• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 64 subscribers
  • Views 407 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.

BQ77PL900: BQ77PL900 Host Mode Cell Balancing TimeOut Problem

Faruk Sözüer
Intellectual 600 points
Part Number: BQ77PL900

Hello everyone.

I used the BQ77PL900 battery charging and protection application.  The BQ77PL900 is in host mode.   The application is connected to the battery card bq77pl900 integrated. 
Balance orders and cell voltage monitoring is done via the charger.  But there are some deficits in the system. The most important of these is that when the balance order is issued, the BQ77PL900 continues to balance when the battery is removed from the charger.  Because there is no processor on the Bms card. Only BQ series integrals are available. In order to avoid this situation, I think it is necessary to add a function such as time-out or Blank Off when I2C buffer is empty while running BQ77PL900 integrated in host mode.   

I will summarize the subject;

BQ77PL900 in host mode --> Read Cell Voltage --> Cell 1 is largest(example) --> Send Cell 1 balance order through line I2C --> If the battery is removed before Balance is off at this time, balance continues.


To prevent the above situation; The BQ77PL900 integrates a time-out feature for the balance status when operating in Host mode.

Thank you for reply. 

  • 0
    TI__Guru 54715 points
    Hi Faruk,
    The BQ77PL900 does not have a time feature as you note and desire. In host mode the host must control balance FETs, both turn on and turn off. This is one reason for architectures which use dedicated MCUs in the battery. There are monitor devices which have timeouts for balancing, these have traditionally been used in more complex or distributed systems.
  • 0 in reply to WM5295
    Intellectual 600 points

    Hello thanks for reply;


    I'm aware of the situation you're talking about. But this is a deficit, right? So in some way, if the communication breaks, the balance will never be closed.

  • 0 in reply to Faruk Sözüer
    TI__Guru 54715 points
    Hi Faruk,
    It is the design of the part. If the host is present it should be present. If the host is failed the battery is failed.
    Using the bq77PL900 in standalone mode or another standalone protector may be a better fit for your architecture.