• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 490 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.

BQ76940: BQ76940 adjacent cell change in the balancing

Big Bill
Expert 1980 points
Part Number: BQ76940

Dear  All：

    Why does the cell voltage change during balancing? In my application, when i balance the  cell, i find the adjacent cell voltage is high more than normal,  I worry that this will affect my  software  judgment of OV or  balance. I can't modify the hardware,  Do you have any good advice to solve  this problem by modifying the software code？ Thanks！

  • 0
    TI__Guru* 81035 points

    Hi Bill,

    The cell measurement does not take place during balancing, but the voltage can take time to settle for cell measurements depending on the input filter component values (Rc and Cc). An example waveform can be found in Figure 5 of this app note: http://www.ti.com/lit/an/slua775/slua775.pdf

    If filter settling is the issue, I do not think you can solve this without modifying the hardware. If the voltage variation is small, maybe you could turn off balancing when you are getting close to the OV voltage - one idea for software modification.

    Best regards,

    Matt

  • 0 in reply to Matt Sunna
    Expert 1980 points

    Dear  Matt:

        As  your  said, the adjacent cell can be  effect during the  balancing，but  in  fact , only when  I  balance the 6th cell or  5th cell & 10th cell  or  11th cell, the adjacent cell can be  effect and  the adjacent  cell is not the same Die as the  balance cell. 

  • 0 in reply to Big Bill
    TI__Guru* 81035 points

    Hi Bill,

    Ok, I understand what you are seeing. The different cell groups are independent, so one group can be balancing while the other group is measuring. This is described in this app note at the top of Page 9: http://www.ti.com/lit/an/slua749a/slua749a.pdf  It suggests this is an issue with the common path resistance of the board.

    Regards,

    Matt