• State TI Thinks Resolved
  • Locked Locked
  • Replies 8 replies
  • Answers 1 answer
  • Subscribers 64 subscribers
  • Views 568 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

BQ40Z80: Relative state of charge

Fabrizio Raggioli
Intellectual 360 points
Part Number: BQ40Z80
Other Parts Discussed in Thread: BQSTUDIO, EV2400, GPCCHEM

Hi,

we built a battery pack based on two Samsung 18650-30Q in series. I configured the BMS with the chemical ID 2085 and all the other parameters should be in compliant with the specification of the batteries.

We have a strange behaviour on the relative state of charge that seems to be not in compliant with the real state of the battery. Hereafter the screenshot that show the RSoC to 100% with the battery not fully charged.

In that condition the BMS stops the charging (the OC flag pops up, you can see the log:

4572.log.log
Fullscreen
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Thu Jan 20 14:51:13 CET 2022
Device Version Info = 4800_0_04
BQZ Device Name = bq40z80
BQZ Firmware Version = V0_04_BLD5
Design Capacity = 2950
Design Voltage = 7200
Specification Info = 0x0031
Manufacturer Date = 2020-10-1
Serial Number = 0x0003
Manufacturer Name = Dronus
Device Name = bq40z80
Device Chemistry = LION
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
.

After the reset, the reset the RSoC returns to a “normal” value and the battery restart the charging. (See the RSoc after reset)

I attached also the parameters. Where is the configuration problem?

0172.Data memory.gg.csv

  • 0
    TI__Guru** 104905 points

    Hello Fabrizio,

    The OC protection indicates the gauge calculated a higher RemCap than FCC by the OC threshold. When you reset the gauge it recalculates FCC and RemCap based on the OCV table in the chemistry ID, so the OC protection status disappears for that reason.

    To determine root cause we would need a bqStudio log from the test. What may have occurred is the gauge predicted a much smaller FCC at the start of charge than what was actually available (section 7.5 FullChargeCapacity(FCC), RemainingCapacity(RemCap), and RelativeStateOfCharge(RSOC))

    If the temperature changes during charge (increases) or the charge currents varies unpredictably, it may lead to this flag being set incorrectly. 

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Intellectual 360 points

    Hi Wyatt, thanks for the answer.

    Yes, I can do the test, but please, can you describe roughly the procedure?
    Should I fully discharge the batteries? Rate of discharge? 

    After the FD, should I fully recharge (rate?) ? Is there some other prescription that I must follow?

  • 0 in reply to Fabrizio Raggioli
    TI__Guru** 104905 points

    Hello Fabrizio,

    You should perform the same test that the original problem occurred, just make sure to log the data with bqStudio. This way we can confirm what was the cause.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Intellectual 360 points

    Hi Wyatt,

    I will do the tests in this week. Anyway, can you confirm that I can put the EV2400 connected to the BMS that is alredy on a I2C bus (with another periferal)?

  • 0 in reply to Fabrizio Raggioli
    TI__Guru** 104905 points

    Hello Fabrizio,

    The EV2400 is not designed to work with other host systems, it does not have collision handling so it will most likely lead to errors in logging or communicating with bqStudio. The system still may work but there would be communication errors if both hosts try to communicate at the same time.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Intellectual 360 points

    Ok, thanks. We connected the EV2400 in parallel to the system and seems that is working correctly. We will do the test in the next days.

  • 0 in reply to Fabrizio Raggioli
    Intellectual 360 points

    This is a first log, but we not finished the charge. In the next days I will provide several log.test_log.log

  • 0 in reply to Fabrizio Raggioli
    TI__Guru** 104905 points

    Hello Fabrizio,

    Thanks for the data, we will wait for the additional logs. It also looks like you're getting a different safety status now for CTOS? This means you're charging for too long most likely.

    Can you also share your GPCCHEM report from finding the chem ID?

    Sincerely,

    Wyatt Keller