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BQ76920: Battery balancing

Deepak Kumar58
Prodigy 30 points
Part Number: BQ76920

Hi, I am using bq76920 for 3 Li-ion Series cell monitoring and balancing. In our system cell balancing is working properly between from 3.5 to 4.2 Volt during charging and discharging but below 3.5 V one of the cells runs out of the race of balancing.

cell 1(volt) cell2(volt) cell3(volt)
4.027  4.04 4.04
3.65 3.68 3.65
3.63 3.64 3.63
3.61 3.62 3.62
3.525 3.361 3.371
3.505 3.288 3.380

  • 0
    TI__Guru 54715 points
    Hi Deepak,
    I don't fully understand your operation, but the bq76920 will not balance adjacent cells. It should be able to balance cells 1 and 3 simultaneously. Balancing will work to a low voltage, but if the cell is approaching a discharged state balancing is not recommended since it is loss of energy and one cell may be dropping more quickly since capacity may not match perfectly. Balancing is typically used to match the cells at full charge.
    If you are working with low voltage cells you would be balancing at a lower voltage of course, again matching the cells near full charge.
  • 0 in reply to WM5295
    Prodigy 30 points
    Should I disable balancing when battery is in discharged mode??
  • 0 in reply to Deepak Kumar58
    TI__Guru 54715 points
    Hi Deepak,
    That is up to you, but generally you would not want to balance during discharge. Certainly not at low voltage.
    You must stop balancing when using the bq76920, it does not stop by itself, it trusts that the host knows what control is programmed.