• State TI Thinks Resolved
  • Locked Locked
  • Replies 10 replies
  • Answers 4 answers
  • Subscribers 65 subscribers
  • Views 357 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-R2: forcing

Ricardo Dominguez
Prodigy 20 points
Part Number: BQ40Z50-R2

We use currently using BQ40Z50-R2 with 22.4Ah, 4S7P battery. Our question is around enabling cell balancing after production. 

From the app note "slua903 Achieving The Successful Learning Cycle" , we have:

 " (...) For multi-cell applications, another charge-relax-discharge- relax cycle may be run to ensure Update Status changes to 0E to activate cell balancing. 

• Before saving the Golden File, set Update Status to 02 to disable IT gauging, set the Qmax Cycle Count to 0, and set the Cycle Count to 0. For a pack side gauge, this ensures that when the pack is assembled and gauging and lifetime data is enabled, the cycle counts start from 0."

 

After production of the PCB (loading golden file and calibration), the PCB is assembled into the battery and we want at this point to activate the cell balancing. The issue is, If we send GAUGE_EN using BQ studio the Update Status changes to "06" and not "0E" and the cell balancing is not activated.

We can't afford to perform another charge/relax/discharge/relax cycle for each battery, as described in the app note, because it would take hours in the production line. The only way to activate the balancing seems to be to manually change Update Status to 0E. Is that something we can without any side effect? Is there any other way to activate the cell balancing?

Thanks

  • 0
    TI__Guru** 105760 points

    Hello Ricardo,

    We don't recommend changing the update status besides resetting it to 0x02. When you upload the golden image with the update status of 0x06 it should update to that value, when the gauge performs a cycle in the field it will change the update status to 0x0E. The charge-relax-discharge- relax cycle only needs to e performed if the first update was not successful to ensure it does update.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Prodigy 20 points

    Thanks Wyatt,

    Why exactly it is not recommended to change Update Status to force cell balancing to enabled?

    Our devices are designed in a way that we don't allow the battery to discharge below 20% SoC to preserve the battery. In this case where we are never going to have a full discharge cycle in the field, can it still automatically update the status to 0E?
    Sorry, what do you mean by "if the first update was not successful"?
    Thanks
    Ricardo

  • 0 in reply to Ricardo Dominguez
    TI__Guru** 105760 points

    Hello Ricardo,

    The gauge performs calculations based on the SOC, by performing a field Qmax update the gauge will use the new SOC values to calculate the time to balnce the cells. If it performs without taking the field Qmax it could balance the cells incorrectly.

    I would read through the cell balancing section in the TRM, section 7.1: https://www.ti.com/lit/ug/sluua43a/sluua43a.pdf?ts=1597265400956&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FBQ40Z50-R2

    The first Qmax update after the learning cycle, if it was not successful it is recommended to do the cycles to ensure it is successful, but it is not always needed. After the update status of 0x06 to get a Qmax update you need to cycle the battery by 37% then it will have the field Qmax update and change to 0x0E.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Intellectual 390 points

    Hello Wyatt,

    You said:

    The first Qmax update after the learning cycle, if it was not successful it is recommended to do the cycles to ensure it is successful, but it is not always needed. After the update status of 0x06 to get a Qmax update you need to cycle the battery by 37% then it will have the field Qmax update and change to 0x0E.

    What do you mean by but it is not always needed: why it's not always needed?Could you elaborate a little bit more.

    We charged by more than 37%, the gauge was at REST before  charging, we fully charged to 100%(not in the flat region at the end of charge), we waited  the  REST flag to be =1 but the Qmax cycle count was not updated?

    The REST current is 80mA, the quit current is set at 100mA, we can see the flag REST =1 but does a high resting current could not allowed the Qmax update to happen?

    During Manufacturing the Max capacity was wrong, but after resting some weeks it seems the battery updated the max capacity to the good value but Qmax cycle count was still 0? it is possible to have an update of the max capacity despite Qmax cycle count staying at 0?

    Thanks,

     

  • 0 in reply to Clement MAGNIEN
    TI__Guru** 105760 points

    Hello,

    The gauge will change update status to 0x0E when a in field Qmax occurs, this should happen when there's a 37% change in DOD and rests. It is recommended to do the cycles to ensure the update status does change to 0x0E, but it should update after a field Qmax update.

    Can you share the log files showing the Qmax not cycling? and export your .gg file so we can check the settings?

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Intellectual 390 points

    Hello Wyatt,

    in attachment the log for  a REST/FULL CHARGE/ REST cycle and the gg.file

    you can see there was no Qmax update

    Regards,

    Clement

    log qmax checking.xlsx0220052101000009_0910058801000016.gg.csv

  • 0 in reply to Clement MAGNIEN
    TI__Guru** 105760 points

    Hello Clement,

    It looks like there is still 84mA flowing in your relax state, the gauge may not be taking the OCV reading because of this, you need to make sure there is no current flowing for the gauge to take an OCV reading and update Qmax.

    Sincerely,

    Wyatt Keller

  • 0 in reply to Wyatt Keller
    Intellectual 390 points

    Hello Wyatt,

    I already asked about the high rest current in my previous message but you didn't answer.

    you said:"the gauge may not be taking the OCV reading because of this", since the flag REST is activated, I assumed the gauge took an OCV reading? How can I check if the gauge works correctly?

    In our application the consumption at rest is between 4mA and 85mA (it depends on the battery charge), we can't change it.

    Regards,

    Clement

  • 0 in reply to Clement MAGNIEN
    Intellectual 390 points

    Hello Wyatt,

    I did the test with the battery outside of the controller( no high rest current), now the rest current is 0 mA.

    Full charge then waited REST flag =1 ( and OCVFR= 0, not in the flat region) then discharge more than 37%(in fact discharge to 30% SOC to be sure to be outside the flat region OCVFR=0), waited REST flag =1, but still no QMax update.

    Something weird just after the last discharge and without to wait REST flag=1 ,CB was activated despite update status still = 06??????

    Also what about these parameters: we use BQ40Z50-R3

    Regards,

    Clement

  • 0 in reply to Clement MAGNIEN
    TI__Mastermind 24870 points

    Hello Clement,

    For the learning cycle, you will need 90% Qpass instead of the 37% Qpass.

    Thanks