• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 64 subscribers
  • Views 412 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: Stand-Alone Cell Balancing Setup

Steven Hansel
Prodigy 30 points
Part Number: BQ77PL900

I have a board with cell balance circuit similar to that shown in the specsheet/appnotes and am questioning the appropriate register values for using the stand-alone cell balancing.

Specifically, the values in OV_CFG (0x06) for the OV level.

My understanding is that in this case, OV2-0 are used as the cell voltage which triggers the balancing algorithm.

If this is the case, the default (0x00) for this field would be the proper value when balancing, correct?

I observe cell voltages exceeding the register value during the balance process, so the process should start as early as possible, correct?

I have studied slus844b and slua463, but any other resource would be helpful.

Thanks

  • 0
    TI__Guru 54715 points
    Hi Steven,
    If cell balancing is enabled the OV threshold is used for balancing. The part both turns off the charge FET to prevent further charge and balances the high cells until they are below the OV hysteresis level, see the datasheet figure 19. Figure 19 assumes the charger maintains the voltage so charge can continue when the OV recovers. Be sure to set an effective hysteresis so that the cells have some time to balance. With a 0 hysteresis it won't balance effectively since balance is likely to stop right away from an IxR drop.
    The part has a tolerance on the OV level but basically should not allow charge past that level if it is controlling the FET. The appropriate level will depend on the cell selected. If you are using the part for balance only you might want to start early, but realize it will balance down to the hysteresis level below the threshold.