• State Resolved
  • Locked Locked
  • Replies 4 replies
  • Subscribers 64 subscribers
  • Views 1424 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: Activate Balancing

Flix
Prodigy 220 points
Part Number: BQ40Z50
Other Parts Discussed in Thread: BQ40Z80

Hello E2E-Community, 

We are planning to use a BQ40z50 in a 4S2P-Battery Pack, but I'm having a hard time activating Cell Balancing. 

When sending a reset command, the Bal_En flag is set, but CB is still set to 0. After the Relax Balance Interval time has been elapsed, the Bal_En flag toggles to zero. 

What conditions toggle the Bal_En flag? 

I would appreciate your help. 

Regards, Felix

7140.Bq40z50-wontbalance.gg.csv.zip

  • 0
    TI__Genius 10830 points

    Hi Felix,

    I wanted to let you know that your post has been assigned to one of our applications engineers. This week takes place our annual Battery Management Deep Dive event for which all our engineers are all hands on deck. He will be able to your post early next week, once this event is over.

    You can check out recordings of much of the material we present at www.ti.com/deepdive

    Thank you for your understanding!

     

  • 0 in reply to David Hien
    Prodigy 220 points
    Thanks for your reply. I will watch some tutorials and I will post here if I solved the Issue myself.
    Regards, Felix.
  • 0 in reply to Flix
    TI__Expert 6575 points
    Hi Felix,
    Even though the BAL_EN flag is set, there are some conditions that need to be met for balancing to actually occur:
    - Successful learning cycle has been performed for the pack, and the Qmax and Ra values are updated. Further, there has been a Field Qmax update such that "Update Status" has automatically updated to 0x0E.
    - The balancing timers are updated when the gauge has had a chance to read the Balancing DODs to compute the difference in capacitates of the cells. typically this will occur on the first valid charge termination after the Field Qmax update.
    - For cell balancing at rest, the RSOC is above the "Min RSOC for Balancing". Also, during rest, there is a 30minute window when BAL_EN will be cleared when the gauge attempts to take an OCV reading. Balancing will not be enabled during these 30 minutes.
    Form your attached gg file, it does not appear that the pack has gone through a learning cycle, and so the gauge does not know the actual capacity of the cells, and can not do balancing yet.
    I would recommend looking at the following app note for bq40z80, since the process is the same for bq40z50 as well in order to complete a successful learning cycle: www.ti.com/.../slua848.pdf
    Regards,
    Swami
  • 0 in reply to Swaminathan Ramanathan75031
    Prodigy 220 points
    We couldn't achieve a successful learning cycle, because the voltage levevl of the unbalanced cells are drifting apart from each other to far. We are not able to reach a fullcharged state...
    We consider using differrent Cell types....
    But Thanks Swami and David