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BQ79612-Q1: BQ79612-Q1

Part Number: BQ79612-Q1
Other Parts Discussed in Thread: BQ76PL455A

Hello to TI support team ,

      I received expand Data sheet from TI according to bq79612 data , I have question according to Autonomous internal cell balancing mode :

1. Is this algorithm operate only in Charge or in Storage too ?  (bq79612 is without system shunt so it doesn't have info according the current ) 

2. Can I set Threshold cell Voltage + Timer to operate and it will balance odd/even cells ?

3. The IC make balance to all the cells by default ?

4. What is the task of External Controller in Autonomous internal cell balancing mode ?

5. How the IC should react if an example all the  cells 4.15V except one cell   3.6V --> What it the reaction of IC  ?  

6. During Shelf time (Storage ) disbalance starts increase --> How IC react ?


Alexander Burtakov

  • Hi Alexander,

    The cell balancing will run for a fixed time on each channel or until the set VCB threshold is hit on that channel. 

    Yes you can enable both the threshold cell voltage and timer, and after writing BAL_GO and AUTO_BAL bits it will balance odd/even cells according the setting in BAL_CTRL1.

    The IC will balance any cells enabled in the CB_CELL16_CTRL through CB_CELL1_CTRL registers.

    I'm not sure what you mean by External Controller, do you mean the MCU? The MCU will need to schedule the balancing cycles. The AUTO_BAL only handles keeping track of the timer, voltage thresholds and even/odd duty cycle. It is up to the MCU to properly schedule the cell balancing cycles.

    If all cells are 4.15V and one cell is 3.6V the behavior will be based on the user defined parameters. Assuming that 3.6V is either at or below the customer set voltage threshold then the 3.6V cell will stop balancing while all other cells continue until either the timer elapses or the threshold is reached.

    The IC won't automatically react or enable cell balancing. This must be started by MCU.



  • Hi Geof ,

       Thanks for your quick response , few more question according autonomeous balance mode .

    1. The span of voltages terminate the balance if configured by the bq are : 2.45V-4V only ?

    2.  It is possible start balance from any cell voltage  , timer at least should be configured mandatory ?

    3.   What is the purpose of balance through GPIO resistor ?

    4.   Can I select odd/even cells balance frequency ? 

    5.    Is any register feedback for  MCU  #times it Switched #cell  ?

    6.  The balanacer in bq76PL455A is the same only without VCB_THRESHOLD TERMINATION ?


    Alexander Burtakov

  • Hi Alexander,

    Correct. 2.45 - 4V in 25mV steps.

    A timer is mandatory. There is no requirements from the IC on the starting cell voltage.

    Through GPIO resistor? Do you mean the module balancing? Typically a system has multiple modules and multiple BQ devices. Each individual IC will balance the cells connected to that particular IC. The module balance is a way to balance the other modules to eachother.

    You can select the duty cycle in BAL_CTRL1. For example if you set DUTY = 0x01 then the device will switch between evens and odds every 10s.

    No. The device can report out the remaining balancing time. Using the initially set timer, the remaining balancing time and the duty cycle you can approximate how many times it has been switched.