, and how to improve to get it updated properly.

Thanks,

JoyAfter first cycling update status go to 06_31jan20.gg.csv

0 joy zhou1 over 4 years ago in reply to joy zhou1

Intellectual 470 points

Total 3 log files. First is attached here.First day logging_30Jan20.xlsx

0 joy zhou1 over 4 years ago in reply to joy zhou1

Intellectual 470 points

Second log file.Second day logging_update status to be 06_31Jan20.xlsx

0 joy zhou1 over 4 years ago in reply to joy zhou1

Intellectual 470 points

The last one. The third.

Thanks,

Joy

0 joy zhou1 over 4 years ago in reply to joy zhou1

Intellectual 470 points

The third.Third day logging_update status keeping 06_03Feb20.xlsx

0 Andy Liu (BMS) over 4 years ago in reply to joy zhou1

TI__Guru 52115 points

Hi Joy,

If you don't see the LStaus() go from 0x06 to 0x0E, that bascially means the cell-balancing has not been enabled.

I would need to look into your logs and see what might be wrong.

Andy

0 joy zhou1 over 4 years ago in reply to Andy Liu (BMS)

Intellectual 470 points

Hi Andy,

Yes, you are right. Please look into and let me know what wrong and how to solve.

Thanks,

Joy

0 Andy Liu (BMS) over 4 years ago in reply to joy zhou1

TI__Guru 52115 points

Hi Joy,

Can you send me your gg file after the 3 learning cycle failed? I need to compare it with the gg file you already shared with us. It was created before you did the learning cycle, right?

Andy

0 Vos over 4 years ago in reply to joy zhou1

TI__Genius 10370 points

Joy,

I see you are using LiFeP04 type cells. These cell create additional gauging complications due to the flat nature of the voltage profile. The issue you are running into is you are not getting a valid QMax DOD update after the full charge. This could be for a few reasons

1) You did not enter relaxation above the "Flat Zone" + 50mV delta. If this is the case you need to wait until the OCVFR bit clears which will take up to 48hours

2) You are overcharging the cell according to the chemID so the DOD update is being disqualified.

To combat this i highly recommend you use the [FAST_QMAX] feature. This is where you charge the device to full and trigger a valid charge termination event, then discharge the device to less than 10% SOC and enter relaxation (~5mins total needed). The key to this is [Fast QMax_LRN] and [Fast_Qmax_FLD] must be enabled. In addition you need to adjust the Ra0 gird point value higher so that DOD@EOC does not register a 0 value.

With these types of cells i have seen an Ra0 value of 200 to 6K or bigger. I would use the TI online tool GPC golden file optimizer with your IVT file and have it attempt to computer a correct value.

Thanks,

Eric Vos

0 joy zhou1 over 4 years ago in reply to Vos

Intellectual 470 points

Hi Andy, Eric,

Thanks for your reply! I am rushing in another project, I will continue this project later, and will answer your question and ask question at that time.

Thank you very much!

Joy

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BQ40Z50: Why QMax cannot update properly?