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BQ76942: Cell balance Interval

Fabio Gou
Expert 3080 points
Part Number: BQ76942

The customer is testing the cell balance function.



1. After "overheating" TH3, the charging MOS was turned off after 8.4s, and then after 9.34s cell balance is disabled.

2. Adjust the adjustable resistor to restore the normal working condition, charging state will recover after 3.28s, and then the cell balance will recover after 17.64s.

Cell Balance Interval is configurated as 20s.

Is it normal? Especially for the OTC?

Besides, the Cell balance interval counter will keep counting at normal working state/sleep mode? Even in protection B/C/D state?

I have read the related description in the datasheet.

"The device evaluates the conditions for continuing balancing every Settings:Cell Balancing

Config:Cell Balance Interval. For example, if the device is configured to avoid balancing during charge, and

while balancing the pack begins charging, balancing will continue until the interval timer expires before it is

disabled. While autonomous cell balancing is underway, the conditions related to continuing or stopping balancing are

re-evaluated at each Settings:Cell Balancing Config:Cell Balance Interval. "

  • 0
    TI__Expert 4085 points

    Dear Fabio,

    Can you clarify a few things for me:

    1. For asking whether it is normal, are you referring to the time it takes to turn off the MOS and cell balancing?
    2. Are the times you are getting for the cell balancing constant values or does the amount of time fluctuate based on different tests?
    3. What is your delay time in the Settings:Protections:OTD:Delay register? This controls the wait time before OTC throws a fault.

    To answer your second question regarding the counter during SLEEP, the counter will keep going if balancing during SLEEP is enabled. This is set by enabling the Settings:Cell Balancing Config:Balancing Configuration[CB_SLEEP]  and [CB_NOSLEEP] bits. If balancing isn’t enabled during SLEEP, the device will finish the interval it is on for balancing and then disable the counter if SLEEP mode is detected. If it is enabled during SLEEP, the cell voltages will be slower to acquire due to delayed polling of cell voltages, but the cells will still try to balance at each interval.

    Best,

    Asher Nederveld